Performance analysis of a noncoherently combined large aperture optical heterodyne receiver

The performance of a noncoherently combined, multiple-mirror heterodyne receiver is analyzed. In the absence of atmospheric turbulence, the performance of the noncoherently combined receiver is shown to be inferior to that of a monolithic, diffraction-limited receiver with equivalent aperture area. when atmospheric turbulence is taken into consideration, however, the efficiency of a monolithic aperture heterodyne receiver, is limited by the phase coherence length of the atmosphere, and generally does not improve with increasing aperture size. In contrast, the performance of a noncoherently combined system improves with an increasing number of receivers. Consequently, given a fixed collecting area, the noncoherently combined system can offer a superior performance. The performance of the noncoherently combined heterodyne receiver is studied by analyzing the combining loss of the receiver SNR (signal-to-noise ratio). It is shown that, given a constant collecting area, the performance of the combined receiver is optimized when the diameter of each of the individual receivers is on the order of the phase coherence length r₀ of the atmospheric turbulence