Temperature-insensitive fiber-optic devices using multimode interference effect.

We show theoretically that the fiber-optic devices using single-multi-single mode fiber structures can be made temperature insensitive by properly adjusting the concentration of P(2)O(5) in the core region of the multimode fiber used. Taking an example of a parabolic index multimode fiber, we obtain the temperature-insensitive transmission spectrum and fiber-optic lens action for a core composition of 1.57 mol. % P(2)O(5) and 13.5 mol. % GeO(2) in the SiO(2) host.