Ultracompact Optical Fiber Sensor for Inner Diameter Measurement

ABSTRACTAn ultracompact optical fiber Fabry–Perot interferometric sensor is proposed and demonstrated for inner diameter measurement of a capillary tube. The device is a section of single-mode fiber with an angle-polished end face of 45°. When the device is placed inside the capillary tube and in close contact with its inner wall surface, the reflected light from the angle-polished fiber end face is directed sequentially to the fiber core–cladding, cladding–air, and air–capillary interfaces, respectively, and reflected back, and finally returned to the fiber core after being reflected by the angle-polished fiber end face again. As a result, a cascaded Fabry–Perot interferometer system is constructed, which is well suitable for the inner diameter measurement of the capillary tube. Moreover, the wall thickness of the transparent capillary tube can also be conveniently measured by using the same device in slightly different configuration. The relative error of the measurement is small compared with the data provided by the manufacturer. Such a device is ultracompact, robust, flexible, and convenient in operation and is especially attractive for implementing the measurement in a tight or hard-to-reach spatial environment.KEYWORDS: Cascade F-P interferometerinner parameter measurementinterferometry Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe work was supported by the the National Natural Science Foundation of China [61975192].Notes on contributorsQ. B. WangQ. B. Wang was born in Zhejiang, China. He obtained a bachelor of science degree from China Jiliang University. He is currently working toward the Master’s degree at the College of Optical and Electronic Technology, China Jiliang University. His research interest is optical fiber sensors.D. N. WangD. N. Wang received the B.Sc. degree in telecommunications from the Beijing University of Posts and Telecommunications, China, in 1982, the MBA degree from the University of Ulster, U. K., in 1989, and the Ph.D. degree from City University, London, U.K., in 1995. His main research interests include femtosecond laser micromachining, fiber laser, and optical fiber sensors. He has more than 240 international journal publications.