363-206-305
Circuit Pack Descriptions
Issue 3 June 2000
7-79
the backplane for STS-1 routing throughout the OC-3 shelf. The 26G2-U also
provides an STS-1 electrical interface to a companion 26G2-U OLIU which allows
the two OLIUs to be cross coupled.
Receive Direction.
7
In the receive direction, the optical receiver converts the light
pulses from an NRZ-encoded OC-1 signal to equivalent electrical pulses. The
output from the optical receiver goes into a recovery device. The transport
overhead processor circuit accepts the STS-1 bit stream, frames on the incoming
signal, descrambles it, and processes OC-1 transport overhead. The overhead
information is sent to the SYSCTL circuit pack.
The STS-1 output from the transport overhead processor is sent to the STS-1
pointer processor which performs pointer interpretation and generation. The
output of the STS-1 pointer processor is sent to the VT1.5 pointer processor.
STS-1 path overhead and VT1.5 pointer processing is performed. 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 two STS-1 signals to the appropriate
Main or Function Unit (MFU) slots and up to 8 VT-Gs to the low-speed slots.
The 26G2-U terminates an STS-1 optical signal, converts it to an electrical signal,
frames on and descrambles the signal, and processes the Transport Overhead
(TO).
Control Circuitry
7
The 26G2-U OLIU circuit pack interfaces with the BBG8/BBG8B system controller
(SYSCTL) via the intershelf control interface. The 26G2-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 26G2-U OLIU responds
to control signals from the SYSCTL such as STS-1 routing, VT1.5 routing,
protection switching, and LED control commands.
The 26G2-U OLIU accesses the SONET transport overhead and routes it to and
from the SYSCTL circuit pack.
Protection Circuitry
7
STS-1 and VT1.5 path protection switching, compliant with SONET specifications,
is provided. The 26G2-U OLIU is protection switched by the SYSCTL in response
to an external command, incoming optical signal failure, or internal equipment
fault. The 26G2-U OLIU circuit pack is protection switched by the SYSCTL when
the SYSCTL detects a fault on the active 26G2-U OLIU, and the companion
26G2-U OLIU is good.
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