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Circuit Pack Descriptions
7-62
Issue 1
December 1997
21G/21G-U/21G2-U OLIU Quick Reference
Summary
7
Transmit Functions
7
The following are the major transmit functions of the 21G/21G-U/21G2-U OLIU
circuit pack:
■
Selects STS-1 inputs from MXRVO, DS3, STS1E, or other OLIU circuit
packs
■
Provides STS-1 signal cross-connections
■
Adds SONET transport overhead
■
Byte-interleaves and scrambles the three selected STS-1 signals to an
STS-3 or STS-3c signal
■
Converts the STS-3 or STS-3c electrical signal to an optical signal and
transmits it over the fiber
■
Monitors laser bias and output power (21G and 21G-U only).
Receive Functions
7
The following are major receive functions of the 21G/21G-U/21G2-U OLIU circuit
pack:
■
Receives an optical OC-3 or OC-3c signal and converts it to an electrical
STS-3 or STS-3c signal
■
Extracts STS-3 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
■
Provides STS-1 signal cross-connections
■
Processes the received clock and provides a reference clock to the TGS
circuit packs (OC-3 shelf only).
Control Functions
7
The following are the major control functions of the 21G/21G-U/21G2-U OLIU
circuit pack:
■
Switches protection for the optical line and DS3, MXRVO, STS1E, and TGS
circuit packs on the OC-3 shelf. On the OC-12 shelf, switches protection for
the TSI and TGS circuit packs.
■
Processes transport overhead
■
Stores inventory information (
CLEI code, date of manufacture, etc.).