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Multimode interference effects in optical fiber for pressure sensing applications

Applications of Multimode Interference (MMI) effects in optical devices have been increased today due their excellent properties and easy fabrication. Incorporation of these effects in optical fiber has been achieved through a single-mode - multimode - single-mode (SMS) fiber structure showing high sensitivity to bending-loss phenomenon. The latter has been efficiently implemented in pressure sensing application such as is presented in this work. Basically, the SMS structure is embedded in a pressure-sensitive membrane to convert pressure in a mechanical displacement resulting in an attenuation of the transmitted intensity proportionally to the applied pressure. Under this configuration, an all-fiber pressure sensor with high sensitivity and repeatability is obtained into a pressure range from -13 psi to +13 psi. The max pressure range can be varied to 140 psi with our configuration when the membrane thickness is changed. Important features of the proposed all-fiber MMI pressure sensor are its easy-fabrication and low-cost since an inexpensive instrumentation is required.