The form factor and electrical interface are often specified by an interested group using a multi-source agreement (MSA). Optical modules can either plug into a front panel socket or an on-board socket.OverviewAn optical module is a typically hot-pluggable optical transceiver used in high-bandwidth data communications. There have been multiple variants of the electrical interface of optical modules that have been used over the years. The earliest forms of optical modules had an analog electrical interface. In the transmit dir. Many different forms of optical modulation and multiplexing have been employed in optical modules. The most common modulation technique historically has been or NRZ.