HIGH-SENSITIVITY REFRACTIVE INDEX SENSORS BASED ON IN-LINE HOLES IN PLASTIC OPTICAL FIBER

Abstract

In this letter, we propose a compact and simple high-sensitivity refractive index sensor based on cascaded in-line holes in multimode plastic optical fiber (POF). Due to multimode nature of the structure, transmittance of a sensor with N in-line holes becomes the N-th power of that for a single hole sensor to achieve high sensitivity easily. Experimental results show that a sensor with three 0.7-mm holes spaced 5-mm in 1.5-mm POF exhibited a sensitivity of 43.8 dB/RIU, which is about three times in logarithmic scale that of a 0.7-mm single-hole sensor, 14.8 dB/RIU. Similarly, a sensor with three 0.9-mm holes showed a sensitivity of 62.9 dB/RIU compared to 22.0 dB/RIU for a 0.9-mm single-hole sensor. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:918-921, 2015