Brief introduction of Synchronous Optical Network (sonet,synchronous optical networking)

1. Introduction

The Synchronous Optical Network (SONET, representing synchronous optical networking) is a standard for digital information communication using optical fibers. In order to transmit a large number of telephone and data services, it has been developed to replace the quasi-synchronous digital system (PDH) system, which is defined by Telcodia's gr-253-core.

2. Summary

SDH (representing the synchronous Digital hierarchy) standard is based on the experience of SONET development. Today Sonet and SDH two technical systems are widely used, SONET applications in the United States and Canada, SDH applications in other countries of the world.
Synchronous networking differs from PDH in that the precise rate at which data is transmitted is strictly synchronized with the network-based clock, so that the entire network operates synchronously. The advent of atomic clocks makes it possible to produce SDH.
Both SONET and SDH systems can be used to encapsulate older digital transmission standards, such as PDH standards, or directly to support ATM and the so-called SONET (Packet over SONET) network.
SONET devices are typically managed using the TL1 protocol.

SONET Optical fiber Transmission system defines the synchronous transmission of the line rate hierarchy, the transmission rate is based on 51.84mb/s, approximately corresponds to the T3/E3 transmission rate, which is called the 1th level synchronous transmission signal, that is STS-1; the light signal becomes the 1th stage optical carrier (optical Carrier, OC), that is, OC-1. The criteria for gbit/s from oc-1-51.84mb/s to oc-3072-about 160 are now defined. usually expressed as oc-n.

3. OC

Optical Carrier (OC) is a set of signal bandwidths in a SONET fiber network with many levels of determination. It is usually represented as Oc-n, where n is a multiplier factor, representing how many times the base rate 51.84 mbit/s. The criteria currently defined are:

Optical Carrier level	Frame Format	SDH level	Frame Format	Line Rate
OC-1	STS-1	-	-	51.840 mbit/s
OC-3	STS-3	SDH-1	STM-1	155.520 mbit/s
OC-9	STS-9	-	-	466.560 mbit/s
OC-12	STS-12	SDH-4	STM-4	622.080 mbit/s
OC-18	STS-18	-	-	933.120 mbit/s
OC-24	STS-24	SDH-8	STM-8	1.244 160 gbit/s
OC-36	STS-36	SDH-12	STM-12	1.866 gbit/s
OC-48	STS-48	SDH-16	STM-16	2.488 gbit/s
OC-96	STS-96	SDH-32	STM-32	4.976 640 gbit/s
OC-192	STS-192	SDH-64	STM-64	9.953 280 gbit/s
OC-256	STS-256	-	-	13.271 040 gbit/s
OC-384	STS-384