Free-Space Communication Turbulence Compensation by Optical Phase Conjugation

Abstract

A new scheme is proposed to mitigate the atmospheric turbulence effect in coherent free-space optical (FSO) communications by employing optical phase conjugation (OPC) to compensate the signal distortion. The compensation performance of the dual-hop FSO transmission link is simulated using the phase screen method for quadrature phase-shift keying (QPSK) signals. The results show that the bite error rate (BER) can be effectively reduced and the OPC correction is tightly affected by the OPC receiving aperture in strong turbulence regimes. The dual-hop FSO link with the OPC correction is experimentally demonstrated in a turbulence-tunable atmospheric cell, where the OPC is achieved by using degenerate four-wave mixing (DFWM) in a 110-m-long highly nonlinear fiber. At the BER of × − , the power penalty for dual-hop link with OPC correction decreases about 1.2 dB and 2 dB compared with the single-trip link and the non-compensation dual-hop link. The result demonstrates that the OPC unit can improve the performances of the coherent FSO communication, and it has the potential to be extended to higher-order modulation formats and higher bit rate processing.

Modulator-Free Variable Multi-Rate FSO Communication 1 km Outfield Demonstration Based on Chirp-Managed Laser

“…For an FSO communication system, the signal quality will suffer deterioration due to background radiation, atmospheric scattering, and scintillation or beam drift caused by atmospheric turbulence [17], [19], which can lead to data loss and increased transmission BER. Furthermore, the stability of the optical antenna, and the noise of the amplifier also influence the signal quality, which consequently degrades the communication performance [20], [21]. Subsequently, we will consider implementing adaptive optics systems to eliminate the effect of atmospheric turbulence, thereby improving the stability of the system.…”

Performance analysis of multiple-beam WDM free space laser-communication system using homodyne detection approach

“…In Ref. [ 20 ], mitigation of turbulences by optical phase conjugation technique. The FSOC reliability was examined in Srinagar, Chandigarh, Jodhpur, and Chennai.…”

Demonstration of an optical phase conjugation based dual‐hop PDM‐QPSK free‐space optical communication link

“…However, for FSO communications, the turbulence can change each information‐carrying dimension of the signal containing its polarization state, and may lead to the crosstalk between two orthogonal polarized signals [11]. Although we have illustrated the validity of OPC compensation for the non‐multiplexing FSO link [6], its compatibility with PDM‐FSO links is still uncertain. In this letter, the compensation of OPC is demonstrated for the turbulence‐induced signal distortion in a dual‐hop FSO transmission with 10 Gb/s PDM quadrature phase‐shift keying (QPSK) signals.…”

“…Despite of great potentials of FSO communications, its performance is strongly influenced by the atmospheric turbulence, which will lead to the random wavefront distortion and serious signal degradation [5]. To compensate the turbulence-induced signal distortions, we have demonstrated the optical phase conjugation (OPC) in the dual-hop FSO communication links [6]. Although many works used OPC with the free space optics, they focused on achieving the laser target-aiming and improving the energy concentration of the laser spot in the imaging systems [7].…”