phalgun revamped

PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012

Name of the Topic

Report on the Seminar 06EC86 Submitted in partial fulfilment of Requirements for the degree of

BACHELOR OF ENGINEERINGIn

ELECTRONICS AND COMMUNICATION ENGINEERING(VISVESVARAYA TECHNOLOGICAL UNIVERSITY, BELGAUM)

ByName, USNFeb 2013

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

ST. JOSEPH ENGINEERING COLLEGE

VAMANJOOR, MANGALORE 575028, INDIA

Optical Transmission characteristics of Optical Fiber Cables And Installed Cable Networks For WDM Applications


OPTICAL TRANSMISSION CHARACTERISTICS OF OPTICAL FIBER CABLES AND INSTALLED OPTICAL FIBR CABLE

NETWORKS FOR WDM SYSTEMS

Phalgun Prajya,4SO09EC075

Contents1. Introduction.......................................................................................................2

2. Introduction to optical fiber cables....................................................................2

3. Wavlength Division Multiplexing........................................................................4

3.1 Why use WDM................................................................................................5

3.2 Advantages of WDM........................................................................................6

4. Optical Networks...............................................................................................6

5. Single and Multimode fibers..............................................................................8

6. Loss characteristics of SM optical fiber cable……………………………………………………………….9

7.Transmission charcteristics of Installed SM optical fiber cable networks………………………..11

8.Conclusion………………………………………………………………………………………………………………15

9. References……………………………………………………………………………………………………………..16



Abstract Recently, there have been studies on wavelength division multiplexing(WDM),designed to increase transmission capacity and flexibility. Many cables in the 1.3um zero dispersion single mode (SM) optical fibersare installed in trunk and access networks. If we can construct WDM systems using SM optical fiber cable networks designed to transmit using wavelengths in the 1.3um window(O Band).it will prove very effective in reducing construction costs. Thus it is important to examine the wavelength dependence of transmission characteristics of SM optical fiber cables and networks that have already been installed and in which several optical fibers are joined. In this paper, we describe the measured optical characteristics of SM optical fibers at diverse wavelengths. The optical characteristics were stable in the 1.46um to 1.625um wavelength range and we confirmed that the installed SM optical fiber cable networks could be used for WDM system applications.

1. Introduction The demand for greater transmission capacity is growing rapidly as a result of increase in broadband multimedia services ( voice, text and image transfer) [1]. To meet the future customer demands, a flexible network construction is necessary.

One of the technologies that has made it possible to improve network capacity and flexibility significantly is Wavelength Division Multiplexing(WDM) technology. Cost advantage can be obtained if WDM systems deploy 1.3um zero dispersion single mode(SM) optical fiber cable network designed to transmit wavelengths in the 1.3um window(O-band) because networks are already constructed using these fibers.

Experimental investigations were done considering two essential problems. The stability of optical loss characteristics of single mode optical fiber cable at various wavelengths and also at various environmental conditions. Also, the optical loss and chromatic dispersion characteristics of installed SM optical fiber cable networks especially in the 1.46-1.625um wavelength range. i.e. lower wavelength of S-Band to upper wavelength of L-Band. This paper discusses the suitability of already installed SM-optical fibe cable networks for WDM system applications.

2.Introduction to optical fiber cables

Fiber-optic cable employs photons for the transmission of digital signals across a strand of ultrapure silica (or plastic in some cases). Optical systems operate in the infrared light range. Photons pass through the cable with



negligible resistance. ( silica is so pure that,, a 3-mile-thick window made of the purified silica would give you the same view as a 1/8-inch-thick glass window). As optical system requirements increase, the purity of the cable becomes even more important. [2]

A fiber-optic cable guides light from end to end.

A signal is injected in one end by an LED (light-emitting diode) or by semiconductor lasers.

LEDs can generate signals up to about 300 Mbits/sec. Lasers can generate signals in the multi-gigabit/sec range. LEDs are used for short-distance optical links such as enterprise backbones while lasers are used for longer distance networks. Lasers are also capable of the higher power levels needed for long-haul backbone links.

Lasers produce light in "windows" of the near infrared range as listed in the following table. A window is an infrared range that is optimized for optical transmissions. The ITU recently defined the following spectral bands in order to clarify the terminology that is used for fiber-optic systems.

Band Descriptor Range (nm)O band Original 1260 to 1360E band Extended 1360 to 1460S band Short wavelength 1460 to 1530C band Conventional 1530 to 1565L band Long wavelength 1565 to 1625U band Ultralong wavelength 1625 to 1675

Figure 1 illustrates the structure of fiber-optic cable. (Fig.a)

The core is the transparent silica (or plastic) through which the light travels.

The cladding is a glass sheath that surrounds the core. The cladding acts like a mirror, reflecting light back into the core. The cladding itself is covered with a plastic coating and strength material when appropriate.



Fig(a)Optical Fiber Cable

3.WAVELENGTH DIVISION MULTIPLEXING(WDM)

In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical signals onto a single optical fiber by using different wavelengths (i.e. colours) of laser light. This technique enables bidirectional communications over one strand of fiber, as well as multiplication of capacity.

The term wavelength-division multiplexing(fig.b) is commonly applied to an optical carrier (which is typically described by its wavelength), whereas frequency-division multiplexing typically applies to a radio carrier (which is more often described by frequency). Since wavelength and frequency are tied together through a simple directly inverse relationship, the two terms actually describe the same concept.

A WDM system uses a multiplexer at the transmitter to join the signals together, and a demultiplexer at the receiver to split them apart. With the right type of fiber it is possible to have a device that does both simultaneously.

The concept was first published in 1970, and by 1978 WDM systems were being realized in the laboratory. The first WDM systems combined only two signals. Modern systems can handle up to 160 signals and can thus expand a basic 10 Gbit/s system over a single fiber pair to over 1.6 Tbit/s.

WDM systems are popular with telecommunications companies because they allow them to expand the capacity of the network without laying more fiber. By using WDM and optical amplifiers, they can accommodate several generations of technology development in their optical infrastructure without having to overhaul the backbone network. Capacity of a given link can be expanded simply by upgrades to the multiplexers and demultiplexers at each end.


http://en.wikipedia.org/wiki/Optical_amplifier

http://en.wikipedia.org/wiki/Telephone_company

http://en.wikipedia.org/wiki/Data_rate_units#Terabit_per_second

http://en.wikipedia.org/wiki/Data_rate_units#Gigabit_per_second

http://en.wikipedia.org/wiki/Receiver_(radio)

http://en.wikipedia.org/wiki/Demultiplexer

http://en.wikipedia.org/wiki/Transmitter

http://en.wikipedia.org/wiki/Multiplexer

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Frequency-division_multiplexing

http://en.wikipedia.org/wiki/Frequency-division_multiplexing

http://en.wikipedia.org/wiki/Duplex_(telecommunications)

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Laser

http://en.wikipedia.org/wiki/Wavelength

http://en.wikipedia.org/wiki/Optical_fiber

http://en.wikipedia.org/wiki/Multiplexing

http://en.wikipedia.org/wiki/Fiber-optic_communication


Fig.b Block diagram of WDM

WDM systems are divided into different wavelength patterns,

conventional/coarse (CWDM) and dense (DWDM).

Conventional WDM systems provide up to 8 channels in the 3rd transmission window (C-Band) of silica fibers around 1550 nm.

Dense wavelength division multiplexing (DWDM) uses the same transmission window but with denser channel spacing.

Channel plans vary, but a typical system would use 40 channels at 100 GHz spacing or 80 channels with 50 GHz spacing.

Some technologies are capable of 12.5 GHz spacing (sometimes called ultra dense WDM). Such spacings are today only achieved by free-space optics technology. New amplification options (Raman amplification) enable the extension of the usable wavelengths to the L-band, more or less doubling these numbers[3]

3.1 Why Use WDMAfter languishing for many years as an interesting technology without a cost effectiveapplication, wavelength-division multiplexing started playing a major role in telecommunications networks in the early 1990s. This resulted from the surge in demand for high-capacity links and the limitation of the installed fiber plant in handling high-rate optical signals over any substantial distance . This limitation led to a rapid capacity exhaustion of long-haul fiber networks. Since installing an optical fiber cable plant is both expensive and extremely time consuming, expanding the capacity of an installed network is economically attractive. Traditionally, carriers upgraded their link capacity by increasing the transmission rate. This worked well initially, with speeds eventually reaching 2.5 Gbps_(SONET OC-48 or SDH STM-16..) Transmission systems operating at these rates have been on the market since 1991 and are now standard SONET SDH building blocks. However, when going to the next


http://en.wikipedia.org/wiki/L-band

http://en.wikipedia.org/wiki/Raman_amplification

http://en.wikipedia.org/wiki/Free-space_optical_communication

http://en.wikipedia.org/wiki/Optical_band#Optical_bands

http://en.wikipedia.org/wiki/Fiber-optic_communication#Transmission_windows

http://en.wikipedia.org/wiki/Fiber-optic_communication#Transmission_windows

PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012 multiplexing level of 10 Gbps ., one starts to encounter effects that can seriously degrade WDM network performance.[4.wdm technology pdf]Among these effects are1. Fiber chromatic dispersion, which limits the bit rate by temporally spreadinga transmitted optical pulse;2. Non uniform gain across the desired wavelength range in erbium-dopedfiber amplifiers _EDFAs.;3. Inelastic scattering processes such as stimulated Raman scattering _SRS.and SBS, which are interactions between optical signals and molecular or acousticvibrations in a fiber;4. nonlinear processes in a fiber that arise from modulation of the refractiveindex of silica by intensity changes in the signal, thereby producing effects such asFWM, self-phase modulation _SPM., and cross-phase modulation _CPM5. Reflections from splices and connectors that can cause instabilities inlaser sources.New fiber designs, special dispersion-compensation techniques, and optical isolatorscan mitigate these limitations, and newly installed links are operating very wellat 10 Gbps rates per wavelength.

3.2Advantages of WDM

Wavelength division multiplexing has several advantages over the other presented approaches to increase the capacity of a link:

Works with existing single mode communication fibre

• Works with low speed equipment

• Is transparent: Doesn’t depend on the protocol that has to be transmitted [4, 2].

• Is scalable: Instead of switching to a new technology, a new channel can easily

be added to existing channels. Companies only have to pay for the bandwidth

they actually need.

• It is easy for network providers to add additional capacity in a few days if

customers need it. This gives companies using WDM an economical advantage.

Capacity of a given link can be expanded by simply upgrading the multiplexers and demulti-


PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012 plexers at each end. This is often done by using optical-to-electrical-to-optical (O/E/O)

translation at the very edge of the transport network, thus permitting interoperation

with existing equipment with optical interfaces.[4]

4. Optical Networks

There has been a rapid development in data communications over the past few years, including the creation of the concept of trunking. Users share connections with each other where trunking is applied so the connections are less dense and more understandable. Trunking uses communication media in parallel with increased bandwidth and communication speed.

Trunking is the mechanism used to form an internetwork, or Internet, comprised of local area networks (LANs), virtual LANS (VLANs) or wide area networks (WANs). The switches are interconnected to establish these networks using trunking. Trunking is not limited to any medium since its main purpose is to maximize the bandwidth available in any type of network.

A trunk network is a line between central offices. A trunk is a single transmission channel between two points, each point being either the switching center or the node. [6]

An access network consists of four areas[1]: a central office, a feeder area, a distribution area, and a user area from residential office to user premises. As we see in the figure, the feeder area extends from fiber termination module(FTM) or integrated distribution module(IDM) in a central office to a distribution point.



Fig. 1. Configuration of optical network and cable structure

In the distribution area, aerial cable is connected to feeder cable at a distribution point, and led to a customer via telecommunication poles.

We mainly use underground cables for trunk networks and for the feeder areas of access networks.

Aerial cables are used for the distribution areas of access networks. The underground cables are composed of fiber ribbons, a slotted rod, a

strength member, water-blocking tape, and a polyethylene (PE) sheath. Two kinds of aerial cableare used. When the cable contains more than 100

fibers, we use SZ slotted-rod type optical-fiber cable, in which fiber ribbons are stored. This is a self-supporting type structure with excess length . For low fiber-count regions, we adopt a simple cable structure with no slotted rod, and we stack the fiber ribbons in the cable sheath. This is also a self-supporting type structure with excess length.

5. Single Mode and Multimode Fibers

Single mode (SM) fiber optic cable[2] has a small diametrical core that allows only one mode of light to propagate. Because of this, the number of light



reflections created as the light passes through the core decreases, lowering attenuation and creating the ability for the signal to travel faster, further.

This application is typically used in long distance, higher bandwidth runs by Telcos, CATV companies, and Colleges and Universities.

Singlemode fiber is usually 9/125 in construction. This means that the core to cladding diameter ratio is 9 microns to 125 microns.

Multimode fiber optic cable has a large diametral core that allows multiple modes of light to propagate. Because of this, the number of light reflections created as the light passes through the core increases, creating the ability for more data to pass through at a given time.

Because of the high dispersion and attenuation rate with this type of fiber, the quality of the signal is reduced over long distances.

This application is typically used for short distance, data and audio/video applications in LANs. RF broadband signals, such as what cable companies commonly use, cannot be transmitted over multimode fiber.

Multimode fiber is usually 50/125 and 62.5/125 in construction. This means that the core to cladding diameter ratio is 50 microns to 125 microns and 62.5 microns to 125 microns.

Step-Index Multimode Fiber - Due to its large core, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding.. This type of fiber is best suited for transmission over short distances.

Graded-Index Multimode Fiber - Contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. This type of fiber is best suited for local-area networks.(LAN)

6. Loss characteristics of SM Optical Fiber CableWe measured the mechanical and temperature characteristics of these underground and aerial cables at the following wavelengths: 1.31, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.625, and 1.65m. We specifically selected and incorporated in each cable sample SM optical fibers, whose optical loss was comparatively easily to increase by fiber bending. Table 1 MECHANICAL CHARACTERISTICS



Fig2. Temperature characteristics of 1000 fiber cable(underground cable)and 100 fiber cable(aerial cable)

A. Underground Cable

We investigated 40-, 300-, and 1000-fiber cables.1) Mechanical Characteristics: Table I shows the test conditions and measured results for various mechanical tests. The optical-loss increase was 0.06 dB or less at each wavelength indicating very stable levels of performance.

2) Temperature Characteristics: We installed a 500-m optical cable in a thermostatic chamber [11], and performed a heatcycling test ( 30 C to 70 C). Fig. 2(a) shows the measured optical-loss increase in a 1000-fiber cable. Although optical loss tends to increase at longer wavelengths, we


PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012 consider this characteristic to be stable up to 1.625- um, as it was 0.10 dB/km or less.

Fig3.Vibration characteristics(100 fiber cable)B. Aerial Cable

All the tests were performed on 40- and 100-fiber cables.1) Mechanical Characteristics: Table I also shows the test conditions and measured results for our mechanical tests on aerial cable. The optical-loss increase was sufficiently small, aswe found with the underground cable.

2) Temperature Characteristics: A complete cable was suspended between telecommunication poles in a thermostatic chamber. Fig. 2(b) shows the optical-loss increase of a 100-fibercable. The optical-loss increase was less than 0.13 dB/km over the whole wavelength range. Other cables produced similar results.

3) Vibration Characteristics: It is necessary to study the effect of wind-induced vibration, especially with regard to aerial cables. We stretched a 35-m aerial cable and vibrated it one million times in a quadratic mode. Fig. 3 shows that the optical-loss change during the whole test was 0.02 dB/35 m or less at each wavelength, and very stable. From these results, we confirmed that each cable has stable optical-loss characteristics up to a wavelength of 1.625 um with regard to WDM system applications.

7. TRANSMISSION CHARACTERISTICS OF INSTALLED SM OPTICAL-FIBER CABLE NETWORKSThe SM optical-fiber cable networks that have already been designed, installed, and which include several joined optical fibers for transmission using wavelengths in the 1.3- um windowcan be classified into two network types as shown in Table II. These are the point to point (trunk network: pattern 1) and the ring (access network: pattern 2) types. We use these configurations to investigate the transmission performance of these


PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012 networks that were constructed using long distance cable (pattern 1), and underground cable only (pattern 1 and 2). We measured the optical-loss and chromatic-dispersion characteristics of these two types of network in a metropolitan area in the 1.25 to 1.625- um wavelength range.

TABLE II MEASURED NETWORK CONFIGURATIONS IN THE FIELD

A. Optical Loss CharacteristicsFig. 4 shows the optical-loss difference between wavelengths of 1.31 and 1.55 um with patterns 1 and 2. The average optical- loss difference is less than 0.15 dB/km for each pattern and the optical loss at 1.55 um is lower than that at 1.31 um. This showed that the optical-loss characteristics have only slight wavelength dependence in the network. [1]Fig. 5 shows the optical-loss differences for the optical loss at 1.55 um in the 1.46 to 1.625 um wavelength range with each pattern. 1.46 m is on the lower edge of the S-band. 1.625 m is on the upper edge of the L-band, and the optical loss at this wavelength increases easily when the optical fiber is bent. We found that the loss difference for patterns 1 and 2 is very small. The optical loss below 1.55 um is higher than that above 1.55 um for pattern 1. However, the optical-loss characteristics for pattern 2 are the opposite of those for pattern 1. This is because of the number of fiber connections, the fiber connection method, and the method used to accommodate fiber in the closure.



Fig4. Optical loss difference between 1.31um and 1.55um wavelengths



Fig.5.Optical loss differences for optical loss at 1.55um in the 1.46 to 1.625um range

The data in the figure are been fitted with formulas to obtain the optical loss differenjce from optical loss in the 1.55um forming the 1.46 to 1.625um wavelength range in each pattern.The following figures 6 and 7 show the results obtained

Fig. 6. Relationship between transmission distance and optical-loss difference for the optical loss at 1.55 _m (a) pattern 1 and (b) pattern 2.



These show that the maximum optical-loss difference is less than 2 dB assuming L=40 kmfor pattern 1 and L=15 km for pattern 2 and is less than 3.5 dB assuming L=80 km for pattern 1 and L=30km for pattern 2 in the 1.46 to 1.625 um wavelength range. Thus, it was found that the optical-loss differences from the S-band to the L-band are small.

B. Chromatic-Dispersion CharacteristicsFig. 8 shows the measured chromatic-dispersion characteristics versus wavelength.It was found that the chromatic-dispersion difference between the maximum and minimum values for eachwavelength were very small.

A signal can be transmitted 100 km or more at a wavelength of 1.625 um and a transmission rate of 2.4 Gb/s without chirp. In contrast, the maximum transmission distance is about 60 km at the same wavelength and transmission rate with chirp.

Moreover, Fig. 9 also shows that the transmission distances at wavelengths of 1.46 and 1.625 m are, respectively, about 60% longer and 30% shorter than those at 1.55 m. The relation between transmission rate and distance is calculated and the results are shown in figure 9.



Fig.8 Chromatic Dispersion Characteristics

Fig9. Relationship between transmission rate and distance

8. ConclusionThis paper described SM optical-fiber cable characteristics for various wavelengths and the optical-transmission characteristics for networks with a view to WDM system applications. First, the optical-loss characteristics of SM fiber cables at various wavelengths were investigated. Then the optical-loss and chromatic-dispersion characteristics of installed SM optical-fiber cable networks, which were designed to transmit using wavelengths in the 1.3- um window were measured. the optical-loss characteristics of SM optical-fiber cable and the optical-loss and chromatic-dispersion characteristics of installed SM optical-fiber cable networks were found to be stable throughout the S- and L-bands in addition to the O-band.. Thus it was found that the installed SM optical-fiber cable networks could be designed and used for WDM system applications.

9. Reference links[1]. Kazuo Hogari, Member, IEEE, Shigekatsu Tetsutani, Jian Zhou, Fumihiko Yamamoto, and Kiminori

Sato, Optical-Transmission Characteristics of Optical-Fiber Cables and Installed


PHALGUN PRAJYA, 4SO09EC075 St Joseph Engineering collegeVIII SEMESTER Vamanjoor, Mangalore 575028Dept. Of Electronics and Communication Engineering Seminar 06EC86,2012 Optical-Fiber Cable Networks for WDM Systems. JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 21, NO. 2, FEBRUARY 2003[2]Gerd Keiser, Optical Fiber Communication, Tata Mcgraw Hill,2000

[3] http://en.wikipedia.org/wiki/Wavelength-division_multiplexing

[4] http://adcom.lums.edu.pk/VLC.pdf

[5] http://www.multicominc.com/active/manufacturer/multicom/Fiber%20Optics/singlemode-multimode.html

[6] http://en.wikipedia.org/wiki/Trunking

[7]

Reference Paper 1:Name of paper :

Authors Name :

Published in Journal, Month and Year of Publishing :


http://en.wikipedia.org/wiki/Trunking

http://www.multicominc.com/active/manufacturer/multicom/Fiber%20Optics/singlemode-multimode.html

http://www.multicominc.com/active/manufacturer/multicom/Fiber%20Optics/singlemode-multimode.html

http://adcom.lums.edu.pk/VLC.pdf

http://en.wikipedia.org/wiki/Wavelength-division_multiplexing

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