Electronics for Analog Signal Processing in an Optical Phased Array

Abstract

Optical free-space communication will be a key building block for future information systems. However, when the link includes part of the atmosphere, clear-air turbulence induces serious phase distortions and fading to the optical link. To mitigate this fading using spatial diversity techniques, it is necessary to replace the single receiver with a receiver array, where each individual detector observes a different section of the received optical beam. Caused by atmospheric turbulence, the individual detectors of the array will detect different amplitudes and phases, which shall be phase corrected and combined in the electrical domain. In this context, the feasibility to restore the modulation contents of an atmospherically distorted wave-front using complex vector modulators needs to be explored. If atmospheric fading information is known for each aperture, the corresponding output electric signals can be adaptively processed, co-phased, and scaled by electronic vector modulators before they are summed, mitigating signal fading caused by atmospheric turbulence. In this activity we plan to characterise electronic properties, such as communication bandwidths and control response time, of several commercially available vector modulators.