Temperature compensation of multimode-interference-based fiber devices.

Single-mode-multimode-single-mode (SMS) fiber structures have been demonstrated to be a simple and effective way to realize multimode interference (MMI) in optical fibers. The temperature dependence of the spectral characteristics of SMS devices is investigated. By utilizing the feature that the response spectra of SMS devices with opposite polarities to temperature and axial tensile strain, I demonstrate that temperature compensation of SMS devices can be realized by using materials with a proper coefficient of thermal expansion. A temperature stability of 1.0 pm/ degrees C has been experimentally demonstrated with a ceramic as the packaging material.