The full form of CSFP is "Compact Small Form-Factor Pluggable." The CSFP is a compact and multifunctional transceiver module designed for use in optical communication systems. It is based on the SFP (Small Form-Factor Pluggable) standard but is smaller in size. The CSFP module is capable of supporting both upstream and downstream data transmission, making it suitable for bidirectional communication over a single fiber optic cable.

CSFP modules are commonly used in scenarios where space is limited or where the deployment of separate transmitters and receivers for upstream and downstream traffic is not practical. They are often utilized in access networks, fiber-to-the-x (FTTx) applications, and other point-to-multipoint fiber optic communication systems.

It's important to note that the CSFP is not as widely adopted as some other transceiver form factors like SFP, SFP+, QSFP, etc., and its use may depend on specific equipment and network configurations.