Question

give introduction to :

1- SONET/SDH rings.

2- SONET/SDH networks.

3- Frame format of SONET/SDH

Note : please write it in word and only 1 page

Answer 1

Answer:-----------

1- SONET/SDH rings:-------------
SONET/SDH networks have a ring structure, which adds high reliability to the overall transmission network. Even if the optical fiber is cut, the transmission path is backed-up and restored within 50 ms.
The ring contains fiber redundancies which allow traffic both unidirectionally and bidirectionally. In case of an accidental snapping of a fiber, the multiplexers can reroute the traffic along an alternate path using redundant fibers.

2- SONET/SDH networks:-------------
Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or light-emitting diodes (LEDs). Lower data rates can also be transferred via an electrical interface. The method was developed to replace the Plesiochronous Digital Hierarchy (PDH) system for transporting larger amounts of telephone calls and data traffic over the same fiber without synchronization problems. SONET generic criteria are detailed in Telcordia Technologies Generic Requirements document GR-253-CORE.Generic criteria applicable to SONET and other transmission systems (e.g., asynchronous fiber optic systems or digital radio systems) are found in Telcordia GR-499-CORE.

3- Frame format of SONET/SDH :--------
SONET STS-1 frame consists of 9 rows and 90 columns. SONET frame is composed of 810 octets (bytes). Transmission is carried out row wise from left to right and from top to bottom. Bits are transmitted serially.

The STS-1 frame of SDH is composed of section overhead, transport overhead, payload overhead and data part. The frame starts with fixed A1/A2 bit pattern of 0xf628 used for bit/octet synchronization. SONET/SDH is referred as octet synchronous. The first three columns of SONET frame is referred as transport overhead. The next 87 columns of the frame are referred as Synchronous payload envelope (SPE). Payload overhead is part of SPE.