Heterodyne detection of partially coherent optical signal
Abstract
The SN ratio is studied for the case when a partially coherent plane wave signal undergoes heterodyne detection after it is focused by a lens of finite size and is mixed with a coherent LO signal. Cases where the natural logarithm of the degree of spatial coherence of the signal on the aperture is proportional to the nuth power of the distance between two arbitrary points are considered. It is found that the mutual coherence function of the signal on the detector can be expressed in series form and that the results can be used to obtain an expression for the SN ratio suitable for numerical calculations. The analysis is also effective for a signal with an arbitrary degree of coherence dependent only on the distance between two points. The SN ratio is investigated numerically with the correlation length on the aperture and the detector radius as parameters. It is found that, regardless of the correlation length, the detector radius of the order of the Airy disk is sufficient for obtaining an SN ratio almost equal to the maximum value determined for each correlation length.
 Publication:

Electronics Communications of Japan
 Pub Date:
 September 1981
 Bibcode:
 1981JElCo..64...97T
 Keywords:

 Coherent Light;
 Optical Communication;
 Optical Heterodyning;
 Signal Detection;
 Background Noise;
 Fourier Transformation;
 Signal To Noise Ratios;
 Optics