1 of 22

MAYURBHANJ SCHOOL OF ENGINEERING � LAXMIPOSI ,BARIPADA,757107

Prepared by Er. Viswanath Behera (Lecturer E & TC Engineering Department)

Subject – WAVE PROPAGATION & BROADBAND COMMUNICATION ENGINEERING

Chapter – 5 –Broadband Communication

Topic – SONET

Semester – 5th

Branch – Electronics & Telecommunication

AY-2021-2022, WINTER-2021

2 of 22

Telephone Networks {Brief History}

  • Digital carrier systems
    • The hierarchy of digital signals that the telephone network uses.
    • Trunks and access links organized in DS (digital signal) hierarchy
    • Problem: rates are not multiples of each other.
  • In the 1980’s Bellcore developed the Synchronous Optical Network (SONET) standard.
  • Previous efforts include: ISDN and BISDN.

3 of 22

North American Digital Hierarchy

Primary

Multiplex

Eg. Digital

Switch

30 chan PCM

4th order

Multiplex

​

x4

2nd order

Multiplex

​

x4

3rd order

Multiplex

​

x4

34.368 Mbps

2.048 Mbps

8.448 Mbps

139.264 Mbps

CEPT 1

CEPT 4

European Digital Hierarchy

28

M13

Multiplex

​

​

M23

Multiplex

​

x7

Primary

Multiplex

Eg. Digital

Switch

24 chan PCM

M12

Multiplex

​

x4

1

DS3 44.736 Mbps

DS1 1.544 Mbps

DS2 6.312 Mbps

DS3 44.736 Mbps

●

●

●

Figure 4.5

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

4 of 22

5 of 22

SONET

  • Transmission links of the telephone network have been changing to SONET where rates are arranged in STS (Synchronous Transfer Signal) hierarchy.
  • The hierarchy is called SDH (Synchronous Digital Hierarchy) defined by CCITT.
  • It is an ITU standard.

6 of 22

SONET

SONET:: encodes bit streams into optical signals propagated over optical fiber. SONET defines a technology for carrying many signals of different capacities through a synchronous, flexible, optical hierarchy.

  • A bit-way implementation providing end-to-end transport of bit streams.
  • All clocks in the network are locked to a common master clock so that simple TDM can be used.
  • Multiplexing done by byte interleaving.
  • SONET is backward compatible to DS-1 and E-1 and forward compatible to ATM cells.
  • Demultiplexing is easy.

7 of 22

Low-Speed

Mapping

Function

Medium

Speed

Mapping

Function

High-

Speed

Mapping

Function

DS3

44.736

DS1

DS2

CEPT-1

CEPT-4

139.264

ATM

150 Mbps

STS-1

STS-1

STS-1

STS-1

STS-1

STS-1

STS-1

STS-1

STS-3c

STS-3c

OC-n

Scrambler

E/O

51.84 Mbps

High-

Speed

Mapping

Function

Mux

STS-n

●

●

●

●

●

●

Figure 4.8

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

8 of 22

9 of 22

SONET Architecture

  • SONET topology can be a mesh, but most often it is a dual ring.
  • Standard component of SONET ring is an ADM (Add/Drop Multiplexer)
    • Drop one incoming multiplexed stream and replace it with another stream.
    • Used to make up bi-directional line switching rings.

10 of 22

a

b

c

d

a

b

c

d

(a) Dual ring

(b) Loop-around in response to fault

Figure 4.12

ADM

ADM

ADM

ADM

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

11 of 22

SONET Ring

12 of 22

MUX

DEMUX

MUX

DEMUX

MUX

DEMUX

(a) pre-SONET multiplexing

remove

tributary

insert

tributary

ADM

remove

tributary

insert

tributary

(b) SONET Add-Drop multiplexing

Figure 4.9

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

13 of 22

a

b

c

3 ADMs

physical loop net

OC-3n

OC-3n

OC-3n

Figure 4.10

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

14 of 22

Inter-Office

Rings

Metro

Ring

Regional

Ring

Figure 4.13

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

15 of 22

STE: Section Terminating Equipment, e.g. a repeater

LTE: Line Terminating Equipment, e.g. a STS-1 to STS-3 multiplexer

PTE: Path Terminating Equipment, e.g. an STS-1 multiplexer

optical

section

optical

section

optical

section

optical

section

line

optical

section

line

optical

section

line

path

optical

section

line

path

(a)

(b)

STS

PTE

LTE

STE

STS-1 Path

STS Line

Section

Section

Mux

Mux

reg

reg

reg

SONET

Terminal

STE

STE

LTE

STS

PTE

SONET

Terminal

Figure 4.14

SONET Architecture

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

16 of 22

17 of 22

Mux

= BIM (Byte Interleaved Multiplexer)

Reg

= Regenerator

  • Boosters power of optical signal
    • Optical signal converted to electrical signal
    • Amplify electrical signal
    • Amplifed electrical signal converted back to optical signal

​

18 of 22

B

B

B

87B

Information

Payload

9 Rows

125 μs

Transport

overhead

90 bytes

Section

Overhead

3 rows

6 rows

Line

Overhead

Figure 4.15

SONET frame

SPE Synchronous Payload Envelope

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

19 of 22

Pointer

87 columns

9

rows

first column is path overhead

Synchronous

Payload

Envelope

frame

k

frame

k+1

Pointer

first octet

last octet

Figure 4.16

Leon-Garcia & Widjaja: Communication Networks

SPE straddling SONET frame

Copyright ©2000 The McGraw Hill Companies

20 of 22

ATM Cells in an STS-3 Frame

21 of 22

STS-1

STS-1

STS-1

STS-1

STS-1

STS-1

Map

Map

Map

STS-1

STS-1

STS-1

STS-1

STS-1

STS-1

Byte

Interleave

STS-3

Incoming

STS-1 Frames

Synchronized New

STS-1 Frames

Figure 4.17

Leon-Garcia & Widjaja: Communication Networks

Copyright ©2000 The McGraw Hill Companies

22 of 22

THANK YOU