On-fiber tunable Bragg gratings for DWDM applications

Apparatus comprising:

• a polarization independent tunable Bragg grating pattern in an optical fiber having a cladding layer surrounding a core, the cladding layer including a section that includes:
• an inner transparent electrode surrounding the core;
• an electrooptic material surrounding the inner electrode, the electrooptic material having an inner surface in contact with the inner electrode and an outer surface spaced radially outward from the inner surface, wherein one of the inner surface and outer surface has a continuous and smooth periodic variation that defines a geometrical first Bragg grating, and the other of the inner surface and outer surface is generally cylindrical so that radial thickness of the electrooptic material varies along a length of the electrooptic material based upon the continuous and smooth variation in the one surface;
• and
• an outer electrode on the outer surface of electrooptic material, and surrounding the electrooptic material so that application of an electric field between the inner and outer electrodes creates a periodic variation in refractive index along the length of the electrooptic material that produces an electrically variable second Bragg grating that together with the geometrical first Bragg grating provides tuning of both a Bragg diffraction angle and a Bragg wavelength of light propagating within the core.