Abstract:
An optical collimator for WDM application. Preventing the adhesive material from blocking the light path, the optical collimator includes a glass ferrule with a hole, at least one optical fiber grasped by the glass ferrule, a GRIN lens having two end surfaces, with one end surface of the GRIN lens combined with the glass ferrule, and a filter combined with another end surface of the GRIN lens. At least one pad with an opening is sandwiched between the filter and the GRIN lens, and, using a thermal-curing epoxy, the pad adheres to the GRIN lens and the filter adheres to the pad.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to an optical collimator, and more particularly to an optical collimator for a WDM unit.  
           [0003]    2. Description of the Related Art  
           [0004]    [0004]FIG. 1 schematically shows a cross-section of a conventional optical collimator. As shown in FIG. 1, the conventional optical collimator  1  for WDM application has a glass ferrule  2 , an optical fiber  3 , a GRIN lens  4  and a filter  5 . The glass ferrule  2  has a hole  2   a , and grasps the optical fiber  3  through the hole  2   a . Next, the end surface  2   b  of the glass ferrule  2  is combined with the end surface  4   a  of the GRIN lens  4  by applying a UV-curing epoxy  6  to their edges, and the filter  5  adheres to another end surface  4   b  of the GRIN lens  4  using a thermal-curing epoxy  7 .  
           [0005]    However, the UV-curing epoxy  6  for combining the glass ferrule  2  with the GRIN lens  4  deteriorates under the wet conditions. If the thermal-curing epoxy  7  replaces the UV-curing epoxy  6 , the time for curing the thermal epoxy applied to the edges of the glass ferrule and the GRIN lens becomes longer. Additionally, the thermal-curing epoxy  7  melts during heat-curing, and permeates the gap  9  between the glass ferrule  2  and the GRIN lens  4 . Thus, the thermal-curing epoxy  7  blocks the light path and reduces the light intensity.  
           [0006]    [0006]FIG. 2 schematically shows a cross-section of another conventional optical collimator. As shown in FIG. 2, another conventional optical collimator  11  for WDM application has a glass ferrule  12 , an optical fiber  13 , a GRIN lens  14 , a first tube  18   a , a second tube  18   b  and a filter  15 . The glass ferrule  12  has a hole  12   a  grasping the optical fiber  13 , and is then positioned in the first tube  18   a . The GRIN lens  14  is positioned in the second tube  18   b , and aligns with the glass ferrule  12 . After obtaining optimum collimated beam from the GRIN lens  14 , the first tube  18   a  is combined with the second tube  18   b  by applying a thermal-curing epoxy  17 . Furthermore, the thermal-curing epoxy  17  is permeated between the glass ferrule  12  and the inner sidewall of the first tube  18   a , and permeated between the GRIN lens  14  and the inner sidewall of the second tube  18   b  by capillarity.  
           [0007]    The conventional optical collimator  11  uses the thermal-curing epoxy to combine the optical parts, and has a better ability to resist the wet conditions. However, the thermal-curing epoxy  17  easily permeates the gap between the glass ferrule and the GRIN lens, and has the same disadvantages of blocking the light path and reducing the light intensity.  
         SUMMARY OF THE INVENTION  
         [0008]    To solve the above problems, it is an object of the present invention to provide an optical collimator for a WDM unit, which includes a ringlike pad with an opening. The filter and the GRIN lens are respectively adhered to each side surface of the ring-like pad using an adhesive material.  
           [0009]    Another object of the invention is to provide an optical collimator for a WDM unit, wherein, using the adhesive material, the glass ferrule and the GRIN lens are respectively adhered to each side surface of the first ringlike pad, and the filter and the GRIN lens are respectively adhered to each side surface of the second ringlike pad.  
           [0010]    A feature of the invention is that the ringlike pad is sandwiched between the GRIN lens and the filter, and using the adhesive material, the filter is adhered to one side surface of the ringlike pad and the GRIN lens is adhered to another side surface of the ringlike pad.  
           [0011]    Another feature of the invention is that another ring-like pad is sandwiched between the glass ferrule and the GRIN lens, and using the adhesive material, the glass ferrule is adhered to one side surface of the ringlike pad and the GRIN lens is adhered to another side surface of the ringlike pad. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    This and other objects and features of the invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the drawings, in which:  
         [0013]    [0013]FIG. 1 schematically shows a cross-section of a conventional optical collimator;  
         [0014]    [0014]FIG. 2 schematically shows a cross-section of another conventional optical collimator;  
         [0015]    [0015]FIG. 3 schematically shows a cross-section of an optical collimator for WDM application according to the first embodiment of the invention;  
         [0016]    [0016]FIG. 4 schematically shows a cross-section of an optical collimator for WDM application according to the second embodiment of the invention;  
         [0017]    [0017]FIG. 5 schematically shows a cross-section of an optical collimator for WDM application according to the third embodiment of the invention;  
         [0018]    [0018]FIG. 6 schematically shows a ringlike pad applied to the optical collimator of the invention; and  
         [0019]    [0019]FIG. 7 schematically shows various shapes of the ring-like pad applied to the optical collimator of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    First Embodiment  
         [0021]    [0021]FIG. 3 schematically shows a cross-section of an optical collimator for WDM application according to the first embodiment of the invention. As shown in FIG. 3, the optical collimator  20  of the first embodiment includes a glass ferrule  21 , a GRIN lens  22 , a ringlike pad  23 , and a filter  24 . The glass ferrule  21  has a hole  21   a  grasping an optical fiber  25 . The glass ferrule  21  is combined with one end surface  22   a  of the GRIN lens  22  using a UV-curing epoxy  26 . A gap  27  of predetermined size between the glass ferrule  21  and the GRIN lens  22  is formed by applying the UV-curing epoxy  26  to their edges.  
         [0022]    Next, the ringlet pad  29  is adhered to another end surface  22   b  of the GRIN lens  22  by applying a thermal-curing epoxy  28  therebetween. The filter  24  is adhered to the ringlike pad  29  by applying the thermal-curing epoxy  28  therebetween. Thus, the ringlike pad  29  is sandwiched and fixed between the GRIN lens  22  and the filter  24 . In the first embodiment of the invention, the thickness of the ringlike pad is 0.18 mm, the outer diameter of the ringlike pad is 0.18 mm, and the inner diameter of the ring-like pad is 0.12 mm. By capillarity, the thermal-curing epoxy is uniformly localized between the ringlike pad and the GRIN lens, and between the ringlike pad and the filter. Accordingly, the first embodiment ensures that the thermal-curing epoxy cannot block the light path.  
         [0023]    Second Embodiment  
         [0024]    [0024]FIG. 4 schematically shows a cross-section of an optical collimator for WDM application according to the second embodiment of the invention. As shown in FIG. 4, the optical collimator  30  of the second embodiment includes a glass ferrule  31 , a GRIN lens  32 , a first ringlike pad  39   a , a second ringlike pad  39   b , and a filter  34 . The glass ferrule  31  has a hole  31   a  grasping an optical fiber  35 .  
         [0025]    The second ringlet pad  39   b  is adhered to one end surface  32   a  of the GRIN lens  32  by applying a thermal-curing epoxy  38  therebetween. The glass ferrule  31  grasping the optical fiber  35  is adhered to the second ringlike pad  39   b  by applying the thermal-curing epoxy  38  therebetween. The first ringlet pad  39   a  is adhered to another end surface  32   b  of the GRIN lens  32  by applying the thermal-curing epoxy  38  therebetween. The filter  34  is adhered to the first ringlike pad  39   a  by applying the thermal-curing epoxy  38  therebetween. Thus, the first ring-like pad  39   a  is sandwiched and fixed between the GRIN lens  32  and the filter  34 . Using the second ringlike pad  39   b , a gap  37  of predetermined size between the glass ferrule  31  and the GRIN lens  32  is also formed.  
         [0026]    In the second embodiment of the invention, the thickness of the ringlike pad is 0.18 mm, the outer diameter of the ring-like pad is 0.18 mm, and the inner diameter of the ringlike pad is 0.12 mm. By capillarity, the thermal-curing epoxy is uniformly localized between the second ringlike pad and the GRIN lens, and between the second ringlike pad and the filter. Additionally, the thermal-curing epoxy is uniformly localized between the first ringlike pad and the GRIN lens, and between the first ring-like pad and the glass ferrule. Accordingly, the second embodiment ensures that the thermal-curing epoxy cannot block the light path.  
         [0027]    Third Embodiment  
         [0028]    [0028]FIG. 5 schematically shows a cross-section of an optical collimator for WDM application according to the third embodiment of the invention. As shown in FIG. 5, the optical collimator  40  of the third embodiment includes a glass ferrule  41 , a GRIN lens  42 , a first ringlike pad  49   a , a second ringlike pad  49   b , and a filter  44 . The glass ferrule  41  has a hole  41   a  grasping a first optical fiber  45   a  and a second optical fiber  45   b.    
         [0029]    The second ringlet pad  49   b  is adhered to one end surface  42   a  of the GRIN lens  42  by applying a thermal-curing epoxy  48  therebetween. The glass ferrule  41  grasping the two optical fibers  45   a ,  45   b  is adhered to the second ringlike pad  49   b  by applying the thermal-curing epoxy  48  therebetween. The first ringlet pad  49   a  is adhered to another end surface  42   b  of the GRIN lens  42  by applying the thermal-curing epoxy  48  therebetween. The filter  44  is adhered to the first ringlike pad  49   a  by applying the thermal-curing epoxy  48  therebetween. Thus, the first ringlike pad  49   a  is sandwiched and fixed between the GRIN lens  42  and the filter  44 . Using the second ringlike pad  49   b , a gap  47  of predetermined size between the glass ferrule  41  and the GRIN lens  42  is also formed.  
         [0030]    Before the thermal-curing epoxy localized between the GRIN lens and the glass ferrule is cured, the optical collimator mentioned above is adjusted by a mechanism (not shown). The GRIN lens is positioned on a fixing frame, and the glass ferrule is adjusted by a five motions controller. A beam with wide band is transmitted in the first optical fiber  45   a , and enters the GRIN lens. After emitting the beam with wide band from the GRIN lens, the beam is incident on the filter and the filter reflects predetermined wavelength of the beam. Next, the reflected light passes the GRIN lens again, and enters the second optical fiber. When the second optical fiber outputs an optimum signal, the five motions controller stops adjusting the GRIN lens. Finally, the thermal-curing epoxy between the glass ferrule and the GRIN lens is cured, and the glass ferrule, the ringlike pad and the GRIN lens are tightly combined.  
         [0031]    In the third embodiment of the invention, the thickness of the ringlike pad is 0.18 mm, the outer diameter of the ring-like pad is 0.18 mm, and the inner diameter of the ringlike pad is 0.12 mm. By capillarity, the thermal-curing epoxy is uniformly localized between the second ringlike pad and the GRIN lens, and between the second ringlike pad and the filter. Additionally, the thermal-curing epoxy is uniformly localized between the first ringlike pad and the GRIN lens, and between the first ring-like pad and the glass ferrule. Accordingly, the third embodiment ensures that the thermal-curing epoxy cannot block the light path.  
         [0032]    [0032]FIG. 6 schematically shows a ringlike pad applied to the optical collimator of the invention. As shown in FIG. 6, the thickness of the ringlike pad  100  is variable so as to obtain minimum insertion loss. FIG. 7 schematically shows various shape of the ringlike pad applied to the optical collimator of the invention. As shown in FIG. 7, the shape of the pad is cylindrical, rectangular or polygonal, and the pad has an opening at its center.  
         [0033]    In the invention, the pad is made of the metal, glass, or immalleable material capable of sustaining 200 degrees centigrade.  
         [0034]    In the invention, the capillarity results from the liquid in the two adjacent planes. When the thermal-curing epoxy is heated and becomes fluid, the thermal-curing epoxy is uniformly localized between the pad and the optical part adhered to the pad. Thus, the thermal-curing epoxy cannot appear in the opening of the pad, and block the light path. Moreover, because of the capillarity, the pad is tightly sandwiched between the filter and the GRIN lens and the invention increases the adhesion. The capillarity poses a benefit and not a disadvantage.  
         [0035]    While the preferred embodiment of the present invention has been described, it is to be understood that modifications will be apparent to those skilled in the art without departing from the spirit of the invention. The scope of the invention, therefore, is to be determined solely by the following claims.