Multiplexing Free Space Optical Communication Research Articles

Hybrid channel coding for OAM division multiplexing free space optical communication systems.

An orbital angular momentum division multiplexing free space optical communication (OAM-DM FSO) system with channel coding can compensate atmospheric channel fading and improve system performance. An OAM-DM FSO system based on hybrid channel coding is proposed in this paper. The coding gain is improved by taking into account mode dependent channel fading difference caused by atmospheric turbulence. Simulation results show that compared with single channel coding, the coding gain is increased by 1.85 dB under Cn2=1E-14, BER=1E-5 with non-uniform LDPC code (0.7 code rate) for an OAM1/OAM3 multiplexing system. In addition, for four OAM modes (+1,+3,+5,+7) multiplexing systems, the coding gain is increased by more than 3.8 dB under Cn2=1E-14 and BER=1E-5.

Performance improvement of mode division multiplexing free space optical communication system through various atmospheric conditions with a decision feedback equalizer

Performance improvement of mode division multiplexing free space optical communication system through various atmospheric conditions with a decision feedback equalizer

Performance Analysis of Relay Assisted Multihop Coherant OFDM System over Malaga Distribution with Pointing Errors

Abstract This paper presents a multi-hop coherent orthogonal frequency division multiplexing free space optical communication system (OFDM-FSO) model which includes a relay transmission mode of decode and forward (DF) over Malaga disrubution (M) and we analyse the results by deriving mathematical expressions for average bit error rate (BER) and outage probability. And the FSO link is characterized by path loss, pointing errors and atmospheric turbulence and also weather conditions like clear air, haze, light fog have been considered in the channel model. The BER and outage probability of the proposed system are examined including the effects of pointing errors and weather conditions. From this work, we can justify that with multi-hop configuration coverage area and signal power improves which bolsters the usage of relay in FSO communication for efficient and reliable system design.

Saturation in wavelength-division multiplexing free-space optical communication systems

The performance of a wavelength-division multiplexing (WDM) free-space optical (FSO) communication system in a turbulent atmosphere employing optical amplifiers to improve capacity is investigated, in the presence of amplified spontaneous emission noise, scintillation, beam spreading, atmospheric attenuation and interchannel crosstalk. Using on-off keying modulation, Monte Carlo simulation techniques are used to obtain the average bit error rate and system capability due to scintillation and the effect of introducing a power control algorithm (PCA) to the system is investigated. The PCA ensures that at any receiving instant, the same turbulence-free powers are received by all the receiving lenses. The performance of various WDM FSO communication system configurations such as non-amplified systems with an adaptive decision threshold (NOAADT), nonamplified systems with a non-adaptive decision threshold, fixed gain amplified systems with an adaptive decision threshold, fixed gain amplified systems with a nonadaptive decision threshold and saturated gain amplified systems with a non-adaptive decision threshold (SOANADT) are investigated. Results obtained show that the SOANADT is superior to the NOAADT and the PCA is only beneficial in amplified systems.

On the Performance of Coherent OFDM Systems in Free-Space Optical Communications

This paper presents a new model of a coherent orthogonal frequency division multiplexing free space optical communication (OFDM-FSO) system that can be tuned with the virtual local oscillator, under the Gamma-Gamma atmospheric turbulence channel, not only considering the intensity scintillation but considering the phase noise caused by atmospheric turbulence effect on the performance of the system as well. The mapping mode of the OFDM signal uses 16-quadrature amplitude modulation (QAM) with better performance. On this basis, we derived the closed form of the symbol error rate and interrupt probability, respectively. In this paper, we analyzed under the premise of the different number of subcarriers, the influence of each parameter of atmospheric channel on the bit error, and the communication interrupt performance of the OFDM-FSO system, respectively. The results show that the coherent OFDM-FSO system can obtain higher sensitivity and can overcome the bad atmosphere influence to obtain good performance of the system.