Synthesis of fiber Bragg grating parameters from experimental reflectivity: a simplex approach and its application to the determination of temperature-dependent properties.

A simple, accurate, and fast method to synthesize the physical parameters of a fiber Bragg grating numerically from its reflectivity is proposed and demonstrated. Our program uses the transfer matrix method and is based on a Nelder-Mead simplex optimization algorithm. It can be applied to both uniform and nonuniform (apodized and chirped) fiber Bragg gratings. The method is then used to synthesize a uniform Bragg grating from its reflectivity taken at different temperatures. It gives a good estimate of the thermal expansion coefficient and the thermo-optic coefficient of the fiber.

Dynamics of a self-Q-switched fiber laser with a Rayleigh-stimulated Brillouin scattering ring mirror.

Backward light scattering can cause passive Q switching in fiber lasers. We propose a self-consistent description of the laser dynamics. Our model quantitatively reproduces the temporal structure of pulsation and is also attractive for analysis of laser stability and statistics. The validity of the model is directly verified in an experiment.

Refractive-index changes caused by proton radiation in silicate optical glasses.

We have studied experimentally, by using a differential interferometric technique, the effect of proton radiation on the refractive index of commercial (Schott) silicate crown glasses, BK7 and LaK9, and their radiation-resistant counterparts. The strongest effect was observed for the radiation-hard lanthanum crown LaK9G15: At a 0.65-Mrad dose the index change was approximately 3 x 10(-5). Radiation-hard glasses are used in optical systems operating in radiation environments because they prevent spectral transmission degradation in the visible. However, such glasses are not protected against radiation-induced refractive-index perturbations, and a diffraction-limited optical system based on such glasses may fail owing to radiation-induced aberrations.

Statistical properties of stimulated Brillouin scattering in single-mode optical fibers above threshold.

We performed numerical simulations to obtain statistical and spectral characteristics of stimulated Brillouin scattering (SBS) initiated by Gaussian noise in single-mode optical fibers. Recently published experimental spectra of SBS power [e.g., Phys. Rev. Lett. 85, 1879 (2000)] are explained completely by a one-dimensional SBS model. We give a clear physical insight into the problem and, for what is to our knowledge the first time, reveal how the probability function of Stokes power, the power-correlation function, and the SBS spectra evolve as key parameters of the model vary, leading to a modification of Stokes field statistics.