Influence of fog on the signal to interference plus noise ratio of the imaging laser radar using a 16-element APD array

Abstract

This paper investigates the signal to interference plus noise ratio (SINR) performance of the imaging laser radar (ILR) system operating at a wavelength of 905 nm using an avalanche photodiode array under the fog condition. We analysis the glow image of the light source, which is formed by the laser spot irradiated on a standard Lambertian target. Based on the proposed theoretical model, we determine the interference due to the glow inter-channel crosstalk under different fog conditions for a targeted channel. We show that, for transmission spans less than several tens of meters the interference due to glow crosstalk is higher than the fog (light to medium) induced losses. However, for a link range longer than 21 m the glow crosstalk induced interference is lower than the heavy fog induced attenuation. The proposed system performance is evaluated by developing an experimental test bed and using a dedicated indoor atmospheric chamber under homogeneously controlled fog conditions. We show that, under different fog conditions experimental results for changing SINR levels match well with the predicted data. The results shown can be used for design optimization of the ILR system when operated under fog conditions.

The propagation loss of ultrashort laser pulses in water clouds

“…In figure 1(c), the DSD in three common water cloud systems and fog are given. One should note that the LWC, and DSD of different types of fog are different, resulting in different magnitudes of light absorption and scattering [4,33]. Additionally, the density distribution of droplets of various sizes in water clouds and fog fluctuates more drastically due to turbulence and the inhomogeneous distribution of aerosol particles (see figure 1(b)).…”

“…When a SW-NIR beam with less than critical intensity enters the water clouds and fog, the linear absorption of the droplet is trivial, and the laser energy and polarization direction of the beam are typically changed by the scattering effect [1,4,30].…”

“…water cloud systems can be regarded as 'Thin Phase Screen' [3], avoiding direct exposure of ultraviolet light to the earth, further reducing near-ground visibility and disrupting the line of sight on the microscopic level [2,4]. On top of that, the absorption and scattering characteristics of light make water clouds strongly interfere with atmospheric remote sensing and the stability and accuracy of light detection and ranging [5].…”

“…Additionally, even weaker laser fields, water clouds, and fog can create significant obstacles to FSOC, reducing radar detection signals [4,8]. For incident laser in the near-infrared (NIR) wavelength, the linear absorption of the laser by the droplet is hardly considered.…”

Analysis of a Real-Time FSO System Utilizing Xia and SRRC Pulses in Multi-Band Carrier-Less Amplitude and Phase Modulation

“…One of the key challenges in FSO systems is that of changing weather conditions causing link outages and impairments, resulting in a large number of reports in this area. Fog can cause reduced visibility [4], acting as a neutral density filter. Turbulence impacts the refractive index along the signal path, resulting in beam wandering at the receiver due to optical power deflection from the direction of propagation [5].…”