The SPB-37120W-1590G series is small form factor pluggable module for IEEE 802.3ah 100BASE-BX and OC-3/STM-1 SONET/SDH single fiber communications by using 1590 nm transmitter and 1510 nm receiver. It is with the SFP 20-pin connector to allow hot plug capability. Digital diagnostic functions are available via an I2C. The transmitter section uses a multiple quantum well 1590 nm laser and is a class 1 laser compliant according to International Safety Standard IEC 60825. The receiver section uses an integrated 1510 nm detector preamplifier (IDP) mounted in an optical header and a limiting post-amplifier IC.