Abstract:
A method and apparatus for measuring the insertion loss of a fiber optic connection is provided. The invention generally comprises a light source providing light to a test connector which contains a juncture of two fiber optic cables. The test connector has one or more opaque portions surrounding the fiber optic juncture. A pyrometer or other heat detection means is then used to measure any temperature increase as a result of light scattered into the opaque portions of the test connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 61/034,387, filed Mar. 6, 2008, the subject matter of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to fiber optic connections and more specifically to a novel apparatus and method to measure the performance of a fiber optic connection. 
     BACKGROUND OF THE INVENTION 
     In order to determine the adequacy of a fiber optic connection, such as the fiber optic connection disclosed in U.S. Pat. No. 7,011,454 which is herein incorporated by reference in its entirety, it is useful to measure the insertion loss of the fiber optic connection in order to verify that it is within acceptable limits. U.S. Pat. No. 4,360,268 (the &#39;268 patent) discloses the use of an integrating sphere to directly measure the amount of scattered light at a single point radial to the fiber optic juncture. U.S. Pat. No. 7,192,195 (the &#39;195 patent) discloses the use of one or more fiber optic strands to collect light and guide it to a measurement device. However, even measuring the scattered light at multiple locations still may not enable an accurate measurement of the total amount of scattered light because the light may not scatter evenly or in the direction of the finite number of light collecting points. Thus, it is unlikely that the total amount of scattered light will be measured by a limited number of light collecting points. 
     As a result, it is desirable to provide a method and apparatus that can measure the total amount of scattered light without extrapolating the total amount from a limited number of light collecting locations. 
     SUMMARY OF THE INVENTION 
     The present invention generally comprises a light source supplying light to a test connector which contains a juncture of two fiber optic cables. The test connector has one or more opaque portions surrounding the fiber optic juncture. A pyrometer or other heat detection means is then used to measure any temperature increase as a result of light scattered into and absorbed by the opaque portions of the test connector. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  is a system overview of a method and apparatus for measuring insertion loss in a fiber optic connection. 
         FIG. 2  is a cross sectional view of a test connector for use in the method and apparatus of claim  1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown by  FIG. 1 , one embodiment of an apparatus  10  to measure the performance of a pre-polished fiber optic connector comprises a light source  12  that can supply light with at least a portion of the light&#39;s emission spectrum in the infrared region of the electromagnetic spectrum. While one embodiment supplies light with a portion in the infrared region of the electromagnetic spectrum, any frequency in which light can be easily and efficiently transmitted by a fiber optic cable and be absorbed by opaque materials in a test connector (as described below) may be employed in embodiments of the present invention. The light source  12  may be comprised of a relatively narrowband emitter, such as a semiconductor LED or laser, or a relatively broadband emitter, such as a gas discharge arc lamp or filament lamp. 
     The light source  12  supplies light to a test connector  22 . The light is transferred from the light source  12  to the test connector  22  via a coupling assembly  14 . In one embodiment, the coupling assembly  14  comprises a fiber optic cable connected to the light source  12  at one end and a test connector interface  16 , which can comprise a fiber optic adapter, at the other end. In another embodiment, the coupling assembly  14  is composed of free space optical components such as lenses and apertures. 
     As the light from the light source  12  reaches the test connector  22  it will either be coupled to the field fiber  24  or be scattered into opaque portions of the test connector  22  that are adjacent to the stub fiber and field fiber interface  20 . The light that is scattered into the test connector  22  will be absorbed by the opaque portions of the test connector  22  and cause a temperature increase in those opaque portions. The amount of the temperature increase will be dependant upon the amount of light scattered into the test connector  22 . Index matching gel may be used to enhance the coupling of the light at the stub fiber and field fiber interface  20 . Additionally, the geometry and composition of the index matching gel and surrounding opaque portions may be optimized to facilitate efficient heat transfer and detection. 
     The temperature of the opaque portions of the test connector  22  can be measured by a pyrometer  18 . The pyrometer  18  can be placed in close proximity to the opaque portion of the test connector  22  in order to increase the accuracy of the temperature measurement. The resulting temperature can be compared to temperature measurements before the light source was energized and the resulting temperature difference can be used to determine the amount of light that is scattered into the opaque portions of the test connector  22 . An analysis circuit  28  can be used to determine the temperature difference and the insertion loss of the connection. The analysis circuit  28  can utilize the peak temperatures measured by the pyrometers  18  after the light source  12  has been turned on for a predetermined time and subsequently turned off to determine the insertion loss of the connection. The analysis circuit  28  can then use the insertion loss to see if it falls within acceptable pass/fail parameters and indicate the result with an auditory or visual pass/fail indicator  30 . 
       FIG. 2  shows a cross sectional view of one embodiment of a test connector  22 . A stub fiber  32  passes through a ferrule  34 . The stub fiber  32  is then mated to the field fiber  24 . The stub fiber  32  and field fiber  24  interface is secured between a top plank  42  and bottom plank  44 . In this embodiment, the top plank  42  and bottom plank  44  are the opaque portions of the test connector  22  which absorb the scattered light. The ferrule  34 , top plank  42 , and bottom plank  44  are secured together by a ferrule holder  36  and cam  46 . The ferrule holder  36  and cam  46 , have a measurement window  40  which may allow a pyrometer or similar device to measure the temperature of the top plank  42  and bottom plank  44  and thus, measure the amount of scattered light as a result of the increase in temperature. 
     In this embodiment, the light that is not coupled from the stub fiber  32  to the field fiber  24  is scattered into and through the index matching gel  38  to the top plank  42  and bottom plank  44 . As a result, the temperature of the top and bottom planks  42 ,  44  will increase. The resulting increase in temperature will be related to the amount of scattered light allowing the measurement of the temperature difference to measure the amount of scattered light. 
     In order to enhance the ability of the top plank  42  and bottom plank  44  or other opaque portions of the test connector  22  to absorb light and to emit radiation, the top plank  42  and bottom plank  44  can be fabricated from a substance having desirable absorption and emission properties. For example, the planks can incorporate nanomaterials exhibiting an efficacious ability to absorb light and emit infrared radiation. Alternatively, the planks can be coated with a substance having the desirable absorption and emission characteristics. Additionally, in a test apparatus where multiple fiber types are to be accommodated (i.e., multimode, singlemode, etc.), independent fiber-specific embodiments may be integrated into the same instrument.