Soft demodulation to the optical pulse position modulated signals

Tian-hua Zhou; Wei-biao Chen

doi:10.1117/12.830690

28 August 2009 Soft demodulation to the optical pulse position modulated signals

Tian-hua Zhou, Wei-biao Chen

Proceedings Volume 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging; 738223 (2009) https://doi.org/10.1117/12.830690
Event: International Symposium on Photoelectronic Detection and Imaging 2009, 2009, Beijing, China

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.

Citation Download Citation

Tian-hua Zhou and Wei-biao Chen "Soft demodulation to the optical pulse position modulated signals", Proc. SPIE 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging, 738223 (28 August 2009); https://doi.org/10.1117/12.830690

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