Phase reconstruction from reflectivity in fiber Bragg gratings

We propose a method for phase, time delay, and impulse response reconstruction from the spectral power reflectance or reflectivity in fiber Bragg gratings (FBGs). This method is based on causality and stability conditions and uses the Hilbert and Wiener-Lee transforms. In order to obtain a complete study of the algorithm, we have applied it to uniform and nonuniform fiber Bragg gratings. Finally, we get a complete characterization of a experimental uniform fiber Bragg grating, from the measured reflectivity, by means of the phase reconstruction algorithm. Results show a good agreement between exact and reconstructed functions     

Field distributions inside fiber gratings

We have developed a technique to calculate the electric field distributions of a light wave propagating through a fiber grating (FG). The technique is based on a transfer matrix method developed for electric field calculations in multilayer thin films. We apply this method to several FG structures of practical interest in optical fiber networks based on wavelength-division multiplexing. Two-dimensional plots of the average internal power versus the distance along the grating axis and light frequency are presented. This representation allows a better understanding of the macroscopic behavior of these structures     

Fiber grating filter for WDM systems: an improved design

We report on a novel technique for the design of fiber gratings whose reflection characteristic closely approximates the ideal rectangular linear phase filter. The technique is based on the design of a suitable grating period variation, following the apodization function, in order to ensure the Bragg condition to remain constant along the grating length     

Arbitrary-Order Ultrabroadband All-Optical Differentiators Based on Fiber Bragg Gratings

We introduce a general approach for designing ultrabroadband arbitrary-order all-optical (all-fiber) time differentiators based on the use of fiber Bragg gratings (FBGs). Specifically, we numerically demonstrate that an Nth-order time differentiator can be implemented using a single specially apodized highly dispersive linearly chirped FBG operated in transmission. A concatenated reflection phase-shifted FBG is also required for implementing any odd-order differentiator. Our numerical simulations show that accurate and efficient time differentiation of optical signals with bandwidths up to a few hundreds of gigahertz can be realized using readily feasible FBG structures.