Abstract
This paper presents a novel design method in which a dual-polymer fiber Fizeau interferometer (DPFFI) is proposed for simultaneously measuring relative humidity (RH) and temperature (T). Since the polymer is intrinsically highly sensitive to both RH and T, the polymer fiber Fizeau interferometer (PFFI) exhibits cross-sensitivity of RH and T. In general, it is difficult to demodulate the optical responses from both variations of RH and T using a single PFFI. If two PFFIs with different structures are combined, they will individually exhibit distinct sensitivity responses with respect to RH and T, respectively. The technical problem of analyzing multiple interferences of the optical spectra of the DPFFI and the individual sensitivity of RH and T to each PFFI is obtained using the fast Fourier transform (FFT). A mathematical method is applied to solve the simultaneous equations of the DPFFI, so that the two variables RH and T can be determined at the same time. Experimental results, indicating good sensitivity and accuracy, with small measurement errors (average errors of ~1.46 °C and ~1.48%, respectively), are shown, determining the feasibility, and verifying the effectiveness, of the proposed DPFFI sensor.
Highlights
Relative humidity (RH) and temperature (T) are two significant physical parameters affecting a variety of industrial processes, such as semiconductor technology, food processing, biomedical engineering, weather forecasting, and environmental monitoring and control
The proposed dual-polymer fiber Fizeau interferometer (DPFFI) device was placed inside a temperature and humidity controlling chamber (THCC), as displayed in Figure 2, which was a closed space in which the T
We have developed a dual polymer fiber Fizeau interferometer (DPFFI) and used it to measure relative humidity (RH) and temperature (T) simultaneously using the fast Fourier transform (FFT) and
Summary
Relative humidity (RH) and temperature (T) are two significant physical parameters affecting a variety of industrial processes, such as semiconductor technology, food processing, biomedical engineering, weather forecasting, and environmental monitoring and control. An interesting fiber optic hybrid device composed of an FBG and a reflection-type photonic crystal fiber interferometer (PCFI) infiltrated with RH-sensitive agarose for simultaneous T and RH measurement was proposed and demonstrated in [2]. A hygroscopic polymer microcavity fiber Fizeau interferometer (PMFFI) incorporating a fiber Bragg grating (FBG) was proposed in [7] for the simultaneous measurement of RH and T. A long-period fiber grating (LPG)-based sensing head with an in-line FBG was proposed in [8] for simultaneous measurement of RH and T. Of all the above-reviewed RH/T sensors, both the sensing sensitivity and resolution may not be high enough for certain high-tech applications Most of these fiber-grating-based sensors usually require complicated laser-written fabrication using expensive equipment. Higher sensing sensitivities for RH and T were achieved, and no expensive equipment for laser-written fabrication of fiber-grating-based sensors was required. Show that the proposed DPFFI sensor is capable of effectively and simultaneously measuring the surrounding RH and T with good accuracy
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