Open AccessTheoretical analysis and experimental demonstration of gain switching for a PPM based UWOC system with picosecond pulses
Author(s) -
Chao Zhang,
Yufan Zhang,
Zhijian Tong,
Haiwu Zou,
Hao Zhang,
Zejun Zhang,
Gong−Ru Lin,
Jing Xu
Publication year - 2022
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.470063
Subject(s) - optics , gain switching , switching time , optical switch , picosecond , materials science , pulse position modulation , pulse width modulation , laser , optical communication , optical burst switching , power (physics) , pulse (music) , semiconductor laser theory , optoelectronics , physics , detector , pulse amplitude modulation , optical performance monitoring , wavelength , wavelength division multiplexing , quantum mechanics
Shortening pulse width can improve the power efficiency and data rate of a pulse position modulation (PPM) based underwater wireless optical communication (UWOC) system at a fixed average optical power, which is more suitable for the energy-limited underwater environment. As a common method to generate short pulses, gain switching has the advantages of a tunable switching frequency and simple structure, facilitating the generation of high-order PPM signals. However, the output characteristics of electrical gain switching seriously affect the demodulation of PPM signals and limit the data rate. To study the performance of gain switching on a PPM communication system, simulation models of the semiconductor laser diode and the driving circuit are built to describe the generation of electrical and optical pulses. The pulse width, pulse peak value, and peak position of optical pulses are analyzed under different symbol durations and PPM orders. Furthermore, a 64-PPM/150-Mbps UWOC system with a 200-ps optical pulse width is demonstrated by using a gain-switched blue GaN-based laser diode in a water tank. The peak average power ratio (PAPR) is 19.5 dB. Via the statistical analysis of experiment results and the output characteristics of electrical gain switching, the main factor limiting the data rate attributes to the time delay fluctuation of gain switching. To the best of our knowledge, this is the first time that gain switching has been experimentally demonstrated and analyzed in a high-order PPM based UWOC system.