Photosensitivity effect in optical fibers: A model for the growth of an interference filter

A photosensitive property of short‐length single‐mode optical fibers has been shown to produce a periodical modification of the refractive index of the core when exposed to high‐intensity laser light. Using a model derived from the coupled‐mode theory, we calculate the space‐time variation of the interaction between two waves traveling in opposing directions that are responsible for the formation of an interference filter along the axis of the fiber. Our proposed model for the formation and growth of the filter is in good agreement with experiments; a characteristic photosensitivity coefficient is deduced.