TXC-06101AILQ Transwitch Corporation, TXC-06101AILQ Datasheet - Page 6

• Manufacturer Part Number: TXC-06101AILQ
• Manufacturer: Transwitch Corporation

Specifications of TXC-06101AILQ

• Operating Temperature (min): -40C
• Operating Temperature Classification: Industrial
• Operating Temperature (max): 85C
• Package Type: PQFP
• Rad Hardened: No
• Lead Free Status / Rohs Status: Not Compliant

SONET TUTORIAL
A primary goal in developing the SONET (Synchronous Optical NETwork) format was to define a synchronous,
optical hierarchy with sufficient flexibility to carry many different payloads. This has been accomplished by
defining a basic signal of 51.84 Mbit/s and a byte-interleaved multiplex scheme that results in a family of stan-
dard rates and formats defined at a rate of N times 51.84 Mbit/s, where N is an integer. Since some signals that
must be transported have speeds greater than the basic rate, a technique of linking several basic rate signals
together to form a transport signal of varying capacity has also been defined. There are three major differences
between the SONET Hierarchy and the North American Digital Hierarchy (NADH)
The Basic modular signal (at 51.84 Mbit/s) is called the Synchronous Transport Signal level One (STS-1). The
optical counterpart is the Optical Carrier level One (OC-1), which is the result of direct optical conversion of the
STS-1 signal. Higher level signals are denoted by STS-N and OC-N, where N is an Integer. At present the
standardized values of N are: 1, 3, 12, 24, 48 and 192. These values provide standardized multiplexing rates
for SONET systems at 51.84 Mbit/s, 155.52 Mbit/s, 622.08 Mbit/s, 1.24416 Gbit/s, 2.48832 Gbit/s and
9.95328 Gbit/s, respectively.
FORMATS
There are four basic formats upon which the SONET Hierarchy is built.
STS-1 Structure
The basic SONET format is the 51.84 Mbit/s signal designated STS-1. It consists of 810 eight-bit bytes
arranged in a matrix of nine rows each of which has 90 columns as shown in Figure 1. This nine by 90 arrange-
ment is referred to as a SONET Frame. It repeats every 125 microseconds. The first three columns consist of
the Transport Overhead (TOH). The remaining 87 columns are referred to as the Synchronous Payload Enve-
lope (SPE). It is this portion of a SONET signal that is allowed to "float." Within the TOH is a pointer that identi-
fies the starting position of the SPE with respect to the TOH Bytes in the Frame. The first column of the SPE is
the Path Overhead (POH). The other 86 columns contain the actual payload information whose capacity is
approximately 50 Mbit/s.
1.
1. SONET
2. SONET
3. SONET
The North American Digital Hierarchy is described in ANSI standard T1.107. The ITU-T term "PDH" (Plesiochronous
Digital Hierarchy) is used to refer generically to an asynchronous multiplexing structure.
NADH
NADH
NADH
Proprietary TranSwitch Corporation Information for use Solely by its Customers
is synchronous. All SONET tributaries in a SONET network must be traceable to one
or more Stratum 1 synchronization sources.
is asynchronous. The tributaries need not be synchronized.
is a harmonic multiplexing structure. All higher rate SONET signals are integer
multiples of a base rate. Lower order SONET tributaries are byte-interleaved to
form the higher order SONET signal.
is hierarchical. Higher order multiplexing is accomplished with bit stuffing to
accommodate speed differences in lower order tributaries.
overhead (Framing, Performance Monitoring, Alarms, etc.) and payload are distinct
entities. In a SONET signal the payload bits do not occupy a fixed position in relation
to the transport overhead bits. A pointer mechanism is used to identify the start of
the payload.
overhead bits and payload bits have a fixed, unvarying relationship to each other.
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DATA SHEET
1
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TXC-06101
Ed. 3, April 2001
TXC-06101-MB
PHAST-1