An in-situ detection method and device for the distribution of doping elements in an optical fiber preform

Abstract

An in-situ detection method and apparatus for distribution of doping elements in an optical fiber preform. The method comprises: focusing a pulse laser to a to-be-detected point on the surface of an optical fiber preform, to form several or dozens of micron-sized light spots, instantly ablating at the laser focusing point, and generating plasma; collecting the plasma at the to-be-detected point, and obtaining coordinate information and element concentration information of the to-be-detected point; obtaining a doping element concentration distribution spectrogram of precision required by the optical fiber preform according to coordinate information and element concentration information of multiple different to-be-detected points; and then improving an analysis result by using a median filter and a frequency domain filter. The apparatus comprises a laser system, an optical path system, a spectrum collection system, and a control analysis system.

Description

technical field [0001] The invention belongs to the technical field of optical detection, and relates to a high-resolution, non-contact, non-vacuum and multi-element in-situ detection method and device for doping element distribution of an optical fiber preform rod. Background technique [0002] In the early optical fiber preparation, people were trying to remove various impurity elements in the optical fiber to improve the purity of the silica optical fiber, thereby reducing the loss of the optical fiber. In the 1980s, Payne and others at the University of Southampton in the UK first discovered that optical fibers doped with rare earth elements have laser oscillation and optical amplification. S.B.Poole and J.E.Townsend found that by strictly controlling the content and type of dopant ions in the core and cladding, the optical fiber can have special properties such as anti-irradiation and anti-photon darkening. For optical fibers with specific doping elements, many new cha...

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Problems solved by technology

[0004] However, the refractive index measurement method can only infer the overall distribution of doping elements through the refractive index distribution, and cannot obtain the distribution information of each element. This method is suitable for detecting single-element doped optical fiber preforms. stick does not apply

The electron probe method not only needs to spray the conductive layer on the optical fiber preform sample before measurement, which will interfere with the low concentration of doping elements, but also requires a vacuum environment, and the operation is too complicated and time-consuming

X-ray fluorescence spectrometry is only suitable for measuring elements with an atomic number greater than 11, and the X-ray focusing ability is limited, making it difficult to achieve high-resolution analysis

Atomic absorption spectrometry can only measure more than 70 elements in the periodic table of elements. Common elements such as phosphorus and sulfur cannot be measured, and the measured elements are different. The excitation light source lamp must be replaced, and simultaneous measurement of all elements cannot be achieved.

Inductively coupled plasma atomic emission spectrometry is currently the most commonly used analysis method, but it needs to dissolve the glass material in hydrofluoric acid first, which will generate highly toxic silicon tetrafluoride gas, and it needs to be diluted first for elements with high content. Therefore, the in-situ analysis of the optical fiber preform cannot be realized, and the distribution of its element content cannot be obtained

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