Laser interferometer with low-frequency phase modulation

An analysis is made of a new interferometer with phase modulation which makes it possible to operate this instrument with tenfold variation in the output signal. The phase modulation parameters of the interferometer are set independently of the band width of the data signal subject to the requirement of the effective suppression of an interference band. Reconstruction of the spectral composition of the signal at the output of a separation filter makes it possible to use a modulation frequency much lower than the upper limiting frequency of the data signal. Examples are given of the use of an interferometer with a data signal band of width 0–1.6 MHz and a modulation frequency ≈1 kHz.