The current invention links to special designed optical grating devices, to a method for tune the wavelength or the spectral response of the device and to systems of communication making use of them. Particularly, it concerns a tunable device along with a support frame for supporting a length of optical waveguide, a waveguide grating consisting of a length of optical waveguide comprising an optical grating where two different gratings of longer period are written in the similar part of the length of optical waveguide, the grating is linked to the support of the opposite sides of the grating and to any extent one mean affecting the optical waveguide by strain or temperature.



Optical fiber gratings are the main components in modern systems of telecommunication. Optical fibers are thin strands of glass able to transmit an optical signal consisting of a large amount of data over long distances with very less loss of information. It is basically a small diameter waveguide consisting of a core having a first index of refraction covered by cladding possessing a second index of refraction or much more. Typical optical fibers are prepared from high purity silica with minor concentrations of dopants for controlling the index of refraction.

Gratings usually comprise a body of material and plurality of considerably equal spaced grating elements like index perturbations, grooves or slits. A normal Bragg grating consists of a length of optical waveguide, like optical fiber, consisting of a plurality of perturbations in the index of refraction considerably spaced equally along with the waveguide length. The remaining wavelengths pass fundamentally unimpeded.

Such Bragg gratings have found to be in use in various applications consisting of adding, dropping, filtering signal channels, stabilization of semiconductor lasers, reflection of fiber amplifier, compensation for waveguide dispersion, pump energy and amplifier gain equalizers. Gratings of waveguide Bragg are fabricated conveniently by doping a core of waveguide and sometimes become part of cladding with one or more dopants that are sensitive to ultraviolet light, e.g. phosphorous or germanium, and exposing the waveguide at spatially periodic intervals to a source of high intensity ultraviolet light. The ultra-violet light communicates with the photosensitive dopant for producing long-term permanent perturbations in the local index of refraction.