Theoretical Study of Nonlinear Coefficient and Optical Switching in Erbium-Doped Optical Fiber

Abstract

Erbium-doped optical fibre (EDOF) is an important platform to study the intensity-dependent nonlinear propagation and nonlinear polarisation rotation, optical switching and four-wave mixing. The source thesis contains both theoretical and computational work. In this paper the work is presented in the format of a research paper that is published by the University Grants Commission. The nonlinear coefficient is expressed in terms of the nonlinear refractive-index coefficient, the operating wavelength and the effective mode area, and the resulting nonlinear phase response is investigated. The consideration of the passive attenuation and the active gain in the theoretical model, and the computational analysis carried out on the basis of MATLAB are discussed. The nonlinear coefficient varies from 1.758 to 1.471 W−1 km−1 over the wavelength range 1480-1630 nm, while at 1550 nm it varies from 2.189 to 1.368 W−1 km−1 for effective mode area increasing from 50 to 80 µm2. The nonlinear phase shift goes up to 0.160 rad at 100 mW, compared to 0.016 rad at 10 mW. For the same input-power range, the nonlinear polarisation rotation increases from 2.4° to 24.0°. The optical-switching analysis shows a transmission of 90% and an extinction ratio of 9.54 dB at 100 mW. Four-wave-mixing analysis shows that the relative FWM response increases from 0.10 to 1.00 when the input power is increased from 10 to 100 mW and decreases from 0.90 to 0.15 when the assumed chromatic-dispersion value is changed from -20 to +15 ps/nm/km. The results show the inter-related roles of nonlinear coefficient, optical power, wavelength, polarisation evolution and chromatic dispersion in erbium-doped fibre systems. Erbium-doped fibre, nonlinear coefficient, Kerr nonlinearity, nonlinear polarisation rotation, optical switching, four-wave mixing, chromatic dispersion.