Optical Capillary Fiber Mode Interferometer for Pressure Sensing

A compact optical fiber pressure sensor is experimentally presented. It consists of a few millimeter long section of a capillary optical fiber spliced between two single-mode fibers (SMFs). Due to the interference between propagating light in the capillary fiber caused by the fundamental core mode of the input SMF, an interference pattern is generated in the transmission spectrum of the device through the output SMF. When pressure is applied to the device, the distributed forces on the capillary tube fiber lead to changes in the visibility of the interference fringes and a wavelength shift. The visibility changes are directly correlated to the pressure applied to the device. The dynamic range of the device can be tailored by selecting a suitable length of the capillary fiber. The response of the device to temperature changes is also discussed.