Reference-beam storage for long-range low-coherence pulsed Doppler lidar

We present a laser Doppler velocimeter that stores and delays the reference beam to preserve coherence with a long-path-length measurement beam. Our s torage and delay technique relaxes the strict coherence requirements associ ated with Lidar laser sources, permitting the use of low-coherence lasers. This technique potentially could reduce the cost and size of lidar systems for commercial applications. Experiments that use fiber-optic ring resonato rs to store the reference beams and generate reference pulse trains validat ed the concept. We obtained results at several simulated distances by beati ng each usable reference purse with a delayed Doppler-shifted measurement b eam reflected off a rotating mirror. (C) 2001 Optical Society of America.