363-206-295
Circuit Pack Descriptions
7-56 Issue 1 December 1997
21G/21G-U/21G2-U OLIU Circuit Pack Description 7
Purpose of Circuit 7
The 21G/21G-U/21G2-U OLIU circuit pack performs the optical/electrical conversion
between the OC-3 and STS-3 signals, multiplexing/demultiplexing between STS-3 and
three STS-1 signals and SONET transport overhead access. The 21G/21G-U/21G2-U
can be used in either the main or function unit slots in an OC-3 shelf, or the function unit
slots only in an OC-12. In the OC-3 shelf, the 21G/21G-U/21G2-U OLIU circuit pack
also provides routing of the STS-1s between the OC-3 interface and other main and
function unit slots in the shelf and will support the STS-1 add/drop feature. In the OC-12
shelf, the routing function is performed in the TSI circuit pack.
21G/21G-U/21G2-U OLIU Faceplate Indicators 7
The 21G2-U OLIU is the same as the 21G/21G-U OLIUs but has improved receiver
overload sensitivity, eliminating the need for a Hi/Low power switch for loopback testing.
The 21G2-U can be used in place of the 21G/21G-U in all applications.
The 21G/21G-U/21G2-U OLIU circuit pack faceplate indicators are shown in
Figure 7-23. The red FAULT LED lights on detection of circuit pack hardware failure. In
the event of an incoming signal failure, this LED will flash ON and OFF. The green
ACTIVE LED lights when the circuit pack is active (carrying service).
Figure 7-23. 21G and 21G-U/21G2-U OLIU Circuit Packs
FAU LT
ATIVCE
Lucent
S1:1
21G
OLIU
x
x
x
x
x
FAU LT
ATIVCE
Lucent
S1:1
OLIU
x
x
x
x
x
Lucent
Lucent
IN
OUT
21G-U
Universal
Optical
Connectors
IN
OUT
R
ST Connectors
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