Article

# Output Power PDF of a Saturated Semiconductor Optical Amplifier: Second-Order Noise Contributions by Path Integral Method

Tech. Univ. of Denmark, Kgs. Lyngby

IEEE Journal of Quantum Electronics (Impact Factor: 2.11). 01/2008; DOI: 10.1109/JQE.2007.906226 Source: IEEE Xplore

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**ABSTRACT:**We present a thorough numerical study of intensity noise mitigation of spectrum sliced wavelength-division multi-plexing (SS-WDM) systems employing a nonlinear semiconductor optical amplifier (SOA) before the modulator. Our simulator of the SS-WDM link, embedded inside a Multicanonical Monte Carlo (MMC) platform, estimates the tails of the probability density functions of the received signals down to probabilities smaller than 10 16 . We introduce a new, simple, and efficient technique to handle intersymbol interference (ISI) in MMC simulations. We address the impact of optical postfiltering on SOA noise sup-pression performance. While previous research experimentally observed the SOA-induced noise cleaning in SS-WDM systems, this is the first complete simulator able to correctly predict the ensuing BER improvement. We measure the BER at different bit-rates and validate predicted BERs with and without post filtering.Journal of Lightwave Technology 07/2009; 27(15). · 2.86 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We address design and optimization of optical filters for spectrum-sliced wavelength division multiplexed (SS-WDM) systems employing saturated semiconductor optical amplifiers (SOAs) to suppress intensity noise. We study the impact of the shape of both slicing and channel selecting optical filters vis-a-vis two important impairments: the filtering effect and the crosstalk. The quantification of bit error rate (BER) is made possible by a parallel implementation of the multicanonical Monte Carlo algorithm. The intensity noise suppression by the SOA and signal degradation by subsequent optical filtering are studied both numerically and experimentally. We find optical filter shape and bandwidth that minimizes BER. By varying channel spacing and width, we estimate the achievable spectral efficiency when using both noise-cleaning SOA and forward error correction. We show that when constrained to use a symmetric architecture, i.e., identical filters for both slicing and channel selecting filters, there is a degradation in achievable spectral efficiency. We show that noise suppression is robust to variations in relative channel powers in multichannel systems. Our numerical simulations, vetted experimentally, provide accurate and quantitative results on optimized system performance.Journal of Lightwave Technology 02/2010; · 2.86 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We present a theoretical method for calculating small-signal modulation responses and noise spectra of active Fabry-Perot semiconductor waveguides with external light injection. Small-signal responses due to either a modulation of the pump current or due to an optical amplitude or phase modulation of the input field can be calculated. Both responses and noise spectra are given through semianalytical expressions taking into account the longitudinal extent and finite end-facet reflectivities of the active device. Different examples of responses and spectra are presented for semiconductor optical amplifiers and an injection-locked laser. We also demonstrate the applicability of the method to analyze slow and fast light effects in semiconductor waveguides. Finite reflectivities of the facets are found to influence the phase changes of the injected microwave-modulated light.IEEE Journal of Quantum Electronics 09/2009; · 2.11 Impact Factor

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