S3057 AMCC (Applied Micro Circuits Corp), S3057 Datasheet - Page 2

• Manufacturer Part Number: S3057
• Description: Bicmos Lvpecl Clock Generator Sonet/sdh/atm Oc-12 Transmitter And Receiver Multirate (oc-48/24/12/3/gbe) Sonet/sdh/atm Transceiver
• Manufacturer: AMCC (Applied Micro Circuits Corp)

SONET OVERVIEW
Synchronous Optical Network (SONET) is a standard
for connecting one fiber system to another at the opti-
cal level. SONET, together with the Synchronous
Digital Hierarchy (SDH) administered by the ITU-T,
forms a single international standard for fiber inter-
connect between telephone networks of different
countries. SONET is capable of accommodating a
variety of transmission rates and applications.
The SONET standard is a layered protocol with four
separate layers defined. These are:
• Photonic
• Section
• Line
• Path
Figure 2 shows the layers and their functions. Each of
the layers has overhead bandwidth dedicated to ad-
ministration and maintenance. The photonic layer
simply handles the conversion from electrical to opti-
cal and back with no overhead. It is responsible for
transmitting the electrical signals in optical form over
the physical media. The section layer handles the
transport of the framed electrical signals across the
optical cable from one end to the next. Key functions
of this layer are framing, scrambling, and error moni-
toring. The line layer is responsible for the reliable
transmission of the path layer information stream car-
rying voice, data, and video signals. Its main functions
are synchronization, multiplexing, and reliable trans-
port. The path layer is responsible for the actual trans-
port of services at the appropriate signaling rates.
Data Rates and Signal Hierarchy
Table 1 contains the data rates and signal designa-
tions of the SONET hierarchy. The lowest level is the
basic SONET signal referred to as the synchronous
transport signal level-1 (STS-1). An STS- N signal is
made up of N byte-interleaved STS-1 signals. The
Figure 3. STS-48/OC-48 Frame Format
2
S3063
A1 A1
A1 A1
48 A1
Bytes
Transport Overhead 144 Columns
144 x 9 = 1296 bytes
A2 A2
SONET/SDH/ATM OC-48 DIFFERENTIAL 16:1 TRANSMITTER
A2 A2
48 A2
Bytes
125 sec
optical counterpart of each STS- N signal is an opti-
cal carrier level- N signal (OC- N ). The S3063 chip
supports the OC-48 data rate (2.488 Gbps).
Frame and Byte Boundary Detection
The SONET/SDH fundamental frame format for STS-48
consists of 144 transport overhead bytes followed by
Synchronous Payload Envelope (SPE) bytes. This
pattern of 144 overhead and 4176 SPE bytes is re-
peated nine times in each frame. Frame and byte
boundaries are detected using the A1 and A2 bytes
found in the transport overhead. (See Figure 3.)
For more details on SONET operations, refer to the
Bellcore SONET standard document.
Figure 2. SONET Structure
Table 1. SONET Signal Hierarchy
SPE mapping
Maintenance,
Elec.
STS-1
STS-3
STS-12
STS-24
STS-48
Functions
Payload to
transmission
protection,
Scrambling,
switching
Synchronous Payload Envelope 4176 Columns
4176 x 9 = 37,584 bytes
Optical
framing
End Equipment
CCITT
STM-16
STM-1
STM-4
STM-8
Photonic layer
Section layer
Line layer
Path layer
Optical Data Rate (Mbps)
OC-1
OC-3
OC-12
OC-24
OC-48
December 6, 1999 / Revision NC
Fiber Cable
51.84
155.52
622.08
1244.16
2488.32
Photonic layer
Section layer
Line layer
Path layer
End Equipment