Optical Communication in Space: Challenges and Mitigation Techniques

Abstract

Abstract-In recent years, free space optical (FSO) communication has gained significant importance owing to its unique features: large bandwidth, license free spectrum, high data rate, easy and quick deployability, less power and low mass requirements. FSO communication uses optical carrier in the near infrared (IR) band to establish either terrestrial links within the Earth's atmosphere or inter-satellite/deep space links or ground-to-satellite/satellite-to-ground links. It also finds its applications in remote sensing, radio astronomy, military, disaster recovery, last mile access, backhaul for wireless cellular networks and many more. However, despite of great potential of FSO communication, its performance is limited by the adverse effects (viz., absorption, scattering and turbulence) of the atmospheric channel. Out of these three effects, the atmospheric turbulence is a major challenge that may lead to serious degradation in the bit error rate (BER) performance of the system and make the communication link infeasible. This paper presents a comprehensive survey on various challenges faced by FSO communication system for ground-to-satellite/satellite-to-ground and inter-satellite links. It also provide details of various performance mitigation techniques in order to have high link availability and reliability. The first part of the paper will focus on various types of impairments that pose a serious challenge to the performance of optical communication system for ground-to-satellite/satellite-to-ground and inter-satellite links. The latter part of the paper will provide the reader with an exhaustive review of various techniques both at physical layer as well as at the other layers (link, network or transport layer) to combat the adverse effects of the atmosphere. It also uniquely presents a recently developed technique using orbital angular momentum for utilizing the high capacity advantage of optical carrier in case of space-based and near-Earth optical communication links. This survey provides the reader with comprehensive details on the use of space-based optical backhaul links in order to provide high capacity and low cost backhaul solutions.

Performance Evaluation of Downlink Design Based on Free Space Optical System

“…A laser beam faces power loss due to various factors as it propagates through the air. One of them is absorption and scattering loss as defined in Beer's Law [7]. Absorption happens due to the photons of the beam bumping with haze particles.…”

Analysis of the effect of BER and Q-factor on free space optical communication system using diverse wavelength technique

“…These natural phenomena cause attenuation in the transmitted signal. This leads to high bit error rate or signal loss at the receiver end [2]. When a laser beam transmits via the atmosphere, it experiences power loss caused by multiple known factors.…”

FSO G2T communications in tropical climate: An overview

“…Properties of an atmospheric path are random in terms of space and time, which makes FSO link depend on random factors such as geometrical and climate changes. In addition to unpredictable environmental changes that include haze, temperature shifts, fog, rain and clouds [11] [10]. They impose attenuations on propagated signals and presented as "losses".…”