Dual-Parameters Optical Fiber Sensor With Enhanced Resolution Using Twisted MMF Based on SMS Structure

A compact and low cost optical fiber sensor by introducing higher order modes interference with fiber twisting based on single-mode-multimode-single-mode structure is proposed and demonstrated for simultaneous measurement of strain and temperature. The sensor is fabricated by heating and twisting a section of multimode fiber (MMF), which is spliced between two single-mode fibers. By adjusting the heating temperature and rotate speed during fabrication, the twisted region is introduced in MMF, which is able to couple more power of light into the cladding and introduce higher order modes in modal interferences. With this method, strain sensitivity of -7 and -2.19 pm/με as well as temperature sensitivity of 17.33 and 13 pm/°C are obtained. By spatial frequency demodulation method, measurement resolution reaches ±2.14 με and ±0.89 °C, which has great potential in dual-parameters measurement of temperature and strain with high resolution.