363-206-305
Circuit Pack Descriptions
7-78
Issue 3 June 2000
Detailed Description of Operation
7
Figure 7-31 is a block diagram of the 26G2-U OLIU circuit pack.
Figure 7-31. 26G2-U OLIU Circuit Pack Block Diagram
Transmission Circuitry
7
STS-1 Router and VT1.5 Cross-Connect.
7
The STS-1 router is used to select STS-
1s for both the transmit and receive directions. All incoming STS-1s are fed to the
VT1.5 cross-connect. The outgoing STS-1 may be sourced by this VT1.5 cross-
connect or sourced directly by an STS-1 input.
Transmit Direction.
7
In the transmit direction (from the low-speed slots toward the
optical interface), the VT-G signals from the low-speed slots are combined into an
STS-1 signal. SONET path overhead is then added to STS-1 sourced by the
VT1.5 cross-connect before the signals are sent to the transport overhead
processor. The transport overhead processor takes the STS-1 signal, adds
SONET transport overhead, then scrambles the signal with a frame synchronous
scrambler. The output from the transport overhead processor is in the SONET
STS-1 format and is used to modulate the amplitude of the laser transmitter,
converting the electrical signal to an NRZ-encoded SONET compatible OC-1
optical signal.
In the OC-3 shelf, the 26G2-U OLIU provides an interface between the STS-1
optical signal and electrical VT-G signals. Three STS-1 paths will be brought out to
Protection
Switch
Selector
7 of 8
VT-G to STS-1
Mulitplexer
(STS-1 to VT-G
Demultiplexer)
VT-G
S1
VT-G
S2
VT-G
S3
VT-G
S4
VT-G
S5
VT-G
S6
VT-G
S7
S8
(P)VT-G
+5V PWR
Timing
VT-G
VT-G
VT-G
VT-G
VT-G
VT-G
VT-G
VT-G
STS-1
VT1.5
Pointer
Processor
Adds STS-1
Path Overhead
Removes STS-1
Path Overhead
STS-1
Pointer
Processor
Wide Section
and Line OH
Converts STS-1
into OC-1
Converts OC-1
to STS-1
Processes
Section and Line
OH
SONET
Transport OH
To/From SYSCTL
Tx Fiber
Transport
Overhead
Processor
OC-1
OC-1
Rx Fiber
Timing
Recovery
Timing
Generator,
Holdover,
Fanout
Timing
To
Function
Unit
Slots
Intrashelf
Control
From Shelf
-48V Fuses
To/From
SYSCTL
Timing
STS-1
To/From
Low
Speed
Slots
To
Low
Speed
Slots
To/From
Companion
OLIU
STS-1
Router
and
VT1.5
Cross-
Connect
and
Path
Protection
Switch
STS-1
To/From
Companion
OLIU
-48 V A
-48 V A
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