Experimental Implementation of FSO System using Low-cost Optical Transmitter

This work presents and analyzes a free-space optical (FSO) communication system under stable laboratory conditions by employing a low-cost (≈ $140) commercial optical transmitter. The considered experimental setup utilizes quadrature-phase shift keying (QPSK) signaling for data transmission. To further improve the system performance, a QPSK-frequency division multiplexing (QPSK-FDM) signaling is employed. To conduct the experimental study, this work also provides algorithms to prepare comma-separated value files for sample values of QPSK and QPSK-FDM signals that can be loaded to arbitrary function generator to generate these signals. Moreover, the decoding algorithm is also provided that consists of match filtering operation, detection criteria, and the calculation of bit error rate (BER). Furthermore, the performance of QPSK and QPSK-FDM is compared for the considered FSO system in terms of BER performance at different optical received power. Additionally, the BER performance of QPSK-FDM is examined at different data rates. The experiment demonstrates that the BER performance of the QPSK signal improves with FDM transmission and also with the increase in the power of the received signal. Additionally, it is concluded that in case of low signal power, the bit rate can be further reduced to improve the BER performance of the system.