FBG Filter Research Articles

Design of triangular FBG filter for sensor applications using covariance matrix adapted evolution algorithm

The design of triangular fiber Bragg grating (TFBG) filters using covariance matrix adapted evolution strategy (CMAES) algorithm is presented. The TFBG filter can be used as a readout device in FBG-based sensor applications. Two different filter design problems are investigated. The first problem is the design of TFBG filter for a specified bandwidth. The other is maximizing the bandwidth of the TFBG filter for a given grating length and maximum index modulation of the FBG. A more practical asymmetrical triangular FBG filter design is also considered. The results show that for the same grating length and maximum index modulation, a larger bandwidth can be achieved with a chirped grating. The maximized bandwidth design can be used to achieve the maximum possible bandwidth for the specified grating length, maximum index modulation and chirp rate. The results obtained using CMAES algorithm (codes available at http://www.ntu.edu.sg/home/epnsugan) is compared with the results of PSO and other algorithms. Comparisons show that the CMAES algorithm is more consistent in obtaining the best solution with reduced computation time. Hence, the CMAES algorithm is effective for the design of TFBG filters for sensor applications.

A dispersionless and bandwidth-adjustable FBG filter for reconfigurable 2R-regeneration

We present a bandwidth-adjustable filter that enables reconfiguration of the bit rate of optical subsystems. This filter is bandwidth-adjustable, wavelength-tunable, and maintains zero dispersion as the bandwidth and wavelength are varied. It also has a transmission spectrum which is Gaussian, to shape Gaussian pulses in the time domain. The ability of the bandwidth-adjustable filter to enable bit-rate reconfiguration is demonstrated in an optical regenerator based on self-phase modulation. The bandwidth-adjustable filter replaces the fixed-bandwidth filter usually used in this kind of regenerator, and enables optical regeneration at both 40 and 80 Gb/s.

Optimal narrowband dispersionless fiber Bragg grating filters with short grating length and smooth dispersion profile

An effective optimization approach to the inverse design problems of complex fiber Bragg grating filters is developed in the present paper. Based on a multi-objective evolutionary programming (MOEP) algorithm, the proposed method can efficiently search for optimal solutions and simultaneously take into account various requirements of the designed filter. To improve the efficiency of the MOEP based algorithm, an adaptive mutation process is proposed and verified. One of the advantages of the proposed optimization method is the capability to impose additional constrains on the desired coupling coefficient, which ensures the convenience and possibility for actually fabricating the designed devices with the commercially available photosensitive fibers. To verify the effectiveness of the proposed method, an optimal narrowband dispersionless fiber Bragg grating filter for DWDM optical fiber communication systems is designed. We successfully demonstrate that complicated dispersionless FBG filters with short grating lengths and smooth dispersion profiles can be obtained by using the proposed algorithm.

Correction to "A unified fourier transform theory for photonic crystal and FBG filters in the strong coupling regime"

Correction to "A unified fourier transform theory for photonic crystal and FBG filters in the strong coupling regime"

A unified Fourier transform theory for photonic crystal and FBG filters in the strong coupling regime

The authors present a new Fourier transform theory which provides analytic results for both strongly coupled fiber Bragg grating and photonic crystal filter structures. Trigonometric and hyperbolic descriptions of these important passive optical devices are well known for the regular grating case. However, the unified approach presented here, which is based upon a modified Debye-Waller approach to the analytical solution of the coupled-mode equations, allows intuitive, yet accurate appraisal of arbitrary-strength-coupled structures. It is also applicable to perturbed-periodic gratings, such as linearly chirped devices for dispersion compensation.

Progress on Fiber-Based Passive Optical Components.

Recent progress on two types fiber-based passive optical devices: fiber gratings and fused-taper couplers, has been reviewed. Narrow-band high reflection FBG filters for add and drop multiplexing, low-reflection FBG mirrors for LD stabilizing, FBG dispersion compensators, and long period fiber gratings and slant/chirped FBGs for gain equalizer are discussed. Polarization beam combiners and polarization maintaining pump/signal combiners manufactured by fused-taper technology using PANDA fibers are also discussed.