The pluggable amplifier can be designed in XFP, QSFP, OSFP, CFP2 and other package sizes. The usage is similar to an optical transceiver supporting hot-pluggability with the same interface protocol. Applications can be single- or multi – channel amplification or Variable Gain Amplifier. The output power of single channel amplifier can be around 10dBm. The gain of a multi-channel VGA gain can be adjusted typ. 10dB, and the power can be above 20dBm. This kind of amplifier are mainly used in OTN, PTN and other compact equipment to save space, development and maintenance costs.