A chemical vapor sensor based on Rayleigh scattering effect in simplified hollow-core photonic crystal fibers

A novel optical fiber sensor for minor chemical vapor content detecting, based on Rayleigh scattering effect in simplified hollow-core photonic crystal fiber (HC-PCF), is proposed in this paper. Both ends of the simplified HC-PCF are aligned with standard single-mode optical fibers without splicing, leaving a very short air gap to allow molecules diffusing. As the concentration of volatile organic compounds (VOCs) in a chamber increases, molecules come into the air holes of the simplified HC-PCF so that the Rayleigh scattering is excited, resulting in an intensity loss of transmission light. We can detect the minor change of VOC content by monitoring the output transmission intensity using an optical power meter. The experimental results show that the ethanol concentration sensitivity is ~0.022 dB/ppm, when a ~5.1 cm long simplified HC-PCF is used. The sensitivity will be further improved when a longer simplified HC-PCF is used. When an optical power meter with 0.01 dBm resolution is used, the ethanol concentration's resolution can reach ~0.45 ppm.