Temperature self-calibrated pH sensor based on GO/PVA-coated MZI cascading FBG

Abstract

A temperature self-calibrated potential of hydrogen (pH) sensor based on the single mode fiber-tapered dual core photonic crystal fiber-single mode fiber (SMF-TDCPCF-SMF) structure cascaded with a fiber Bragg grating (FBG) is proposed and demonstrated. The TDCPCF structure formed Mach-Zehnder interferometer (MZI) is modified with a coating of graphene oxide/polyvinyl alcohol (GO/PVA) hybrid hydrogel to realize the measurement of pH, and the uncoated FBG is used to calibrate temperature. In our experiment, the sensitivity coefficient of 0.69 nm/pH with R2=0.99 and the hysteresis loss of less than 0.007 are achieved within the pH range from pH 4.00 to pH 9.85. The measured response time from pH 7.00 to pH 4.00, 6.00 and 9.85 are no higher than 10s. Moreover, the resonant wavelengths of MZI and FBG also exhibit good linear relationship with the temperature sensitivity coefficient of 0.15 nm/°C (R2=0.99) and 0.09 nm/°C (R2=0.97) respectively. It is demonstrated successfully that the proposed sensor has broad application prospects in the field of environmental monitoring, biological sensing and chemical analysis, due to the good performance of the temperature self-calibrated pH monitoring, repeatability, linearity, response time and reversibility.

Rapid-Response and Wide-Range pH Sensors Enabled by Self-Assembled Functional PAni/PAA Layer on No-Core Fiber

“…Obviously, it does not accurately detect the pH of the liquid environment. The GO/PVA-based sensor [ 18 ] cascaded the MZI and FBG to form a temperature self-calibrating pH sensor with excellent stability and good repeatability. Although this reduces temperature crosstalk during testing, it cannot ensure detection for universal pH conditions.…”

“…The surface plasmon resonance (SPR) sensor realizes the high sensitivity detection of pH by utilizing a characteristic of the sensitive film: expanding/contracting with the change of pH. Yan et al [ 18 ] reported a pH sensor with a Mach–Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG), by coating the graphene oxide/polyvinyl alcohol (GO/PVA)-sensitive film for pH detection, while the FBG was used for temperature calibration, which realized the temperature-self-calibrating pH monitoring. However, the disadvantages of complex optical fiber structures and fabrication processes have hindered their practical application.…”

Strain and Temperature Discrimination Based on a Mach-Zehnder Interferometer With Cascaded Single Mode Fibers

“…By differentiating ( 4) to (7), the wavelength shifts of the four sets of spectrum dips caused by the variation of strain ( ε Δ ) and temperature ( T Δ ) are determined by [21] ( )…”

“…In-fiber Mach-Zehnder interferometers (MZIs) have been studied recently for various sensing applications such as the sensing of strain [1][2][3][4][5], temperature [6], pH [7,8], pressure [9,10], curvature [11,12], humidity [13], refractive index [14][15][16], and magnetic field [17,18]. An in-fiber MZI can be manufactured with multiple methods, for instance, using down-tapering structures [3], up-tapering structures [1], core-offset splicing structures [14] or simply splicing fibers with mismatched cores [4].…”

Demodulation Algorithm for Fiber Bragg Grating Sensors

“…(5) Owing to the wavelength modulation, changes in the light source intensity, link loss, and the electrical signal intensity of an optical fiber sensing system will not influence the measurement results. Therefore, FBG sensors are widely used to monitor physical parameters such as temperature, (6,7) strain, (8) and displacement in the aerospace, civil engineering, petroleum, and petrochemical fields. (9)(10)(11) Accurate wavelength demodulation is the key to FBG sensing systems.…”