Mach-Zehnder interferometry as a spectral analyzer for molecular Doppler wind lidar

The theoretical performance of a Mach-Zehnder interferometer used as a spec tral analyzer for windspeed measurement by direct-detection Doppler lidar i s presented. The interferometer is optimized for measurement of wind veloci ty from the signal backscattered by the molecules. Two arrangements are pro posed, involving two detection channels (DMZ) or four detection channels (Q MZ). Using the assumption of a pure molecular signal with a Gaussian spectr al profile, we derive an analytic expression for the standard deviation of the measurement error for each arrangement. They are then compared with the ideal spectral analyzer (ISA) and with the double-edge Fabry-Perot (DFP) i n the case of a shot-noise-limited signal. The DMZ measurement error is sho wn to be only 1.65 times that of the ISA and is 1.4 times lower than that g iven by the DFP. The QMZ arrangement provides a measurement that is insensi tive to the aerosol scattering contribution but gives a measurement error t hat is 1.4 times higher than that of the DMZ. (C) 2001 Optical Society of A merica OCIS codes: 280.0280, 280.3640, 010.3920.