363-206-305
Circuit Pack Descriptions
7-84
Issue 3 June 2000
A faceplate-mounted universal optical connector allows the 28G-U/28G2-U OLIU
to accept fiber terminated with ST, SC, or FC connectors. The 28G-U/28G2-U
OLIU operates over single mode fiber. Various combinations of buildout
attenuators and connectors are also available. See Chapter 10, "Technical
Specifications," for a list of universal buildout attenuators.
General Description of Operation
7
The 28G-U/28G2-U circuit pack accepts eight VT-G signals from the DS1 circuit
packs, performs protection switch selections, combines the selected signals to
form an STS-1 signal, inserts STS-1 path overhead, inserts SONET transport
overhead bytes (line and section) and STS path overhead bytes, and scrambles
the resulting signal which drives a separate laser transmitter to create an OC-3
output.
The 28G-U/28G2-U circuit pack converts a received OC-3 signal back to an
electrical STS-3, descrambles and demultiplexes it, and processes the transport
overhead. It sends some of the overhead (for example, section data
communications channel) via serial data links to the control packs, and processes
other bytes (for example framing, parity check) on board. It performs STS-1
pointer processing to guarantee STS-1 frame alignment and STS-1 path overhead
and VT1.5 pointer processing. The 28G-U/28G2-U then performs VT1.5 TSI,
multiplexes four VT1.5 signals to VT-Gs, and sends the VT-Gs to the low-speed
slots or sends up to 3 STS-1s to the function unit slots.
On the FiberReach wideband shelf, the 28G-U/28G2-U OLIU provides an
interface of eight VT-G signals. These groups are multiplexed into an STS-1
signal. A VT1.5 cross-connect allows VT1.5 switching as required.
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