The WAN PHY module will appear to your SDH network as a SONET tributary interface. Its signal will need to be carried intact as an OC-192 (approximately 10 Gbps) across the SDH network since it's not a bunch of STS payloads but rather a single 10 Gbps IP stream encapsulated in SONET framing. Other than that, it should be able to feed your SDH network's ADM just fine (given attention to your optical power levels, etc.).
Hope this helps, please rate helpful posts.
