1.1 Overview of POS and CPOS Interfaces
This section describes concepts of SONET and SDH, channelization and non-channelization,
and frame structure of SDH.
Introduction to SONET and SDH
Synchronous Optical Network (SONET) is the synchronous digital transmission standard
defined by the American National Standards Institute (ANSI) and mainly used in North America
and Japan. Clocks at each level in an entire network are provided by a very precise master clock.
SONET defines the line rate hierarchical structure of synchronous transmission for the optical
transmission system. The basic transmission rate of the SONET is 51.84 Mbit/s and
approximately equals the transmission rate of E3/T3.
l For an electrical signal, the transmission rate is called Level 1 Synchronous Transport
Signal, namely, STS-1.
l For an optical signal, the transmission rate is called Level 1 Optical Carrier, namely, OC-1.
Adopting synchronous signals, SONET can easily multiplex multiple signals.
Based on SONET, Synchronous Digital Hierarchy (SDH) is an international standard defined
by the ITU-T and mainly used in Europe. The corresponding standard of SDH is the proposals
from G.707 to G.709 passed in 1988 and the proposals added in 1992.
SDH is similar to SONET to a great extent. The basic rate of SDH is 155.52 Mbit/s, which is
called Level 1 Synchronous Transfer Module, STM-1. This rate equals the OC-3 rate in SONET.
Adopting synchronous multiplexing and flexible mapping, SDH can multiplex or demultiplex
low-speed tributary signals from SDH signals without using multiplexing or demultiplexing
devices. This reduces signal consumption and equipment investment.
Table 1-1 lists the common transmission rates of SONET and SDH. The hierarchical relationship
between common transmission rates is four times. For convenience, the approximations in the
parentheses are often used to express transmission rates.
Table 1-1 Relationship between common transmission rates of SONET and SDH
SONET
SDH Transmission Rate
(Mbit/s)
Electrical
Signal
Optical Signal Optical Signal
STS-1 OC-1 - 51.840
STS-3 OC-3 STM-1 155.520 (155)
STS-9 OC-9 STM-3 466.560
STS-12 OC-12 STM-4 622.080 (622)
STS-18 OC-18 STM-6 933.120
STS-24 OC-24 STM-8 1244.160
Quidway S9300 Terabit Routing Switch
Configuration Guide - WAN Access 1 POS Interface Configuration
Issue 02 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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