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Analytic and simulative comparison of turbulent FSO system with different modulation techniques
摘要： In this paper, we characterize the performance of Intensity Modulation/Direct Detection (IM/DD) and coherent detection modulation techniques in free-space optical (FSO) communication system in terms of bit error rate (BER). The system of interest includes M-ary Pulse Position Modulation (M-PPM) in correspondence to IM/DD and M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) with respect to coherent detection. The system is subjected to weak turbulence regime of log-normal channel with scintillation index less than 0.75. Coherent techniques involve the amount of signal pulses transmitted in a particular time as the major component of their generation, except IM/DD which is a result of photon intensity, i.e. the number of photons forming a pulse. It is worth mentioning that in previous studies, the performance of IM/DD techniques had been evaluated in terms of photon-count fluctuation statistics and thus the impact of fading strength of channel on signal intensity was not discussed anywhere. In this work, an objective equivalence has been achieved between these two kinds of detection by deriving the BER expression of M-PPM in terms of probability density function of signal intensity, while considering fading strength, scintillation index, thermal noise and outage probability as system parameters for numerical analysis.
关键词： M-ary Pulse Position Modulation (MPPM),M-ary Phase Shift Keying (MPSK),M-ary Quadrature Amplitude Modulation (M-QAM),Intensity Modulation/Direct Detection (IM/DD),Scintillation index,Coherent detection
更新于2025-09-19 17:15:36
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Envelope Detection of 16QAM Single Carrier Signal for IM/DD RoF System at Q-band
摘要： In this paper, an envelope detection scheme of single carrier 16-ary Intensity-Modulation/Direct-Detection (IM/DD) radio-over-fiber (RoF) system is theoretically and experimentally investigated. Based on the proposed scheme, the mm-wave 16QAM signal is down-converted to the intermediate frequency (IF) 16QAM one by an envelope detector (ED) and there is no use of a mixer at the user side. We theoretically and experimentally study the performance of the signal under various conditions. In the system, 2GBaud 16QAM signal is delivered over 25km standard single mode fiber (SSMF) link and 2.9m wireless link under bit error rate (BER) of 3.8×10-3.
关键词： Radio-over-fiber (RoF),Intensity-Modulation/Direct-Detection (IM/DD),Envelope detection
更新于2025-09-19 17:15:36
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Long Distance IM/DD Transmission with OFDM-QAM based Quantum Noise Stream Cipher
摘要： We propose a QAM-based quantum noise stream cipher (QNSC) scheme for IM/DD transmission employing orthogonal frequency division multiplexing (OFDM) modulation. 2.5Gbit/s IMDD-OFDM signal is demonstrated over 1000 km distance. The experimental results show that Q penalty using IMDD-OFDM based QNSC is only 1.6 dB compared to QPSK without encryption in the cases of back-to-back condition and 1000km transmission.
关键词： orthogonal frequency division multiplexing (OFDM),quantum noise stream cipher (QNSC),intensity modulation/direct detection (IM/DD)
更新于2025-09-16 10:30:52