Differential Laser Doppler Velocimeter With Enhanced Range for Small Wavelength Sensitivity by Using Cascaded Mach–Zehnder Interferometers

A differential laser Doppler velocimeter (LDV) with enhanced wavelength range for small wavelength sensitivity is proposed by using cascaded Mach-Zehnder interferometers (MZIs) for shifting the position of the beam at the input plane according to the wavelength. The cascaded MZI structures are used to enhance the position shift of the beam at the input plane compared with the use of single-stage MZIs. The gradual shift in the incident angle of the beam to the object is brought about with the combination of cascaded MZI structures, lenses and apertures. The simulation results indicate that the wavelength range for small wavelength sensitivity can be successfully enhanced by using two-stage cascaded MZI structures.