Patent ID: 6941044

Claim:
A tunable optical structure for the compensation of chromatic dispersion in a light signal having a plurality of wavelength channels, each wavelength channel having accumulated a different chromatic dispersion, said optical structure comprising: an optical waveguide having a light propagation axis; a Bragg grating provided in said waveguide across the light propagation axis, said Bragg grating having a plurality of grating components, each of said grating components being respectively associated with a limited number of said plurality of wavelength channels of the light signal and having a characteristic spatially variable Bragg wavelength selected to compensate for a given chromatic dispersion, said Bragg grating defining a longitudinal refractive index profile in said waveguide as defined by the equation: n ⁡ ( z ) = n eff ⁡ ( z ) + ∑ i = 1 m ⁢ ⁢ Δ ⁢ ⁢ n i ⁡ ( z ) ⁢ sin ⁡ ( ∫ 0 z ⁢ 2 ⁢ π p i ⁡ ( z ′ ) ⁢ ⁢ ⅆ z ′ + ϕ i ) where z is the propagation axis of the waveguide, n eff (z) is the average effective index in the waveguide considered slowly varying along the propagation axis, m is the number of grating components in the Bragg grating, Δn i (z) is the spatially dependent index modulation amplitude of a i th grating component, p i (z) is the spatially variable period of the i th grating component and φ 1 is a relative phase associated with the i th grating component; and tuning means for tuning the spatially variable Bragg wavelength of each of said grating components to compensate for the chromatic dispersion of the corresponding limited number of wavelength channels associated with a said grating component.