Hydrogen sensor apparatus and method of fabrication

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG.
1, one type of commercial hydrogen sensor apparatus 10 comprises a blue light source 13, an optical fiber 11 having a thin film palladium or platinum tip 12, and a detector 15.
In use, the source 13 directs light down the fiber 11 to the tip 12 causing a reflected light interference pattern that is measured by the detector 15.
The fringe pattern in the interference signal gives a direct indication of the thickness of the palladium film.
In the presence of hydrogen, the thickness of the tip 12 changes producing an interference pattern 14 in the detector 15, representative of the presence of hydrogen.
Referring to FIG.
2, another type of commercial hydrogen sensor 16 detects the presence of hydrogen by using a palladium film 17 deposited over a Bragg grating 19 in an optical fiber 18.
The fiber 18 is stretched and the deposited film 17 covers the grating 19.
In use, light launched down the fiber 18 is reflected by the Bragg grating 19 at a specific wavelength, determined by the grating geometry.
In the presence of hydrogen, the film 17 alters the grating characteristics to produce reflected light at a wavelength representative of the hydrogen concentration.
Referring to FIG.
3, another type of commercial hydrogen sensor 20 comprises an optical fiber 21 coated with a tungsten oxide film 23 and a palladium film 22 on top.
In use, the palladium tip 22 places a charge on the tungsten oxide 23 when hydrogen is present, causing the tip to change color.
Referring to FIG.
4, a hydrogen sensor apparatus 24 of the invention comprises a transmitting fiber 25 and a reflecting fiber 26 in a dual optical fiber arrangement forming a common tip 27.
The tip 27 is fitted with a palladium/tungsten oxide sensor rod 28 fabricated in accordance with the principles of the invention.
The rod 28 may include a mirrored surface 35.
A light source 29 within the range of 400 to 700 nanometers is coupled to the transmitting fiber 25 and an optoelectronic detection unit 30 is coupled to the reflecting fiber 26