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Optical Engineering

Pulse position modulation for compact all-fiber vehicle laser rangefinder development
Author(s): Xuesong Mao; Yongzhi Cheng; Ying Xiong; Daisuke Inoue; Manabu Kagami
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Paper Abstract

We propose a method for developing small all-fiber vehicle laser rangefinders that is based on pulse position modulation (PPM) and data integration and present a theoretical study on its performance. Compared with spatial coupling, which is employed by most of the current commercial vehicle laser rangefinders, fiber coupling has the advantage that it can guide laser echoes into the interior of a car, so the electronic components following the photodiode can operate in a moderate-temperature environment. However, optical fibers have numerical apertures (NAs), which means that a laser beam from a receiving lens cannot be coupled into an optical fiber if its incident angle exceeds the critical value. Therefore, the effective size of the receiving lens is typically small since it is limited by its focal length and the NA of the fiber, causing the power of the laser echoes gathered by the receiving lens to be insufficient for performing target identification. Instead of increasing the peak transmitting laser power unrestrictedly, PPM and data integration effectively compensate for the low signal-to-noise ratio that results from the effective receiving lens size reduction. We validated the proposed method by conducting numerical simulations and performance analysis. Finally, we compared the proposed method with pseudorandom noise (PN) code modulation and found that, although the two methods perform equally well in single-target measurement scenarios, PPM is more effective than PN code modulation for multitarget measurement. In addition, PPM enables the transmission of laser beams with higher peak powers and requires less computation than PN code modulation does.

Paper Details

Date Published: 12 October 2017
PDF: 8 pages
Opt. Eng. 56(10) 107102 doi: 10.1117/1.OE.56.10.107102
Published in: Optical Engineering Volume 56, Issue 10
Show Author Affiliations
Xuesong Mao, Wuhan Univ. of Science and Technology (China)
Yongzhi Cheng, Wuhan Univ. of Science and Technology (China)
Ying Xiong, Wuhan Univ. of Science and Technology (China)
Daisuke Inoue, Toyota Central R&D Labs., Inc. (Japan)
Manabu Kagami, Toyota Central R&D Labs., Inc. (Japan)

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