The present invention relates to an optical 
transceiver that installs an optical transmitting 
assembly and an optical receiving 
assembly both are compact, inexpensive, and capable of operating at a high speed. The optical transmitting 
assembly of the present invention provides the 
metal bottom that installs the thermoelectric cooler thereon and the 
semiconductor optical device is mounted, via the insulating substrate, on the thermoelectric cooler. The first and second multi-layered 
ceramic substrates are provided to surround the thermoelectric cooler. The DC 
signal or the low-frequency 
signal for the thermoelectric cooler and the 
semiconductor optical device is supplied through the first 
ceramic substrate, while the 
high frequency signal for the 
semiconductor device, with the complementary signal having the opposite phase to the 
high frequency signal, is provided to the 
semiconductor device through the inner layer of the second 
ceramic substrate and the insulating substrate. The semiconductor light-receiving device, which monitors light emitted from the semiconductor light-emitting device, is mounted on the top layer of the second 
ceramic substrate. Thus, the transmission path for the 
high frequency signal from the drive circuit installed outside of the transmitting assembly to the light-emitting device becomes substantially linear.