Analysis of Optical Attenuation from Measured Visibility Data in Islamabad, Pakistan

Abstract

FSOL (Free-Space Optical Links) are becoming very popular due to the inherent advantages of high data rates, rapid deployment, portability, cost effective and immunity to electromagnetic interference. FSOL is a line-of-sight technology that uses a modulated beam of light to transmit and receive the data of multiple of Giga Bit per second. FSOL uses the free space or atmosphere as a communication channel. Optical signal launched at transmitter end, travels through the atmosphere and reaches to the receiver, is severely affected by the local atmospheric conditions. Atmosphere contains different atmospheric particulates like fog, rain, snow, smog, clouds and haze. These atmospheric particulates, particularly fog, effect the propagation of optical signal passing through the atmosphere and cause significant amount of optical attenuation. In order to deploy FSO system, a detailed analysis of local weather condition is much more important. Here, we present the measured visibility data for analysis of optical attenuation. Visibility data was measured at COMSATS Institute of Information Technology from 2009-2012. Percentage CDF (Cumulative Distribution Function) is used to find out the detailed insight about the optical attenuation of FSOL. Yearly based CDFs is compared with each other which clearly suggest that almost 99% of time optical attenuation remains within the range of 2 dB/km.

Ensemble Consensus Representation Deep Reinforcement Learning for Hybrid FSO/RF Communication Systems

“…In Equation ( 4), V is measured in km and λ in µm. We have selected the range of 100dB/km to 120dB/km attenuation thresholds based on work in [13]. According to analysis of results given in [13] show that over 70% of the time attenuation of FSO links approaches to 120dB/km based on Kruse and Kim model, thereby requiring link switched to RF.…”

“…We have selected the range of 100dB/km to 120dB/km attenuation thresholds based on work in [13]. According to analysis of results given in [13] show that over 70% of the time attenuation of FSO links approaches to 120dB/km based on Kruse and Kim model, thereby requiring link switched to RF. On the other hand, attenuation less than 100dB/km is considered too weak for optical communications, therefore RF link is used to increment the reward to train the DRL agent under attenuation values less than 100dB/km.…”

“…It can be observed from Algorithm 1 that the actor neural network is initialized with θ and critic with parameter µ. The actor neural network maps an observation O link at time slot t to an actions a from A using the optimal policy π * as given in (13). In the Equation, A is discrete and the normalized probability of each action is calculated using the Softmax function at the output layer of the actor-network.…”