This document specifies the technical details of the DWDM-SFP10G-40-C57-T02 10G 1531.90nm 40km DWDM SFP+ transceiver. It includes specifications for optical and electrical characteristics, functional diagrams, pin definitions, digital diagnostic monitoring interface support, and ordering information. The transceiver is designed for 10GbE links up to 40km over single-mode fiber and supports real-time monitoring of parameters like temperature, power levels, and bias current through its digital diagnostic interface.