Coupling refractive index meter for evanescent field among optical fibers and detecting method of coupling refractive index meter

Abstract

The invention discloses a coupling refractive index meter for an evanescent field among optical fibers and a detecting method of the coupling refractive index meter. The coupling refractive index meter comprises a light source, an optical fiber sensor probe, an optical fiber coupler/circulator, a first photoelectric detector, a second photoelectric detector and a data collecting and processing module, wherein the optical fiber sensor probe comprises an optical fiber engraved with inclined optical fiber gratings and a D-type optical fiber which are parallelly arranged and tightly closed; the light source is connected with one end of the optical fiber engraved with the inclined optical fiber gratings through the optical fiber coupler/circulator; the optical fiber engraved with the inclined optical fiber gratings is connected with the input end of the second photoelectric detector through the optical fiber coupler/circulator; one end of the D-type optical fiber is connected with the input end of the first photoelectric detector through a single mode optical fiber; one end, connected with the optical fiber coupler/circulator, of the optical fiber engraved with the inclined optical fiber gratings and one end, connected with the first photoelectric detector, of the D-type optical fiber are on the same side; the first photoelectric detector and the second photoelectric detector are separately connected with the data collecting and processing module. The coupling refractive index meter has the advantage of being higher in refractive index measuring accuracy.

Description

technical field [0001] The invention relates to the design field of a refractive index sensor, in particular to an optical fiber inter-fiber evanescent field coupling refractometer and a detection method thereof. Background technique [0002] Refractive index is an important physical parameter of liquid, and the measurement of refractive index is very important in the fields of environmental monitoring, food, chemistry and so on. The refractive index of a liquid is usually related to its concentration, composition, substance content and other parameters, so its physical and chemical properties can be grasped by measuring the change of the refractive index. Tilted fiber grating is a new type of optical fiber sensor. Due to the introduction of the grating tilt angle, the core mode of the forward transmission can effectively excite the cladding mode of the backward transmission. These cladding modes have different effective refractive indices, which are harmful to the environme...

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Problems solved by technology

However, these probe-type refractive index measurement methods based on the modification of the internal structure of the optical fiber couple to a relatively narrow cladding mode spectrum, which limits the measurement range of the refractive index, especially for biomedical reagents with low refractive index (close to 1.33). measurement, its low sensitivity

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