Optical fiber sensor with light absorbing moisture-sensitive coating

Apparatus for sensing changes in moisture conditions in an environment comprising:

• a moisture sensitive optical fiber capable of modulating light passing therethrough by absorption and of undergoing a change in its light absorption properties depending upon the degree of moisture in a surrounding fluid environment, said fiber being adapted for being mounted in an environment where changes in moisture conditions are to be sensed;
• means for emitting light to be transmitted through said fiber;
• and
• means for detecting changes in the spectra of the transmitted light.

A method for sensing changes in moisture conditions in a fluid environment comprising:

• providing an optical fiber which has been coated with a moisture sensitive coating by plasma polymerization of hexamethyldisiloxane and ammonia onto the surface thereof;
• placing said coating optical fiber in a fluid environment where changes in the moisture are to be sensed;
• causing light to be transmitted through said fiber;
• and
• detecting changes in the light transmitted through the fiber as a function of changes in the moisture conditions in the environment.

An optical fiber moisture sensor comprising:

• an optical fiber;
• and
• a coating on said fiber capable of altering the optical transmission characteristics of the fiber as a function of moisture conditions in an environment to which the coating is exposed,
• said coating comprising a plasma polymerized polymeric coating made by plasma polymerization of hexamethyldisiloxane and ammonia.

Apparatus for sensing changes in moisture conditions in an environment comprising:

• a moisture sensitive optical fiber adapted for being mounted in an environment where changes in moisture conditions are to be sensed, said moisture sensitive optical fiber comprising a transparent substrate and a polymeric coating thereon made by plasma polymerization of hexamethyldisiloxane and ammonia on the substrate;
• means for emitting light to be transmitted through said fiber;
• and
• means for detecting changes in the transmitted light.