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Circuit Pack Descriptions
7-112 Issue 3 June 2001
A faceplate-mounted universal optical connector allows the 22D-U OLIU to accept
fiber terminated with
ST
, SC, or FC connectors. The 22D-U OLIU comes with a
0dB
ST
buildout. Various combinations of buildouts and connectors are also
available. See Section 10, "Technical Specifications," for a list of universal
buildout attenuators. A 10 dB attenuator is required for loopback testing. The 22D-
U OLIU circuit pack provides cost effective interconnect for intra-office
applications and is used only for DDM-2000 OC-3 and OC-12 or
SLC
-2000
interworking over multimode fiber.
General Description of Operation 7
The 22D-U OLIU circuit pack multiplexes three STS-1 signals to an STS-3, inserts
the SONET transport overhead bytes (line and section), and scrambles the
resulting signal. This STS-3 signal drives an LED transmitter to create the IS-3
output.
The received IS-3 signal is converted back to an electrical STS-3. This STS-3 is
descrambled and demultiplexed to three STS-1 signals, and transport overhead is
accessed. Some of the overhead (for example, section datacom channel) is
passed via serial data links to the control packs, while other bytes (for example
framing, parity check) are processed on-board. The STS-1 signals go through a
pointer processor to guarantee frame alignment to the local system clock before
being routed to the other main and function unit slots.
If an incoming STS-1 signal from the fiber is to be VT1.5 cross-connected, VT1.5
pointer-processing is performed on this pack and STS-1 path overhead
termination is performed on these signals. All signals entering this pack from
either the backplane or from the optical interface may be routed as STS-1s. If
appropriate, VT1.5 routings may be established between STS-1s using a VT1.5
cross-connection.
The 22D-U OLIU circuit pack provides timing signals to and receives timing
signals from the TG circuit packs.
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