Underwater Laser Communication Using an OFDM Modulated 520 nm Laser Diode
In this letter, we propose and experimentally demonstrate an underwater wireless optical communication system based on a simple and cost effective TO56 transversal multi mode green light laser diode (LD) and a low cost 150 MHz positive intrinsic negative detector. We use quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing modulation, with fine frequency granularity and high spectral efficiency, to tackle the challenging issue imposed by the ragged and uneven frequency response of the green LD within a limited bandwidth. We have demonstrated that a bit rate of 1.118 Gb/s (net bit rate: 0.927 Gb/s) can be achieved at a bit error rate of 2.98 x 10 3, with the assistance of bit loading (using both 16 QAM and 256 QAM signals) A spectral efficiency as high as 6.18 bit/s/Hz is also obtained in the proposed underwater wireless optical communication system.
IEEE Photonics Technology Letters