Phase-Locked Synthetic Wavelength Interferometer Using a Femtosecond Laser for Absolute Distance Measurement without Cyclic Error

Abstract

We present a phase-locked synthetic wavelength interferometer that enables a complete elimination of cyclic errors in absolute distance measurements. With this method, the phase difference between the reference and measurement paths is fed back into a phase lock-in system, which is then used to control the synthetic wavelength and set the phase difference to zero using an external cavity acousto-optic modulator. We validated the cyclic error removal of the proposed phase-locked method by comparing it with the conventional phase-measuring method of the synthetic wavelength interferometer. By analyzing the locked error signal, we achieved a precision of 0.6 mrad in phase without any observed cyclic errors.

Impact of Cyclic Error on Absolute Distance Measurement Based on Optical Frequency Combs

“…Data processing and some algorithms are useful for compensating cyclic error [ 36 , 37 , 38 , 39 , 40 ]. H. Kang et al demonstrated a cyclic-error-free system by dynamically linking the synthetic wavelength to a divisor of the distance under test [ 41 ]. However, eliminating all the crosstalk signals from one system is extremely difficult.…”

Study on TPD Phasemeter to Suppress Low-Frequency Amplitude Fluctuation and Improve Fast-Acquiring Range for GW Detection

“…For GW detection, the displacement accuracy should be at least 1 pm/Hz 1/2 , taking the laser frequency, RIN, TTL, etc., into consideration, and the noise of the phase readout system should be less than 0.2 pm/Hz 1/2 , which corresponds to about 1 μrad/Hz 1/2 . The phasemeter is also used in beam pointing, data communication, GNSS, and absolute distance measurement [ 9 , 10 , 11 ].…”