Fiber Optic Pressure Sensor Using a Conformal Polymer on Multimode Interference Device

We report experimental results on an optical fiber pressure sensor based on multimode interference effects (MMIs). The key component is a small multimode fiber (MMF) section without cladding, which is placed on a direct contact with a polydimethilsiloxane polymer layer previously attached to a pressure-sensitive membrane. When the applied pressure is increased, both the polymer contact area and the induced stress on the MMF increase directly proportional with the applied pressure. Both effects contribute to losses of the propagating modes, and since the MMI spectrum is formed by the interference of the propagating modes, the net effect is that the intensity of the spectral response of the MMI is reduced as the pressure is increased. Therefore, by tracking a single wavelength, the intensity changes are correlated to the applied pressure values. The response of the sensor is highly linear within a pressure range of 0-960 kPa with a sensitivity of - 0.145 ×10
^-3
mW/kPa. The key features of the MMI pressure sensor are its low-cost and high repeatability.