Local-oscillator excess-noise suppression for homodyne and heterodyne detection

The present investigation is concerned with a simple receiver arrangement which realizes the local-oscillator excess-noise-reduction scheme. The theoretical performance of the receiver is derived, and experimental results of excess-noise cancellation for GaAlAs laser local oscillators are presented. A comparison is conducted concerning the performance of the excess-noise-reduction receiver and that of a conventional receiver which uses a single detector. A mathematical model reported by Yuen and Chan (1983) is employed. The investigation involves the experimental demonstration of local-oscillator excess-intensity noise-power reduction in a receiver which uses two detectors. This receiver can achieve near-quantum-limited performance by using two matched detectors. It is pointed out that the considered receiver scheme should significantly affect the design of coherent homodyne/heterodyne laser-communication systems and sensor systems, particularly those which use semiconductor lasers as local oscillators.