Abstract:
An electrochromic test port provides an actively tunable system for building an optical test port for an optical waveguide with enhanced SNR properties over conventional approaches.

Description:
FIELD OF INVENTION 
       [0001]    In general, the invention relates generally to optical systems and nanocrystal-in-glass materials. In more detail, the invention relates to a nanocrystal-in-glass material for providing fiber optics telecommunications functionality. 
       BACKGROUND 
       [0002]    It is critical to test the optical signal transmission characteristics of fiber optic communication lines at various points along the line. Conventional optical fiber consists of a core and a cladding and as such may be utilized as an optical waveguide. 
         [0003]    Conventional optical test ports utilize a tapered fiber approach, which introduces some amount of optical loss for light that traverses the testing port. In particular, conventional optical test ports require mounting a certain section of the fiber such that the fiber is stretched rendering the core and cladding much thinner compared to rest of fiber. When the optical light passes through the stretched section, because the diameter of fiber is thinner in that area it results in optical loss in the propagated signal. A photodetector is introduced to measure the leakage light. 
         [0004]    Applicants have identified significant shortcomings with conventional approaches to optical testing of waveguides. In particular, a major limitation of conventional approaches such as the tapered fiber approach, is that there is no way to turn the optical test functionality “on” or “off” in an active manner. 
       SUMMARY OF INVENTION 
       [0005]    The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
         [0006]    According to one embodiment an optical test port for testing an optical waveguide comprises a nanocrystal-in-glass member coupled to the optical waveguide, the nanocrystal-in-glass member comprising a transmission portion and a testing portion, at least one electrode coupled to the nanocrystal-in-glass member such that an optical transmission through at least one of the transmission portion and the testing portion is varied continuously based upon a voltage established on the electrode, and a photodetector coupled to the testing portion, the photodetector receiving a light signal from the testing portion and indicating a transmission characteristic of the optical waveguide. 
         [0007]    According to an alternative embodiment, an optical test port for testing an optical waveguide comprises a nanocrystal-in-glass member coupled to the optical waveguide, a first electrode and a second electrode coupled to the nanocrystal-in-glass member and a detector coupled to the first electrode for measuring electrons generated by absorbed photons passing through the nanocrystal-in-glass member. 
         [0008]    According to an alternative embodiment, an optical test port for testing an optical waveguide comprises a nanocrystal-in-glass member coupled to the optical waveguide, the nanocrystal-in-glass member comprising a transmission portion and a testing portion, at least one electrode coupled to the nanocrystal-in-glass member such that an optical transmission through at last one of the transmission portion and the testing portion is varied continuously based upon a voltage established on the at least one electrode, and a detector coupled to the testing portion, the detector measuring an electromagnetic property of the testing portion. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  depicts a cross-section of an electrochromic material structure for use in an optical test port according to one embodiment. 
           [0010]      FIG. 2A  depicts an optical test port incorporating an electrochromic material according to one embodiment. 
           [0011]      FIG. 2B  depicts an optical test port incorporating an electrochromic material in which the test port is in an “off” state according to one embodiment. 
           [0012]      FIG. 2C  depicts an optical test port incorporating an electrochromic material in which the test port is in an “on” state according to one embodiment. 
           [0013]      FIG. 3  depicts an alternative embodiment of an optical test port incorporating an electrochromic material in which an induced photo-voltage is utilized to monitor an optical transmission characteristic according to one embodiment. 
           [0014]      FIG. 4  depicts an optical test port incorporating an electrochromic material that combines a splitting structure and an induced photo-voltage measuring approach according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Applicants have developed a technique that allows for active tuning of optical test ports and makes use of electrochromic materials, which may be optically tuned by an applied electric field. The optical test port is arranged to include a transmission portion and a testing portion, both of which are comprised of electrochromic materials. If testing is desired, a voltage signal may be applied to the electrochromic material associated with the testing portion to cause a portion of the light to propagate through the testing portion. If no testing is desired, no voltage is applied so that all of optical signal will pass through the transmission portion with a minimum of optical loss and interruption to optical transmission line. 
         [0016]      FIG. 1  depicts a cross-section of an electrochromic material structure  100  for use in an optical test port according to one embodiment. According to one embodiment, electrochromic material structure  100  comprises electrode  102 ( 1 ), electrode  102 ( 2 ) and a nanocrystal-in-glass material  104 . According to one embodiment electrochromic material structure  100  incorporates a nanocrystal-in-glass material. According to alternative embodiments, an electro-optic material such as a semiconductor material (i.e., gallium arsenide or lithium niobate) may also be used to control light transmission via an applied voltage. Other materials may be substituted so long as their optical transmission properties may be varied based upon application of a control signal. 
         [0017]    For example, light transmission properties of nanocrystal-in-glass material  104  may be modulated by application of a voltage to nanocrystal-in-glass material  104  via electrodes  102 ( 1 ) and  102 ( 2 ), which form a pair. The voltage applied may be obtained from a voltage source and vary over a range. Nanocrystal-in-glass material  104  may incorporate nanocrystals covalently bonded in amorphous material and may enable dynamic control of near-infrared and visible light transmission depending upon an applied voltage to the material. 
         [0018]      FIG. 2A  depicts an optical test port incorporating an electrochromic material according to one embodiment. Electrochromic optical test port  200  comprises waveguide  202 , testing portion  204 ( 1 ) and transmission portion  204 ( 2 ). Testing portion  204 ( 1 ) comprises nanocrystal-in-glass material  104 ( 1 ) and electrodes  102 ( 1 ) and  102 ( 2 ), which form a pair. Transmission portion  204 ( 2 ) comprises nanocrystal-in-glass material  104 ( 2 ) and electrodes  102 ( 3 ) and  102 ( 4 ), which form a pair. Testing portion  204 ( 1 ) and transmission portion  204 ( 2 ) are coupled to waveguide  202 . As shown in  FIG. 2A , the coupling is arranged through a Y-Junction. However, other arrangements are possible in other embodiments. 
         [0019]    Upon arriving at the Y-Junction, a portion of light propagating through waveguide  200  will travel through transmission portion  204 ( 2 ). As will become evident with respect to  FIGS. 2B-2C , upon arriving at the Y-Junction, a portion of light propagating through waveguide  200  will travel through testing portion  204 ( 1 ) depending upon whether a voltage is applied to electrodes  102 ( 1 ) and  102 ( 2 ). Electrodes  102 ( 1 )- 102 ( 4 ) may be made of indium tin oxide (ITO) or other conductive material suitable for optical applications. The light transmission through testing portion  204 ( 1 ) may be measured by photodetector  210 . 
         [0020]    Electrochromic optical test port  200  provides a distinct advantage over convention optical test port methodologies such as those that utilize a tapered fiber approach in that it allows active tuning of the transmission properties of the testing portion  204 ( 1 ) in relation to the transmission portion  204 ( 2 ). This use of electrochromic material allows active tuning of the light transmission properties, which results in a higher signal-to-noise ratio (SNR) for induced light absorption when desired. 
         [0021]      FIG. 2B  depicts an optical test port incorporating an electrochromic material in which the test port is in an “off” state according to one embodiment. As shown in  FIG. 2B , voltage source  208  is applied to electrode  102 ( 1 ) of testing portion  204 ( 1 ). In this configuration, nanocrystal-in-glass material  104 ( 2 ) in transmission portion  204 ( 2 ) does allow transmission of light from waveguide  202 . However, in this configuration, nanocrystal-in-glass material  104 ( 1 ) in testing portion  204 ( 1 ) does not allow transmission of light from waveguide  202 . 
         [0022]      FIG. 2C  depicts an optical test port incorporating an electrochromic material in which the test port is in an on state according to one embodiment. As shown in  FIG. 2C , voltage source  208  is applied to electrode  102 ( 1 ) of transmission portion  204 ( 2 ) while electrode  102 ( 2 ) of transmission portion  204 ( 2 ) is grounded. In this configuration, nanocrystal-in-glass material  104 ( 2 ) in transmission portion  204 ( 2 ) allows transmission of a portion of the light from waveguide  202 . In addition, in this configuration, nanocrystal-in-glass material  104 ( 1 ) in testing portion  204 ( 1 ) also allows transmission of a portion of the light from waveguide  202 . The proportion of light passing through testing portion  204 ( 1 ) relative to transmission portion  204 ( 2 ) will depend upon the voltage applied to electrode  102 ( 1 ). The light transmission through testing portion  204 ( 1 ) may be measured by photodetector  210 . 
         [0023]      FIG. 3  depicts an alternative embodiment of an optical test port incorporating an electrochromic material in which an induced photo-voltage is utilized to monitor an optical transmission characteristic according to one embodiment. Electrochromic optical test port  200  comprises waveguide  202 , electrode  102 ( 1 ) and electrode  102 ( 2 ) which form a pair, and nanocrystal-in-glass material  104 . Further, as shown in  FIG. 3 , an ammeter or voltmeter  302  is applied to electrode  102 ( 1 ). As an optical signal passes from waveguide  202  through nanocrystal-in-glass material  104 , a small portion of the passing photons may be absorbed by nanocrystal-in-glass material  104  and converted to electrons, which generates a photo-current or photo-voltage that may be measured by ammeter/voltmeter  302  for diagnostic purposes. An advantage of the approach shown in  FIG. 3  is that it does not require a splitting structure nor a photodetector, which thus yields a lower cost design. 
         [0024]      FIG. 4  depicts an optical test port incorporating an electrochromic material that combines a splitting structure and an induced photo-voltage measuring approach according to one embodiment. As shown in  FIG. 4 , rather than utilizing a photodetector as shown in the embodiment in  FIG. 2A , voltmeter/ammeter  302  is coupled to electrode  102 ( 2 ) while electrode  102 ( 1 ) is grounded. Voltage source  208  coupled to electrode  102 ( 4 ), which is coupled to nanocrystal-in-glass material  104 ( 2 ) in transmission portion  204 ( 2 ), allows modulation of light transmission through testing portion  204 ( 1 ). As an optical signal passes from waveguide  202  through nanocrystal-in-glass material  104 ( 1 ) in testing portion  204 ( 1 ), a small portion of the passing photons may be absorbed by nanocrystal-in-glass material  104 ( 1 ) and converted to electrons, which generates a current or voltage that may be measured by ammeter/voltmeter  302  coupled to electrode  102 ( 2 ) for diagnostic purposes. 
         [0025]    These and other advantages maybe realized in accordance with the specific embodiments described as well as other variations. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.