OFDM-based broadband underwater wireless optical communication system using a compact blue LED

• Over a 2-m underwater channel, we achieve net bit rates of 161.36 Mb/s only using one blue LED, by carefully optimizing OFDM parameters.
• The bias voltage is as low as 3.7 V in our scheme where only one compact 40-lm LED is used.
• We further increase the QAM order to 64 and achieve a net bit rate of 127.07 Mb/s over a 2-m underwater channel.
• We have numerically studied scattering effect.

We propose and experimentally demonstrate an IM/DD-OFDM-based underwater wireless optical communication system. We investigate the dependence of its BER performance on the training symbol number as well as LED's bias voltage and driving voltage. With single compact blue LED and a low-cost PIN photodiode, we achieve net bit rates of 225.90 Mb/s at a BER of 1.54×10−3 using 16-QAM and 231.95 Mb/s at a BER of 3.28×10−3 using 32-QAM, respectively, over a 2-m air channel. Over a 2-m underwater channel, we achieve net bit rates of 161.36 Mb/s using 16-QAM, 156.31 Mb/s using 32-QAM, and 127.07 Mb/s using 64-QAM, respectively. The corresponding BERs are 2.5×10−3, 7.42×10−4, and 3.17×10−3, respectively, which are all below the FEC threshold.