Coherent-Circular Polarized Shift Keying Modulation Analysis over Malaga Distribution and Ғ Distribution with Pointing Errors in Free Space Optical Communication

• Published in: Optical and quantum electronics 2023-12, Vol.55 (13), Article 1135
• Main Authors: Saw, Bipin K., Janyani, Vijay, Singh, Ghanshyam
• Format: Article
• Language: English
• Subjects: Atmospheric turbulence; Characterization and Evaluation of Materials; Communications systems; Computer Communication Networks; Distribution channels; Electrical Engineering; Error analysis; Error correction; Free space optics; Free-space optical communication; Keying; Lasers; Noise threshold; Optical Devices; Optics; Outages; Phase noise; Photonics; Physics; Physics and Astronomy; Polarization; Variance
• ISSN: 0306-8919; 1572-817X
• DOI: 10.1007/s11082-023-05297-4

In this paper, a proposed circular polarized shift keying (CPolSK) is analyzed for free space optical (FSO) communication system under Ғ distribution channel model and Malaga ( M ) distribution channel model. The proposed CPolSK FSO system contains two feedback paths at the receiver section, in which one for correcting the polarization error in the polarization controller and the other for correcting the slow frequency fluctuations in the local oscillator (LO). Also, two 90 0 optical hybrids are used for mixing the incoming polarized signal and the polarized LO signal. Average BER (ABER) expressions and outage probability expressions are derived for the CPolSK FSO communication system under Ғ distribution channel model and M distribution channel model. The results for different atmospheric turbulence (AT) conditions, phase noise variance and polarization control error are analyzed. Also, the system outage probability for different phase noise variance 0.085 π , 0.25 π and 0.625 π for different SNR thresholds for low AT condition are analyzed. In the results, it can be observed that the ABER performance improves as AT conditions improve, as the phase noise variance decreases and as the polarization control decreases. Also, when AT conditions get worse, then to get same outage probability, we have to increase the SNR threshold. Varying the phase noise variance for δ 2 = 0.085 π to δ 2 = 0.625 π at low AT condition resulted in a power penalty of more than 4 dB for the same outage probability at 0.3. Additionally, it is observed that the M distribution channel model has a steeper slope in the outage probability against normalised threshold graph than the Ғ distribution channel model.