Optical fiber hydrogen sensor based on a no-core fiber structure

A novel and simple optical fiber structure with a section of no-core fiber for measuring hydrogen concentration is presented. Palladium is sputtered to form the coating on the no-core fiber by magnetron sputtering coater. Under different hydrogen conditions, the absorption of hydrogen induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output spectrum. Different concentrations of hydrogen are tested, from 4%-0.5%, shows the concentration is relevant with the response time and recovery time. The response time of this sensor is from 300s (4% H-2) to 1800s (0.5% H-2) depending on the hydrogen concentration. The recovery time of this sensor is from 1200s (4% H-2) to 4800s (0.5% H-2) depending on the hydrogen concentration. Furthermore, the repeatability and response time of the sensor of this study are investigated experimentally.