We use the well-known duality between paraxial diffraction in space and dispersion time to propose a time-domain analog spatial Fraunhofer diffraction. This permits design of real-time optical Fourier-transformer systems. These systems are shown be realizable by linearly chirped fiber gratings as dispersive media.

We have developed a technique to calculate the amplitude of electric field lightwave propagating through fiber Bragg grating (FBG). The is based on transfer matrix method for calculations in multilayer thin films. internal distribution FBG structures having uniform, tapered chirped, and phase-shifted index modulations has been calculated. Two-dimensional plots average power versus distance along axis light frequency are presented.

We propose and demonstrate what we believe to be a new, simple, compact all-fiber design for arbitrary-order ultrafast optical temporal differentiation. The proposed allows us implement any desired differentiation order using maximum of two concatenated fiber gratings, both operating in transmission. A single specially apodized chirped Bragg grating is required implementing even-order differentiator, whereas the immediately next odd-order differentiator can implemented by concatenating...

In this paper, we present a general methodology suitable for analyzing any IBG (Integrated Bragg Grating) as linear time-invariant (LTI) system using the effective refractive index (ERI) and transfer matrix method (TMM). This approach is based on translation of IBG’s physical structure into indexes, neff, which wavelength-dependent describes behavior light in while avoiding use approximations like Coupled Mode Theory does. procedure allows to obtain very accurate reflection transmission...

We analyze the two classic methods for chirped Integrated Bragg Gratings (IBGs) in Silicon-on-Insulator technology using transfer matrix method based on effective refractive index (neff) technique, which translates geometry of an IBG into a neff depending wavelength. also implement procedure that allows engineering parameters, given required bandwidth (BW) and group delay (GD). Finally, complementary designing is proposed, showing significant improvement device or moderation variation...

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 is based on causality stability conditions uses Hilbert Wiener-Lee transforms. In order to obtain complete study of algorithm, we have applied it uniform nonuniform gratings. Finally, get characterization experimental grating, measured reflectivity, by means phase algorithm. Results show good agreement between exact...

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 differentiator can be implemented using single specially apodized highly dispersive linearly chirped FBG operated in transmission. A concatenated reflection phase-shifted is also required implementing any odd-order differentiator. Our numerical simulations show...

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

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

We propose a method for phase, time-delay, and impulse-response reconstruction from spectral power reflectance or reflectivity apply it to uniform fiber Bragg gratings. This is based on causality conditions uses Hilbert Wiener-Lee transforms. Results show good agreement between exact reconstructed functions.

We report the experimental realization of an ultrafast (terahertz-bandwidth) linear optical signal processor, particularly a picosecond flat-top pulse shaper, based on fiber Bragg grating (FBG) working in transmission. The used FBG design technique, specially apodized linearly chirped FBG, enables synthesis readily feasible devices with processing bandwidths well terahertz range. specific device reported here is successfully demonstrated for reshaping ultrashort (400 fs FWHM) Gaussian-like...

We propose a method to reconstruct the grating period in fiber structures from field reflection coefficient or related impulse response. The is based on joint time-frequency signal analysis and uses Wigner-Ville spectrogram distributions. Results show good agreement between exact reconstructed functions.

We demonstrate a general linear pulse-shaping technique based on integrated III-V Bragg gratings (BGs). Such allows for the synthesizing of complex waveforms with picosecond resolution using compact single-waveguide design. This approach is experimentally demonstrated by fabricating and testing series ultrafast optical pulse shapers BG geometries acting as time-domain code generators operating at 500 Gbits/s.

A general and practical approach for designing ultra-fast all-optical (all-fiber) signal processing devices based on chirped fiber Bragg gratings (C-FBGs) working in transmission is presented. The can be used to design any minimum-phase linear optical device, e.g., first high-order time differentiators integrators a large variety of pulse shapers, significantly overcoming the bandwidth limitations previous FBG-based designs. Processing speeds THz range, corresponding sub-picosecond features,...

This paper reviews the state of art fiber Bragg gratings (FBGs) as analog all-optical signal processing units. Besides intrinsic advantages FBGs, such relatively low cost, losses, polarization insensitivity and full compatibility with fiber-optic systems, they have proven to deliver an exceptional flexibility perform any complex band-limited spectral response by means variation their physical parameters. These features made FBGs ideal platform for development broadband filters pulse...

This work deals with the application of femtosecond-laser-inscribed fiber Bragg gratings (FsFBGs) for monitoring internal high-temperature surface distribution (HTSD) in solar receivers concentrating power (CSP) plants. The fiber-optic sensor system is composed 12 FsFBGs measuring points distributed on an area 0.4 m2, which leads to obtain temperature map at receiver by means two-dimensional interpolation. An analysis FsFBG performance harsh environment was also conducted. It describes...

A new photosensitivity physical model for Ge-doped silica preforms based on color-center photoreactions is presented. Simulation results are in close agreement with experimental obtained by several condensed matter physics research groups working this field, suggesting that the of may, indeed, describe processes involved preform photosensitivity. The proposed defined two differential equations temporal evolution a set concentrations. first modification very fast reversible reaction...

We propose a new, general approach to implement an arbitrary linear optical pulse processing operation, generally requiring nonminimum phase spectral response, using minimum-phase filter. This is valid for implementing any desired as long it can be limited over prescribed time window, such short processors or reshapers. The proposed concept particularly interesting the design of based on fiber/waveguide Bragg gratings (BGs) operating in transmission, enabling us overcome bandwidth...

THz-bandwidth photonic Hilbert transformers (PHTs) are implemented for the first time, to best of our knowledge, based on fiber Bragg grating (FBG) technology. To increase practical bandwidth limitation FBGs (typically <200 GHz), a superstructure two superimposed linearly-chirped operating in transmission has been employed. The use FBG involves conversion non-minimum phase response PHT into minimum-phase by adding an anticipated instantaneous component desired system temporal impulse...

We present an alternative method for the complete characterization of linear passive optical devices using measurement spectral power density intermediate interferometric transfer function. Important advantages this compared to other published methods are simplicity setup and fact that iterative algorithms not required. This makes use interferometry implement function which is mathematically related device whose phase response proven be minimum. last permits unique retrieval from magnitude...

Abstract We have developed a simple method to analyze the growth process of fiber gratings (FGs) in core photorefractive optical fibers. It is based on exponential saturation model and it takes into account type photosensitive used, exposure times, incident power. The has been characterized by two parameters: photoinduced refractive index change energy, which can be obtained experimentally. carry out numerical investigation for uniform FG. experimentally observed phenomena shifting Bragg...

A new cost-effective radiometer has been designed, built, and tested to measure direct normal solar irradiance (DNI). The proposed instrument for measurement is based on an optical fiber as the light beam collector, a semiconductor photodiode power, calibration algorithm convert power into irradiance. offers advantage of separating point, where collects irradiation, from place measured. factor mandatory because only spectrally responsive limited part spectral Experimental tests have...