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Sensors 2017, 17(5), 944; doi:10.3390/s17050944

A Cost-Effective Relative Humidity Sensor Based on Side Coupling Induction Technology

Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China
Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China
Author to whom correspondence should be addressed.
Academic Editors: Francisco J. Arregui and Jesús M. Corres
Received: 21 March 2017 / Revised: 16 April 2017 / Accepted: 21 April 2017 / Published: 25 April 2017
(This article belongs to the Special Issue Humidity Sensors)
View Full-Text   |   Download PDF [7528 KB, uploaded 25 April 2017]   |  


A intensity-modulated optical fiber relative humidity (RH) sensor based on the side coupling induction technology (SCIT) is presented and experimentally demonstrated. The agarose gel and the twisted macro-bend coupling structure are first combined for RH sensing applications. The refractive index (RI) of the agarose gel increases with the increase of the RH and is in linear proportion from 20 to 80%RH. The side coupling power, which changes directly with the RI of the agarose gel, can strip the source noise from the sensor signal and improve the signal to noise ratio substantially. The experiment results show that the sensitivity of the proposed sensor increases while the bend radius decreases. When the bend radius is 8 mm, the sensor has a linear response from 40% to 80% RH with the sensitivity of 4.23 nW/% and the limit of detection of 0.70%. A higher sensitivity of 12.49 nW/% is achieved when RH raises from 80% to 90% and the limit of detection decreases to 0.55%. Furthermore, the proposed sensor is a low-cost solution, offering advantages of good reversibility, fast response time, and compensable temperature dependence. View Full-Text
Keywords: relative humidity sensor; side coupling induction technology; agarose; twisted macro-bend coupling structure relative humidity sensor; side coupling induction technology; agarose; twisted macro-bend coupling structure

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Zhang, Y.; Hou, Y.; Liu, W.; Zhang, H.; Zhang, Y.; Zhang, Z.; Guo, J.; Liu, J.; Zhang, L.; Tan, Q.-L. A Cost-Effective Relative Humidity Sensor Based on Side Coupling Induction Technology. Sensors 2017, 17, 944.

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