Multimode-single- fiber surface plasma mode structured optical resonance sensor and detection method thereof

Abstract

The invention provides a multimode-single-mode structured optical fiber surface plasma resonance sensor and a detection method thereof. The sensor comprises a broad-band light source, an optical isolator, an optical fiber coupler, an optical circulator, a multimode fiber, a coating sensing unit, a spectrograph and a computer. Light emitted by the broad-band light source is transmitted to the core of the multimode fiber, and at the junction of the multimode fiber and a single-mode fiber, because the core diameter of the single-mode fiber is far smaller than that of the multimode fiber, an optical signal in the core of the multimode fiber is partially leaked to the cladding of the single-mode fiber, and surface plasma resonance effect is generated at the sensing unit so as to carry out online detection on external substances. According to the invention, light leaking to the cladding of the single-mode fiber is sufficiently used for detection, treatment on the cladding is avoided, influence of the cladding of the fiber on the sensor is eliminated, the detection sensitivity of the sensor is improved, the making difficulty of the sensor is reduced, and compared with a sensor with a multimode-single-mode-multimode structure, the light transmission efficiency of the sensor is improved, and detection for a weak signal is realized.

Description

technical field [0001] The invention relates to the technical field of on-line detection of optical fiber sensing, in particular to a new-structure optical fiber surface plasmon resonance sensor composed of a multimode optical fiber and a single-mode optical fiber and a detection method thereof. Background technique [0002] Optical fiber surface plasmon resonance sensor is a new type of surface plasmon resonance sensor proposed by R.C.Jorgensen of Washington University in 1993 based on the principle of prism-type surface plasmon resonance sensor. The surface plasmon resonance sensor with this structure uses multi-mode or single-mode optical fiber instead of a prism as the coupling medium for exciting the surface plasmon resonance effect, which improves the stability of the sensor and enables better remote real-time online detection. At present, fiber optic surface plasmon resonance sensors have received extensive attention and research. Optical fiber surface plasmon resona...

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Problems solved by technology

[0003] However, traditional optical fiber surface plasmon resonance sensors and optical fiber surface plasmon resonance sensors with tapered, wedge-shaped, and D-shaped structures all need to treat the fiber cladding as a sensitive unit, and the cladding is likely to remain when the cladding is removed, which limits the sensitivity of the sensor. , the optical fiber surface plasmon resonance sensor with multimode-single-mode-multimode (MSM) structure uses the light leaked into the cladding of the single-mode fiber for detection, which avoids the processing of the cladding of the fiber, but the sensor light of this structure Loss up to 60%, difficult to detect weak signals

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