Frequency-Path Modeling for Three-Longitudinal-Mode Interferometer

In this paper, a frequency-path model for three-longitudinal-mode interferometer (TLMI) is presented. The model describes two main error sources that affect the accuracy of displacement in heterodyne interferometers. Unwanted leakage between the reference and the target paths and inter-modulation error due to the nonlinearity of current to voltage converter, double balanced mixer, and pre-amplifier are two main error sources in the TLMI. Using a three-longitudinal-mode stabilized He-Ne laser, six frequency-path components and 21 distinct interference terms is produced.