Optical Service Channel Module

The optical service channel module (OSCM) provides a point-to-point, bidirectional communications link between DWDM nodes. This communications linkthe optical service channel (OSC)is similar in function to the data communications channel (DCC) used in Synchronous Optical Network (SONET) topologies. However, in addition to providing an out-of-band DWDM communications link, the OSCM interface card provides other functions in an MSTP network, such as clock synchronization and orderwire channel communications. The OC-3 formatted optical service channel is considered out-of-band because it operates at the 1510 nm wavelength, which is typically outside of the erbium-doped fiber amplifier (EDFA) pass-band of 1528 to 1565 nm.

Because the optical service channel is a point-to-point link, two OSCM interface cards are required for most configurationsone for the East-to-West span, and one for the West-to-East span. The OSCM interface card operates solely in Slots 8 or 10 on the ONS 15454 shelf assembly. It is important to note that the OSCM is used in amplified MSTP configurations only. For amplified MSTP systems, the optical service channel is split from the composite DWDM fiber signal at the booster amplifier before being distributed to the OSCM card. For unamplified (passive) DWDM configurations, the optical service channelcombiner/separator module (OSC-CSM) interface card (detailed in the next section) is used.

In addition to the OC-3 formatted optical service channel, the OSCM card provides a 100-Mbps user data channel (UDC). The UDC uses the OC-3 payload bandwidth of the optical service channel and can be accessed on the front faceplate of the OSCM using an RJ45 connector.

Figure 9-3 shows the faceplate layout of the OSCM.

Figure 9-3. OSCM Card Faceplate Diagram