Abstract
In this paper uniform and apodized nonlinear chalcogenide glass fiber Bragg gratings (FBG) as novel and promising devices for all-optical switching are investigated. The transmission response of these devices is discussed theoretically. The continuous wave in the investigated FBGs induces the nonlinear variation of the refractive index that causes changes in the FBG transmission characteristics. This effect can be modified depending on incident light power what is assumed to be due to the optical Kerr effect responsible for optical switching. The incident intensity thresholds of the bistable regimes were analyzed numerically to deduce possible switching properties of FBGs based on various chalcogenide glass samples. The influence of grating parameters on the optical bistability behaviour is researched. The nonlinear coupled mode theory was used for numerical investigation.
Highlights
Ultrafast optical switches are necessary parts of optical network nodes in high bit rate all-optical communication networks [1, 2] including systems of wavelength division multiplexing (WDM)
We numerically investigate the threshold of the bistable behaviour in nonlinear chalcogenide fiber Bragg gratings (FBG)
Apodization is a well-known technique in which the refractive index is graded in the direction perpendicular to the grating length. This technique can effectively remove the undesirable sidelobes in the reflection/transmission spectra of linear FBGs used as WDM multiplexers/demultiplexers or optical filters
Summary
Ultrafast optical switches are necessary parts of optical network nodes in high bit rate all-optical communication networks [1, 2] including systems of wavelength division multiplexing (WDM). Optical bistability (OB) in nonlinear media is a phenomenon that can be preferably used for all-optical switching. This optical phenomenon refers to the situation in which it is possible to have two stable output transmission states associated with a single input state, depending upon the history of the input. In nonlinear switches using the optical Kerr effect, the nonlinearity must be high and the nonlinear absorption must be low [1,2,3]. The switching behaviour is controlled by the intensity of the input optical pulse. We numerically investigate the threshold of the bistable behaviour in nonlinear chalcogenide FBGs. We assume uniform and apodization profiles of the FBG refractive index. Characteristics of various samples taken from [4,5,6, 8] of ChGs containing different chalcogens are supposed to be the nonlinear media
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