Abstract:
The interior surfaces of the holes in holey optical fibers has adsorbed optically material which may be detected by propagating laser light down the axis of the fiber and detecting Raman, Infrared, or visible fluorescence or absorption.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part (CIP) of copending U.S. application Ser. No. 10/317,744 filed Dec. 12, 2002 (now U.S. Pat. No. 6,661,957 issued Dec. 09, 2003) which was a continuation-in-part (CIP) of copending U.S. application Ser. No. 09/907,241 filed Jul. 17, 2001 (now U.S. Pat. No. 6,496,634 issued Dec. 17, 2002), the above applications being incorporated herein by reference in their entirety including incorporated material. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is the field of optical fibers for the conduction of electromagnetic radiation, wherein the fibers have holes running along the fiber axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of a “holey” optical fiber of the invention. 
         FIG. 2  is a sketch of the system of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Copending U.S. application Ser. No. 10/317,744 filed Dec. 12, 2002 (now U.S. Pat. No. 6,661,957 issued Dec. 09, 2003) and its parent application Ser. No. 09/907,241 filed Jul. 17, 2001 (now U.S. Pat. No. 6,496,634 issued Dec. 17, 2002), included a detailed description of an optical fiber having fluid filled holes for Raman amplification of light.  FIG. 1  shows a sketch of a cross section of the optical fiber  10  of the invention. The fiber  10  comprises a core region  12  and a transparent cladding region  14  surrounding the core region. The core region contains a plurality of holes  16  elongated in the axial direction of the fiber. The core region may or may not contain a central hole region  18 . The walls of at least one hole or the central region have an optically active material  17  adsorbed on to the wall. 
     Optical fibers will have a useful life measured in decades, and the material of the cladding  14  is usually fused silica. 
     When light is propagated down the fiber  10 , it will propagate a great distance with high power. If the optically active material  17  is a Raman active material, Raman light will be generated and will also propagate down the axis of the fiber or may escape through the transparent walls of the fiber. The Raman light may be detected and thus the presence of the Raman active material may be detected. 
     Similarly, if the adsorbed material is an infrared, visible, or ultraviolet active material, light propagating down the optical fiber will be absorbed or scattered or fluoresced, and the presence of the material can be detected by detectors placed either at the output of the axis of the fiber or at the side of the fiber. 
     It is well known that molecules adsorbed on surfaces often have a much enhanced Raman cross section. Polar molecules such as air pollutants carbon monoxide, nitrogen oxide, and nitrogen dioxide are particularly preferred embodiments of the invention. Detection of biothreat materials such as bacteria and nerve gas material are also preferred embodiments of the invention. For purposes of investigation of relatively large entities like bacteria, the central hole region  18  may be much larger than the core region of a single mode optical fiber. 
     The method of the invention comprises introducing optically active molecules or other entities into the hollow core region  18  or into the holes  16  of the holey fiber, and propagating light down the axis of the core. The light will be guided by the holey fiber, and the intensity and interaction length will be much larger than if the light is merely focused in a gas or other fluid medium. It is well known that optically active molecules like carbon monoxide or nitrous oxide can be made to “stick” to either the clean walls of the holes or to specially prepared material of the walls. 
       FIG. 2  shows a sketch of the system of the invention. Light output from one or more lasers or other sources of light  22  is introduced into the fiber of the invention  20  by an optical apparatus  24  as is known in the art. Optical apparatus  26  is used to conduct light from the fiber  20  to detectors, spectral analysis units, signal splitters, demodulators, etc  28  as are known in the art. Control apparatus  26  controls the light generator  22  and optical apparatus  24  and communicates with detectors etc.  28 . 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.