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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.).
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