Limitation on the local oscillator power in heterodyne detection

An experimental study on the characteristic of laser Doppler velocimetry known as heterodyne detection is reported. The experimental arrangement for the local-to-signal-beam ratio (LSR) determination is illustrated. The value of this ratio has been measured as a function of the power of the local beam, with an error not exceeding 10%. The height of heterodyne peak as a function of the power of the local beam has also been measured. The threshold power of heterodyne effect was estimated with an error of 9%.