SEQUENCE-CODED LASER RANGE-FINDERS
Most laser range-finders are based on the transmission of short, isolated and intense pulses, and measurement of the time-of-flight of reflected echoes. The instantaneous peak power levels of transmitted pulses in such devices must be rather high. Our group and collaborators have proposed and demonstrated an alternative scheme for a laser range-finder, which is based on the transmission of extended, coded sequences. The peak power levels that are necessary are lower by orders of magnitude. Range is recovered through the proper post-processing of extended detected echoes. The principle was successfully implemented based on simple semiconductor laser diode sources and semiconductor optical amplifiers. Sensitivity may be enhanced further in using coherent detection. We have recently demonstrated successful distance measurements over fiber with a collected energy of only 800 photons, spread over many code bits. The average energy of collected back reflection during each coding symbol was the equivalent of only 0.002 the photon energy.
• K. Shemer, G. Bashan, H. H. Diamandi, Y. London, T. Raanan, Y. Israelashvili, A. Charny, I. Cohen, A. Bergman, N. Levanon, and A. Zadok, "Sequence-coded coherent laser ranging with high detection sensitivity," OSA Continuum 3, 1274-1282 (2020).
• N. Arbel, L. Hirschbrand, S. Weiss, N. Levanon and A. Zadok, "Continuously Operating Laser Range Finder Based on Incoherent Pulse Compression: Noise Analysis and Experiment," IEEE Photonics 8, 6801211, (2016).