On The Characterization Of A Green-Light Directly-Modulated Diode-Pumped Solid-State Laser

Directly modulated semiconductor lasers for underwater wireless optical communication (UWOC) have limitations in output power and beam quality. Diode pumped solid- state lasers (DPSSLs) have the merits of long lifetime, high stability, large power and good beam quality, which are promising to realize long reach UWOC. We compose a DPSSL with discrete components and measure its key parameters. The bandwidth constraint of the DPSSL imposed by the long lifetime of the gain medium is circumvented with the strategy of orthogonal frequency-division multiplexing (OFDM). After 5.74-m underwater transmission, the BERs of the 40.28-Mb/s 32- quadrature amplitude modulation (QAM) signal and the 50.78-Mb/s 16-QAM signal are 1.09 x 10(-3) and 3.53 x 10(-3), respectively. We also demonstrate that the QAM order generated by the directly modulated DPSSL can be as high as 128.