Simple high-sensitivity optical fiber humidity sensor

Abstract

A new optical fiber humidity sensor with high sensitivity is reported. We effectively control the light-intensity changes in a smaller sensing area and achieve a significant increase in sensitivity by adjusting the depth of the evanescent field of the tapered fiber. The sensor is designed with an 8 µm diameter single-mode tapered fiber structure coated with a thickness of a 10 mm length carbomer layer in the tapered area. The average and maximum relative humidity (RH) sensitivities are 2.59 dB/%RH and 5.43 dB/%RH in the range of 68%–90%. To our best knowledge, the sensitivity of the sensor is highest compared with that of the previously reported. Moreover, the fast response time and recovery time of the sensor are ideal. In addition, the proposed humidity sensor has good repeatability and lower-temperature cross talk. Due to the excellent indicators, the proposed sensor has promising potential for highly sensitive RH sensing applications, especially early warning of special environments.

Moisture sensitive composite fiber based on agarose gel surface modification

“…In the high‐temperature area of 50–70°C, The effect of temperature on the sensor is very limited. The crosstalk is only 0.02 dB/°C, which is a significant advantage over previously reported sensors 12–15 …”

“…The crosstalk is only 0.02 dB/°C, which is a significant advantage over previously reported sensors. [12][13][14][15] The stability of the composite fiber is measured by four times repeat test. The interval between each test is 1 h. The measured result is shown in Figure 7.…”

“…From the cross‐sectional SEM, we can see the average thickness of the film is around 50 nm and the thinnest area of the film is approximately 43.6 nm. Since the film thickness of the sensor does not affect the sensing trend of the sensor in a certain area, 13 this study only focuses on the case of single‐layer coating.…”

Polyimide-Based High-Performance Film Bulk Acoustic Resonator Humidity Sensor and Its Application in Real-Time Human Respiration Monitoring

“…Therefore, relative humidity sensor-based respiration monitoring is less affected by the environmental conditions as compared to the mechanical sensors, conventional air flow meters and thermal sensors. Generally, there are various kinds of humidity sensors, such as optical fibers [ 7 , 8 , 9 ], capacitance [ 10 , 11 , 12 , 13 , 14 ], impedance [ 13 , 14 , 15 , 16 , 17 , 18 ], piezoelectric [ 19 ], surface acoustic wave (SAW) [ 20 , 21 , 22 ], and bulk acoustic wave (BAW) [ 23 , 24 , 25 ]. Among them, film bulk acoustic resonator (FBAR), a typical BAW, has gained wide attention in recent years due to their merits such as high sensitivity, high stability and fast response.…”