Simultaneous measurement of temperature and RI based on an optical microfiber coupler assembled by a polarization maintaining fiber

Abstract

A temperature and refractive index simultaneous measurement sensor based on an optical microfiber coupler (OMC) combined with a polarization maintaining fiber (PMF) is proposed and experimentally demonstrated. The OMC-PMF sensor is fabricated by inserting a section of PMF between two output ports of the OMC. The interference spectrum of the OMC-PMF sensor has different responses to temperature and refractive index variations. Temperature and the refractive index can be measured by monitoring the dip intensity variation and the dip wavelength shift of the interference spectrum, respectively. The experimental results show that the refractive index sensitivity is 12 020 nm/RIU, and the temperature sensitivity is 0.88 dB/°C upon increasing temperature from 35 °C to 41 °C.

State-of-the-Art Optical Microfiber Coupler Sensors for Physical and Biochemical Sensing Applications

“…For the tip structure, the end of the MFC acts as a reflection-based probe to get access to samples through a tiny point of insertion [ 24 ]. The loop structure also makes the input and output at the same end, which is convenient for practical implementation and is easy to realize multiparameter coexistent monitoring by combining with other sensing elements [ 32 ].…”

“…The first method has to monitor the various target parameters using the various optical feature demodulation. For example, in Reference [ 32 ], the dip wavelength is sensitive to RI change but slightly responsive to temperature change, as the intensity of the transmission spectrum is sensitive to temperature change but insensitive to RI change. The sensitivities for temperature and RI can be valued by the intense and dip wavelength, respectively.…”

“…The two fibers penetrate and stick to one another, in the waist region, under the high temperature. Additionally, MFC tip [ 23 , 24 ] and MFC loop [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ] are made by cutting off the waist region and connecting the two output ports, respectively. The two MFC-based structures are reported as having potential in the sensing area with their advantages.…”

“…Refractive index (RI) [ 25 , 28 , 29 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], force [ 50 ], twist [ 27 , 51 ], vibration [ 52 ], and strain [ 53 ] have direct effect on the signal transmission of MFC waist region. By covering and well packaging the waist region with functional materials, monitoring of temperature [ 23 , 24 , 28 , 31 , 32 , 37 , 42 , 43 , 46 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ], humidity [ 31 , 57 , 61 , 62 , 63 , 64 , 65 , 66 ], magnetic field [ 30 , 67 , 68 , 69 ], flow velocity […”

Ultra-Sensitive Fiber Refractive Index Sensor with Intensity Modulation and Self-Temperature Compensation

“…Fiber refractive index (RI) sensors have been widely applied in biology, chemistry, medicine, and other fields with the merits of high sensitivity, compact size, and low-cost [1]. Recently, massive RI sensors include fiber Bragg grating (FBG) sensors [2,3], long-period fiber grating sensors [4,5], surface plasmon resonance refractometers [6,7,8], photonic crystal fiber refractometers [9,10,11], microfiber/microfiber coupler [12,13,14,15], and model interferometer [16,17,18,19,20,21] have been extensively investigated and the sensitivity record is continuously updated. So far, to the best knowledge of the authors, wavelength sensitivity as high as ~2 × 10 5 nm/RIU (RIU: refractive index unit) is achieved in a polarization-maintaining microfiber based structure [22].…”