363-206-285
Circuit Pack Descriptions
Issue 3 June 2001
7-129
Receive Direction. 7In the receive direction, the optical receiver converts the light
pulses from an NRZ-encoded OC-12 signal to equivalent electrical pulses and
recovers received clock (622.08 MHz) and uses it to retime the received data. The
demultiplexer circuit accepts the retimed STS-12 bit stream, frames on the
incoming signal, descrambles it, demultiplexes it into twelve STS-1 signals, and
processes OC-12 transport overhead. The overhead information is sent to the
SYSCTL circuit pack via the intra-shelf control bus and to the OHCTL circuit pack
by the transport overhead channel interface.
The STS-1 outputs from the demultiplexer are sent to the STS-1 pointer processor
which performs pointer interpretation and generation on each of the twelve
received STS-1, using the local timing signals. The output of the STS-1 pointer
processor is twelve STS-1 signals, frame synchronous to each other. Any three of
these STS-1s then are sent to the VT1.5 pointer processor. VT1.5 pointer
processing is performed on each STS-1 that is to be VT1.5 cross-connected.
STS-1 path overhead termination is also done on these VT1.5 based signals.
STS-1s that do not require VT1.5 cross-connections are passed through without
VT1.5 pointer processing or STS-1 path overhead termination. The output from
the VT1.5 pointer processor is sent to the STS-1/VT1.5 router. The router cross-
connects the appropriate VT1.5 tributaries and sends each of the three STS-1
signals to the appropriate main or function unit slots. All twelve of the received
STS-1s are passed through the faceplate connector to the other main OLIU.
Control Circuitry 7
The 24G-U OLIU circuit pack interfaces with the BBG8/BBG8B SYSCTL and with
theBBG9OHCTLcircuitpacks.
The 24G-U OLIU provides maintenance elements for reporting the status of the
circuit pack, status of the incoming optical and electrical signals, as well as
inventory information (
CLEI
code, date of manufacture, etc.). These maintenance
elements are used by the SYSCTL for fault detection and isolation. Conversely,
the 24G-U OLIU responds to control signals from the SYSCTL, such as STS-1
routing, VT1.5 routing, protection switching, and LED control commands.
The 24G-U OLIU accesses the SONET transport overhead and routes it via the
transport overhead channel interface to the OHCTL.
The 24G-U OLIU accesses the STS-1 path overhead and routes it via the intra-
shelf control bus to the SYSCTL circuit pack.
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