Investigation and fabrication of palladium-copper composite layer as an adsorbent layer of tapered fiber optic hydrogen gas sensor

In this research, the effect of adsorbent layer on the hydrogen gas sensing of tapered optical fiber sensors has been investigated. First, the taperd optical fiber is prepared by heating and pulling a single mode optical fiber. Then, by using magnetic sputtering method, two samples of palladium and palladium-copper layers were deposited on one-side of the surface of the fiber as an adsorbent layer. The results of X-ray energy dispersion spectroscopy analysis (EDX) showed that the ratio of palladium to copper in the sample area is 97. 53 to 2. 47%. Sensor operation tests for different percentages of hydrogen gas showed that the palladium-copper composite layer (Pd97. 53Cu2. 47) demonstrates lower sensitivity in comparison to the palladium layer Typically, the percentage change in output power in the presence of 3% hydrogen gas was 3. 38% for sensors with palladium-copper adsorbent layer and 16. 77% for sensors with palladium adsorbent layer. But anyway the response of the composite layer to different hydrogen precentages exposure is linear, in contrast to the palladium layer which shows a nonlinear behavior.