Catalyst-type-an optical fiber sensor for hydrogen leakage based on fiber Bragg gratings

A highly sensitive hydrogen gas sensor based on a fiber Bragg grating (FBG) has been developed. Various potential hydrogen sensor materials were screened by assessing the catalytic activities of oxide-supported platinum particles prepared by a sol-gel method. It was determined that a Pt/SiO2 film was the most appropriate sensor material; exposure of this film to 4 vol% H2 in humid air for 30 s at room temperature produced a temperature change of 65 K. In addition, the Pt/SiO2 was able to respond to a concentration as low as 0.1 vol% H2 in dry air. Two types of sensor structures were fabricated and evaluated. The device incorporating a quartz glass substrate covered with the sensor film on one side was able to detect 0.4 vol% H2 in dry air at room temperature with a response time of approximately 25 min. The other device, in which the sensor film was immobilized on the periphery of the FBG section, exhibited rapid response to 0.6 vol% H2 within 20 s.