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Circuit Pack Descriptions
7-136 Issue 3 June 2001
A faceplate-mounted universal optical connector allows the 26G2-U OLIU to
accept fiber terminated with
ST
, SC, or FC connectors. The 26G2-U OLIU comes
witha0dB
ST
buildout. A 10 dB attenuator is required for loopback testing.
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 26G2-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-1
output.
The 26G2-U circuit pack converts a received OC-1 signal back to an electrical
STS-1, 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 to the local system clock and STS-1 path
overhead and VT1.5 pointer processing. The 26G2-U then performs VT1.5 TSI,
multiplexes four VT1.5 signals to VT-Gs, and sends the VT-Gs to the low-speed
slots.
The 26G2-U provides an interface of eight VT-G signals in both the wideband
shelf and the OC-3 shelf. These groups are multiplexed into an STS-1 signal. A
VT1.5 cross-connect allows VT1.5 switching as required.
Detailed Description of Operation 7
Figure 7-48 is a block diagram of the 26G2-U OLIU circuit pack.
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