HETERODYNE LADER SYSTEM EFFICIENCY ENHANCEMENT USING SINGLE-MODE OPTICAL-FIBER MIXERS

A theoretical performance analysis of a heterodyne radar system incorp orating a single-mode fiber receiver has been performed. For our purpo ses, the performance parameters of interest are the coupling and mixin g efficiency of the ladar receiver, as they relate to the overall syst em carrier-to-noise ratio. For a receiver incorporating a single-mode fiber mixer, the received and local-oscillator fields are matched both spatially and temporally at the detector, yielding 100% mixing effici ency. We have therefore focused our efforts on determining an expressi on for the efficiency with which a diffuse return from a purely speckl e target can be coupled into the receiving leg of a monostatic, untrun cated cw radar system. Through numerical analysis, the expected coupli ng efficiency for a ladar system with negligible truncation of the tra nsmit beam has been determined to be 30.6%.