Circuit Pack Descriptions
7-88 Issue 8.0 July 2002
reset and the FAULT LED on the circuit pack is continuously lighted. If an
incoming OC-48 signal fails, the FAULT LED will flash on and off.
General Description of Operation 7
The OC48 RCVR A/D circuit pack accepts the incoming OC-48 signal (2.5 Gb/s)
and converts it to an electrical STS-48 signal. The STS-48 signal is descrambled
and demultiplexed into sixteen 155.52 Mb/s signals. The SONET transport
overhead bytes are also extracted and sent to the Overhead Controller - Terminal
[OHCTL (TERM)] circuit pack. The 839B2 and 839B4B OC48 RCVR A/D circuit
pack then passes the sixteen 155.52 Mb/s signals to the low speed interface
circuit packs or the OC48 TRMTR A/D circuit pack in the opposite direction
(bidirectional ring applications).
The 839B5 OC48 RCVR A/D circuit pack demultiplexes the STS-48 electrical
signal into sixteen 155.52 Mb/s signals, which are fanned out to 54 STS-3 output
ports through two parallel STS-1 time slot assignment (TSA) crosspoint switch
devices. The sixteen 155.52 Mb/s signals are then passed to the low speed
interface circuit packs or the OC48 TRMTR A/D circuit pack in the opposite
direction (bidirectional ring applications).
Detailed Description of Operation 7
Transmission Circuitry 7
Figure 7-27 shows an overall block diagram of 839B2 and 839B4B OC48 RCVR
A/D circuit packs, and Figure 7-28 shows an overall block diagram of the 839B5
and 839E5 OC48 RCVR A/D circuit pack. The OC48 RCVR A/D circuit pack
accepts one 2.5 Gb/s non-return-to-zero (NRZ) SONET compatible optical signal.
Fiber access to the OC48 RCVR A/D circuit pack is via a fixed
ST
-type buildout
block and a removable
ST
-type, FC/PC-type, or SC-type lightguide buildout on the
circuit pack faceplate. Lightguide buildouts are chosen based on the attenuation
desired, and the type of connector interface the single-mode lightguide jumper is
equipped with. There are three types of lightguide buildouts available for the
OC48 RCVR A/D circuit pack:
ST
-type, FC/PC-type, and SC-type. All
factory-equipped OC48 RCVR A/D circuit packs come with a removable
ST
-type
0-dB lightguide buildout. When installing or removing lightguide buildouts, do not
pull the beam (front tab) outward. Pulling the beam (front tab) outward could result
in breaking the beam (front tab).
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