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A Mach-Zehnder interferometer for measurement of temperature is proposed and experimentally demonstrated, which consists of two sections of single mode fiber (SMF) and a section of thin core fiber spliced between the two SMFs. The two welding areas are heated and stretched to improve the split and recombination of light. The wavelength of the resonant dip will shift when temperature varies due to the thermo-optic and thermal expansion effect. The experimental results show that a temperature sensitivity of 65 pm/°C with a linear correlation coefficient of 0.996 can be achieved in a temperature range from 25 °C to 80 °C. Due to its ease of manufacture, low cost, and high sensitivity, the fiber optic temperature sensor is suitable for temperature measurement applications. [ABSTRACT FROM AUTHOR]

A fiber sensor for simultaneous measurement of temperature and strain based on a fiber Bragg grating (FBG) with the pigtail fiber covered with epoxy resin is presented. The side mode suppression ratio of the FBG will vary with the temperature due to the Fresnel reflection from the interface between the pigtail fiber and the epoxy resin whose refractive index is sensitive to the temperature. The sensor is also capable of simultaneous measurement temperature and strain by combining the Bragg wavelength shift characteristics as the temperature and strain of the FBG. [ABSTRACT FROM AUTHOR]

A simple fiber-optic displacement sensor based on reflective intensity modulated technology is demonstrated using a fiber collimator. The sensing range is over 30 cm, which is over 100 times that of the conventional fiber-optic displacement sensor based on the normal single-mode fiber. The measured data are fitted into linear equation very well and the values of R-square are more than 0.995. The sensitivity of the device achieves 0.426 dB/cm over the range of 5-30 cm. By applying the relative technique, the errors resulted from the fluctuation of light source and influences of environment are effectively eliminated, and the stability for wide range measurement can be improved. The simplicity of the design, high dynamic range, stability and the ease of the fabrication make it suitable for applications in industries. [ABSTRACT FROM AUTHOR]

In this paper, a new, automatic method of measuring air dew-point (DP) is presented. The system also realizes a relative-humidity sensing function, based on dew point and temperature measuring channels acquired data. The DP is detected on the surface of a lithium chloride-polyvinyl alcohol film fabricated on an optic fiber head using an optical system. The refractive index of the sensing film will be at its maximum value when the dew or frost starts to form at DP. A setup which includes a dew point sensor head and a measurement/control/data collection interface is assembled to enable automated measurements. Several programs are designed using the LabVIEW 8.6 environment to measure the dew point sensing properties of our sensor, such as response-recovery curves, temperature characteristic, and humidity calculation. Anti-interfered and good stability are its main advantages. The sensor can operate in the range of dew point temperature from 0 to 30 °C and relative humidity (RH) from 11% to 83% RH. The repeatability of the sensor was implemented with a standard deviation of 0.09 °C. The results showed that the measured dew point values and RH values were in very good agreement with reference values and with an accuracy of less than ±0.3 °C, 1% RH, respectively, over the whole temperature range. [ABSTRACT FROM AUTHOR]