An optical transceiver implemented with a tunable LD is disclosed. The tunable LD is installed within a TOSA (Transmitter Optical Subassembly). The optical transceiver provides two circuit boards arranged in the up-and-down relation. The TOSA is primarily connected to the second board but signals to drive the tunable LD are carried on an FPC board directly connected to the first board that mounts a driver circuit for the tunable LD.