Abstract: The present invention relates to a fiber grating filter optical waveguide device, comprising an optical fiber consisting essentially of silica, whereby said optical fiber has an area with a diffractive grating region and wherein said area with a diffractive grating region is covered with a material having a negative thermal expansion coefficient &agr; satisfying the following equation:

Abstract: The present invention relates to a fiber grating filter optical waveguide device, comprising an optical fiber with an optical filter, both consisting essentially of silica, whereby said optical filter has an area with a grating region, wherein said area with a grating region is covered with a layer comprising a material having a refractive index which is the same or higher than the refractive index of the material of the optical fiber. The variation of the physic-chemical nature of said material allows to match the changes in the refractive index of the optical fiber of the optical filter when specific requirements for a high transmission spectrum of the filter are required.

Abstract: The invention proposes a photosensitive optical fiber for inscribing a Bragg grating by UV illumination, in which the photosensitivity is very high either to reduce the exposure time or to increase the contrast of the optically induced refraction index variations, whilst retaining a reasonable exposure time. Thanks to this high contrast, the fiber of the invention, imprinted with a linear chirp, in addition to correcting chromatic dispersion, is also effective in correcting the chromatic dispersion slope of a fiber of ordinary contrast, imprinted with a quadratic chirp. In a preferred embodiment, the fiber of the invention is photosensitive in the cladding. In a particularly advantageous embodiment, a non-photosensitive dopant is added to the core of said fiber to reduce the refractive index in the core, reducing the birefringence of the fiber.

Abstract: The invention relates to the field of optical fiber wavelength division multiplexed transmission, and more particularly to the field of narrow-band optical filters for dense multiplexing. The invention proposes a narrow-band optical filter with a group-delay response that is very flat in the working band, obtained by cascading two Bragg gratings having group delays that are linear as a function of wavelength in the working band, but with their gradients being of opposite signs. The present solution is easier and less costly to implement than the prior art solutions, and it should also offer higher performance.

Abstract: An angled Bragg grating optical waveguide section adjusts the spectral response of a transmission filter in an optical waveguide or in an optical fiber. To smooth the response of the filter, which is subject to modulation due to coupling to the various cladding modes, the pitch of the Bragg grating is caused to vary in a linear fashion along the length of the filter. To adapt the attenuation band to a required band, the cladding of the optical fiber is doped with a photosensitive material so that the grating is also formed in the cladding. The photosensitivity of the cladding is advantageously greater than that of the core, in a ratio in the order of 5:1.

Abstract: It is shown that by modifying the photosensitivity profile it is possible to provide better adjustment of the characteristic curve of a filter, and in particular to eliminate a reflection peak that is present within the working band. The photosensitivity profile is inverted to a considerable extent. In practice, the core of the fiber has only 20% of photosensitive doping material compared with the quantity of photosensitive doping material present in the cladding of the fiber.

Abstract: To adjust the spectral band of an attenuating optical fiber, a section of the optical fiber is formed that has a sloping Bragg grating. To smooth the spectral band of the attenuation, it is shown that the filter section must be short. Independently of selectivity, the smoothing makes it possible to avoid distorting the filtered signal. The length of the filter section is preferably 0.7 mm.

Abstract: A band-pass filter written into an optical waveguide includes at least one Bragg grating creating coupling between two propagation modes. In one version the pitch of the grating is equal to the length of beating of these two modes, to create codirectional coupling for the LP01 and LP0i modes. In another version the grating couples the LP01 mode to any contradirectional radiation mode. The filter includes, at one point at least of the grating, an area in which one half-period of the grating is omitted to create a phase-shift of .pi. between the two coupled modes.

Abstract: An optical filter is formed by writing at least one long-period Bragg array into an optical fiber which is tapered to define two substantially adiabatic transition areas delimiting an intermediate area in which the long-period Bragg grating is written to produce codirectional coupling between two guided modes in the intermediate area at a wavelength that is a function of the period of the grating.

Abstract: A system for writing a Bragg grating point-by-point in an optical waveguide includes an illumination system for producing a primary beam. It further includes a diffraction grating to receive the primary beam and to produce a zero order secondary beam and two symmetrical secondary beams of higher order and a focusing optical device for focusing the secondary beams onto a writing area of the waveguide. The diffraction grating and the focusing optical device define an intensity function of writing in the area of the guide including a central peak and two secondary peaks spaced from the central peak by a distance equal to the pitch of the grating.

Abstract: An all-optical time slot interchange device comprises at least two wavelength selective delay lines disposed in series and each comprising a delay line for delaying the propagation of an optical signal by increasing the length of the optical path it travels. An optical signal at a given wavelength is extracted from a guide structure and re-injected into the guide structure via the delay line so as to apply a time-delay to the optical signal at a given wavelength. Applications include wavelength-division multiplexing optical telecommunication systems.

Abstract: The invention provides a Fabry-Perot filter for guided light, the filter comprising two Bragg gratings that follow each other along a common light guide, a gap being left between the two gratings, wherein the two gratings have respective different lengths. The invention is particularly applicable to optical fiber telecommunications systems.

Abstract: In a laser device, notably for optical pumping, the wafer includes an expansion segment adjacent the exit to prevent degradation of the exit facet of the semiconductor wafer that constitutes the amplifying part of the laser. The other facet is reflective and a Bragg grating is formed in a coupling fiber disposed near the exit facet. Applications include optical pumping of erbium-doped fiber amplifiers.

Abstract: A laser source supplies a primary laser beam. A phase grating generates two secondary beams from the primary beam so as to form interference fringes that are inscribed in an optical fiber by photo-refraction. An optical system of variable focal length varies the gap between the interference fringes so as to vary the pitch of the Bragg grating discretely for successive segments of the optical fiber. Means displace the primary laser beam and the optical fiber relative to each other by successive segments of said fiber. These means are synchronized with the variation of the focal length of the optical system. Application to telecommunications.

Abstract: To modify the longitudinal pitch distribution of a diffraction grating, longitudinal dimensional variation is imparted, over time, to a support along the entire length of a line on which said support carries, at least indirectly, a succession of diffraction elements of the grating. By way of example, the support is an auxiliary part on which an optical fiber is stuck, said fiber including said grating. An elongation coefficient dl/l represents the local relative value of dimensional variation. This value varies along said line. The invention is particularly applicable to making variable pitch light-refracting filters in optical fiber telecommunications systems.