363-206-295
Circuit Pack Descriptions
Issue 1 December 1997 7-73
The STS-1 signals are byte-interleaved and scrambled in a frame synchronous
scrambler to produce a SONET format compatible STS-12 signal. The STS-12
signal is used to amplitude modulate a laser transmitter to convert the electrical
signal to an NRZ-encoded SONET compatible OC-12 optical signal.
Receive Direction. 7The 23H/23H-U OLIU circuit pack receives an OC-12 optical
signal that is an NRZ-coded SONET compatible signal. An optical receiver
converts the optical OC-12 signal to an electrical STS-12 signal. An STS-12 rate
clock is recovered and used to retime the data.
The 23H/23H-U OLIU frames on the retimed STS-12 data, demultiplexes it into 12
STS-1 signals, and provides the transport overhead access.
The 23H/23H-U OLIU performs pointer interpretation, frequency justification, and
pointer generation on each of the STS-1 signals, using the local clock and frame
from the selected TSI circuit pack. The result is 12 STS-1 signals that are frame
synchronous with each other and with the local clock and frame sync.
Each STS-1 signal is bridged to the service and protection TSI circuit packs.
The 23H/23H-U OLIU sends a clock derived from the recovered receive clock to
the TGS circuit packs for loop timing. The 23H/23H-U OLIU provides transport
overhead access in the receive direction.
Control Circuitry 7
The 23H/23H-U OLIU circuit pack interfaces with the SYSCTL and the OHCTL
circuit packs.
Control and Maintenance Functions. 7The 23H/23H-U OLIU provides
maintenance elements for reporting the status of the circuit pack and the incoming
STS-1 and OC-12 signals to the SYSCTL. Conversely, the 23H/23H-U OLIU
responds to control signals from the SYSCTL.
■ SYSCTL: The 23H/23H-U OLIU communicates with the SYSCTL circuit
pack via a control interface. The 23H/23H-U OLIU provides maintenance
elements for reporting the status of the circuit pack and the incoming STS-
1 and OC-12 signals. These maintenance elements are used by the
SYSCTL for fault detection and isolation. Conversely, the 23H/23H-U OLIU
responds to control signals from the SYSCTL, such as LED and protection
switching controls.
■ Transport Overhead Channel Interface: The 23H/23H-U OLIU accesses
the SONET overhead and routes this data to the OHCTL.
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