Sanmukh Kaur* and Amayika Kakati Analysis of Free Space Optics Link Performance Considering the Effect of Different Weather Conditions and Modulation Formats for Terrestrial Communication https://doi.org/10.1515/joc-2018-0010 Received January 22, 2018; accepted April 30, 2018 Abstract: Free space optics (FSO) links provide an effec- tual and efficient way of transmission of data throughout free channels due to its higher bandwidth and inbuilt capability of security. In this research analysis, the FSO link is evaluated on the basis of Q value for different modulation formats and weather conditions. Gamma– Gamma and log-normal scintillation models have been analyzed for different index of refraction in terms of Q factor versus a range of a proposed FSO link. Attenuation increases during the occurrence of different fog condi- tions, and there might be complete link failure in the case of dense fog and for some of the cloud conditions. Keywords: free space optical communication, NRZ, Q-factor, scintillation, weather conditions 1 Introduction Transmission of data throughout the air with the modu- lated optics signal or in other words a beam of narrow optics signal fed into a Tx end, propagating within the free space and later fed in to a Rx end, is termed as free space optics (FSO). FSO as well as optical fiber commu- nication uses the same infrared (IR) wavelengths of light and high bandwidth capacity. FSO is often denoted as “fiber less optics” transmission. An end-to-end wireless communication link is designed by FSO and it provides higher privacy, less power, less cost and higher data rates due to unlicensed capability of bandwidth utilization. These types of links are suitable for 1 to 2 Gbps over distances up to 1 to a 5 km range [1–4]. Moreover, it can be used as an option or an improvement for extended range fiber less communication. Few advantages of FSO are as follows: easy installation, there is no need for licensed frequency band allocation, for radiation fre- quency there is no radiation hazards, high transmission data rate and immunity to noise [5]. With the reality that FSO has extra benefits, the most important cause that limits the FSO link for terrestrial communication performance is a climatic condition [6, 7]. As the guide or path of communication is air inter- face and it can cost FSO link to attenuate per kilometer from a few decibels to hundreds of decibels and at the receiver section, the signal tends to distort [8]. The signal propagating through FSO is affected by atmospheric attenuation or turbulence which leads to complete link failure at the Rx end as well as degrades the performance of the link [9]. The analysis of an FSO link performance can be exam- ined on the basis of two parameters: one is internal para- meter (IP) and another one is external parameter (EP). IP refers to the design of the system and comprises of receiver sensitivity, divergence angle, optical loss, optical power, wavelength, transmitter and the receiver aperture diameter on. EPs are mostly denoted by different atmospheric condi- tions. They cause fluctuation and link deformation of an FSO system [10, 11]. FSP links are extremely responsive to the existence of tiny aerosol particles inside the narrow shaft such as fog and cloud [12]. In the majority of the presented literature, the analy- sis of a FSO link is studied with different modulation schemes. In [13], for different intensity modulation (IM) formats an earth to satellite FSO link has been analyzed on the basis of BER. The main features of FSO link have been reviewed for terrestrial as well as intersatellite com- munication to illustrate the possible link degradation in [14]. In [15], the theoretical analysis of a free space wire- less communication link has been studied using on–off keying with different transmitters. In [16], an FSO link performance has been analyzed by exploiting different phase shift key. In [17], an FSO system has been designed using the amplitude shift keying and pulse position modulation schemes. FSO link has been analyzed and simulated with real data on haze weather conditions using *Corresponding author: Sanmukh Kaur, Amity School of Engineering and Technology, Amity University, Noida, Uttar Pradesh 201303, India, E-mail: sanmukhkaur@gmail.com Amayika Kakati, Amity School of Engineering and Technology, Amity University, Noida, Uttar Pradesh 201303, India, E-mail: amy24sc@gmail.com J. Opt. Commun. 2018; aop Brought to you by | University of Michigan-Flint Authenticated Download Date | 5/20/18 11:03 AM