363-206-305
Transmission and Synchronization
5-2
Issue 3 June 2000
T1 Transmission Interface
5
The DDM-2000 FiberReach wideband shelf supports a T1 interface. The interface
accepts two T1 signals. The two signals are mapped into a standard VT1.5 signal,
and then multiplexed into one VT-G signal.
Transmission and Architecture
5
Wideband Shelf Interfaces and Multiplexing
5
The DDM-2000 FiberReach wideband shelf supports DS1, HDSL (with 28G-U/
28G2-U [Release 3.1] and 29-type [Release 4.0] OLIUs) and T1 carrier extension
interfaces. The DS1 interface accepts any DSX-1 compatible signal (clear channel
interfaces). When equipped with 28-type or 29-type OLIUs, the shelf supports 1
protected or 2 unprotected DS3 interfaces, or a single OC-3c interface. When
equipped with 26G2-U OLIUs and with Release 4.0, the shelf supports 1
protected or 2 unprotected DS3 interfaces.
Figure 5-1 is an overall block diagram of the DDM-2000 FiberReach Multiplexer.
Internally, the Multiplexer uses synchronous optical network (SONET) standard
multiplexing. (Refer to Appendix A.) On the low-speed side, asynchronous DS1
signals map into floating mode VT1.5 signals. The VT1.5 signals are combined
into virtual tributary groups (VTGs) and then multiplexed to one STS-1 signal. This
VT structured STS-1 signal can be combined with an STS-1 signal from the
function unit slots along with a pass through STS-1 to form an OC-3 signal.
In the opposite direction, a received OC-N signal is converted back to “N”
electrical STS-1 signals. A DS1-formatted STS-1 signal is demultiplexed to VT
groups and then to VT1.5 signals. The VT1.5 signals are then converted to DS-1
signals prior to connecting to the DS1 interface.
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