U-bent Fiber Probe Research Articles

Plastic Optical Fiber as Water-Level Sensor

This research presents a low-cost sensor for measuring liquid levels using plastic optical fibers (POF). The sensor reduces the scattering-based optical losses in the fiber, which increase linearly with the liquid height. A U-bent fiber probe and photodetector are used to detect the change in optical intensity. The U-bent probe serves as a test probe for measuring the liquid level. The voltage response difference of the photodetector provides liquid level measurement. This study demonstrates the sensor's responsiveness to liquid level fluctuations above 55 cm at varying temperatures. Sensitivity levels of 1.4 and 3.3 mV/mm were achieved for water level fluctuations below and above 45 cm, respectively. Furthermore, the sensor demonstrated consistently stable responsiveness over multiple cycles.

Highly Stable Plasmonic Nanostructures on a Nickel-Sputtered Glass and Polymeric Optical Fiber Sensors

This study shows development of highly sensitive and stable localized surface plasmon resonance (LSPR)-active U-bent glass and polymeric optical fiber (GOF and POF) sensor probes by a seed-mediated in situ growth technique. Here, the nickel/nickel oxide seeds (Ni/NiO, 3 to 5 nm size) were formed on the U-region of the fiber probe by sputter coating nickel under a low vacuum (3 Pa), and then, gold nanostructures (AuNSs) were grown over the Ni/NiO seeds. The evanescent wave absorbance (EWA) phenomenon in the U-bent fiber probe was exploited to monitor the growth kinetics of AuNSs in real-time. Experimental observations point to a potential galvanic replacement of Ni by Au. The newly formed AuNSs on U-bent GOF and POF probes gave rise to a LSPR-based refractive index sensitivity of 27.66 and 25.65 ΔA/ΔRIU with plasmonic peak at 600 and 570 nm, respectively. These plasmonic probes show an excellent chemical and mechanical stability, in addition to high surface enhanced Raman scattering (SERS) activity. This quick and facile technique is highly suitable for large-scale manufacture of reliable plasmonic fiber optic sensor probes for chemical and bio sensing applications.