Novel waveguide structures for enhanced fiber grating devices

An emerging class of fiber waveguide structures is being used to increase t he functionality of fiber gratings, enabling new devices critical to the pe rformance of next generation lightwave communications systems. These device s rely on advances in the fabrication of optical fiber waveguides, which go beyond the conventional doped silica design and fall into two general cate gories: 1) local modifications to the waveguide after fabrication and 2) fi bers drawn with modified claddings that include nonsilica regions throughou t their length. This paper provides a comprehensive review of emerging fibe r waveguide structures that enhance the functionality of optical fiber grat ing devices. Two examples of technologies that fall into the first category are thin metal films deposited onto the cladding surface, which can be use d for thermal tuning and infusion of nonsilica materials into the air regio ns, which change the waveguide structure and can provide enhanced tunabilit y. The second category is typified by air-silica microstructured optical fi bers, which contain air-voids that run along the length of the fiber. These fibers have unique cladding mode properties that can be exploited in fiber grating based devices.