Linearization of the frequency sweep of a frequency-modulated continuous-wave semiconductor laser radar and the resulting ranging performance

The performance of a frequency-modulated continuous-wave (FMCW) semiconduct or laser radar has been examined, Frequency modulation (linear chirp) has b een studied experimentally in detail. To create a linear frequency sweep, w e modified the modulating function according to the measured frequency resp onse of the laser, using an arbitrary function generator. The measurements indicate the possibility of achieving a spectral width of the signal peak t hat is transform limited rather than limited by the frequency modulation re sponse of the laser, which permits the use of a narrow detection bandwidth. The narrow width results in a relatively high signal-to-noise ratio for lo w output pourer and thus also in relatively long-range and high-range accur acy. We have performed measurements of a diffuse target to determine the pe rformance of a test laser radar system. The maximum range, range accuracy, and speed accuracy for a semiconductor laser with an output power of 10 mW and a linewidth of 400 kHz are presented. The influence of the laser's outp ut power and coherence length on the performance of a semiconductor-laser-b ased FMCW laser radar is discussed. (C) 1999 Optical Society of America.