Abstract:
Apparatus, systems and methods for separating a selected optical signal wavelength component from a plurality of optical signal wavelength components of an aggregate optical signal, and for passing the selected optical signal wavelength component while suppressing the remaining wavelength components are provided. Generally, the apparatus provides an optical signal wavelength selective element enabling output of a selectable optical signal wavelength component. The system contains a fiber optic cable carrying an optical signal, an optical signal measurement apparatus to measure optical signal characteristics, and an optical wavelength selector to pass the selected optical signal wavelength component to the optical signal measurement apparatu

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is generally related to optical signals, and more particularly is related to an optical wavelength selector for selecting and passing an optical wavelength from an aggregate optical signal having two or more optical wavelengths.  
       BACKGROUND  
       [0002]     Advances in fiber optic technology have resulted in the ability to transmit multiple optical signals on a single fiber optic cable. Optical signals can be transmitted using different signal wavelengths, where the different wavelengths are combined for transmission through the fiber optic cable. It is sometimes desirable to measure the characteristics, for example the power level, of the individual optical signal components. Presently, there are two primary pieces of test equipment used to distinguish signal characteristics of individual wavelength signals from the mixed wavelength optical signal: the diffraction grating-based optical spectrum analyzer, and the interferometer-based wavelength meter. Both of these pieces of equipment, however, involve sophisticated technology, are bulky and heavy, and are expensive.  
         [0003]     When measuring optical signals, an adapter cap is often used as an interface between a fiber optic cable connector and an optical power meter used to measure optical signal power levels. Existing adapter caps are used for measuring aggregated optical signal power levels. In the case of mixed optical signals with more than two optical wavelengths, however, an optical power meter is unable to distinguish the power levels of the optical signals at the individual optical wavelengths using existing adapter caps. Therefore, the above-mentioned bulky and expensive pieces of test equipment are the only alternatives when measurements of individual optical wavelengths are necessary.  
         [0004]     Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.  
       SUMMARY  
       [0005]     Broadly described, the present invention provides apparatus, systems and methods for separating a selected optical signal wavelength component from a plurality of different optical signal wavelengths of an aggregate optical signal, and for passing the selected optical signal wavelength component while suppressing the remaining wavelength components. Generally, in operation, an aggregate optical signal having two or more optical wavelength components is input to the optical wavelength selector. Using an optical signal wavelength selective element, the optical wavelength selector passes a user-selected optical wavelength component while suppressing the remaining optical components of the aggregate optical signal.  
         [0006]     One embodiment of a system, among others, can be implemented as follows. The system contains an optical signal measurement apparatus, an optical wavelength selector connected to the optical signal measurement apparatus, and an aggregate optical signal connected to the optical wavelength selector. The optical wavelength selector selectively passes a wavelength component of the aggregate optical signal to the optical signal measurement apparatus while suppressing the remaining aggregate optical signal wavelength components.  
         [0007]     The present invention can also be viewed as providing methods for selecting and passing individual optical signal wavelength components of an aggregate optical signal. In this regard, one embodiment of such a method, among others, can be broadly summarized by: connecting an optical wavelength selector to an optical signal measurement apparatus, inputting an aggregate optical signal to the optical wavelength selector, and selecting the optical wavelength component to be passed by the optical wavelength selector.  
         [0008]     Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
         [0010]      FIG. 1  is a diagram illustrating the operation of an embodiment of the present invention.  
         [0011]      FIG. 2  is a perspective view illustrating a first exemplary embodiment of the optical wavelength selector.  
         [0012]      FIG. 3  is a side view illustrating a first exemplary embodiment of the optical wavelength selector.  
         [0013]      FIG. 4  is a side view illustrating a first exemplary embodiment of the optical wavelength selector.  
         [0014]      FIG. 5  is a perspective view illustrating an exemplary embodiment of the optical wavelength selector.  
         [0015]      FIG. 6  is a perspective view of a first housing according to a first exemplary embodiment of the optical wavelength selector.  
         [0016]      FIG. 7  is a perspective view of a second housing according to a first exemplary embodiment of the optical wavelength selector.  
         [0017]      FIG. 8  is a plan view of a first side of a filter disk according to a first exemplary embodiment of the optical wavelength selector.  
         [0018]      FIG. 9  is a plan view of a second side of a filter disk according to a first exemplary embodiment of the optical wavelength selector.  
         [0019]      FIGS. 10A and 10B  are side views illustrating a second exemplary embodiment of the optical wavelength selector.  
         [0020]      FIG. 11  is a block diagram illustrating a measurement system according to an exemplary embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0021]      FIG. 1  is a diagram illustrating the operation of an embodiment of the present invention. As shown in  FIG. 1 , an aggregate optical signal  15  having a plurality of optical wavelength components may be input to an optical wavelength selector  100 . The optical wavelength selector  100  passes a selected optical wavelength component  20  of the aggregate optical signal  15  while suppressing the remaining optical signal components. To selectively pass an optical wavelength component  20  of an aggregate optical signal  15 , the optical wavelength selector  100  may incorporate an optical signal wavelength selective element  25 . Embodiments of the optical wavelength selector may incorporate interchangeable wavelength selective elements  25  and/or a plurality of wavelength selective elements  25 .  
         [0022]      FIGS. 2, 3  and  4  illustrate a perspective view and side views, respectively, of a first exemplary embodiment of an optical wavelength selector  100 . The first exemplary embodiment of the optical wavelength selector  100  may have an optical adapter  105  coupled to a first housing  110 , and a second housing  115  coupled to the first housing  110  forming a cavity  120  between the first housing  110 , and the second housing  115 , with a filter disk  125  at least partially disposed within the cavity  120 .  
         [0023]     In the first exemplary embodiment, a fiber optic cable may be coupled to the optical adapter  105 . The optical adapter  105  may be, for example, but not limited to an SC, FC, ST, LC or universal optical adapter. As illustrated in  FIG. 6 , the first housing  110  may have a hollow portion  130  arranged to receive the optical adapter  105 , and a first surface  135  forming a hole  140  as part of the optical signal path. The optical adapter  105  may be removably coupled to the first housing  110  allowing for interchangeability of optical adapters  105 , for example, but not limited to, those exemplified above. In another embodiment, the optical adapter  105  may be formed as part of the first housing  110 . A further embodiment may employ a single housing  117  as exemplified in  FIG. 5 .  
         [0024]      FIG. 7  is a perspective view of a second housing  115  of the first embodiment of the optical wavelength selector  100 . The second housing  115  may be constructed as an adapter for connecting an exemplary embodiment of the optical wavelength selector  100  to, for example, but not limited to, an optical power meter. Referring to  FIG. 7 , the second housing  115  may have a hollow portion  145  and a first surface  150  forming a hole  155  as part of the optical signal path. The first surface  150  may have a hub portion  160  perpendicular to the first surface  150  having a diameter providing a center of rotation for the filter disk  125 .  
         [0025]      FIGS. 8 and 9  illustrate a filter disk  125  according to the first exemplary embodiment of the optical wavelength selector  100 . The filter disk  125  may have a first circular surface  165  having a first diameter spaced apart from and parallel to a second circular surface  170  having the first diameter, and forming a concentric inner hole  175  having a second diameter through the first circular surface  165  and the second circular surface  170 . The second diameter is sized to allow the filter disk  125  to rotate about the hub portion  160  (see  FIG. 7 ) of the second housing  115 .  
         [0026]     The filter disk  125  may have a plurality of openings  180  extending through the first circular surface  165  and the second circular surface  170 . The plurality of openings  180  may be equally spaced around a concentric circle adjacent to the concentric inner hole  175 . In the first exemplary embodiment, three openings  180  may be spaced  120  degrees apart around the concentric circumference adjacent to the concentric inner hole  175 . The openings  180  are positioned on the filter disk  125  such that one opening  180  at a time may be aligned with the hole  140  in the first housing  110  and the hole  155  in the second housing  115  completing an optical signal path through the optical wavelength selector.  
         [0027]     In the first exemplary embodiment, the second housing  115  is constructed to allow the circular filter disk  125  to rotate around the hub portion  160 . The filter disk  125  may be constructed in other shapes, for example, but not limited to, square, hexagonal, octagonal and wedge-shaped, having openings  180  correspondingly positioned to complete the optical signal path.  
         [0028]     The filter disk  125  may be at least partially disposed within the cavity  120  formed between the first housing  110  and the second housing  115 . As illustrated in  FIGS. 2 and 3 , a protruding portion  127  of the filter disk  125  protruding from the cavity  120  may be used to position the selected opening  180  in the optical signal path.  
         [0029]     Referring to  FIG. 8 , in the first exemplary embodiment, the first circular surface  165  of the filter disk  125  may have a plurality of radial depressions  200  formed in a direction between the outer circumference of the concentric inner hole  175  and the outer circumference of the first circular surface  165  forming detents corresponding to the locations of the openings  180  to properly position the selected opening  180  in the optical signal path.  
         [0030]     As illustrated in  FIG. 8 , thin film optical filters  185 ,  190 ,  195  as the optical wavelength selective element may be disposed in the openings  180  of the filter disk  125 . Each optical filter  185 ,  190 ,  195  may act as an optical bandpass filter having a specified center wavelength. Alternatively, at least one opening  180  may not contain an optical filter, thereby passing the aggregate optical signal. In the first exemplary embodiment illustrated in  FIG. 8 , the filter disk  125  comprises an opening  180  having an optical bandpass filter  185  with a 1550 nanometer center wavelength, an opening  180  having an optical bandpass filter  190  having a 1490 nanometer center wavelength, and an opening  180  having no optical bandpass filter  195 .  
         [0031]     As noted above, the protruding portion  127  (see  FIGS. 2 and 3 ) of the filter disk  125  protruding from the cavity  120  may be used to position the selected opening  180 , and thereby the selected optical filter  185 ,  190 ,  195 , in the optical signal path. The filter disk  125  may have markings  205  visible on the protruding portion  127  to indicate which of the optical bandpass filters  185 ,  190 ,  195  is positioned in the optical signal path. In the first exemplary embodiment illustrated in  FIG. 8 , the markings  205  are located directly across the first circular surface  165  from the corresponding optical bandpass filters  185 ,  190 ,  195 , adjacent the outer circumference of the first circular surface  165 . Selecting the optical signal wavelength indicated by the markings  205  on the protruding portion  127  of the filter disk positions the corresponding optical bandpass filter  185 ,  190 ,  195  into the optical signal path, thereby filtering the unwanted optical signal wavelength components and passing the selected optical signal wavelength component to the measurement apparatus.  
         [0032]     In a second exemplary embodiment illustrated in  FIGS. 10A and 10B , optical bandpass filters  185 ,  190 ,  195  may be arranged in a linear fashion in openings  250  on a filter block  240  and positioned in the optical signal path by sliding the filter block  240  in a cavity  245  of matching shape formed between the first housing  110  and the second housing  115 .  
         [0033]      FIG. 11  is a block diagram illustrating a measurement system according to an exemplary embodiment of the present invention. A fiber optic cable  220  may be connected to an optical signal measurement apparatus  230 , for example, but not limited to, an optical power meter, through an optical wavelength selector  100 . A measurement of a characteristic of a specific wavelength component of an aggregate optical signal may be made by selecting the specified optical signal wavelength component using the protruding portion  127  of the filter disk  125 . In this manner, the specified optical bandpass filter  185 ,  190 ,  195  ( FIG. 8 ) is inserted into the optical signal path allowing only the specified wavelength component to be passed to the optical signal measurement apparatus  230 .  
         [0034]     It should be emphasized that the above-described embodiments of the present invention are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.