Characterizing the performance of mirrorless concentric large core bundled plastic optical fiber displacement sensor for liquid concentration detection

Abstract

Fiber optic displacement sensor is one of the most important technology of modern world due to its versatility to detect various physical and chemical parameters. The objective of this research is to demonstrate a mirrorless plastic optical fiber displacement sensor (POFDS) as a device for liquid concentration detection. The sensor is characterized by using 780 nm laser with maximum output power of 130 mW. The sensor performance is tested by replacing mirror with various colour paper of the same material. The sensitivity of the sensor towards the changes of colour and the output power obtained are 0.0228 mW/μm, 0.1718 mW/μm, 0.1122 mW/μm, 0.106 mW/μm and 0.1267 mW/μm for black, blue, green, red and white colour paper, respectively. The experimental results prove that as the colour changes from dark to bright, the peak output power increases proportionally. The sensor shows a good response to colour paper as reflector thus it is used as a target to replace mirror. The sensor also used to detect paracetamol (PCM) concentration from 5 ppm to 45 ppm in aqueous solution using red and white colour paper as a reflector as both of it projected the highest peak output power compare to others. The sensor has a 98% and 95% of linearity for red reflector and white reflector respectively. The sensor sensitivity towards the changes of output power against the changes in concentration of the solution for each reflector is then compared with mirror. For red colour paper, white colour paper and mirror, the sensitivity is 0.0004 mW/ppm, 0.0008 mW/ppm and 0.02 mW/ppm respectively. The experimental results indicate that the sensor can measure and detect the concentration of paracetamol in aqueous solutions using non-mirror reflector. This research manages to construct a highly stable and persistent sensor, with additional advantages of practicality of design, high efficiency, comprehensive depth of field and low cost of production, which could be beneficial for applications in the sensing field.