Large-Range and Highly Sensitive Displacement Measurement with an Optical Carrier-based Microwave Interferometry

In this paper, we proposed a wide-range and highly sensitive displacement measurement system based on the optical carrier-based microwave interferometry (OCMI), in which two kinds of optical carriers are used. Theoretical analyses have been carried out to investigate the effect of the initial phase caused by the length difference between the sensing arm and the reference one on the measurement sensitivity. It suggests that the smaller the initial phase induced by the arm length difference, the higher the measurement sensitivity is. Experimental results show that the system utilizing lasers as optical carriers can greatly reduce the initial phase and the measurement sensitivity is more than twice that of the system using broadband light source acting as carrier in a 3 GHz bandwidth. The measurement accuracy is 4 μm and the measurement range is more than 40 mm, as well as the stability is within ±2 μm. As a result, the proposed displacement measurement system possesses the merits of wide measurement range, high sensitivity and high accuracy, which offers great potentials in the fields of precise displacement measurement.