The superposition of basic non-diffracting beams triggered new research hotspots lately,laying opportunities for long-distance wireless optical communication.The Lommel-Gaussian(LMG)beam formed by the superposition of Bessel-Gaussian light not only possesses non-diffraction feature,but also has tunable symmetry.With the help of Poynting vector analysis,we observed a smaller radial energy flow component during the propagation of the high order symmetrical LMG beam,which allows it to maintain the original beam profile over long distance.Thanks to the energy oscillation of the mainlobe and sidelobes,the mainlobe blocked by the symmetrical LMG beam can be restored.Also,the random phase screen with angular spectrum method is used to describe the beam behaviors in turbulence.The results show that the symmetry LMG is preferred in free space optical communication,and the asymmetric LMG performs poorly due to asymmetric energy transfer.
CHEN XiangYUAN YaboYAN BaoluoZHANG RuoyuLIU HaifengLU ZehuiLIU Bo
Laser communication is essential part of maritime-terrestrial-air intelligent communication/sensor network. Among them, different modulation formats would play a unique role in specific applications. Based on Rytov theory, we discussed system performance of the maritime laser communication with repeated coding technology in several modulation schemes. The closed-form expression of average bit error rate(BER) from weak to moderate atmospheric turbulence described by log-normal distribution is given. Differential phase shift keying(DPSK) modulation, as a potential solution for future maritime laser communication, has attracted a lot of attention. We analyzed the effects of atmospheric turbulence parameters(visibility, refractive index structure coefficient, non-Kolmogorov spectral power-law exponent, turbulence inner scale) and DPSK system parameters(receiver aperture diameter, repeat time) on average BER in detail. Compared with the aperture-averaging effects, the system BER can be well suppressed through increasing repeat time. This work is anticipated to provide a theoretical reference for maritime laser communication systems.
QIAO Yuan-zheLU Ze-huiYAN Bao-luoLI Chang-jinZHANG HaoLIN WeiLIU Hai-fengLIU Bo
A 473-nm-laser-tuned whispering gallery mode(WGM) silica microbubble resonator integrated with iron oxide particles is demonstrated in this paper. Owing to the photo-induced thermal effect, the WGM resonance wavelength could be tuned by adjusting laser power density of the illuminating light absorbed by the iron oxide particles. A wavelength tuning sensitivity of 0.03 nm/(mW·mm^(-2)) and a tuning range of 0.18 nm are experimentally achieved. Moreover, the influence of ambient temperature on the WGM spectral characteristics is experimentally studied, and a silica-microbubble-based reference scheme is demonstrated to compensate for the temperature-caused resonance wavelength variation. The proposed laser-tuned microresonator has great potential in optical modulation and high-precision optical filtering applications.
A novel high sensitivity all-fiber micro-displacement sensor is proposed and experimentally demonstrated.This sensor consists of a long period fiber gating and a fiber tip,which is achieved only by a commercial arc discharge fusion splicer,and thus possesses a lower cost.The wavelength sensitivity of the proposed sensor could be up to 934 pm/μm,which is four times higher than that of the long period fiber grating(LPFG) with an air cavity structure.The intensity change sensitivity is-1.973 dB/μm.
