Simple Optical Fiber Sensor for Express and Cross-Sensitive Hydrogen Detection

The utilization of hydrogen as an energy source is becoming more and more widespread. Since hydrogen is a highly explosive gas, its use requires the development of inexpensive and simple sensors capable of measuring hydrogen concentrations under a variety of conditions. These sensors must meet several parameters, such as small size, light weight, corrosion resistance, and remote operation capability. The ideal hydrogen sensors should also be insensitive to the presence of various interfering gases and humidity or temperature variation and be protected against potential poisoning. In this work, we present a simple optical hydrogen sensor that satisfies most of the above criteria. The sensor is based on a plasmon-active multimode optical fiber coated with Pd and PDM layers in a stepwise manner. The Pd layer, deposited on the plasmon active area, ensures sensitivity toward hydrogen through hydrogenation of Pd, leading to a significant shift in the plasmon absorption band wavelength position. An additional PDMS layer ensures sensor protection against various interfering gases (NO₂, CH₄, CO₂, CO, and NH₃), including the moisture of sulfur-containing compounds. The sensor response is measured within tens of seconds, while its regeneration takes approximately 2 min. The operating temperature range is from RT to 80 °C, with a slight decrease in sensor functionality at an elevated temperature. The proposed structure is simple, allows the removal of hydrogen detection, and can be used under various operation conditions.