Analysis of signal-to-noise ratio and heterodyne efficiency for reference-beam laser Doppler velocimeter

Heterodyne efficiency is a very important factor in a laser Doppler velocimeter (LDV). Gaussian-Airy mode is put forward to analyze the heterodyne efficiency. By studying the distribution of the optical field, the mathematic expression and simulation results of heterodyne efficiency are given under the conditions of both exact match and mismatch. The results of numerical analysis show that heterodyne efficiency of LDV depends on Gaussian beam's parameter Q, detector's parameter X0, angle of collimation mismatching θa, parameter of offset mismatching Xa and the radius of curvature of the reference beam on the detector R(z). Heterodyne efficiency can reach 83.39% when Q=4.15×10−7, X0=6.1×10−7, θa=Xa=0, R(z)=∞. But it declines to 0.5 when Fθa enhances to 0.28. It decreases with the increment of the offset Xa and the diminishment of the radius of curvature R(z). Results of experiment are in good accordance with the theoretical analysis.

► Formula of the signal-to-noise ratio is researched in reference beam laser Doppler velocimeter. ► Simulation results of heterodyne efficiency are given when there are exact match and mismatch. ► Reference-beam LDV presented in this paper is used for a vehicle inertial navigation system.