Raman assisted four-wave mixing in optical fiber and its applications

Pao Yue-kong Library Electronic Theses Database

Raman assisted four-wave mixing in optical fiber and its applications


Author: Wang, Shaohao
Title: Raman assisted four-wave mixing in optical fiber and its applications
Degree: Ph.D.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Raman effect
Parametric amplifiers
Fiber optics
Optical fiber communication
Department: Dept. of Electronic and Information Engineering
Pages: xxii, 171 p. : ill. (some col.) ; 31 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2393058
URI: http://theses.lib.polyu.edu.hk/handle/200/5938
Abstract: Next generation fiber-optic communication systems will require novel fiber optical amplifiers. Raman-assisted fiber optical parametric amplifiers (RA-FOPAs) are attractive as they combine the advantages of fiber Raman amplifiers (FRAs) and fiber optical parametric amplifiers (FOPAs). RA-FOPAs can provide higher gain efficiency than FRAs and are more flexible in selecting parametric pump wavelength than conventional FOPAs which are limited by booster EDFAs. The design of RA-FOPAs is rather complex because of constraints such as target peak gain, types of fiber used, noise and polarization mode dispersion (PMD). In this thesis, we first characterize the gain of RA-FOPAs. We derived a normalized phase-matched model to determine the peak gains of RA-FOPAs operating in the small signal region. We showed that these tools can be used to design and optimize the Raman pump and parametric pump power of RA-FOPAs for high gain and high efficiency in a given fiber. By reducing the external noise sources, we demonstrated that close to 3-dB noise figure can be achieved in RA-FOPAs. We also proposed a hybrid fiber Raman parametric amplifier (HFRPAs) by cascading a RA-FOPA and a FOPA, which can further optimize the indirect Raman amplification process. The current works also include a theoretical model describing the polarization dependence of RA-FOPAs and the effect of randomly varying birefringence in the fiber on the performance of RA-FOPAs. By using this model, we investigate the effect of polarization mode dispersion on the gain of RA-FOPAs in terms of diffusion length, Raman and parametric pump powers, and fiber PMD coefficient. We found that the long diffusion length assumption can be used to approximate most RA-FOPAs. When the diffusion length is much shorter than fiber length, PMD effects set a major limit of the future application of RA-FOPAs. Moreover, for RA-FOPAs with large Raman pumps, PMD effect on the Raman gain can be reduced. Finally, we investigate the direct and indirect contribution of the Raman pump(s) to the phase matching condition in Raman-assisted four-wave mixing (RA-FWM). We successfully demonstrated that multi-pump Raman pumps can be used to assist FWM-based all-optical wavelength convertors, which can reduce the frequency dependency of Raman gain in wavelength conversion, which determines set by the single Raman pump. We also proposed an all-optical multicast switch employing RA-FWM with wavelength control capability to select the multicast channel groups.

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