Optical components and technology in laser space communications systems

Passive linear optical components play a primary role in an optical communications system for use in space applications. The important functions of acquisition, tracking, transmit-beam off-set, and background-noise discrimination may be efficiently implemented using passive optical elements. These specific system functions are discussed with reference to a representative system in order to identify the required features of particular optical components. This is followed by a detailed discussion of the optical components including: a 1/2-Å Fabry-Perot filter; a transfer-lens/optical-image-divider combination capable of 0.1-second of arc tracking accuracy; variable deviation wedges for transmit-beam offset; dichroic beamsplitters for isolation between the transmit and receive beams; and an axicon for redistributing the Gaussian energy profile from a TEM
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-mode laser to match the obscured circular aperture of a conventional Cassegrainian telescope.