which makes SFP 1.25Gb/s as the upgrade

The SFP 1.25Gb/s transceiver modules are hot-pluggable I/O devices that plug into module sockets. The transceiver connects the electrical circuitry of the module with the optical or copper network. GBIC transceiver, short name for the Gigabit Interface Converter, is a media conversion device between Gigabit Ethernet and fiber optic networks. Via the GBIC transceiver, Gigabit network equipment can directly connect to copper wires, single mode fiber ports or multimode fiber ports. SFP 1.25Gb/s can be regarded as the upgrade version GBIC. Unlike GBIC with SC fiber optic interfaces, cisco SFP is with LC interface. Moreover, its main body size of SFP is only about half of GBIC, which makes SFP space saving Sopto’s SFP 1.25Gb/s support both Gigabit Ethernet and 1x Fiber Channel applications and comply with Gigabit Ethernet requirements. They provide communications over SM and MM fiber and use an connector. Transmission occurs over VCSEL, FP, Distributed Feedback (DFB), or CWDM laser sources, and with PIN or APD receiver options. This product family also has Internal Digital Diagnostic options.