Common Management Interface Specification (CMIS) defines, starting with revision 4.0, a standard mechanism for managing the firmware of compliant transceivers. This mechanism allows for transceivers’ firmware to be updated without having to remove the transceiver from the switch. Firmware updates may be necessary in a testing or production environment to resolve potential firmware bugs. Some transceivers may also support firmware management operations in a hitless manner (without impacting traffic).

Coherent transceivers, compliant with Coherent Common Management Interface Specification (C-CMIS) maintain two sets of thresholds to detect and report two types of link degradation: FEC excessive degrade (FED) and FEC detected degrade (FDD).

Common Management Interface Specification (CMIS) compliant transceivers are configured by selecting an

In an optical transceiver, electrical signals leaving the switch are converted to optical signals in the transmit path. Optical signals arriving at the transceiver are converted to electrical signals that enter the switch in the receive path. At the point of conversion, an automatic decision can be made to turn off (squelch) output when the input level drops below a certain threshold of usability (usually, LOS condition.) This is referred to as automatic squelching.