Meanwhile, the EoS solution uses SONET ADM units to add/drop traffic from the TDM
ring (either OC-48 or OC-192). Here, each ADM has the ability to groom traffic in multiples
of STS-1 and comprises an STS cross-connect fabric. In addition, the EoS approach
uses SONET-based transponders and thin-mux blades. The latter commonly support
advanced features such as GFP and LCAS to optimize full/fractional rate EPL support.
For the purposes of this study, the SONET thin-mux is assumed to be a simple blade for
aggregating eight full-rate Fast Ethernet signals onto a OC-192c payload. Note that both
EoWDM and SONET solutions also require protection modules. Namely, SONET APS is
commonly done using the robust BLSR approach, whereas ROADM-based offerings can
deliver (proprietary) path protection in a dedicated or shared manner (see Table 8.8).
The overall cost summary of the EoWDM and EoS approaches is given in Table 8.9
(presented for OC-192 rates only). Here, it is seen that EoWDM is generally more
cost-effective for full-rate demands, particularly as the number of high-rate EPL demands
increases. Namely, EoWDM provides an almost 40 percent lower cost for the
large traffic scenario, and operational overheads are also expected to be much lower as
no ???box-stacking??? is needed.
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