A Novel Method to Calculate the Initial Phase Difference between the Two Fibre Arms of Laser Homodyne Interferometer

We suggest a novel method to calculate the initial phase difference between two fibre arms of a laser homodyne interferometer. Put the two fibre arms in a temperature controller, whose short term stability is 0.02°C (measured in an hour), then measure the interference photocurrent and the photocurrents from the two fibre arms at a fixed temperature. With these three photocurrents we can calculate the value of the initial phase difference. We set up a simple laser homodyne interferometer to test the theory. The experimental results are repeatable and the measurement precision is about 0.04°. It is theoretically and experimentally proven that this method is potentially easy and practical.