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Proceedings Paper

Soft demodulation to the optical pulse position modulated signals
Author(s): Tian-hua Zhou; Wei-biao Chen
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Paper Abstract

The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the low average power and the high peak power. The transmitted PPM information depends on the location of the coming optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The key of PPM digital soft modulation is the establishment of the synchronization that involves the segment synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head. Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the experiments, results with high sensitivity and low bit error rate have been achieved.

Paper Details

Date Published: 29 August 2009
PDF: 7 pages
Proc. SPIE 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging, 738223 (29 August 2009); doi: 10.1117/12.830690
Show Author Affiliations
Tian-hua Zhou, Shanghai Institute of Optics and Fine Mechanics (China)
Shanghai Key Lab. of All Solid-State Laser and Applied Techniques (China)
Wei-biao Chen, Shanghai Institute of Optics and Fine Mechanics (China)
Shanghai Key Lab. of All Solid-State Laser and Applied Techniques (China)


Published in SPIE Proceedings Vol. 7382:
International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging

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