期刊名称：Beni-Suef University Journal of Basic and Applied Sciences
印刷版ISSN：2314-8535
电子版ISSN：2314-8543
出版年度：2015
卷号：4
期号：2
页码：99-108
DOI：10.1016/j.bjbas.2015.05.002
语种：English
出版社：Elsevier
摘要：AbstractWe investigate the dynamics and noise of semiconductor lasers (SLs) subject to analog modulation with the frequency plan of the National Television Standards Committee (NTSC) for use in the community access television (CATV) systems. The investigations are done in both the time and frequency domains as important methodologies to upgrade the optical CATV systems. The study is based on the rate equation model of the laser. The modulation dynamics is classified into four distinct types according to the waveform of the modulated signal, and the frequency spectra of the relative intensity noise (RIN) of these types are characterized. We show that the laser emits continuous and regular period signals under weak modulation. When the modulation index exceeds 43%, i.e. the modulation current exceeds the bias level above threshold, the laser emits clipped signals superposed by relaxation oscillation. The increase in the modulation index by about 50% in channels beyond channel #24 makes the laser emitting clipped pulsed signals superposed by relaxation oscillation. The laser attains higher noise levels (∼−108 dB/Hz) when it emits pulses, whereas the noise is lowest (∼−170 dB/Hz) when the signal is continuous.
关键词：Semiconductor laser diode;CATV system;NTSC channel plan;Direct analog modulation;Modulation dynamics
