363-206-295
Applications
2-18
Issue 1
December 1997
DDM-2000 OC-3, OC-12, and FT-2000 OC-48 Lightwave Systems can be
configured to offer this topology. Often the DDM-2000 equipment is used for the
loop feeder access ring, and the FT-2000 OC-48 Lightwave System equipment is
used for the interoffice ring. Figure 2-11 shows a DDM-2000 OC-3 (or OC-12)
path switched ring interworking with an FT-2000 OC-48 Lightwave System
bidirectional line-switched ring.
In this application, the DDM-2000 provides an appearance of loop traffic at both
the primary and secondary nodes by dropping traffic at the primary node and
simultaneously continuing it on to the secondary node. This capability is called
"drop-and-continue." The DDM-2000 OC-3 Multiplexer allows DS1 signals to be
multiplexed for handoff at an economical EC-1 or OC-3 rate in the COs. Also, the
DDM-2000 OC-3's flexible TSI can be used to prepackage all DRI protected DS1s
into a single EC-1 for economical handoff to the OC-48 ring. This capability allows
for the easy mixing of DRI and non-DRI services on the same ring network. In this
way, only specially tariffed services need to be configured for the extra reliability
that DRI provides. DS3/STS1 clear channel services are also supported. The
companion FT-2000 OC-48 Lightwave System ring picks up the traffic at these two
nodes and carries it to the destination node, unless a failure condition causes a
protection switch to the secondary signal. In the reverse direction, a similar
process is followed with the OC-48 ring handing off the two copies of the signal at
the primary and secondary nodes and the OC-3 ring providing the switching at the
destination node.
