[Site Name]Advantages and disadvantages of O F transmission
Pre SDH System
The distance between two successive peaks of a wave
The length of the light wave, which determines its color. Common units of measurement are the micron, the nanometer (10-9)
Bandwidth:
The measure of how quickly you can move information from one point to another (bits/s)
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Bit:
A bit is a binary digit, taking a value of either 0 or 1. For example, the number 10010111 is 8 bits long
dB/dBm:
loss/gain is measured in dB, it is a logrithmic ratio dB = 10 log10 (P1/P2)
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Optical telecommunication in the near & short infrared is technically often separated Or
O-band 1,260–1,360 nm ---------- Original
E-band 1,360–1,460 nm ---------- Extended
S-band 1,460–1,530 nm------------- Short wavelength
C-band 1,530–1,565 nm----------- Conventional
L-band 1,565–1,625 nm------------ Long Wavelength
U-band 1,625–1,675 nm-----------Ultra long wave length
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Cladding
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Concept Of Reflecting
The angle at which light is reflected is dependent on the refractive indices of the two materials .
In our case, the core and the cladding
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Refractive Index
The refractive index of a medium is a measure for how much the speed of light is reduced inside the medium
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Optical Fibers
n>n1
Multi-Mode
LED is used as optical source
Uses in high speed LAN
Cheaper fiber
Cheaper system
Types of optical fibers
G.652: A single-mode optical fiber that has a nominal zero-dispersion wavelength in the 1310nm transmission region. (dispersion un-shifted fiber)
G.653: Dispersion-shifted fiber; zero dispersion at 1550nm transmission region
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0.3 dB/km ~ 0.4 dB/km
0.15 dB/km ~ 0.25 dB/km
1550 nm
1550 nm
Large Bandwidth… more Data
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12) High-Quality Transmission
BER: Typically 10-09 to 10-11 & 10-12 for Optical Fiber Medium
BER: Typically 10-05 to 10-07 for Copper and Microwave Media
13) Environmental Stability
-Low temperatures as – 20 to – 40 Celsius increase in attenuation in optical fiber, while in copper cables temperature has continuous effects)
-Lower Corrosion Rates
Expensive to install
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Attenuation (reduction in strength of signal):
decrease the transmission distance, measure in dB/Km
2) Dispersion
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Terminal Multiplexer (TM )
Add/Drop Multiplexer (ADM)
Optical Amplifiers (OA)
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Synchronous & Plesiochronous ?
All the NEs use the same clock and are synchronized with the one clock source (PRC) in Synchronous operations
Plesiochronous:
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European Standard in Pakistan
E2……… 8.448 Mbps
E3……… 34.368 Mbps
E4……… 139.264 Mbps
E5……… 565 Mbps
No worldwide optical interface standard
Week Monitoring due to insufficient capacity for network management
No direct extraction of lower order signal
Lower data rates for current and future demands
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Synchronous Digital Hierarchy
SDH is a hierarchical set of digital transport structures, standardized for the transport of suitably adapted payloads over physical transmission networks
*
SDH Signal Rates
* STM-0 is not SDH signal rate, however, it is equal to SONET basic rate 51.84Mbps
STM-N
*
simple and direct adding or dropping of electrical signals
Network Management System (NMS)
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Advantages of SDH
All current PDH signals can be transmitted within the SDH except 8 Mb/s (E2) which has no container.
A reduction in the amount of equipment & an increase in network reliability.
Compatible….PDH, ATM, DQDB
Disadvantages of SDH
Lower Bandwidth utilization
Complicated SDH equipments due to variety of management traffic types and options
Software based..vulnerable to computer viruses, software bugs, configuration problems, etc.
Direct add/drop needs pointer, which make it complex and introduce jitter
Can’t carry E2 due to un-availability of container.
*
*
SDH Terminology
SDH refers to the rates and formats specified by ITU-T for synchronous data transmission over fiber optic networks.
Few Common Standards of SDH
ITU-T G.707: Network Node Interface for SDH
ITU-T G.781: Structure of Recommendations on Equipment for SDH
ITU-T G.783: Characteristics of SDH Equipment Functional Blocks
ITU-T G.803: Architecture of Transport Networks Based on SDH
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1
3
4
5
9
SOH
Term Mux
Term Mux
Add-Drop Mux
*
Regenerator Section Overhead (RSOH)
*
Higher order (HPOH)
*
B2
B2
B2
K1
K2
D4
D5
D6
D7
D8
D9
D10
D11
D12
S1
M1
E2
where services are put in the STM-N frame
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Administrative Unit Pointer (AU-PTR)
Locate lower rate signal inside a higher rate signal of a STM-N frame (payload).
comprises of 9 bytes
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AU-4 pointer addresses only every 3rd payload byte.
Last 3 bytes (H3) of AU-PTR are provided as additional transmission capacity in order to equalize clock difference.
Justification operation (positive or negative) can be carried out no more than once in every 3rd STM-1 frame.
AU-PTR bytes: H1, Y, Y, H2, 1, 1, H3, H3, H3
H1=N N N N S S I D; H2=I D I D I D I D
* 10 bit pointer value indicated by I & D bits
*
PDH → STM-N: Synchronous Multiplexing & Flexible Mapping
140M→STM-N
34M→STM-N
2M→STM-N
*
Container is an information structure, mainly in-charge of adaptation functions so that commonly used PDH signals can occupy fixed space
ITU-T G.709 recommendations have stipulated 5 kinds of standard containers:
C-11, C-12, C-2, C-3 & C-4
*
Container (C-4)
C-4 container is 260x9 bytes in dimension (2340 bytes or 18720 bits)
*
C-3 container is 9x84 bytes (756 bytes or 6048 bits)
Only 3xC-3 (3x6048 bit) of maximum can be transmitted in one STM-1
Actual space required by E3 signal is 34.368 Mbps / 8000 = 4296 bits
*
C-12 container is 34 bytes or 272 bits in size.
Actual space required by E1 signal is 2.048 Mbps/8000=256 bits.
Over capacity bits include clock alignment, justification opportunity bits, justification control bits, & overhead bits.
63 E1s can be transmitted through one STM-1.
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Virtual Container
The digital flow from the standard container combined with path overhead forms a virtual container (VC).
C-4 + POH (9 bytes) = VC-4 (9x261 bytes)
C-3 + POH (9 bytes) = VC-3 (9x85 bytes)
C-12 + POH (1 byte) = VC-12 (35 bytes)
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AU & TU
The Administration Unit (AU) is an information structure that performs adaptation functions for the high order path layer and multiplexing segment layer.
AU-4 = AU-PTR + VC-4
The Tributary Unit (TU) is an information structure that performs adaptation functions for the low order path layer and high order path layer.
TU-3 = VC-3 + PTR (3 bytes)
TU-12 = VC-12 + PTR (one byte)
*
TU-3 = VC-3 + 3 bytes pointer
*
*
TUG-2 = 3 x TU-12
TUG-3 = 7 x TUG-2
One or more AU with fixed locations in the STM-N frame form an Administration Unit Group (AUG). A single AU-4 can form one Administration Unit Group (AUG).
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Mapping
A process used when tributaries are adapted into Virtual Containers (VCs) by adding justification bits and Path Overhead (POH) information
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Alignment
This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the first byte of the Virtual Container to be located.
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Multiplexing
This process is used when multiple lower-order path layer signals are adapted into a higher-order path signal, or when the higher-order path signals are adapted into a Multiplex Section.
This type of multiplexing comes under synchronous multiplexing category
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Stuffing
When tributary signals are multiplexed & aligned, some spare capacity is required in SDH frames to provide space for various tributary rates
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C-4 (Container-4): standard information structure for 140M signal.
VC-4 (Virtual Container-4): standard information structure related to C4, supervising real time performance of the loading 140M signal.
1
140M
AU-4 (Administrative Unit-4): information structure related to VC4.
Mapping way: 140MC4 VC4AU-4AUGSTM-1
* only one 140Mbps signal can be carried in STM-1.
Pointer alignment
C3 (Container 3): standard information structure for 34M signal.
VC3 (Virtual Container 3): standard information structure related to C3, supervising real time performance of the loading 34M signal.
1
1
34M
C3
1
84
9
125us
Multiplexing procedure of 34M into STM-1
TU3 (Tributary Unit 3): standard information structure related to VC3, finishing the first level pointer alignment.
TUG3 (Tributary Unit Group 3): standard information structure related to TU3.
Mapping way: 34MC3VC3TU3TUG3; 3*TUG3VC4AU-4AUGSTM-1
3 x34M can be multiplexed in one STM-1.
First level pointer alignment
C12 (Container-12): standard information structure for 2M signal, finishing rate adjustment, 4 basic frame forming a multi-frame.
VC12 (Virtual Container-12); standard information structure related to C12, supervising real time performance of the loading 2M signal.
TU12 (Tributary Unit 12): standard information structure related to VC12, finishing the first level pointer alignment of VC12.
125us
TUG-2 (Tributary Unit Group-2) TUG-3 (Tributary Unit Group-3)
2MC12VC12TU12; 3xTU12TUG-2; 7xTUG-2TUG-3; 3xTUG3VC4AU-4AUGSTM1
3x7x3=63x2M signals can be multiplexed in STM-1. Multiplexing structure of 2M signal is 3-7-3 structure.
1
12
TUG2
R
R
TUG3
1
86
A1=F6H & A2=28H
Generate Alarms OOF, LOF
STM identification byte
Every STM-1 frame is assigned an identification number before being multiplexed to an STM-N.
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User Channel Byte: F1
Provide a 64 kb/s data or voice channel for local maintenance purpose to network operator.
Only transmitted in STM-1 #1 of STM-N signal.
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Data Communication Channel Bytes: D1~D12
These 12 bytes are provided for the transport of monitoring & control data in Network Management System.
D1-D3 belongs to RSOH, bandwidth is 3x64 kb/s
D4-D12 belongs to MSOH, bandwidth is 9x64 kb/s
D1-D12 are transmitted in STM-1#1 of STM-N only.
OAM Massages: performance, alarm, operation commands etc.
DCC Channel
Provide 64 kb/s digital telephone channels
E1 transmit RS order wire message
E2 transmit MS order wire message (express channel)
Only present in STM-1#1 of STM-N
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Regenerator section error code monitoring
Detect unit is bit block
B1 BBE represented by RS-BBE
Only transmitted in STM-1 #1 of an STM-N
Bit Interleaved Parity 24 code (BIP-24) byte: B2
Multiplexing section error code monitoring
Detect unit is bit block
B2 BBE represented by MS-BBE
Only transmitted in STM-1 #1 of an STM-N
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B1: In unit of 1 byte (8 bits)
B2: In unit of 3 byte (24 bits)
x1 00110011
x2 11001100
x3 10101010
x4 00001111
B 01011010
Multiplex Section Remote Error Indication (MS-REI) byte: M1
A return message from Rx to Tx when Rx find MS-BBE
By evaluating the 3xB2, the M1 byte can report back the number of parity code violations.
MS-REI will be generated in Tx.
M1 byte is one per STM-N frame.
Find B2 Error: MS-BBE
Used for network multiplex protection switch function
K1 & K2 only transmitted in STM-1 #1 of STM-N
Multiplex Section Remote Defect Indication (MS-RDI): K2 (b6-b8)
Return alarm message from Rx to Tx
Indicate Rx receiving alarm
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SSM indicates the status & quality level of SDH signal
Value indicates quality level of available clock source (b5-b8)
0010 = G.811 = External Clock
1011 = G.813 = Internal Clock
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1
261
1
9
J1
B3
C2
G1
F2
H4
F3
K3
N1
VC4
Using J1 byte, every path can be assigned a trace.
Required matching at transmit and receive ends.
Set value as needed
Verify B3
Example:
13H means ATM cells
Report back the fault from path end to path start
It is set in POH of opposite direction
HP-REI: Higher Order Path Remote Error indication (sum of receiving error block of VC4)
HP-RDI: High Order Path Remote Defect Indication
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Indicate the multi-frame types and location of the payload.
For 2M PDH to SDH multiplexing structure, H4 indicates the current frame, which frame of the multi-frame, allowing Rx to find TU-PTR & drop 2M signals.
H4: 00H-03H
Other Bytes
F2 and F3: Network providers can use it for exchange of data (local maintenance)
K3: APS for high order path
N1: another byte for network operator usage (maintenance purposes)
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Consist of four bytes
1
1
9
Pointed by TU-PTR
Error block monitoring: b1-b2
Signal label: b5-b7
*
N2: byte for network operator usage
K4: APS for low order path
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Self-Healing Network?
It is a network which can automatically resume its loaded services within a very short time in case of fault.
Its terminal users do not notice any service interruption.
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Self-Healing Basic Principle
When the working route fails or experience problems, services will be switched to the protecting route automatically within a very short time (<50ms).
Redundancy routes are essential for self-healing networks.
Working Path
Protection Path
Ring Network Service Protection
1:1 Multiplex Section Protection
TR
CS
TR
CS
OL
OL
OL
OL
W
P
Chain Network 1+1 Path Protection
At sending end, the STM-N signal is sent simultaneously over both segments of the work and protect.
At receiving side, only one (work or protect) path is selected based on quality.
Send Together Receive One
Chain Network 1+1 Multiplex Section Protection
At sending end, the STM-N signal is sent simultaneously over both segments of the work and protect.
At receiving side, only one (work or protect) path is selected based on quality.
Send Together Receive One
OL
OL
Work
CS
OL
OL
CS
Protection
Work
The 1:1 structure is the subset of the 1:N (where N=1) structure.
It has the capacity to work in the 1+1 structure and to interconnect with the 1+1 structure of the other end.
Protection
Self-Healing Networks
In Multiplexing segment 1:1 protection The working payload is transmitted through the working path while the protection path can be used to carry extra payload which is of inferior class.
When the working path fails, the extra payload on the protection path will be superseded by the working payload according to APS protocol. Thus the working payload is protected.
Under normal circumstances, 1:1 becomes 2+0.
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*
According to the flow, the services in the transmission network can be classified into UNIDIRECTIONAL and BIDIRECTIONAL services.
Unidirectional: A-D-C & C-B-A
Bidirectional: A-D-C & C-D-A
2-fiber Bidirectional Multiplex Section Protection Ring
4-fiber Bidirectional Multiplex Section Protection Ring
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2-Fiber Unidirectional Path Protection Ring
It adopts 1+1 protection mode, the switching criteria is PATH-AIS, & APS protocol is not needed.
At the source NE, the payload is send to the working path and protection path simultaneously. The destination NE detect and compare the coming signal from both paths, then determine to receive the payload of better quality.
switching
AC
2 fiber: Two fibers between a pair of nodes
Bi-direction: Service between two NEs use the same section of the network and are transmitted by reverse direction
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Working path
*
Protecting Path
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Relationship between working & protecting paths
The protecting path of one direction protect the working path of the other direction, i.e, P1 protects S1, & P2 protects S2.
A
C
B
D
Use S1 & S2 to transmit services.
Service AC is sent in S1 through path A->B->C
Service CA is sent in S2 through path C->B->A
P1 and P2 can be used to send extra service now.
AC Tx
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Switching Procedure
SwitchIf the fiber between B and C is broken, switching occurs in B and C
B node: service AC crosses from S1 to P1, and sent through A->B->A->D->C
C node: service CA crosses from S2 to P2, and sent through C->D->A->B->A
AC Tx
Features of 2 Fiber Bidirectional MSP Ring
Advantages: Time slots between two nodes can be reused, thus increasing the transmission capacity. Standby path P1 and P2 can be used to transmit extra services of inferior class.
Disadvantages: longer switching time due to APS protocol. Numbers of maximum nodes supported by APS is limited to 16.
Transmission capacity: (k/2) x STM-N (k=no. of nodes).
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*
*
858mm (height) * 440mm
(width) * 290mm (depth)
*
*
*
*
1 time/2s normal
Indicator
Critical Alarms
Emergency situation like fiber cut or some system failure, Need immediate attention, interrupt services
Major Alarms:
Minor Alarms:
Growth of voice traffic
“DWDM”
An optical technology used to increase capacity over existing fiber cables
transmitting multiple signals simultaneously at different wavelengths on the same fiber
one fiber is transformed into multiple virtual fibers.
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Different signals with specific wavelengths are multiplexed into a fiber for transmission.
DWDM concept
LA: Line amplifier (gain 30-33 db)
BA: Booster amplifier (gain 23 db)
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Insert/extract data
Order wire (E1 & E2 Bytes)
GNE1
NE2
TS0: FAS
TS1: E1
TS2: F1
TS3-TS14: D1-D12
TS15: E2
TS16-TS31: reserved
1
2
3
4
5
6
7
9
8
10
11
12
Note: 1. -48V ( Ist. Supply source Line); 2. -48V (2nd.Supply source Line);
3. Alarm clearing switch; 4. Sound/light test switch; 5. Indicator; 6. Master
switch (the first line); 7. Master switch (the second line); 8. Protection
ground; 9. Power ground; 10. Power switch of the upper subrack; 11. Power
switch of the lower subrack; 12. PMU board.
*
*
5 to 20: M16I1-M16I16 (From SDH)
23 to 38: D16-O1- D16-O16 (To SDH)
42-43: SC2-RM2-SC2-TM2
Middle/Lower ODF
*
*
2- RWC Receiving Wavelength Conversion Board
3- LWC Line Wavelength Conversion Board(TWC+RWC)
4- M16/D16 16 Channel Multiplexer/De-Multiplexer Board
5- SCA Supervisory Channel Access Board
6- SC1/2 Single/Dual Supervisory Channel Board
7- MR2 Two Wavelength Add/Drop Multiplexer Board
8- SCC System Control & Communication Board
9- OHP Overhead Processor Board
10- WPA Wavelength Pre-Amplifier Board
11- WBA Wavelength Booster Amplifier Board
12- WLA Wavelength Line Amplifier Board
*
D
1
6
O
H
P
S
C
C
S
C
1
S
C
A
M
S
2
M
1
6
W
B
A
W
P
A
13.unknown
2.5 Gb/s MULTI ADD/DROP MULTIPLEXER (MADM)
DWDM OPTICAL LINE AMPLIFIER (OLA)
EXISTING OPTICAL FIBRE LINK
30% Traffic Density
70% Traffic Density
OAN SYSTEM Hardware Structure
OAN basically consists of following components to perform three major functions
a) service access, b) transmission and c)network management,
OLT (Optical Line Terminal).
ONU (Optical Network Unit).
SDH / PDH Transmission System
Optical line terminal (OLT)
collecting point of various services of the exchange such as voice, data and image
provides the network interface of multiple services.
As a modularly structured unit, the OLT is composed of multiple service interface modules which are stacked together.
*
Optical line terminal (OLT)
Optical Line Terminal (OLT) belongs to the service node equipment of the access network. It is connected with the service node through service node interface to perform the service access of the access network.
Flat screen
E1 leased line interface conforming to ITU-T G703
ISDN services,V5.2 if connected to ISDN exchanges.
DDN connection.
Internet ISP connection, Broadband services (ATM switch, ATM server etc.)
CATV service
subscriber equipment of the access network
and provides subscribers with integrated
services of voice, data and image.
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SIP module,
built-in primary power supply,
U interface. ISDN BRI (2B+D).ISDN PRA (30B+D).
Nx64kbps or subrate interface of V.35/V.24 to provide various data services for subscribers.
E1 interface to provide 2M leased line through coaxial cable.
CATV signal through coaxial cable, connected to TV sets at
subscribers
LE
V5.2
Centrex
CID
SDH
OLT
ONU
ONU
ONU
Sub-rate ( 2.4/4.8/9.6/19.2/48K, V.24 )
High gain (10-30 dB)
…..Extensive applications in DWDM Systems
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The outer shell has 3 levels structure (E1, E2, E3)
E1……ground state
E2……metastable state
Pumping lasers are used to excite the EDF
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Continue…
E3 is not stable and ions are dropped to E2 state (radiation-less decay process)
Particles at E2 state are transited to E1 state via stimulated radiation on passing input optical signal
This results in generation of photons identical to photons of incident signal light
Continuous amplifying is implemented
Another name is Optical Mux
*
protects transmitter from interference
Protects the generation of large noise when reflected at the input end and reenters EDF
O/P ISO
*
Pumps the ions from low to high level
Amplification is implemented by transferring energy to signal light
*
Tap off a small part of the signal for monitoring
Optical Detector (PD)
*
utilizing heavily aluminum plus erbium-doped optical fiber and Gain Equalization Filter (GEF)
optimizing the optical structure (1525-1560)
*
*
.
45.unknown
46.unknown
LA: Line amplifier (gain 30-33 db)
BA: Booster amplifier (gain 23 db)
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Amplifier Sub-rack
LAN / WAN