S3041 AMCC (Applied Micro Circuits Corp), S3041 Datasheet - Page 3

• Manufacturer Part Number: S3041
• Description: Sonet/sdh/atm OC-48 8:1 Transmitter
• 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:
Figure 3 shows the layers and their functions. Each
of the layers has overhead bandwidth dedicated to
administration and maintenance. The photonic layer
simply handles the conversion from electrical to optical
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
carrying voice, data, and video signals. Its main
functions are synchronization, multiplexing, and reli-
able transport. The path layer is responsible for the
actual transport of services at the appropriate signaling
rates.
Data Rates and Signal Hierarchy
Table 1 contains the data rates and signal designations
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 optical counter-
Figure 4. STS–48/OC–48 Frame Format
June 24, 1999 / Revision E
SONET/SDH/ATM OC-48 1:8 RECEIVER
• Photonic
• Section
• Line
• Path
A1 A1
A1 A1
48 A1
Bytes
Transport Overhead 144 Columns
144 x 9 = 1296 bytes
A2 A2
A2 A2
48 A2
Bytes
125 sec
Figure 3. SONET Structure
Payload to
SPE mapping
Maintenance,
protection,
switching
Scrambling,
framing
Functions
Optical
transmission
part of each STS- N signal is an optical carrier level- N
signal (OC- N ). The S3042 chip supports OC-48 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 repeated nine times in each frame. Frame and
byte boundaries are detected using the A1 and A2
bytes found in the transport overhead. (See Figure 4.)
For more details on SONET operations, refer to the
Bellcore SONET standard document.
Table 1. SONET Signal Hierarchy
Elec.
STS-1
STS-3
STS-12
STS-24
STS-48
End Equipment
Synchronous Payload Envelope 4176 Columns
4176 x 9 = 37,584 bytes
CCITT
STM-16
Photonic layer
STM-1
STM-4
STM-8
Section layer
Line layer
Path layer
Optical Data Rate (Mbps)
OC-1
OC-3
OC-12
OC-24
OC-48
Fiber Cable
51.84
155.52
622.08
1244.16
2488.32
Photonic layer
Section layer
Line layer
Path layer
End Equipment
(Embedded Ops
Layer Overhead
Channel)
576 Kbps
192 Kbps
0 bps
S3042
3