1 May 2014 Numerical investigation of noise chracteristics of telecommunication laser sources for various modulation formats
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We present numerical investigation of noise properties of lasers for telecommunication purposes with emphasis on widely used distributed feedback (DFB) lasers and its influence on multi-level modulation formats. DFB lasers can be used in optical transmitters with internal and external modulation, as well as in optical receivers employing coherent detection, where they act as local oscillator. The main noise factors influencing signal characteristics of semiconductor-based lasers are intensity and phase noise. These random impairments cause degradation of fundamental output laser characteristics such as power and phase fluctuation, which are directly related to the optical signal-to-noise ratio and the laser linewidth. In case of implementation of new modulation formats into the transmission system, these stochastic processes are of main importance and significantly impact the transmission properties of modulated signals and total performance of fiber-optic transmission systems. Throughout this paper, the noise influence on the multi-level modulation formats is evaluated by effective signal-to-noise ratio (SNR) algorithms in combination with bit-error ratio (BER) formulas for appropriate type of modulation format. The obtained results have shown that the noise of DFB laser is serious restriction for multi-level modulation formats and can be improved by higher power levels, yielding to higher SNR, as required for better values of BER.
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Jan Litvik, Jan Litvik, Daniel Benedikovic, Daniel Benedikovic, Jozef Dubovan, Jozef Dubovan, Michal Kuba, Michal Kuba, "Numerical investigation of noise chracteristics of telecommunication laser sources for various modulation formats", Proc. SPIE 9131, Optical Modelling and Design III, 91311Y (1 May 2014); doi: 10.1117/12.2052352; https://doi.org/10.1117/12.2052352

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