Abstract

The integrated-optic technology can provide rugged and compact devices/circuits for fiber sensors such as gyro [1,2] and LDV (laser Doppler velocimeter) [3,4]. In particular, the integrated-optic LDV seems to be promising for the practical use, because the Doppler-shifted signal light can be steadily heterodyne-detected via waveguides and fibers without influence of phase fluctuation caused by ambient temperature change. Very recently, we demonstrated the integrated-optic LDV pigtailed with a polarization-maintaining fiber, in which the whole heterodyne optics was integrated on a LiNbO₃ [3,4]. This is called the reference-beam (one-beam) type of LDV. On the other hand, the relatively higher signal-to-noise ratio is in general obtained in the differential (two-beam) type of LDV [5]. The latter type has more often been used in practice for velocity measurement. In this paper, we propose and demonstrate a novel integrated-optic differential LDV consisting of a LiNbO₃ waveguide device and a micro Fresnel lens (MFL) array.

© 1989 Optical Society of America