Receiver sensitivity improvement of OFDM-FSO link using SRM device

Abstract

Free space optical (FSO) link based on orthogonal frequency division multiplexing (OFDM) over turbulent channel gives improved performance due to narrow-band interference, high bandwidth efficiency and robustness against fading. The multi-path in FSO can lead to dispersion which is linear distortion. The square-law characteristic of photo diode detector at the receiver side, converts the linear distortion into non-linear distortion resulting in performance degradation of OFDM-FSO link. To overcome this non-linear distortion, the square root module (SRM) device is used for maintaining linearized receiver circuit resulting in performance improvement of OFDM-FSO link. This paper analytically analysis the performance of OFDMFSO link with and with-out SRM device. For BER of 10-3, there is 9.8 dB improvement in receiver sensitivity of OFDM-FSO link with SRM device as compared to OFDM-FSO link without SRM device.