The Key Differences Between GPON SFP Class B+ and C+ are their TX power and RX Sensitive. Class C+ ONU. SFP stands for "Small Form-factor Pluggable," and GPON SFP is a gigabit optical transceiver designed specifically for GPON systems, adhering to the ITU-T G. This bidirectional module, equipped with an SC receptacle, operates over simplex single-mode fiber optic cables. These modules are typically installed in Optical Line Terminals (OLTs) at the service provider's central office and Optical Network Units (ONUs) or Optical Network. Otherwise, the optical module may be burnt. In practice, the maximum upstream service bandwidth is 1. 5~5dBm, and its receiver sensitivity is -28dBm while the sending power of Class C+ is 3~7dBm and receiver sensitivity -32dBm.