363-206-285
Circuit Pack Descriptions
Issue 3 June 2001
7-121
Receive Direction. 7In the receive direction, the optical receiver converts the light
pulses from an NRZ-encoded OC-3 signal to equivalent electrical pulses and
recovers the received clock (155.520 MHz) and uses it to retime the received
data. The demultiplexer circuit accepts the retimed STS-3 bit stream, frames on
the incoming signal, descrambles it, demultiplexes it into three STS-1 signals, and
processes OC-3 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 received STS-1,
using the local timing signals. The output of the STS-1 pointer processor is three
STS-1 signals, frame synchronous to each other, which 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.
Control Circuitry 7
The 22G-U/22G2-U/22G3-U/22G4-U OLIU circuit pack interfaces with the BBG8/
BBG8B SYSCTL and with the OHCTL circuit packs.
The 22G-U/22G2-U/22G3-U
/22G4-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 22G-U/22G2-U/22G3-U
/22G4-U OLIU responds to
control signals from the SYSCTL, such as STS-1 routing, VT1.5 routing,
protection switching, and LED control commands.
The 22G-U/22G2-U/22G3-U
/22G4-U OLIU accesses the SONET transport
overhead and routes it via the transport overhead channel interface to the
OHCTL.
The 22G-U/22G2-U/22G3-U
/22G4-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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