PolSK and ASK Modulation Techniques Based BER Analysis of WDM-FSO System for Under Turbulence Conditions

This paper details a novel model of Wavelength Division Multiplexed (WDM) system using Polarization Shift Keying (PolSK) modulation to increase the capacity of a Free-Space Optical System. The proposed system reduces the cross-channel effects and phase related variations of transmitting signal since PolSK transmits signals in two orthogonal polarized directions. A mathematical model for the system is developed and simulated. The closed-form expressions for the PolSK based WDM system is derived. A case study has been done to implement virtual class rooms in JJCET, Trichy to explore the benefit of using WDM using PolSK for different climatic conditions. The parameters like Bit Error Rate (BER) are analyzed for different weather conditions. The BER of 10⁻¹⁰ is obtained for a link distance of 15.3 km under gamma–gamma turbulence channel in heavy rain conditions, and 5.8 km link distance is achieved for fog conditions using this novel method. Four separate channels each with a data rate of 2.5 Gbps are multiplexed to increase the capacity of the system to 10 Gbps. The system is compared with WDM employing Amplitude Shift Keying under the same environmental conditions. The simulation results obtained for BER and received power against different atmospheric conditions are compared for both the modulation schemes and proved that PolSK based WDM offers better performance.