Gpon Tutorials at 8:56 AM Posted by Share Online  0 comments

1. ODN of Fiber Access Network 2. Network elements Gpon 3. PON - Passive Optical Network 4. Basic concepts of Passive Optical Networks 5. T-CONT Bandwidth Terms 6. GPON Framing 7. Optical Power Attenuation 8. GPON Protocols 9. GPON Technology 10. What is a PON ? 11. Optical networking and network topology 12. GPON fundamentals 13. ISAM 7342 GPON 14. 7342 ISAM FTTU based solutions 15. Gigabit Passive Optical Network 16. Gigabit Ethernet Passive Optical Network Tutorial 17. PON properties 18. Splitter Gpon Basics 19. Advantages of fiber 20. Fiber Optic Tutorial

1.ODN of Fiber Access Network

 at 6:01 AM Posted by Share Online  0 comments

+ ODN( Optical Distribution Network) ,between OLT and ONT. is composed of 5 parts:

Feeder Optical Cable, Distribution Point, Distribution Optical Cable, Access Point and Drop  Cable.

+ Drop Cable is the most difficult part in the 5 parts of ODN deployment, usually be separated as “Home pass” and

”Home entry”.  

+ FMS (Fiber Management System)  is used for maintenance and trouble location. 

+ FMP(Fibre Management point ) is easy  for trouble location and link loss detection.

+ The ODN construction cost  accounts for 72% of total FTTH  network construction cost.  ODN deployment mode

impacts network construction cost and deeply relates to city planning, so ODN must deployed  in one- stop.

2.Network elements Gpon

 at 9:02 AM Posted by Share Online  0 comments

ONT Alcatel

A PON takes advantage of wavelength division multiplexing (WDM), using one wavelength for downstream traffic

and another for upstream traffic on a single Non-zero dispersion-shifted fiber (ITU-T G.652). BPON, EPON, GEPON,

and GPON have the same basic wavelength plan and use the 1,490 nanometer (nm) wavelength for downstream

traffic and 1310 nm wavelength for upstream traffic. 1550 nm is reserved for optional overlay services, typically RF

(analog) video.

As with bit rate, the standards describe several optical budgets, most common is 28 dB of loss budget for both

BPON and GPON, but products have been announced using less expensive optics as well. 28 dB corresponds to

about 20 km with a 32-way split. Forward error correction (FEC) may provide another 2–3 dB of loss budget on

GPON systems. As optics improve, the 28 dB budget will likely increase. Although both the GPON and EPON

protocols permit large split ratios (up to 128 subscribers for GPON, up to 

32,768 for EPON), in practice most PONs are deployed with a split ratio of 1x32 or smaller.

A PON consists of a central office node, called an optical line terminal (OLT), one or more user nodes, called optical

network units (ONUs) or optical network terminals (ONTs), and the fibers and splitters between them, called the

optical distribution network (ODN). ONT is an ITU-T term to describe a special, single-user case of an ONU. In

Multiple Tenant Units, the ONU may be bridged to a customer premises device within the individual dwelling unit

using technologies such as Ethernet over twisted pair, G.hn (a high-speed ITU-T standard that can operate over any

existing home wiring - power lines, phone lines and coaxial cables) or DSL. An ONU is a device that terminates the

PON and presents customer service interfaces to the user. Some ONUs implement a separate subscriber unit to

provide services such as telephony, Ethernet data, or video.

OLT Alcatel

The OLT provides the interface between the PON and the service providers network services. These typically

include:

Internet Protocol (IP) traffic over gigabit/s, 10 Gbit/s, or 100 Mbit/s Ethernet..

standard time division multiplexed (TDM) interfaces such as SONET or Synchronous Digital Hierarchy (SDH)

Asynchronous Transfer Mode (ATM) User–network interface (UNI) at 155–622 Mbit/s

The ONT or ONU terminates the PON and presents the native service interfaces to the user. These services can

include voice (plain old telephone service (POTS) or voice over IP (VoIP)), data (typically Ethernet or V.35), video,

and/or telemetry (TTL, ECL, RS530, etc.). Often, the ONU functions are separated into two parts:

The ONU, which terminates the PON and presents a converged interface – such as xDSL, coax, or multiservice

Ethernet – toward the user, and

network termination equipment (NTE), which provides the separate, native service interfaces directly to the user

Splitter 1:16

A PON is a shared network, in that the OLT sends a single stream of downstream traffic that is seen by all ONUs.

Each ONU only reads the content of those packets that are addressed to it. Encryption is used to prevent

eavesdropping on downstream traffic.

Source : Alcatel And Wikipedia

3.PON - Passive Optical Network

 at 1:53 AM Posted by Share Online  0 comments

The PON, is a concept in it's infancy.  If they can ever get the Genie out of the bottle, and get it to work as

envisioned (in the network core). . . PON promises to be the most revolutionary idea since the development of car

engines  that run on hydrogen and water.

With PONs, one access line can be shared among multiple buildings--and it can be done at a minimal cost. That's

because PONs use low-cost components that don't require a lot of care and upkeep. As a result, PONs cost a

fraction of what it takes to run new fiber or rework existing Sonet (synchronous optical network) rings.

Right now PON is last-mile - and they have come a long way, and several flavors are already available -  APON (ATM

PON), BPON (Broadband PON), EPON (Ethernet PON), and GPON (Gigabit PON).  Standards are in place for PON

networks; the two most important are the International Telecommunication Union (ITU) standards G983.1,

Broadband Optical Access Systems Based on Passive Optical Networks (PON), and G983.2, ONT Management and

Control Interface Specification for B-PON.

Currently, the most promising application for PONs is as an optical feeder for telcos, cable TV companies and

wireless providers. PONs complement emerging broadband access technologies such as xDSL (copper), HFC (coax)

and LMDS (wireless), rather than competing against them, by allowing for shorter access drops and higher

bandwidth. Because it provides a low cost, high bandwidth, fault-tolerant solution for carriers interested in

delivering lucrative revenue generating broadband services, PON is the best solution for the next generation

broadband local loop.

CO to User - PONs allow offer multiple data paths by bundling together multiple light wavelengths (up to 32 at

present) so they can be carried over a single access line from the carrier's central office (CO) to a manhole or

controlled environmental vault close to a cluster of customer sites. At that point, the wavelengths are broken out

and each one is steered into a different short length of fiber to an individual site.

User to CO - a different scheme is used for collecting traffic traveling in the opposite direction - from user sites to

the CO. In this case, each site is given a specific time slot to transmit, using a polling scheme similar to the one

used in old IBM networks.

Real-World PON

+ OLT (Optical Line Terminal) - located at the CO, the OLT interfaces with the metropolitan network. It must be high

power because it sends optical signals out, which are immediately broken into several streams.  The main

functionality of the OLT is to adapt the incoming traffic (Voice and Data) from the metropolitan rings into the PON

transport layer.

+ ONT (Optical Network Termination) and ONU (Optical Network Unit) - ONT and ONU are basically the same device

- however, the ONT is located at the customer premise, and the ONU isd located outside the home.  These devices

are the interface between the customer equipment and the PON.  They talk to the OLT via the PON. 

+ PON Splitters - With a single PON splitter, 32 subscribers can be served with two-way ATM. This way, it is not

necessary to include a lot of add/ drop multiplexers and install the dreaded OSP cabinet. The PON splitters can be

arranged in star, ring, or tree configurations to increase reliability.

Optical Network Unit (ONU) or an Optical Network Termination (ONT) receives the optical signal and converts it into

an electrical signal for use in the customer premises. (ONTs are used when the fiber extends into the customer

premise, whereas ONUs are used when fiber is terminated outside of the home.) DSL then brings the signal to the

customer premises.

Although PON has a long way to go, there have been some very exciting advances made in the field.  A PON system

typically consists of:

an optical terminal at the customer site that terminates the optical signal and delivers voice and data

an optical switch or other device that sits at the central office to send the PON protocol to the terminal at the

customer premises

the passive couplers and splitters that actually sit on the fiber loop

The PON equipment in the loop is placed at a fiber junction to act as a T-connector would on a garden hose,

splitting two fibers into eight fibers, for example, to enable multiple customers to share fibers.  PON networks can

be designed using three different topologies:

Those PON devices on the loop, which can be as small as a pen, typically cost only a couple hundred dollars vs. the

hundred of thousand dollars it would cost to install a SONET add/drop multiplexer and the environmentally-

controlled housing and power that would have to go with it. And because PON couplers and splitters are passive,

meaning they don't require power, the carrier doesn't have to do as much ongoing maintenance of the equipment

because there's no need for backup power or batteries in the outside plant.

PON can decrease the spectral interference created by copper-fed applications like ADSL and DS1, which clash if

put in the same cable bundles, and instead roll the DS1 onto a passive fiber. PON is also less expensive to maintain

because there are no active loop devices and fiber is less expensive to maintain in the long run than is copper in

any case.

PON lets carriers go into new markets and share fibers among residential and small business customers like gas

stations, strip malls and smaller establishments with automatic teller machines fed by 56kbps lines. It can also

enable carriers to reach buildings that are just out of reach of fiber in a metropolitan network or even in-building

networks that want to bring fiber to additional customers.

Types of PON's

APON (ATM PON) - ATM-based PONs (APONs) work just like standard ATM networks. Customers establish Virtual

Circuits (VCs) across the APON to a destination, such as another office or the ISP's premises. These VCs are bundled

into what's known as Virtual Paths (VPaths) for faster switching in the carrier's network. 

The speed of operation depends on whether the APON is symmetrical or asymmetrical. Symmetrical APONs operate

at OC-3 speeds (155.52Mbit/sec). For Asymmetrical APONs, the downstream transmission from the OLT in the CO to

the customer premises ranges from 155.52 to 622.08Mbit/sec. Upstream transmission from the customer premises

to the CO occurs at 155.52Mbit/sec. All network topologies support both configurations, unless the fiber extends to

the home, in which case asymmetrical operation isn't supported.

The upstream and downstream transmissions occur over two channels, which can be different wavelengths on the

same cable or two different cables. The original APON specification called for downstream transmission on a single

fiber occuring between 1,480 and 1,580 nanometers (nm); on dual fibers, between 1,260nm and 1,360nm.

Upstream transmissions always occur between 1,260nm and 1,360nm.

BPON (Broadband PON) - BPON is an ITU-based standard, based on APON, but uses WDM.  It defines how ATM data

is encapsulated into frames in groups of 54 cells.  AN important group called FSAN (Full Services Access Networks)

work with one goal - to find the best way to achieve early and cost-effective deployment of broadband optical

access systems.  The group is composed of Nippon Telegraph and Telephone, BellSouth, France Telecom, British

Telecommunications plc, and SBC.  They have developed a set of common technical specifications (CTS) for a B-

PON system based on ITU-T Recommendations G.983.1, G.983.2 and G.983.3.

EPON (Ethernet PON) - a standard for Ethernet Passive Optical Networks (EPON) is being developed in the Institute

of Electrical and Electronics Engineers (IEEE) 802.3ah Ethernet in the First Mile (EFM) Task Force. Ethernet PONs are

point-to-multipoint fiber optic networks suitable for Fiber to the Home (FTTH) and Fiber to the Building (FTTB)

applications.  EPON is the newest member of the PON family and is described in detail in the EPON section.  

The key difference between Ethernet and ATM PONs is that in Ethernet PONs data is transmitted in variable-length

packets of up to 1,518 bytes according to the IEEE 802.3 protocol for Ethernet, whereas in ATM PONs data is

transmitted in fixed-length 53 byte cells (with 48 byte payload and 5 byte overhead).  The Internet protocol calls for

data to be segmented into variable-length packets of up to 65,535 bytes. For an ATM PON to carry IP traffic the

packets must be broken into 48 byte segments with a 5-byte header attached to each one. This process is time

consuming and complicated and adds additional cost to the OLT and ONUs. Moreover, 5 bytes of bandwidth are

wasted for every 48-byte segment creating an onerous overhead that is commonly referred to as the ATM cell tax.

By contrast, Ethernet was tailor made for carrying IP traffic and dramatically reduces the overhead relative to ATM.

GPON (Gigabit ethernet PON) - EPON is Fast Ethernet (100 Mbps) PON, while GPON is GigE (10 Gbps) PON.  Ethernet

PONs build on the ITU standard G.983 for ATM PONs and seek to bring to life the dream of a full services access

network that delivers converged data, video and voice over a single optical access system. 

Video PON's

PON is initially being considered for business office applications; however, it is a perfect technology for

disseminating video.  

Asymmetric DSL (ADSL) (1.5 Mbps downstream) can support one video channel (actually, hundreds of channels can

be accessed, but only one can be watched at a time within a household). 

Very High Speed DSL (VDSL) (50 Mbps downstream) can support 7 channels including High-Definition Television

(HDTV) which is fine, being the average U.S. household has 2-3 TVs, and PON can provide speeds downstream in

the Gigabit range supporting 1000s of TV channels, including HDTV. This is even better than Hybrid Fiber Coax

(HFC) with 35 Mbps downstream, which supports hundreds of TV channels, including HDTV. 

AON (Active Optical Network)

To understand PON you must first understand AON, which is used in 99% of today's networks.  The biggest hurdle

to realization of the infinite bandwidth capabilities of fiber, is the electrical-to-optical and optical-to-electrical

conversions that are required.  Telecom companies have built huge SONET networks, comprised of long-haul rings.

These rings are like high-speed freeways . . . the problem, is that just as with freeways and cars, the rings needed

entrance and exit ramps for data.  But instead of ramps - the rings have complex devices called ADM's (Add-Drop

Multiplexors).  They also need Regenerators (repeaters), since the fibers do have loss, and light will not travel

forever is a lossy environment.  

AON Equipment

This is the real reason why a "true PON" has yet to be developed - the equipment required is electrical !!

Since fiber rings allow bi-directional data flow, two fibers are required (and another two for backup).  The ADM

allows removal and insertion of data streams to/from the ring.  For example, on an OC-48 ring (a total of 18, OC-

3's), an ADM may pull out one OC3 and also insert one OC3, while passing all the other traffic straight through.

However, since the entire OC-48 is in one stream, it cannot intercept just a single OC3.  Instead, it must intercept

the entire OC-48, strip out one of the OC-3's, and then mux the incoming customer's OC3 data stream back in with

the other 17 OC3's (i.e. reassemble the entire OC-48) and re-transmit.  Therefore, an ADM does three things

simultaneously:

passes most of the data, along the ring, transparently

on the receive fiber - takes incoming optical signals from the ring, converts them to electrical signals, demuxes

them and pulls out a portion, and transmits that portion to the end customers

on the send fiber - takes electrical signals from customers (quite often these are optical signals that have been

converted to electrical), muxes them together with other existing signals received from the ring, converts them to

optical signals, and transmits them onto the fiber ring. 

The regenerators so not strip out data - nor do they insert data.  However, they must reshape the signal and

amplify it.  This requires electrical circuitry, and therefore requires:

conversion from light to electric

signal processing - regeneration and amplification

conversion from electric to light

The Expense, or In-expense of PON

Whether to use PON or traditional AON (Active Optical Networks) is debatable, due to the high cost of PON.  A

reasonable goal for PON access to the first telco POP, would be for the subscriber links to support 3.6km at a

minimum and 7.2km max. If we further assume every man is born with entitlement to 100Mb/s or 155Mb/s

bandwidth, at least until he is an adult, we have many commercially available technologies to choose from.  Here is

an economically feasible, traditional fiber access system - and the reasons why PON can compete with it:

AON System - 850nm VCSEL lasers over Corning Infinicor SX+ - this system will do GigE (GbE) at 10 Gbps over 3km,

and  155Mb/s at 8 km. (verified).  Today you can buy 155Mb/s transceivers at $25, and they are projected to drop

even more. So the cost of these optics on both ends of the subscribers link is now cheaper than the passive splitters

and combiners in the PON ODN, and you have 155Mb/s secure, symmetrical, simple. No $500 optics at the home.

No need for complex electronics at the home to assure network fairness and security.

PON System - PON devices typically cost only a couple hundred dollars vs. the hundred of thousand dollars it would

cost to install a SONET add/drop multiplexer and the environmentally-controlled housing and power that would have

to go with it. And because PON couplers and splitters are passive, meaning they don't require power, the carrier

doesn't have to do as much ongoing maintenance of the equipment because there's no need for backup power or

batteries in the outside plant.

Source : infocellar.com

4.Basic concepts of Passive Optical Networks

 at 5:43 AM Posted by Share Online  0 comments

What is Optical Network? 

It is a network containing both active and passive elements. Active elements are in Central Office, at customer, in

repeaters, switches and etc. All that equipment add cost and complexity to the network. What can be done instead?

Passive Optical Network (PON) which had no active components between CO and customer. Passive equipment has

no electrical power needs, it guides the traffic signals contained within specific optical wavelengths. Voice, video

and data traffic flows (triple play) can be easily implemented using different wavelengths.

In PON there is no active optical elements at any intermediate points along the network path. 

Typical PON, where central office equipment is connected with multiple subscribers using fiber optic network is

shown in Figure 1. Central office could contain multiple equipment, such as public switched telephone network

switches (PSTN), Ethernet switches, asynchronous transfer mode switches (ATM), IP routers, video-on-demand

servers, backup storage systems (high capacity disk arrays and tape-drive libraries).

 

Passive optical power splitter is allocated near a building (housing complex, apartment or office building, a business

park or other campus environment), and is connected to central office using one single-mode optical fiber wire.For

the use of subscribers, signal is divided into N paths using splitting device. The power level for each subscriber can

be easily calculated, dividing the optical power entering the splitter(P) by number of paths(N). Multiple splitters

could be implemented in the specific path (possibly having different splitting ratios). Path can be splitted up to 64

paths, each of them would have individual single-mode fiber, running to each building or serving equipment. In

PON, distance from central office to the customer could be up to 20 km, while having active devices only in central

office and end terminal.

Active modules in the network can be divided in two main groups: OLT (Optical Line Terminal) located in central

office and ONT (Optical Network Terminal) or ONU (Optical Network Unit) at the far end of the network. ONT is just

connected directly to customer premises.  ONU is allocated somewhere near cluster of homes or business (usually

in telecommunication cabinet). ONU is connected to the premises by any twisted-pair wire, such as telephone lines

or digital subscriber links or coaxial cable.

ometimes it is more convenient and cheaper to put a single-fiber line from main splitter to distant localized cluster

of homes or small business or within a centralized location in the neighborhood. In figure, a small optical splitter is

located near the users’ houses, having one single-fiber line as input and multiple lines as output. Comparing to the

long fiber link to each user form the main splitter, this type of network costs much less. ODN (Optical Distribution

Network) is a collection of fibers, passive equipment and couplers that are allocated between the OLT and ONTs

and ONUs.

 

Feeder cable is a link connecting central office and the optical splitter, which can split signal up to 32 subscribers. 

Optical splitter is allocated in 10 km from central office and 1 km from the subscribers. Multiple distribution cables

are connected directly to users or to the access terminal (local splice box). Access terminal is connected to users

using individual drop cables.  

5.T-CONT Bandwidth Terms

 at 6:19 AM Posted by Share Online  0 comments

Transmission containers (T-CONTs):  Dynamically receives the authorization delivered by the OLT to manage the

upstream bandwidth allocation of the PON system TC layer. This improves the upstream bandwidth of the PON

system.

T-CONT bandwidth types: FB, AB, NAB, and BE

Five T-CONT types: Type1, Type2, Type3, Type4, and Type5

Relations Between T-CONT Types and Bandwidth Types

Based on the service priority, the system sets an SLA for each ONU to limit the bandwidth of the service. 

The maximum and minimum bandwidth restricts the bandwidth of each ONU to ensure that the bandwidth varies

according to the priority. In general, the voice service is of the highest priority, and the data service is of the lowest

priority.

The OLT allocates bandwidth according to the service, SLA, and actual ONU conditions. The service with a high

priority can be allocated high bandwidth to meet the requirements.

DBA Implementation

T-CONT Type 1 is characterized by the fixed bandwidth only. The assured bandwidth equals the maximum

bandwidth and has the highest priority.

T-CONT Type 2 is characterized by Assured bandwidth only. The assured bandwidth is the provisioned maximum

bandwidth. DBA Type 1 and DBA Type 2 do not participate in the bandwidth competition. If the assured bandwidth

exceeds the maximum bandwidth, the extra will be discarded.

DBA Type 2 has Assured bandwidth and Non-assured bandwidth. DBA Type 3 will be allocated bandwidth equivalent

to its Assured bandwidth, only when it has cells at a rate equivalent to Assured bandwidth or more than Assured

bandwidth. Non-assured bandwidth shall be allocated across all T-CONTs with Assured bandwidth that are

requesting additional bandwidth in proportion to the Assured bandwidth of the individual T-CONTs on the PON, e.g.

Weighted Round Robin method.

T-CONT Type 4 has Best-effort bandwidth only. T-CONT Type 4 shall only use bandwidth that has not been allocated

as Fixed bandwidth, Assured bandwidth or Non-assured bandwidth to T-CONTs in the PON. Best-effort bandwidth is

allocated to each T-CONT Type 4 equally, e.g. based on the Round Robin method, up to the Maximum bandwidth.

T-CONT Type 5 is the super set of all of DBA types. Fixed bandwidth is assigned first. If Fixed bandwidth is

insufficient, check whether the assured bandwidth meets the requirement. If yes, the assured bandwidth is

assigned. If not, the request for the additional bandwidth is tagged and competes with the DBA 3 tagged

bandwidth, eg. based on the Round Robin method. If additional bandwidth is still requested, Best-effort bandwidth

is assigned up to the Maximum bandwidth.

AES Encryption of a GPON System

GPON supports the AES128 encryption of downstream broadcast data.

Only the payload in the GEM frames can be encrypted.

The GPON system periodically changes and updates the AES key to improve the reliability of line data.

The OLT initiates the request for changing the AES key, The ONU responds to the request and generates a new key,

and sends the new key to the OLT. The AES key is divided into two parts for transmission and is transmitted three

times. The OLT switches to the new key after receiving the key,  After that, the OLT uses the account of the new

key to notify the ONU three times by a corresponding command, and the ONU switches the check key on the

corresponding data frames.

Activation Procedure in the ONU

The activation process is performed under the control of the OLT. The ONU responds to messages, which are

initiated by the OLT.

The ONU adjusts the transmission optical power level based on OLT requirement. 

The OLT discovers the serial number of a new connected ONU in the broadcast and the random delay way.

The OLT assigns an ONU-ID to the ONU.

The OLT measures the arrival phase (RTD) of the upstream transmission from the ONU.

The OLT notifies the ONU of the EqD.

The ONU calculate the upstream data transmit window based on the notified EqD and the BW Map. 

According to the ONUID query/configuration table, a password request is sent if password authentication is

required. No password request is sent if password authentication is not required.

Source : Huawei Technologies CO..

6.GPON Framing

 at 6:36 AM Posted by Share Online  0 comments

Downstream GPON Framing

Upstream GPON Framing

Mapping Mode of Ethernet Service in GPON

The GPON system resolves the Ethernet frames and maps the data part to the GEM payload for transmission. 

The GEM frame can automatically encapsulate the header information.

Clear mapping mode, easy implementation, good compatibility

Mapping Mode of TDM Service in GPON

The TDM service is first imported to the buffer to wait in a queue and is multiplexed to the GEM frame for

transmission.

In this mode, the specific TDM service cannot be sensed, and the service packets are transparently transmitted.

Source : Huawei Technologies CO..

7.Optical Power Attenuation

 at 6:40 AM Posted by Share Online  0 comments

Calculating optical splitter attenuation :

Insertion loss of the optical splitter (<1dB):

∑(Power_input) - ∑(Power_output of all branches)

10 log(0.5) = - 3.01

Attenuation of a 1:2 optical splitter: 3.01 dB 

Attenuation of a 1:16 optical splitter: 12.04 dB 

Attenuation of a 1:64 optical splitter: 18.06 dB

Optical Fiber Attenuation and Optical Power 

The optical fiber attenuation varies according to the lengths of optical fibers.

The attenuation of the optical fiber splicing point is less than 0.2 dB generally.

Other points such as optical fiber bending may also cause attenuation. 

About 0.35 dB per km for 1310, 1490nm

Technical Specifications of the GPON port (Class B+)

Source : Huawei Technologies CO..

8.GPON Protocols

 at 7:50 PM Posted by Share Online  0 comments

ITU-T G.984.1

Description of GPON network parameters

Requirements on protection switching network

ITU-T G.984.2

Specifications of the PMD layer

Specifications of the 2.488 Gbps downstream optical port

Specifications of the 1.244 Gbps upstream optical port

Allocation of physical layer cost

ITU-T G.984.3

Specifications of the GPON TC layer

Introduction to the GTC multiplexing structure and protocol stack

Introduction to the GTC frame structure

ONU registration and activation process

DBA specifications

Alarm and performance

ITU-T G.984.4

Introduction to the OMCI message structure

Framework of the OMCI device management

Overview of OMCI implementation principles

Protection Mode of a GPON Network

The OLT is not protected in any mode.

If the active optical fiber fails, you can manually switch the data to the backup optical fiber.

During switching, the service must be interrupted. The interruption time depends on the line recover time.

If the line to a subscriber fails, the service for the subscriber is interrupted  and cannot recover automatically.

There are two GPON ports on the OLT.

If the active optical fiber fails, the system automatically switches to the standby system to protect the active optical

fiber.

Only the OLT board, and the optical fiber between the OLT and the POS are protected. Therefore, this mode may

lead to security hazards and cannot meet the requirements of customers.

Both the OLT and ONT provide two GPON ports and the two GPON ports of the OLT work in the 1:1 mode.

This mode is a full backup mode for protecting optical fibers. In this mode, there are two channels between the OLT

and the ONU and all faults can be located.

When the active PON port or the subscriber line of the ONU fails, the ONU automatically switches the service to the

standby PON pot. Then the service is transmitted in the upstream direction through the standby line and the

standby PON port of the OLT. In this mode, the service is not interrupted.

Difficult implementation and high cost

One port of them is always in the idle state, which causes low bandwidth usage. 

The OLT provides two GPON ports, which work in the 1＋1 backup mode.

This mode is a full backup mode for protecting optical fibers. In this mode, there are two channels between the OLT

and the ONU and all faults, including the faults on passive optical splitters and links can automatically recover.

In a network of this mode, different types of ONUs supported. That is, the ONUs that provide one PON port and the

ONUs providing two ports can be selected according to the requirements of customers.

Difficult implementation and high cost

Source : Huawei Technologies CO..

9.GPON Technology

 at 8:15 AM Posted by Share Online  0 comments

Data Multiplexing

The GPON system uses the WDM technology to implement the bi-directional transmission over a single fiber (a

forced transmission mode).

Over a single optical fiber, to separate the Tx and Rx signals of multiple subscribers, the GPON system uses the

following two multiplexing technologies:

+ The downstream data streams use the broadcast technology.

+ The upstream data streams use the TDMA technology.

Downstream Data

Broadcast mode: The length of any downstream GPON frame is fixed to 125 us and the frames are broad cast to all

the ONUs. In this way, all the ONUs can receive the same data. The ONUs differentiate the frames by Gemport ID

and filters the frames to receive its own data.

Upstream Data

TDMA mode: The upstream GPON data is transmitted in the TDMA mode. The uplink is divided into different time

slots, which are allocated to each ONU according to the upstream bandwidth map field in the downstream frames.

Hence, all ONUs can transmit their own data based on a specific sequence and no conflict for competing timeslots

occurs.

Basic Performance Parameters of a GPON Network

GPON supports the following asynchronous transmission rates:

         0.15552 Gbit/s up, 1.24416 Gbit/s down

0.62208 Gbit/s up, 1.24416 Gbit/s down

1.24416 Gbit/s up, 1.24416 Gbit/s down

0.15552 Gbit/s up, 2.48832 Gbit/s down

0.62208 Gbit/s up, 2.48832 Gbit/s down

1.24416 Gbit/s up, 2.48832 Gbit/s down (mainstream rates supported currently)

2.48832 Gbit/s up, 2.48832 Gbit/s down

 Maximum logical reach: 60 km

 Maximum physical reach: 20 km

 Maximum differential between the farthest and nearest ONUs from the OLT: 20 km

 Optical split ratio: 1：64. It can be upgraded to 1: 128.

Source :Huawei Technologies CO

10. What is a PON ?

 at 6:08 AM Posted by Share Online  0 comments

 A PON network is a point to multiple points (P2MP) passive optical network.

 A PON network consists of the Optical Line Terminal (OLT),  Optical Network Unit (ONU), and Passive Optical

Splitter (POS) .

Model of a GPON Network

ONU     Optical Network Unit     

ONT     Optical Network Terminal

ODN     Optical Distribution Network

OLT      Optical Line Terminal

WDM    Wavelength Division Multiplex Module

NE       Network Element

SNI      Service Node Interface

UNI     User Network Interface

PON Standards

APON: ATM Passive Optical Networks 

EPON: Ethernet Passive Optical Networks

GE-PON: Gigabit Ethernet Passive Optical Networks

GPON: Gigabit-capable Passive Optical Networks

Why GPON is Preferred?

GPON (Gigabit-capable Passive Optical Networks)

Three advantages:

 1. Longer transmission distance: Transmission over optical fibers reaches the maximum of 20 km transmission

distance.

  2. Higher bandwidth: downstream 2.5 Gbit/s and  upstream 1.25 Gbit/s (the PMD layer) for each subscriber 

  3. Optical split feature: The single optical fiber from the CO is split to multiple drop optical fibers to save the

resources.

GPON supports the triple play service. It provides full-service solution to solve the bandwidth bottleneck of twisted

pair access, and to meet the requirement for high-bandwidth services, such as high definition TV and live show.

GPON is the best choice for the triple play service.

Complete GPON standards and high technology requirements

Preferred by global big carriers

Source : Huawei Technologies CO

11. Optical networking and network topology

 at 9:27 AM Posted by Share Online  0 comments

Point to Point

+ Hi capacity

- High fiber plant cost because of point to point configuration of fiber pairs

Active Star

+  High capacity

-   High operations and maintenance cost

-   High cost of outside plant electronics

Passive Star

+  High capacity

+  Standardized

+  Passive and flexible cable plant

+  Low operations cost

+  All services over one fiber

+  Low fiber plant cost

PON fiber sections

Centralised splitters

centralised splitter scenario

splitters in primary fexibility point only

distributed splitter scenario

splitters in both primary and secondary flexibility point

PON benefits

purely passive fiber plant  

low maintenance costs and high reliability

shares feeder fiber over multiple users

less fibers needed, less ports needed at CO

fiber is virtually not limiting the bandwidth

much higher bandwidth x distance than copper networks

fiber’s bandwidth can be further exploited by WDM or equipment upgrade 

installed fiber infrastructure is future-proof

PON offers bundled services over a single fiber

triple play – voice / data / video

Author : Alcatel - Lucent

12. GPON fundamentals

 at 7:35 PM Posted by Share Online  0 comments

Although the chapter is named GPON fundamentals, most of the topics described in here

also are applicable to APON and BPON.

 PON properties

 PON – Passive Optical Network

 passive components

splitters + WDM-device

 star topology

p2mp – point to multipoint

 lambdas

 1490nm – downstream data

 1310nm – upstream data

 1550nm – downstream (optional)

 ranging distance

 60 km logical reach

 20 km physical reach

differential distance

 split-ratio

 64 subscribers (or even more)

According to the GSR, a GPON must be a full-service network, which means that it should

be able to carry all service types.

> These include 10- and 100-Mbps Ethernet, legacy analog telephone, digital T1/E1 traffic

(I.e., 1.544 and 2.028 Mbps), 155-Mbps asynchronous transfer mode (ATM) packets, and

higher-speed leased-line traffic.

> The nominal line rates are specified as 1.25 Gbps (1244.160 Mbps) and 2.5 Gbps (2488.320

Mbps) in the downstream direction, and 155 Mbps, 622 Mbps, 1.25 Gbps, and 2.5 Gbps in

the upstream direction.

> The data rates can be either symmetrical (the same rate in both directions) or

asymmetrical, with higher rates being sent downstream from the OLT to the ONTs.

> A service provider can offer a lower upstream rate to those GPONs in which the

downstream traffic is much larger than in the upstream direction, as is the case when

subscribers use the IP data service mainly for applications such as lower-rate upstream

Internet surfing or e-mail and higher-rate downstream downloads of large files.

> The wavelengths are specified to be in the range 1480 to 1500 nm for downstream voice

and data traffic and 1260 to 1360 nm for its corresponding upstream traffic. Thus, the

median values are the standard 1490- and 1310-nm wavelengths as used in BPON and EPON

systems. In addition, the wavelength range 1550 to 1560 nm can be used for downstream

video distribution. Depending on the capabilities of the optical transmitters and receivers,

the GPON recommendation specifies maximum transmission distances of 10 or 20 km. For a

GPON the maximum number of splitting paths is 64.

> ---

> The 60 km max. distance is also referred to as a logical distance: this is related to the

ranging procedure, where an ONT will add some equalisation delay depending on the

distance the ONT is away from the OLT. This leads to all ONTs being virtually away 60 km

from the OLT.

> About the split: the standards already took care of having a split of up to 128 subscribers,

which is sometimes referred to as a logical split.

Optical power budget

 loss in splitters

 cascaded splitter can be used

e.g. 1:4 splitter followed by 1:8 splitter or vice versa

 so a one-step 1:32 splitter can be used

 loss in WDM coupler

 loss per km fiber

 loss in connectors

 loss in splices

distance = f(loss),

• splitters

• WDM coupler

• fiber ( x dBm/km)

• splices

• application (data or video)

The loss budget requirement for the PON, based on ITU Recommendation G.983.4, is 22 dB

total loss budget for Class B PON and 27 dB for Class C PON. What differentiates Class B and

Class C PON is the power of the laser used and, marginally, the quality of the optical

components. This loss budget is really tight, especially when high-port-count splitters are

used in the design. The splitters in a PON cause an inherent loss because the input power is

divided between several outputs. Splitter loss depends on the split ratio and is about 3 dB

for a 1 x 2 splitter, increasing by 3 dB each time the number of outputs is doubled. A 1 x 32

splitter has a splitter loss of at least 15 dB. This loss is seen for both downstream and

upstream signals. Combine the losses of the WDM coupler, splices, connectors and fiber

itself, and it is easy to understand why a precise bidirectional measurement of end-to-end

optical loss at the installation is a must.

> In addition to the optical loss, the end-to-end link optical return loss (ORL) is very

important to measure. Undesirable effects of ORL include:

• Interference with light-source signals

• Higher bit error rate in digital systems

• Lower system optical-signal-to-noise ratio

• Strong fluctuations in the laser output power

• Permanent damage to the laser

example:

 budget: 28,0 dBm

 16 way splitter loss: 13,8 dBm (theor. 12dBm)

 connector+splicing loss: 3 dBm (24*0,1 dBm + 2*0,3 dBm)

 aging: 1 dBm

 attenuation:

0,30 dBm/km – downstream

0,42 dBm/km – upstream

 distance:

 (28,0 – 13,8 – 3 – 1) / 0,42 = 10,2 / 0,42 = 24,28 km

 interpretation:

 for a 1:16 split, the max distance of an ONT is 24 km

13. ISAM 7342 GPON

 at 8:30 PM Posted by Share Online  0 comments

Objectives

At the end of the course, you will be able to …

explain why the 7342 is needed

list and explain several solutions based on the 7342 product

range

describe the architecture of the P-OLT

explain the functions present in different types of ONTs

describe some functions and features of the 7342

explain the solutions for managing the 7342

Why optical access?

Market for residential broadband is booming

Technology continues to evolve which makes

FTTU more viable and cost effective

Copper - Litespan, ASAM

Wireless - LMDS

Market segments for optical access

Greenfield

Refurbishment

Overbuild

Network drivers

Single network supports multiple applications

Flexibility to support new services

Reduced operations and maintenance costs

Triple play

+ In existing areas (overbuild), FTTH can be justified in specific situations

– especially in aerial plant or in existing duct structures

– in areas where otherwise the copper plant must be rehabilitated

+ In greenfield areas FTTUser is the preferred approach

– Although slightly more expensive, is the end-game

– Fiber in new trench is lower cost and is absorbed by 100% of POTs subs

Is fiber in access needed?

14. 7342 ISAM FTTU based solutions

 at 8:41 PM Posted by Share Online  0 comments

+ voice and data over a single fiber

• two wavelengths in opposite directions

+ video

+ one wavelength in downstream direction

- Although the slide gives rates, mileage and split-ratio for alcatel’s GPON implementation,

the general concept of having a passive optical network between the OLT and the ONT also

applies to APON/BPON.

+ However, this document only describes the implementation of GPON => the 7342 FTTU

product (range)

+ The 7342 ISAM FTTU provides a GPON-based access network using three main functional

components:

• the packet OLT (P-OLT),

• the ONT-series,

• and the element management station (EMS)

+ The P-OLT provides the central switching, processing, and control functions for the 7342

ISAM FTTU.

+ The ONTs provide the connectivity between the subscriber equipment and the P-OLT.

Different types of ONTs do exist: indoor, outdoor, business and modular ONTs.

+The EMS provides the element management functions, including operation, administration

and maintenance. The main manager for the 7342 ISAM FTTU is the 5520 AMS (Access

Management System).

The application of PON technology for providing broadband connectivity in the access

network to homes, multiple-occupancy units, and small businesses commonly is called

fiber-to-the-x. This application is given the designation FTTx. Here x is a letter indicating

how close the fiber endpoint comes to the actual user. This is illustrated in the drawing

above. Among the acronyms used in the technical and commercial literature are the

following:

• FTTB – fiber-to-the-business, refers to the deployment of optical fiber from a central

office switch directly into an enterprise.

• FTTC – fiber-to-the-curb, describes running optical fiber cables from central office

equipment to a communication switch located within 1000 ft (about 300m) of a home

or enterprise. Coaxial cable, twisted pair copper wires (e.g. for DSL), or some other

transmission medium is used to connect the curbside equipment to customers in a

building.

• FTTH – fiber-to-the-home, refers to the deployment of optical fiber from a central

office environment directly into a home. The difference between FTTB and FTTH is

that typically, business demand larger bandwidths over greater part of the day than do

home users. As a result, a network service provider can collect more revenues from

FTTB networks and thus recover the installation costs sooner than for FTTH networks.

• FTTO – fiber-to-the-office, is analogous to FTTB in that an optical path is provided al

the way to the premises of a business subscriber.

• FTTP – fiber-to-the-premises, has become the prevailing term that encompasses the

various FTTx concepts. Thus FTTP architectures include FTTB and FTTH

implementations. An FTTP network can use BPON, EPON or GPON technology.

• FTTU – fiber-to-the-user, is the term used by Alcatel-Lucent to describe their products

for FTTB and FTTH applications.

15. Gigabit Passive Optical Network

 at 10:17 PM Posted by Share Online  0 comments

By : Alcatel

Introduction and Market Overview: The Need for Fiber

The way people use the Internet today creates a great demand for very high bandwidth: More and more workers

are telecommuting. Consumers watch multiple HDTV channels, often on several TVs in the same household at the

same time. They upload and download multimedia files and use bandwidth-hungry peer-to-peer services. They play

online games that demand high speeds and immediate reactivity. Web 2.0-based communities and hosted services

such as social networking sites and wikis are pervasive, fostering interactivity, collaboration and data-sharing while

generating a need for capacity. Bringing optical fiber to every home is the definitive response to such demands for

greater bandwidth.

Bringing Fiber to the Home: Benefits of GPON

One way of providing fiber to the home is through a Gigabit Passive Optical Network, or GPON (pronounced 'djee-

pon').

GPON is a point-to-multipoint access mechanism. Its main characteristic is the use of passive splitters in the fiber

distribution network, enabling one single feeding fiber from the provider's central office to serve multiple homes

and small businesses. 

GPON has a downstream capacity of 2.488 Gb/s and an upstream capacity of 1.244 Gbp/s that is shared among

users. Encryption is used to keep each user's data secured and private from other users. Although there are other

technologies that could provide fiber to the home, passive optical networks (PONs) like GPON are generally

considered the strongest candidate for widespread deployments.

Why choose GPON?

When planning a fiber-to-the-home (FTTH) evolution for their access networks, service providers can choose

between three generic FTTH architectures: point-to-point; active Ethernet; and passive optical networking (PON)

such as GPON.

"Point-to-point" is an Ethernet FTTH architecture similar in structure to a twisted-pair cable phone network; a

separate, dedicated fiber for each home exists in the service provider's hub location. The point-to-point architecture

has merits for small-scale deployments such as citynets, but is not suitable for large-scale deployments due to its

poor scalability in terms of hub location space or the number of required hub locations, power consumption and

feeder fibers.

An "active Ethernet" architecture is based on the same deployment model as fiber to the node (FTTN) with active

street cabinets; it is therefore feasible as a complement or migration path towards FTTH for larger deployments in

very high-speed digital subscriber line (VDSL)-dominated environments. 

GPON is a fully optical architecture option that offers the best of all worlds. A GPON system consists of an optical

line terminal (OLT) that connects several optical network terminals (ONTs) together using a passive optical

distribution network (ODN). Like active Ethernet, it aggregates users in what is called the "outside plant" or OSP,

which means no mess of fibers in a central office somewhere; like point-to-point, it avoids the need for active

electronics in the field by employing a passive OSP device (the optical splitter). Being a passive device, the GPON

splitter requires no cooling or powering and is therefore extremely stable; in fact, it virtually never fails.

How does GPON work?

GPON has been called "elegant" for its ability to share bandwidth dynamically on a single optical fiber. Like any

shared medium, GPON provides burst mode transmission with statistical usage capabilities. This enables dynamic

control and sharing of upstream and downstream bandwidth using committed and excess information rate (CIR and

EIR) parameters. Users can be assured of receiving their committed bandwidth under peak demand conditions, and

of receiving superior service when network utilization is low. While subscribers rarely require sustained rates of 100

Mb/s each, bursting beyond this to the full line rate of a PON system (about 1.25 Gb/s upstream or 2.5 Gb/s

downstream in the case of GPON) is easily enabled using the right subscriber interface. This allows a GPON to be

used for many years even if subscribers have a regular need to transmit beyond an engineered guaranteed limit of

100 Mb/s.

GPON was developed with the support of the FSAN (Full Service Access Network) Group and the ITU (International

Telecommunication Union). These organizations bring the major stakeholders in the telecoms industry together to

define common specifications, ensuring full interworking between OLTs and ONTs. The IEEE (Institute of Electrical

and Electronics Engineers) has also defined a PON standard, called Ethernet PON or EPON. The EPON standard was

launched earlier than GPON and has been deployed successfully. IEEE specs are however restricted to the lower

optical and media access layers of networks, and full interoperability for EPON must therefore be managed in a

specific case-by-case way at every implementation. Additionally, EPON runs at only 1 Gb/s, upstream as well as

downstream, providing a lower bandwidth than GPON. These factors make EPON a less attractive technology choice

for providers making FTTH investment decisions today.

Implementing GPON

One of Alcatel-Lucent's first GPON implementations is Jönköping Energi.

Jönköping is a mid-sized city in Sweden where about 98 percent of households enjoy high-speed broadband access.

This is to a very large extent due to the activities of one company, Jönköping Energi. It is a utility provider that, in

addition to its traditional electricity offering, delivers optical connectivity to residential and business users

throughout the Jönköping area. 

Jönköping Energi deployed one of the first GPON architectures in the region. Their customers are enthusiastic: once

installed, their "box" works almost effortlessly, delivering voice, video and Internet without any upkeep after the

initial setup.

Jönköping Energi have found that their Alcatel-Lucent GPON solution delivers smooth, maintenance-free, highly

reliable performance which can be run with a limited operational staff. Revenues have been considerably

augmented, as the company is now able to provide triple play services to consumers throughout the city in a

scalable, cost-effective way. Perhaps most importantly, Jönköping Energi feels they have a system that will easily

accommodate new or evolving systems, as they become available.

16. Gigabit Ethernet Passive Optical Network Tutorial (GEPON)

 at 2:41 AM Posted by Share Online  0 comments

A Passive Optical Network (PON) is a single, shared optical fiber that uses inexpensive optical splitters to divide the

single fiber into separate strands feeding individual subscribers. PONS are called "passive" because, other than at

the CO and subscriber endpoints, there are no active electronics within the access network. Using these techniques

to create a passive optical infrastructure, Ethernet in the First Mile PON (EFMP) builds a point-to-multi-point fiber

topology that supports a speed of 1 Gbps for up to 20 km. While subscribers are connected via dedicated

distribution fibers to the site, they share the Optical Distribution Network (ODN) trunk fiber back to the Central

Office. Eliminating the need for electrical equipment in the first mile network is a key facet of the EFMP topology.

Another advantage is that much less fiber is required than in pointto-point topologies. To visualize the lower fiber

requirements, it is useful to look at the topologies of point to point Ethernet and “curb switched” Ethernet along

with EPON. Figure 1 illustrates all of these options. EPON is based on the Ethernet standard, unlike other PON

technologies, which are based on the ATM standard. This lets you utilize the economies-of-scale of Ethernet, and

provides simple, easy-to-manage connectivity to Ethernet-based, IP equipment, both at the customer premises and

at the central office. As with other Gigabit Ethernet media, it is well-suited to carry packetized traffic, which is

dominant at the access layer, as well as

time-sensitive voice and video traffic.

Point-to-point Ethernet might use either N or 2N fibers, and thus has 2N optical 

transceivers. Curb-switched Ethernet uses one trunk fiber and thus saves fiber and space 

in the Central Office (CO). But it uses 2N+2 optical transceivers and needs electrical 

power in the field.  

EPON also uses only one trunk fiber and thus minimizes fibers and space in the CO, and 

also only uses N+1 optical transceivers. It requires no electrical power in the field. The 

drop throughput can be up to the line rate on the trunk link. EPON can support 

downstream broadcast such as video.

The IEEE 802.3ah EPON specification defines Multi-Point Control Protocol (MPCP), 

Point-to-Point Emulation (P2PE), and two 1490/1310 nm PMDs for 10 and 20 km, 

required to build an EPON system. 

Typical EPON-based systems may include extra features above the IEEE 802.3ah 

standard, including security, authentication and dynamic bandwidth allocation. 

EPON Topologies  

As Figure 2 shows, EPON is typically deployed as a tree or tree-and-branch topology, 

using passive 1:N optical splitters.  

EPON Network  

An EPON network includes an optical line terminal (OLT) and an optical network unit

(ONU).   

The OLT  resides in the CO (POP or local exchange).  This would typically be an 

Ethernet switch or Media Converter platform.

The ONU resides at or near the customer premise. It can be located at the subscriber 

residence, in a building, or on the curb outside.  The ONU  typically has an 802.3ah 

WAN interface, and an 802.3 subscriber interface. 

In Figure 3, the OLT is on the left and several ONUs are shown on the right

EPON Systems  

EPON is configured in full duplex mode (no CSMA/CD) in a single fiber point-tomultipoint (P2MP) topology.

Subscribers, or ONUs, see traffic only from the headend; 

each subscriber cannot see traffic transmitted by other subscribers, and peer-to-peer

communication is done through the headend, or OLT.. As Figure 4 shows, the headend 

allows only one subscriber at a time to transmit using a Time Division Multiplex Access 

(TDMA) protocol.

                                                Figure 4: EPON Configuration  

EPON systems use an optical splitter architecture, multiplexing signals with different 

wavelengths for downstream and upstream as such:  

 + 1490 nm downstream

 + 1310 nm upstream  

Though configured as point to multipoint, Ethernet PON can be deployed in an Ethernet 

access platform, with both point-to-point and point-to-multipoint access cards, as shown 

in Figure 5.  

EPON Protocol  

To control the P2MP fiber network, EPON uses the Multi-Point Control Protocol 

(MPCP).  

MPCP performs bandwidth assignment, bandwidth polling, auto-discovery, and ranging. 

It is implemented in the MAC Layer, introducing new 64-byte control messages:  

• GATE and REPORT are used to assign and request bandwidth  

• REGISTER is used to control the auto-discovery process  

MPCP provides hooks for network resource optimization. Ranging is performed to 

reduce slack, and bandwidth reporting satisfies requirements by ONUs for DBA.  Optical 

parameters are negotiated to optimize performance.

ONU and OLT Operation  

The ONU performs an auto-discovery process which includes ranging and the assignment 

of both Logical Link IDs and bandwidth.  Using timestamps on the downstream GATE 

MAC Control Message, the ONU synchronizes to the OLT timing. It receives the GATE 

message and transmits within the permitted time period.  

The OLT generates time stamped messages to be used as global time reference. It 

generates discovery windows for new ONUs, and controls the registration process. The 

OLT also assigns bandwidth and performs ranging operations.  

Author: Exfiber Optical Technologies Co.,Ltd

17. PON properties

 at 8:45 AM Posted by Share Online  0 comments

PON – Passive Optical Network

passive components

star topology

lambdas

1490nm – downstream data

1310nm – upstream data

1550nm – downstream (optional)

ranging distance

60 km max distance

20 km differential distance

split-ratio

64 subscribers (or even more)

Optical power budget

distance depends on loss in different components:

loss in splitters

cascaded splitter can be used e.g. 1:4 splitter followed by 1:8 splitter or vice versa

so a one-step 1:32 splitter can be used

loss in WDM coupler

loss per km fiber

loss in connectors

Optical power budget – Data

power budget has it’s impact on

reach

split ratio

trade-off  example

no split ----1 user @ 52,5 km

1:2 -----2 users @ 45 km

1:4 -----4 users @ 37.5 km

…

1:32----- 32 users @ 15 km

1:64------64 users @ 7.5 km

high quality fiber with lower attenuation gives better distances

Optical power budget – Analog video

maximum practical level ~16 dBm (long spans)

minimum receive level for 48 dB C/N ~-5 dBm

at 1550 nm, fiber exhibits loss of about 0.25 dB/km, so maximum distance without amp. is ~80 km

each two-way split results in a loss of nominally ~3.5 dB of level, assume 4 dB worst case.

Notes: based on nominal fiber and splitter loss, not worst case.  Practical distances are less.  Includes 2 dB for

connectorization loss, 1550 nm externally modulated transmitter

PON lambdas

voice and data over a single fiber

two wavelengths in opposite directions

video 

one wavelength in downstream direction

Author : Alcatel

18. Splitter Gpon Basics

 at 10:28 PM Posted by Share Online  0 comments

Passive Optical Network (PON) splitters play an important role in Fiber to the Home (FTTH) networks by allowing a

single PON network interface to be shared among many subscribers. Splitters contain no electronics and use no

power. They are the network elements that put the passive in Passive Optical Network and are available in a variety

of split ratios, including 1:8, 1:16, and 1:32.

PLC Splitters are installed in each optical network between the PON Optical Line Terminal (OLT) and the Optical

Network Terminals (ONTs) that the OLT serves. Networks implementing BPON, GPON, EPON, 10G EPON, and 10G

GPON technologies all use these simple optical splitters. In place of an optical splitter, a WDM PONnetwork will use

an Arrayed WaveGuide (AWG).

A PON network may be designed with a single optical splitter, or it can have two or more splitters cascaded

together. Since each optical connection adds attenuation, a single splitter is superior to multiple cascaded splitters.

One net additional coupling (and source of attenuation) is introduced in connecting two splitters together.

A single splitter is shown in the GPON network diagram below. Note that the splitter can be deployed in the Central

Office (CO) alongside the OLT, or it may be deployed in an OutSide Plant (OSP) cabinet closer to the subscribers. A

splitter can also be deployed in the basement of a building for a Multiple Dwelling Unit (MDU) installation (not

shown).

An interesting (and strange) fact is that attenuation of light through an optical splitter is symmetrical. It is identical

in both directions.  Whether a splitter is combining light in the upstream direction or dividing light in the

downstream direction, it still introduces the same attenuation to an optical input signal (a little more than 3 dB for

each 1:2 split).

There are two basic technologies for building passive optical network splitters: Fused Biconical Taper (FBT) and

Planar Lightwave Circuit (PLC). Fused Biconical Taper is the older technology and generally introduces more loss

than the newer PLC splitters, though both PLC splitter and FBT splitters are used in PON networks.

A Fused Biconical Taper 1:2 optical splitter is diagrammed below. A Fused Biconical Taper (FBT) splitter is made by

wrapping two fiber cores together, putting tension on the optical fibers, and then heating the junction until the two

fibers are tapered from the tension and fused together. FBT attenuation tends to be a bit higher than attenuation

from PLC splitters.

                                           Fused Biconical Taper Optical Splitter

A 1:8 Planar Lightwave Circuit (PLC) splitter is diagrammed in the figure below. A PLC splitter is made with

techniques much like those to manufacture semiconductors, and these optical splitters are very compact, efficient,

and reliable. A single 1:32 PLC splitter may be no larger than 1cm x 2 cm.

                                        Planar Lightwave Circuit (PLC) Optical Splitter

The loss to be expected from a 1:8 splitter like the one diagrammed above is less than one dB greater than what

would be expected from a perfect splitter, which has exactly 9 dB of loss (3dB for each 1:2 split). A good 1:32 PLC

splitter has an attenuation in both directions of less than 17 dB or even 16 dB (a perfect 1:32 splitter would

introduce 15 dB of loss).

By : exfiber 

19. Advantages of fiber at 8:42 PM Posted by Share Online  0 comments

+ Extremely high bandwidth

+ Smaller-diameter, lighter-weight cables

+ Lack of crosstalk between parallel fibers

+ Immunity to inductive interference

+ High-quality transmission

+ Low installation and operating costs

+ Extremely high bandwidth

• Fiber today has bandwidth capability theoretically in excess of 10Ghz and attenuations

less than 0.3 db for a kilometer of fiber.

• The limits on transmission speed and distance today lies largely with the laser, receiver

and multiplexing electronics.

• With the future advent of stable narrow line single-mode lasers and coherent optics, 10

to 100 Gb/s transmission is possible.

+  Smaller diameter – lighter weight cables

• Even when fibers are covered with protective coatings, they still are much smaller and

lighter than equivalent copper cables.

+  Negligible crosstalk

• In conventional circuits, signals often stray from one circuit to another, resulting in

other calls being heard in the background. This crosstalk is negligible with fiber optics

even when numerous fibers are cabled together.

+  Immunity to inductive interference

• Fiber optic cables are immune to interference caused by lightning, nearby electric

motors, relays, and dozens of other electrical noise generators that induce problems

on copper cables unless shielded and filtered.

+ High quality transmission

• Fiber routinely provides communications quality orders of magnitude better than

copper or microwave, this as a result of the noise immunity of the fiber transmission

path. (BER: 10-9 – 10-11 for fiber, 10-5 – 10-7 for copper or microwave)

+  Low installation and operating costs

• Low loss increases repeater spacing, therefore reducing the cost of capital in the

outside plant. The elimination (or reduction) of repeaters reduces maintenance,

power and operating expenses.

Optical fiber types

G.651 – MMF – Multi-mode fiber

large(r) core: 50-62.5 microns in diameter

transmit infrared light (wavelength = 850 to 1,300 nm)

light-emitting diodes

G.652 – SMF – Single mode fiber

small core: 8-10 microns in diameter

transmit laser light (wavelength = 1,200 to 1,600 nm)

laser diodes

The glass used in a fiber-optic cable is ultra-pure, ultra-transparent, silicon dioxide, or

fused quartz. During the glass fiber-optic cable fabrication process, impurities are

purposely added to the pure glass to obtain the desired indices of refraction needed to

guide light.

+ Germanium, titanium, or phosphorous is added to increase the index of refraction.

+ Boron or fluorine is added to decrease the index of refraction.

+ Other impurities might somehow remain in the glass cable after fabrication. These residual

impurities can increase the attenuation by either scattering or absorbing light.

+ For data center premise cables, the jacket color depends on the fiber type in the cable. For

cables containing SMFs, the jacket color is typically yellow, whereas for cables containing

MMFs, the jacket color is typically orange. For outside plant cables, the standard jacket

color is typically black.

+ Single mode fibers are the most prominently used type in telecommunication applications.

Author : Alcatel - Lucent

20. Fiber Optic Tutorial

 at 2:23 AM Posted by Share Online  0 comments

Return Loss

When a high-speed signal enters or exits a component, such as a fiber optic connector, discontinuities and

impedance mismatches will cause a reflection, or echo, which is know as return loss.

While insertion loss is measured as the resultant signal after it encounters a loss, return loss is seen as data enters

the connector or is leaving the other end of the connector, and is a measurement of the signal that is reflected

back. Ideally, a fiber connector in a system wants to have a very clean passage of a signal so return loss is desired

to be minimal.

Return Loss values are expressed as dB. A typical specification could range from -15 to -60 dB, Most designers

target –10dB as the critical value of connector performance and try to keep return loss lower than -10dB at the

desired signal speeds. In most cases, -60 is more desirable.

The graph shows that via architecture has a large affect on the return loss of a connector. 

Therefore, designers can minimize via effects to optimize connector performance. The thru via has a worse effect

on the signal reflection, or return loss, than the blind via.

In an optical fiber system, insertion loss is introduced by things such as Fibre Optic Pach Leads, Fibre Pigtails, fibre

optic connectors, splices, and couplers.

According to industry standard, Ultra PC polished fiber optic connectors return loss should be more than

50dB,Angled polished generally return loss is more than 60dB. PC type should be more than 40dB.

During the fiber optic products manufacturing procedure, Exfiber have professional equipment to test the fiber optic

products insertion loss and return loss, our products are 100% tested on each single piece before shipment, and

they are fully compliant or exceed the industry standard.

Insertion Loss

Insertion loss and return loss are two important data to evaluate the quality of many passive fiber optic

components, such as fiber optic patch cord and fiber optic connectors, etc.

In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a

transmission line or optical fiber and is usually expressed in dBs. Insertion loss (IL) is a measure of attenuation,  but

is a more precisely defined term. For instance, attenuation can include loss due to the source and load impedances

not matching, but is not included in insertion loss since this is a loss that was already present before the "insertion"

was made.

If the power transmitted to the load before insertion is PT and the power received by the load after insertion is PR,

then the insertion loss in dB is given by,

    10 \log_{10} {P_\mathrm T \over P_\mathrm R}

In metallic conductor systems, radiation losses, resistive losses in the conductor as well as losses in the surrounding

dielectric all reduce the power. Line terminations play an important part in insertion loss because they reflect some

of the power. All of these effects can be conceptually modelled as various elements which make up the equivalent

circuit of the line.

In an optical fiber system, insertion loss is introduced by things such as Fiber Optic Pach Cables, Fibre Optic Pigtails,

fiber optic connectors, splices, and couplers.

According to industry standard, Ultra PC polished fiber optic connectors return loss should be more than

50dB,Angled polished generally return loss is more than 60dB. PC type should be more than 40dB.

During the fiber optic products manufacturing procedure, Exfiber have professional equipment to test the fiber optic

products insertion loss and return loss, our products are 100% tested on each single piece before shipment, and

they are fully compliant or exceed the industry standard.

How Do Fiber Optic Connectors Work?

The history of fiber optic telecommunication deserves a book by itself since it took several generations to get the

industry today.

Optical fiber is a long thin cylindrical fiber made from glass or plastic, as tiny as one tenth of a human hair. A

standard telecom optical fiber is composed of three cylindrical layers, counted inside out: fiber core (diameter

8~10um), cladding (diameter 125um) and buffer coating (diameter 900um).

Fiber core and cladding is made from glass or silica. Fiber Core and cladding layers work together to confine the

light inside the core without leaking. Fiber buffer coating is made from acrylic or plastic and provides handling

flexibility and physical protection for the fiber.

Optical fibers utilize an optical phenomenon called total internal reflection. When light is injected into the fiber from

end face, it is confined inside the core without leaking outside and losing its energy.

Then light is digitally modulated to represent 1 and 0 just like a computer, so information can be carried from one

site to another site which may be from San Francisco all the way to New York.

What are fiber optic connectors and how do they work?

Now you know how optical fibers work. So what is a fiber optic connector and what's its function in a fiber optic

telecommunication network?

Put it simple, a fiber optic connector's function is just like an electric power plug, it connects light from one section

of optical fiber to another section of optical fiber.

Since optical fibers are so tiny, fiber optic connectors have to be made with high precision, at the scale of 0.1um

which is one hundredth of a human hair.

Fiber optic connectors align two fibers end to end so precisely that light can travel from one fiber into another

without bouncing off the interface and loss its signal.

Besides, fiber optic connectors provide cross connect flexibility for the telecommunication network. So a

complicated computer network could be made modular and easy to manage.

Just like any other connectors used in electric industry, electronic industry and computer industry, many different

kinds of fiber optic connectors were invented along the development of fiber optic communication industry. Some

of them once were very popular in the industry and now have served their purposes and are fading away.

The most popular fiber optic connectors used nowadays are SC, ST, LC, FC, MTRJ, SMA and a few of other less

popular ones. Sure you will see new connectors invented with the progress of this industry.

Fiber Optic Comminication

Fiber optic communication is a method of transmitting information from one place to another by sending pulses of

light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry

information. First developed in the 1970s, fiber-optic communication systems have revolutionized the

telecommunications industry and have played a major role in the advent of the Information Age. Because of its

advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core

networks in the developed world.

The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal

involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too

distorted or weak, receiving the optical signal, and converting it into an electrical signal.

Source: Wikipedia and Exfiber Optical Technologies