363-206-295
Circuit Pack Descriptions
Issue 1
December 1997
7-55
21D/21D-U OLIU Quick Reference Summary
7
Transmit Functions
7
Major transmit functions of the 21D/21D-U OLIU circuit pack are as follows:
■
Selects STS-1 inputs from TSI circuit packs
■
Adds SONET transport overhead
■
Byte-interleaves and scrambles the three selected STS-1 or optional
STS-3c signals to produce an STS-3 or STS-3c signal
■
Converts the STS-3 or STS-3c signal to an IS-3 or IS-3c optical signal for
transmission over the optical fiber.
Receive Functions
7
The following are major receive functions of the 21D/21D-U OLIU circuit pack:
■
Receives an optical IS-3 or IS-3c signal and converts it to an electrical
STS-3 or STS-3c signal
■
Extracts STS-3 or STS-3c clock and retimes the received data
■
Demultiplexes the STS-3 or STS-3c signal into three STS-1 signals
■
Extracts transport overhead
■
Processes the STS-1 or STS-3c pointers and frame-synchronizes the
STS-1 signals
■
Sends the three STS-1 signals to both TSIs.
Control Functions
7
The major control functions are as follows:
■
Protection switching for TSI circuit packs
■
Transport overhead processing
■
Inventory information (
CLEI code, date of manufacture, etc.).
Maintenance Signal Functions
7
The major maintenance signal functions are as follows:
■
Inserts and detects STS-1 path AIS
■
Inserts STS-1 path unequipped signal
■
Inserts and detects IS-3 line AIS
■
Inserts and detects far-end receive line failure (FERF)
■
Detects IS-3 line failures (LOS, LOF, AIS, and BER)
■
Detects IS-3 line signal degrade BER.
