Simultaneous Measurement of RI and Temperature Based on a Composite Interferometer

Abstract

A novel double-parameters sensor based on a composite interference structure has been designed and implemented in this paper. It can be regarded as a cascade of the conventional single mode fiber (SMF)-multimode fiber (MMF)-Photonic crystal fiber (PCF) -SMF structure, which forms a reflected Fabry-Perot interferometer (FPI) and a transmitted Mach-Zehnder interferometer (MZI) at the same time. In addition, a simultaneous measurement of temperature and refractive index has been achieved by monitoring the correlative moves of reflected spectrum and transmitted spectrum. The fact that these two spectra do not interfere with each other makes it easier to obtain a demodulation method that does not involve complex fast Fourier transform (FFT) and matrix computation. The sensitivities of temperature and refractive index can reach up to 27.5 pm/°C and 108 nm/RIU, respectively.Index Terms-optical fiber sensor, refractive index measurement, temperature measurement, composite interference structure, PCF.

Simultaneous Measurement of Temperature and Refractive Index Using an Exposed Core Microstructured Optical Fiber

“…where ΔλFBG and ΔλMZ are the wavelength shifts of the FBG peak and Mach-Zehnder interference spectrum, respectively. Using (9) we calculated the measured concentration and temperature. The measured values, target values and the measured differences between the measured values and target values were shown in Fig.5.…”

“…It can be seen from Fig.5 that the measured values are in good agreement with a maximum measured difference between the target values and the sensor values of 0.0296% (4.81×10 -5 RIU) and 0.214°C, for concentration and temperature, respectively. Thus, we can accurately obtain the unknown external RI and temperature variations by simultaneously monitoring the wavelength shifts of the FBG peak, and Mach-Zehnder interference spectrum and using (9).…”

“…Several hybrid interferometers have been proposed, such as two different Mach-Zehnder interferometers [7], a Mach-Zehnder interferometer combined with a Fabry-Perot interferometer [8,9], and a Sagnac interferometer combined with a Mach-Zehnder interferometer [10,11]. Multimode interferometers with standard diameter fibers have been demonstrated for the simultaneous measurement of RI and temperature by utilizing different order modes have different sensitivities to the external RI and temperature, and other parameters [12][13][14].…”

Design and fabrication of a heterostructured cladding solid-core photonic bandgap fiber for construction of Mach-Zehnder interferometer and high sensitive curvature sensor

“…Many methods have been proposed to construct Mach-Zehnder interferometer, and most of which generate the interference by exciting cladding mode and core mode within fiber [19]. The cladding mode can be effectively excited by the particular structures, and the SMF-MMF-SMF structure is the easiest one [20]. When light in MMF is coupled to SMF, a strong cladding mode would be excited in the SMF because of the occurrence of mismatching mode field.…”

High sensitivity temperature sensor based on a polymer filled hollow core optical fibre interferometer

“…Different types of optical fibre sensor structures have been developed including fibre Bragg gratings (FBG) [1,2], long period gratings (LPG) [3], special fibres such as D-shaped fibres and photonic crystal fibres [4,5], multimode fibres (MMF) [6,8], and multi-core fibres [9]. Grating-based temperature sensors are the most popular sensor type but they provide sensitivity in the range of only a few tenths of pm/ o C [10][11][12].…”