Abstract: A dispersion compensator for the compensation of chromatic dispersion in a multi-channel light signal is provided. The compensator includes a pair of optical structures each having a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. An optical assembly propagates the light signal sequentially through both optical structures. The periods of the grating components are selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components of each optical structures, and proper selection of the tuning parameters allows tuning independently both the dispersion and dispersion slope.

Abstract: An optical sensor is provided. The sensor includes an optical fiber having a free extremity on which a polymer layer is deposited normal to the longitudinal axis. A light source injects a analytical light beam in the fiber, which is reflected by the polymer layer. The reflected beam is analyzed by a spectrum analyzer, which determines the thickness of the polymer layer based on the Fabry-Perot effect. This thickness is related to a substance to be detected. An optical nose made from a plurality of such sensors is also provided, and may be used to detected a variety of substances.

Abstract: A tunable optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particular channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal. Tuning means are also provided in order to adjust the dispersion of the grating components to the required values.

Abstract: An optical structure and devices based thereon for the compensation of chromatic dispersion in a multi-channel light signal are provided. The optical structure includes a waveguide and a Bragg grating provided therein. The Bragg grating has a plurality of grating components, each associated with one or a few of the channels to be compensated. The period of each grating component is selected to allow compensation of chromatic dispersion experienced by this particular channel or these particluar channels, thereby taking into account the wavelength-dependent dispersion slope of the light signal.

Abstract: A method and an apparatus for recording optical gratings in a photosensitive medium are provided. The invention uses a phase mask in combination with a scanning of the recording light beam. The phase mask, or alternatively the photosensitive medium, is translated along a direction parallel to the scanning of the light beam, so that the period of the recorded grating may be locally adjusted. To ensure a proper recording efficiency over a large range, an appropriately selected wavefront curvature is provided in the light beam. The method of the invention is particularly advantageous for the recording of superimposed grating components in a photosensitive medium.

Abstract: The method for scanning a turbid medium involves displacing an optical signal source over a first face of the medium and a corresponding optical detector over an opposite face from one respective spatial location to another. Each spatial location is associated with a corresponding input region on the first face and a corresponding output region on the opposite second face. The optical detector in response to optical signals detected from each of the output regions generates a primary set of image data, secondary and/or tertiary image data by scanning the turbid medium using input regions and output regions of different sizes. The various sets of image data obtained may be manipulated in any manner, namely subjected to a data processing technique, so as to, for example, highlight the differences or similarities between the images.

Abstract: A scanning module for imaging through scattering media is provided. The scanning module image through scattering media while alleviating adverse effects of the weak transmission through highly scattering media. The injection of photons is optimized so that the overall transmission is increased compared to the conventional art. Cross-talk effects in a multi-port geometry are eliminated thereby increasing parallelism.

Abstract: An optical sensor is provided. The sensor includes an optical fiber having a free extremity on which a polymer layer is deposited normal to the longitudinal axis. A light source injects a analytical light beam in the fiber, which is reflected by the polymer layer. The reflected beam is analyzed by a spectrum analyzer, which determines the thickness of the polymer layer based on the Fabry-Perot effect. This thickness is related to a substance to be detected. An optical nose made from a plurality of such sensors is also provided, and may be used to detected a variety of substances.

Abstract: A method of optical imaging through a scattering medium is provided in which a fit is made to an inhomogeneous diffusion model. The method facilitates good differentiation between scattering and absorption. The variation of the diffusion curve associated with the presence of an inclusion is considered rather than the diffusion curve itself. An empirical model is provided which describes the variation of the diffusion curve. A linear curve fitting process is performed to provide two parameters, one parameter associated with the scattering property of the inclusion and the other parameter associated with the absorption property of the inclusion.

Abstract: A method and an apparatus to photoinduce a grating or other type of modulated refractive index change in a photosensitive optical medium such as optical fiber. The resulting grating has a variable and controllable intensity profile and average value of the index change. The modulated refractive index change is photoimprinted in the medium in a series of writing steps, each comprising exposing a segment of the medium to a writing beam for a predetermined exposure time. To change the modulation intensity from step to step, the angle of incidence of the writing beam is dithered for an appropriate fraction of the exposure time at each step. This allows to control the amount of incident light on the medium for each step. If the exposure time is the same for each writing step, the average value of the index change may be kept constant avoiding undesired structure in the grating frequency response.

Abstract: A method for spatially controlling the period and amplitude of Bragg filters in an optical medium having a longitudinal axis that is sensitive to at least some wavelength of electromagnetic radiation. A phase mask of period .LAMBDA. is laid close to the optical medium at an angle .alpha. with respect to the longitudinal axis of the optical medium. A single beam of electromagnetic radiation is directed at an incidence angle .phi. with respect to normal incidence on the phase mask so that the radiation is diffracted, resulting in an interference pattern having a period P impinged into the optical medium so that the period P of the interference pattern may be altered by changing the incidence angle .phi. or the angle .alpha.. This method is simpler, more flexible and more suitable for mass production than existing methods.

Abstract: A method for spatially controlling the period and amplitude of Bragg filters in an optical medium having a longitudinal axis that is sensitive to at least some wavelength of electromagnetic radiation. A phase mask of period .LAMBDA. is laid close to the optical medium at an angle .alpha. with respect to the longitudinal axis of the optical medium. A single beam of electromagnetic radiation is directed at an incidence angle .phi. with respect to normal incidence on the phase mask so that the radiation is diffracted, resulting in an interference pattern having a period P impinged into the optical medium so that the period P of the interference pattern may be altered by changing the incidence angle .phi. or the angle .alpha. . This method is simpler, more flexible and more suitable for mass production than existing methods.

Abstract: An optical device for modulating or interacting with radiation guided and propagating along an optical longitudinal axis of an optical waveguide, such as, an optical fiber, has a different directional geometry compared to conventionally comparable devices such as, for example, plasmon or planar surface modulators for optical fibers. The geometry includes a nonlinear, electro-optic medium formed between two spatially disposed electrodes. The medium/electrode sandwich is aligned along the waveguide longitudinal propagating axis and extends in a radial direction from the optical waveguide core with the inner end of the medium in spatial proximity to the waveguide core for evanescent coupling with the radiation field propagating in the waveguide.