This study mainly compares two optimized interrogation techniques for an interferometric fiber-optic surface plasmon resonance (SPR) sensor. For this sensor, both SPR and interference effects are excited in a single fiber structure and they can be applied for dual-parameter measurement. On the other hand, the interference fringe patterns are mixed into the SPR transmission spectra, and the novel interrogation technique should be evaluated. In this study, two optimized interrogation techniques are proposed and their performances are compared. For the first one, the non-linear least square method is used to filter out the interference components and only retain the SPR signal. For the second one, the wavelength-distributed spectra are converted into the spatial frequency-distributed spectra, hence SPR components and the interference components can be discussed individually. The advantages and disadvantages of the two interrogation techniques are discussed thoroughly.
This study proposes a novel interferometric fiber optic SPR sensor which is able to realize both the temperature and the strain sensing with high sensitivity. Firstly, it is fabricated by splicing a no core fiber between two single-mode fibers to form the multimode interference structure. Then, half-length of the no core fiber is deposited by the gold film layer to form the classic three-layer SPR sensor. Finally, PDMS is covered onto the whole surface of the no core fiber, which performs as a medium to convert the external temperature changes into its refractive index variations. When compared with the other fiber optic sensors, the proposed sensor realizes the temperature and strain measurements based on two independent sensing mechanisms, particularly speaking, the temperature sensing is realized based on the SPR mechanism, and the strain sensing is realized based on the multimode interference. Hence, its inherent cross-sensitivity can be largely suppressed since the two sensing mechanisms are independent of each other. Besides, the proposed sensor shows both high-temperature sensitivity (1.13 nm/℃) and strain sensitivity (54.1 pm/με), which is suitable for the dual-parameter measurements.
This study proposes a novel fiber-optic interferometer based on the single-mode fiber-no core fiber-single mode fiber structure with the coated polydimethylsiloxane (PDMS). The no core fiber is the key carrier to excite the modal interference, and the PDMS that covers onto the fiber cascade structure is able to enhance the sensor sensitivity and also protect the sensor structure. The experimental results verify that the proposed sensor owns a high temperature sensitivity and the strain sensitivity, and it is particularly suitable for multi-parameter measurements.