Optimization of Superstructured Fiber Bragg Gratings for Microwave Photonic Filters Response

Abstract

Abstract-The microwave photonic responses of superstructured fiber Bragg gratings in combination with dispersive fiber are investigated theoretically and experimentally. The superstructured gratings are optimized, taking account of the spectral response of the broad-band source, Erbium-doped fiber amplifier, and optical tunable filter to achieve a filter response with sidelobe suppression of more than 60 dB.Index Terms-Microwave photonic filter, superstructure fiber Bragg grating (SFBG).

Chromatic dispersion effect in a microwave photonic filter using superstructured fiber Bragg grating and dispersive fiber

“…It should be pointed out that all the gratings used in the experiments are weak gratings in order to ensure the source has a Gaussian spectral density function. It is well known that in a weak grating the reflectivity can be treated as the Fourier transform of coupling coefficient distribution along the grating [4]. Generally a Gaussian apodisation function is used to suppress sidelobes in the grating reflection.…”

“…In such a structure time delays between optical taps are determined by the product of wavelength spacing of adjacent optical reflections and the dispersion introduced by the fiber, therefore precisely matched to produce higher rejection level [3] [4]. The distortion in the filters' responses happens at high frequencies, which is as attributed to the power degradation caused by fiber chromatic dispersion, although the theoretical simulations based on the well-known analysis [5] do not match well to the experimental results in [3] [4].…”

Continuously tunable incoherent microwave photonic filter using a tunable Mach‒Zehnder interferometer as the slicing filter

“…Stable microwave photonic filter can be implemented in the incoherent operation regime since the phase fluctuation will not have much influence and consequently more stable to the environmental variation [4]. Several approaches to the implementation of some tunable incoherent microwave photonic filters were reported, among which sliced broadband light sources and dispersive media are widely adopted due to their advantages of cost-effectivity and low phase fluctuation noise [5,6]. Microwave photonic filter using a sliced light source can hardly be tuned continuously [7] unless it incorporates the dispersion with a tunable linearly chirped fiber Bragg grating as a tunable dispersive medium, which will greatly increase the complexity and the cost (furthermore, the tunable range and the accuracy are limited).…”

Tunable microwave photonic filter based on a fiber ring and erbium-doped fiber amplifier

“…Microwave photonic filters can overcome the limitations of the traditional microwave filters, e.g., the electronic bottleneck and other sources of degradation, and show good application in the RoF systems. Several approaches to the implementation of microwave photonic filters have been proposed, such as two FBGs and gain media based recirculating cavity configuration [2] and superstructured FBG and dispersive media based filtering configuration [3] . Microwave photonic filters based on laser array and linearly chirped fiber Bragg grating (LCFBG), tunable laser and LCFBG are also proposed to achieve the reconfigurability and tunability [4][5][6] .…”