Multiplexing in SONET

By-: Er. Amit Mahajan

Introduction to SONET •

SONET stands for “Synchronous Optical Network”, and Is a method for communicating digital information using laser or LED’s LED’s and a single clock  is used to handle the timing, control and functionality of all the network equipments . FIBER  CPE RX

CPE TX LED

RX

Introduction to SONET •

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SONET is a standard, which is established in United States of America and in Canada, while a similar standard synchronous digital hierarchy (SDH) is established in Europe.

Basic building block of SONET is STS1 51.840 Mbps SDH = STM-1 = 155.520 Mbps

SONET Multiplexing DS1 1.544

DS2 6.312

Overhead

51.84 Mbps

E1 2.048 DS3 44.736

STS-1

STS-1

Overhead l l l

l l l

STS Mux

STS-3c STS-1 STS-1 ATM

Overhead 150 Mbps

STS-1

OC-n

STS-n Scrambler

E/O

SONET Frame 90

(125 micro second = 8000 frames/second )

9 90*9*8 bits/byte

* 8000 frames/sec = 51 .840 Mbps

SONET Frame

86*9*8*8000= 49.536 Mbps H

the ma imum efficie cy of th

f

me is

49 536 /51 840 95 5 %

An 2.488 gigabit/sec SONET STS-1 TO STS-48 Byte Multiplexer and De-multiplexer.   This paper describes the Architecture, Implementation and Results of high speed components of the byte multiplexer and demultiplexer.

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Architecture

De-Mux / Framer   Works at higher speed

  Works at lower speed

Consists of byte alignment circuitry , and (A1A1A1A2A2A2 )

Program 1 

library IEEE;

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use IEEE.STD_LOGIC_1164.all;

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entity mux is port(

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a : in STD_LOGIC;

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clk : in STD_LOGIC;

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b : buffer STD_LOGIC;

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c : buffer STD_LOGIC );

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end mux;

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--}} End of automatically maintained section

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architecture mux of mux is constant M_d:time:=10ns;

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begin

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pmux:process(a,clk)

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variable temp1:std_logic

;

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variable temp2:std_logic

;

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begin

program 2(cascaded multiplexer) 

library IEEE;

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use IEEE.STD_LOGIC_1164.all;

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entity mux is port(

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a : in STD_LOGIC;

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clk: in STD_LOGIC;

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ctrl: in std_logic_vector(0 to 1);

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b : buffer STD_LOGIC;

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c : buffer STD_LOGIC;

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d,e,f,g : buffer STD_LOGIC;

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h,i,j,k : buffer STD_LOGIC );

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end mux;

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--}} End of automatically maintained section

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architecture mux of mux is constant M_d:time:=10ns;

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begin pmux:process(a,clk,ctrl)

program 2(cascaded multiplexer)  

if clk'event and clk='1' then

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temp1:=a;

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b temp3:=b;

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when "01"=> temp4:=b;

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when "10"=> temp5:=b;

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when "11"=> temp6:=b;

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when others =>temp12:='X';

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end case;

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end

if;

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if clk'event and clk='0' then

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temp2:=a;

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c temp7:=c;

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when "01"=> temp8:=c;

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when "10"=> temp9:=c;

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when "11"=> temp10:=c;

Output waveforms

Mux / Phase Aligner

It aligns the phase of the external byte clock with the

Result and conclusion •

When demux/framer and mux/phase aligner are connected back to back separately. They give BER 10-12.

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When the total architecture are connected back to back. BER is 10-11 .

Metro- Ring Case Study TDM Upgrade path

WDM upgrade path-: we build multiple virtual rings at different wavelengths over the same pair of fiber. Let it be working at speed OC-3 . suppose the capacity on the ring is exhausted and Only a pair of fiber is available, i.e. no spare fiber available

Metro- Ring Case Study

Metro- Ring Case Study

The TDM upgrade is not future proof, while the WDM upgrade path more future proof as the capacity of the existing ring is future  CONCLUSION scalable by adding additional ADMs at different wavelengths. Although we can increase the capacity of the existing ring by using TDM upgrade but at higher cost of  scrap. 

Metro- Ring Case Study

The analysis clearly shows that, if we have exhausted ring at lower bit-rate then the TDM upgrade path is followed as compared to WDM. But at higher bit-rates above OC-48 the WDM upgrade path is more future proof and cost effective. 

References 1. Network For Computer Scientists and Engineer by Shakhil Akhatar. 2. ATM Transport and Integrity By Tosng- Ho-Wo And Noriaki Yoshikai. 3. SONET/SDH Demystify by Steven Shaperd. 4. Optical N/w Design and Implimentation by Vivek Alwayn. 5. D.K. Mynbaeu & L. Scheiner, ‘Fiber optic Communication Technology, Pearson Edu. Asia 6. Uyless Black, ‘Optical Networks’, Pearson education 7. Optical Network by Rajiv Raja swami . 8. Mehcan Bagheri, Dennis T. Kong, Wayne S. Holden, Fernando C. xrizany, Derek D. Mahoney, and Douglas C. Larson “An Experimental 2.488 Gigabit/Sec SONET STS-3C to STS-48 byte Multiplexer And Demultiplexer”

References 9.Data Communications and Networking by Behrouz A Forozan. 10.Online lecture (in CD ) 11.Synchronous Optical Network; R.J. Riehl; Defence Information Systems Agency. 12.Computer Communications; K.G. Beauchamp and G.S.Poo; International Thompson Computer Press.

Section overhead ü A1,A2-:used to identify

the beginning of the frame to receiving equipment for synchronization purposes. The pattern is the hexadecimal number 0xF628 (1111 0110 0010 1000) ü C1-: Identification byte-: to numbering the STS-1 in STS-N. ü B1-: Bit interleave parity byte. ü E1-: which is used by

C1

Section overhead ü F1-:

is user configurable and can be employed for a variety of  purposes. It is not standardized. Can be used for application management or network management. ü D1,D2,D3-: DCC is a 192kbps data

C1

R

Line Overhead Ø H1,H2(pointer byte) Ø H3 (Pointer Action

Byte). if more than 783 bytes are ready to be transmitted with in single 125 ms.  Then it is placed in this byte. Ø B2-: this is a Bit interleaved parity byte for LOH and is used to carry error checking information for

Line Overhead ü K1,K2

(Automatic protection switching). ü D4-D12(Data comm. Channel) is a 576kbps, OAM&P Information such as control signal, monitoring, alarm information etc. ü Z1,Z2 future growth bytes. ü E2Order-wire byte-: is used by the Z1 technician as a voice channel (64kbps) while troubleshoot

Z2

Path Overhead v  J1 (Trace byte)-: used by the CPE at the end to ensure that it is properly connected to the transmitting device by using 64-byte repeating code. v B3 (path BIP) For error checking of path overheads of previous frame. v C2(Path signal label) is used to tell a receiving device what is actually contained in the SPE.  This permits the simultaneous transport of multiple traffic

Path Overhead Ø G1 (Path Status Byte) used to communicate overall transmission status of duplex circuited. Ø F2 (User byte) to transport network management data. Ø H4 (indicator) which points the starting of the virtual tributaries. Ø Z1,Z2,Z3 (future growth byte)

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Pointer Bytes H1,H2 Ø H1,H2 pointer byte-:Is a 16 bit payload pointer. 

ØPa y lo a d p o in te r is o n ly o f 1 0 b its, corre sp o n d in g 7 8 3 lo ca tio n s in S P E ( 8 6 * 9 = 7 8 3 ). 

Pointer Bytes H1,H2 IF payload starts from the beginning of the byte then no proplem .

1 BYTE in SPE IF payload starts from 1st bit of the byte in SPE, then no problem . It can be easily predicted by last 10 bits.

Pointer Bytes H1,H2 IF payload starts from the beginning of the byte then no proplem .

1 BYTE in SPE If starts from 4th bit, the exact location can be detected by NDF. R

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K1,K2(Automatic protection switching). •

In case of failure of one fiber it automatically route the traffic on the backup fiber.

R