Communication transceiver architecture

A free space communication transceiver is provided with the following. A telescope for laser beam transmission and reception, A laser transmitting machine which generates a transmitting laser beam modulated by data and which can be aligned, A euphotic machine which processes a receiving laser beam received from a telescope, and recovers data and which can be aligned, A beam splitter which leads a transmitting laser beam to a telescope and leads a receiving laser beam from a telescope to a euphotic machine and which can be aligned. Transmission and a receiving laser beam pass through between a telescope and beam splitters along with a common optic axis as a parallel free spatial beam on the same straight line. Transmission and the receiving laser beam operate on an exchangeable different wavelength, and realize full duplex operation by it. An etalon filter in which the penetration characteristic of the wavelength dependence is adjusted according to a wavelength of transmission and reception and which can be aligned is used for a beam splitter. Alternatively, it may be combined with a common optic axis, and RF signal may be transmitted and received through a telescope.