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Circuit Pack Descriptions
7-114 Issue 3 June 2001
LED transmitter, converting the electrical signal to an NRZ-encoded SONET
compatible IS-3 optical signal.
Receive Direction. 7In the receive direction, the optical receiver converts the light
pulses from an NRZ-encoded IS-3 signal to equivalent electrical pulses. The
output from the optical receiver goes into a timing recovery device. The device
recovers 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 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 22D-U OLIU circuit pack interfaces with the SYSCTL and with the OHCTL
circuit packs.
The 22D-U OLIU circuit pack 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 22D-U OLIU circuit pack responds to control signals from the
SYSCTL, such as STS-1 routing, protection switching, and LED control
commands.
The 22D-U OLIU circuit pack accesses the SONET transport overhead and routes
it via the transport overhead channel interface to the AUXCTL slot and/or to the
SYSCTL. The transport overhead is routed from the main slots to both the
AUXCTL and SYSCTL slots and from the function unit slots to the AUXCTL slot.
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