Alcatel Alsthom Compagnie Generale D'electricite

Alcatel

Fatima Bakhti

Pierre Sansonetti

Isabelle Riant

Francedillaois Gonthier

An optical filter has little variation in chromatic dispersion over its passband, the filter being constituted by a Bragg grating whose pitch varies as a function of distance along the filter with a change in the sense of its concavity. The filter also presents apodization, e.g. apodization by a super-Gaussian function or Blackman apodization. The filter of the invention is adapted to high data rate dense WDM transmission systems.

Optical filter with little variation in chromatic dispersion

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.

Band-pass filter in an optical waveguide

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.

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Palaiseau, France

Fatima Bakhti