Analysis of Internal Design Parameters to Minimize Geometrical Losses in Free-Space Optical Communication Link

Abstract

During the last two decades, free-space optical links got considerable importance due to their benefits of higher data rates, license free-spectrum, easy and rapid deployment and mobility. Free-space optical links use carrier frequency in the range of 20 THz to 375 THz (in near infrared (IR) region and visible band in wavelengths) to establish a communication link for terrestrial communication, inter-satellite links, deep space links, ground-tosatellite and satellite-to-ground links. Free-space optical links are also useful for different military applications, disaster recovery and last mile access. However, despite of having all these advantages the performance of freespace optical links depends upon the atmospheric conditions and parameters of system design. Geometrical losses of free-space optical links are directly related to parameters of system design or internal parameters. In this paper we analyzed different parameters of system design to minimize the geometrical losses. We presented the analysis of internal design parameters like divergence angle, diameter of receiver aperture, diameter of transmitter aperture, link distance and suggested the suitable parameters of system design.

Investigation of optimum FSO communication link using different modulation techniques under fog conditions

“…Kruse model estimates the less optical attenuation for visibility of 1 km with less accuracy at higher wavelengths [ 7 ]. Kim has presented different values of size distribution q, when visibility is less than half of km there is no advantage of using a higher wavelength [ 20 ]. Values of q for Kim model are given in Eq.…”

“…These geometrical losses depend upon diameter of transmitter diameter, receiver aperture, link distance and divergence angle. These losses can be reduced by properly choosing receiver aperture and diameter of transmitter with divergence angle that minimizes pointing error at receiver end [ 20 ]. FSO link performance for 10 Gbps is investigated for Lahore airfield under dust attenuation for 1523 μg/m 3 concentration in the railway’s station area for 2 km link distance that is easily achievable [ 21 ].…”

Performance Analysis of Dual-Beam Free Space Optical Communication Link under Dust and Rain Conditions

“…CW laser is used for an optical source with a frequency of 193.1 THz at 30 dBm transmitter power. The scattering effect will fade the signal on the receiver side, so while designing an optical transmitter, it is also important to select a suitable size of divergence angle, a diameter of the transmitter, and receiver apertures so that geometrical losses can be reduced [23]. The geometrical design parameters of FSO channels are 1.5 mrad divergence angle and 5 cm and 20 cm diameters of transmitter and receiver apertures.…”

“…Geometrical design parameters are fixed parameters of a communication system that have significant importance. FoV (Field of View) on the receiver side must be according to the footprint because the greater FoV will also produce noise in the original information signal [23]. The investigation report shows that, in geometrical design elements, divergence angle size is an important factor for long-distance FSO communication links.…”

Experimental Study of the Free Space Optics Communication System Operating in the 8–12 µm Spectral Range

“…The main advantage of FSOs is their wide application field that includes outdoor wireless access, backhaul, fiber backup, last mile [4,5], bridging Wide Area Network (WAN) [6], and military access [7]. Several factors can significantly reduce the transmission efficiency, in particular, physical obstructions, rain [8], temperature fluctuations in different air layers [9], geometric losses [10], absorption [11], atmospheric turbulence [12][13][14], and atmosphere attenuation and scattering [15]. In commercial FSO communication systems, strictly defined wavelengths of approximately 0.8 µm and 1.5 µm are used [16,17].…”