Patent Publication Number: US-2016223750-A1

Title: System for optically coupling optical fibers and optical waveguides

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to optical couplers, and more particularly to a fiber optic structure with a longitudinal surface configured to optically couple an optical waveguide with an optical fiber. 
     BACKGROUND 
     Optical or light signals carrying information may be transmitted over optical communication links, such as optical fibers or fiber optic cables. Optical integrated circuits may receive the optical signals and perform functions on the optical signals. Communicating the optical signals between the optical fibers and the optical integrated circuits with a maximum amount of coupling efficiency is desirable. Alignment techniques, including active and passive alignment techniques, may be used to achieve maximum coupling efficiency. Active alignment may be costly because it involves active electronics and feedback loops. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top view of a front end of an optical integrated circuit and an end of an optical fiber. 
         FIG. 2  illustrates an axial cross-sectional view of an optical fiber. 
         FIG. 3  illustrates a cross-sectional side view of an example optical coupler. 
         FIG. 4  illustrates perspective view of the example optical coupler in  FIG. 3 . 
         FIG. 5  illustrates a cross-sectional axial view of the example optical coupler in  FIG. 3 . 
         FIG. 6 . illustrates a second cross-sectional axial view of the example optical coupler in  FIG. 3 . 
         FIG. 7  illustrates a third cross-sectional axial view of the example optical coupler in  FIG. 3 . 
         FIG. 8A  illustrates a cross-sectional axial view of an alternative example optical coupler. 
         FIG. 8B  illustrates a cross-sectional axial view of a second alternative example optical coupler. 
         FIG. 8C  illustrates a cross-sectional axial view of a third alternative example optical coupler. 
         FIG. 9  illustrates a side view of an optical coupler formed from an optical fiber. 
         FIG. 10  illustrates a cross-sectional side view of a fourth alternative example optical coupler. 
         FIG. 11  illustrates a cross-sectional axial view of the optical coupler in  FIG. 10 . 
         FIG. 12  illustrates a cross-sectional side view of a fifth alternative example optical coupler. 
         FIG. 13  illustrates a cross-sectional axial view of the optical coupler in  FIG. 12 . 
         FIG. 14  illustrates a cross-sectional side view of a sixth alternative example optical coupler. 
         FIG. 15  illustrates a cross-sectional axial view of the optical coupler in  FIG. 14 . 
         FIG. 16  illustrates a cross-sectional side view of an example optical system. 
         FIG. 17A  illustrates a cross-sectional axial view of the example optical system in  FIG. 16 , showing an example embodiment of a top layer of optical system. 
         FIG. 17B  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing an alternative example embodiment of the top layer. 
         FIG. 17C  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing a second alternative example embodiment of the top layer. 
         FIG. 17D  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing a third alternative example embodiment of the top layer. 
         FIG. 17E  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing a fourth alternative example embodiment of the top layer. 
         FIG. 17F  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing a fifth alternative example embodiment of the top layer. 
         FIG. 17G  illustrates another cross-sectional axial view of the example optical system in  FIG. 16 , showing a sixth alternative example embodiment of the top layer. 
         FIG. 18  illustrates an exploded view of the example optical system in  FIG. 16 . 
         FIG. 18A  illustrates the coupling efficiency of variations of the example optical system in  FIG. 16 . 
         FIG. 19  illustrates a cross-sectional axial view of the example optical system, showing an optical fiber disposed in a support structure. 
         FIG. 20  illustrates another cross-sectional axial view of the example optical system, showing an optical coupler disposed in a support structure. 
         FIG. 21  illustrates a cross-sectional side view of an example optical coupler disposed in an example housing. 
         FIG. 22  illustrates a cross-sectional axial view of the optical coupler and housing in  FIG. 21 . 
         FIG. 23  illustrates a cross-sectional side view of an example coupler disposed in an alternative example housing. 
         FIG. 24  illustrates a cross-sectional axial view of the optical coupler and alternative housing in  FIG. 23 . 
         FIG. 25  illustrates an axial view of an alternative optical system that includes a plurality of optical couplers. 
         FIG. 26  illustrates an axial view of another alternative optical system that includes a plurality of optical couplers disposed in a housing. 
         FIG. 26A  illustrates a top view of the optical system in  FIG. 26 , showing the optical system optically coupled to a multi-core optical fiber. 
         FIG. 27  illustrates a flow diagram of an example method of manufacturing an optical coupler and optically coupling the optical coupler with an optical integrated circuit and an optical fiber. 
         FIG. 28  illustrates a flow diagram of another example method of manufacturing an optical coupler. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     An apparatus includes an optical coupler that has a fiber optic structure that comprises a core portion and a cladding portion. The fiber optic structure also has an outer surface that includes a first outer surface portion configured to optically couple the optical coupler with an optical waveguide. The first outer surface portion extends in a longitudinal direction of the fiber optic structure. The outer surface also includes a second outer surface portion that is adjacent to the first outer surface portion. The second outer surface portion extends transverse to the longitudinal direction of the fiber optic structure. The outer surface also includes a third outer surface portion configured to optically couple the optical coupler with an optical fiber. 
     Another apparatus includes an optical coupler configured to optically couple a waveguide core of an optical integrated circuit with an optical fiber. The optical coupler includes a fiber optic structure that comprises a core portion and a cladding portion. The fiber optic structure has a flat outer surface portion that extends in a longitudinal direction of the fiber optic structure, where the flat outer surface portion comprises both the core portion and the cladding portion. 
     A system includes an optical waveguide structure of an optical integrated circuit. The optical waveguide structure includes a substrate and a waveguide core forming an optical waveguide path disposed on the substrate. The system also includes an optical coupler disposed over the waveguide core. The optical coupler includes a fiber optic structure that comprises a core portion and a cladding portion. An outer surface of the fiber optic structure includes a first outer surface portion that extends in a longitudinal direction of the fiber optic structure, where the first outer surface portion is a substantially flat surface that includes the core portion and the cladding portion. Also, the first outer surface portion faces the waveguide core to optically couple the optical coupler with the waveguide core. The outer surface also includes a second outer surface portion adjacent to the first outer surface portion. The second outer surface portion extends transverse to the longitudinal direction of the fiber optic structure. The outer surface also includes a third outer surface portion that includes the core portion and the cladding portion. 
     Description of Example Embodiments 
     The present disclosure describes an optical coupler or coupling mechanism that is configured to optically couple one or more optical waveguides or waveguide paths with one or more optical fibers. The optical waveguides may be included with or as part of an optical waveguide structure, which may be located “on chip” or included as part of an optical integrated circuit (IC). The optical IC may be configured to process or perform functions on optical signals, such as modulation, bending light, coupling, and/or switching, as examples. The optical fibers may be optical components that are external to the optical IC. The optical fibers may be configured to communicate or carry the optical signals to and/or away from the optical IC. The optical coupler may be configured to optically couple the optical waveguide paths with the optical fibers so that the optical signals may be communicated between the optical IC and the optical fibers with optimum coupling efficiency (or minimum coupling loss). 
       FIG. 1  shows a top view of an example IC front end  102  of an optical IC  104  and an example fiber end  106  of an optical fiber  108 . The optical IC  104  and the optical fiber  108  may be configured to communicate optical signals between each other through the IC front end  102  and the fiber end  106 . The IC front end  102  may include an optical waveguide or waveguide structure that may include an optical waveguide core  110  disposed on a top planar surface  112  of a substrate  114 . The waveguide structure may also include an optical waveguide cladding (not shown in  FIG. 1 ) that encases or surrounds the optical waveguide core  110 . The optical waveguide core  110  may make up or form an optical waveguide path through which optical signals may propagate.  FIG. 1  shows an example configuration of the IC front end  102  that includes a single waveguide core  110  making up a single optical waveguide path. In alternative example configurations, multiple optical waveguide cores making up multiple optical waveguide paths may be included in the IC front end  102 . The optical waveguide path may communicate optical signals to and from processing circuitry (not shown) of the optical IC that performs the functions on the optical signals. 
     The optical waveguide core  110  may include a nanotaper  116  (also referred to as taper or an inverse taper) to couple optical signals received from the optical fiber  108  to the IC front end  102  and/or to couple optical signals to be transmitted to the optical fiber  108  away from the IC front end  102 . The nanotaper  116  may have an associated length extending in the direction of propagation from a first end  118  to a second end  120 . In addition, the nanotaper  116  may inversely taper or increase in width from a first end  118  to a second end  120 . The first end  118  may be located at or near (e.g., a couple of microns away from) an edge  121  of the substrate  114  of the optical IC  104 . At the first end  118 , the nanotaper  116  may have a width such that the optical mode at the first end  118  matches or substantially matches the mode of the optical fiber  108  and hence supports an optical fiber mode of the optical signals received from optical fiber  108 . The second end  120  may have a width that supports a waveguide mode of the optical signals in the optical waveguide structure. At the second end  120 , optical signals may be confined or concentrated to the optical waveguide structure. 
     The nanotaper  116  may increase in width from the first end  118  to the second end  120  in various ways. In one example configuration of the nanotaper  116 , as shown in  FIG. 1 , the width of the nanotaper  116  may have a linear profile in which the nanotaper  116  linearly increases in width from the first end  118  to the second end  120 . In alternative configurations, the width of the nanotaper  116  may increase in accordance with other profiles, such as a non-linear profile (e.g., an exponential or higher-order polynomial profiles) as an example. In addition or alternatively, the nanotaper  116  may have different profiles for its two opposing longitudinally extending sides. For example, one side may linearly extend from the first end  118  to the second end  120 , and the opposing side may non-linearly extend from the first end  118  to the second end  120 . Additionally, for some example configurations, the nanotaper  116  may be a single-segmented structure in which the width of the nanotaper  116  may continuously increase in accordance with a single profile from the first end  118  to the second end  120 , as shown in  FIG. 1 . In alternative configurations, the nanotaper  116  may be a multi-segmented structure in which the width of the nanotaper  116  may increase differently in accordance with different profiles over different segments of the multi-segmented nanotaper  116 . Various configurations or combinations of configurations for the nanotaper  116  are possible. 
     Additionally, the nanotaper  116  may be an adiabatic optical waveguide structure, in which minimal energy loss occurs as the optical signals propagate over the adiabatic structure. To achieve or ensure minimal energy loss, the length of the nanotaper  116  may be sufficient to cause or enable single modal propagation of the optical signals through the nanotaper  116  with minimal or no coupling of optical energy to other optical modes or radiation modes. The length of the nanotaper  116  may be significantly greater than the wavelengths of the optical signals, and the closer in effective index the modes are, the longer the length may be. In some cases the length may be at least ten times greater than the wavelengths. 
     As shown in  FIG. 1 , the optical waveguide core  110  making up the optical waveguide path may also include a uniform waveguide portion  122  connected to the second end  120  of the nanotaper  116 . The uniform waveguide portion  122  may have a substantially uniform width through which optical signals may be confined to the optical waveguide path and may be communicated between the nanotaper  116  and other portions of the optical IC  104 , such as processing circuitry (not shown). 
     The optical fiber  108  may include a fiber optic core  124  (denoted by dots), and a fiber optic cladding  126 , which may surround the fiber optic core  124 . The fiber optic core  124  and cladding  126  may each be made of an optical fiber material. Example fiber optic materials may include glass or plastic, and the material used for the cladding  126  may have a lower index of refraction than the core  124 , although other types of fiber optic materials and/or index of refraction configurations for either single or multimode operation, either currently existing or later developed, may be used. 
     As shown in  FIG. 2 , the optical fiber  108  may have a generally circular cross-sectional axial profile, which may be defined or determined by the cross-sectional axial shape of the fiber optic cladding  126 . The fiber optic core  124  may similarly have a circular cross-sectional axial shape. Each of the fiber optic core  124  and the fiber optic cladding  126  may have an associated cross-sectional axial size, which may be defined or determined by their respective diameters. 
     The optical fiber  108  shown in  FIGS. 1 and 2  may be single-core optical fiber of various types. For example, the optical fiber  108  may be a single-mode optical fiber that is configured to transmit optical signals in a single fiber optic mode. Example diameters for a single-mode optical fiber  108  may include a core diameter between 8 and 10.5 micrometers (μm or microns), such as 9 μm, and a cladding diameter of 125 μm, although optical fibers having other diameters may be used. Alternatively, the optical fiber  108  may include a multi-mode optical fiber configured to transmit optical signals in multiple fiber optic modes. In addition or alternatively, the optical fiber  108 , either as a single-mode or a multi-mode optical fiber, may be a polarization-maintaining optical fiber (PMF). Examples of currently existing and commercially available optical fibers may include Corning® SMF28®, Corning® SMF28e®, Corning® SMF28e+®, Corning® ClearCurve®, Corning® ClearCurve® ZBL, or Fujikura PANDA polarization maintaining optical fiber, as examples. Other types of single-core optical fibers may be used. In alternative configurations, instead of being a single-core optical fiber, the optical fiber  108  may be a multi-core optical fiber configured to be optically coupled with multiple waveguide paths of the optical IC  104 , as described in further detail below. 
       FIGS. 3-7  show various views of an example optical coupler  300  that may be configured to optically couple an optical waveguide or waveguide path of a front end of an optical IC and a fiber end of a single-core optical fiber, such as the IC front end  102  of the optical IC  104  and the fiber end  106  of the optical fiber  108  shown in  FIGS. 1 and 2 .  FIG. 3  shows a cross-sectional side view of the optical coupler  300  taken along a central axis of the optical coupler.  FIG. 4  shows a perspective view of the optical coupler  300  shown in  FIG. 3  rotated 90 degrees.  FIGS. 5-7  are cross-sectional axial views of the optical coupler  300  taken along lines  5 - 5 ,  6 - 6 , and  7 - 7 , respectively.  FIG. 6  has been enlarged for clarity. 
     The optical coupler  300  may include a fiber optic structure extending an overall longitudinal length L 0  from a first end  331  to a second end  333 . By being a fiber optic structure, the optical fiber  300  may include a core portion  330  and a cladding portion  332 . The core and cladding portions  330 ,  332  may be made of optical fiber materials, such as glass or plastic, which may be the same or similar to the optical fiber materials making up the core  124  and cladding  126  of the optical fiber  108  shown in  FIG. 1 . The optical coupler  300 , being a fiber optic structure, may be formed from an optical fiber having a cladding diameter d 0  and a core diameter d 1 . The cladding diameter d 0  may be a maximum outer diameter of the cladding portion  332  over its axial cross-section, and the core diameter d 1  may be a maximum outer diameter of the core portion  330  for the optical coupler  300  over its axial cross-section. 
     The optical coupler  300  may include a contact portion  335  having a longitudinal outer surface portion  334  and a transverse outer surface portion  340  of an outer surface of the optical coupler  300 . The longitudinal outer surface portion  334  may extend in a longitudinal direction of the optical coupler  300 . The longitudinal outer surface portion  334  may extend parallel or substantially parallel to a longitudinal axis of the optical coupler  300  from a first end  331  to a second end  339 . The longitudinal axis of the optical coupler  300  may extend through the center of the optical coupler  300 . The longitudinal outer surface portion  334  may be rectangular in shape. The transverse outer surface portion  340  may be adjacent to the longitudinal outer surface portion  334 . The transverse outer surface portion  340  may be perpendicular or substantially perpendicular to the longitudinal outer surface portion  334 . The transverse outer surface portion  340  may be semi-circular in shape, as shown in  FIG. 7 . The longitudinal outer surface portion  334  and the transverse outer surface portion  340  may both contact edge or corner  342 , as shown in  FIGS. 3 and 7 . 
     The longitudinal surface portion  334  and the transverse outer surface portion  340  may include both the core portion  330  and the cladding portion  332  of the fiber optic structure, as shown in  FIGS. 3, 4, and 7 . Over the longitudinal surface portion  334  and the transverse outer surface portion  340 , the core and cladding portion  330 ,  332  may be flush or co-planar with each other so that the surfaces are substantially smooth or flat, planar surfaces. In addition, the longitudinal surface portion  334  may be an exposed outer surface in that the longitudinal surface portion  334  and the transverse outer surface portion  340  may expose the core portion  330  to outer surroundings of the optical coupler  300 . As shown in  FIG. 4 , each of the core and cladding portions  330 ,  332  over the exposed longitudinal surface portion  334  may have a rectangular shape. As shown in  FIG. 7 , each of the core and cladding portions  330 ,  332  over the transverse outer surface portion  340  may have a semi-circular shape. 
     An overall width W 1 , including the cladding portion, of the exposed longitudinal surface portion  334  and a width W 2  of the core portion  330  of the exposed longitudinal surface portion  334  may be determined relative to the core and cladding diameters d 1 , d 0  of the fiber optic structure and by the distance D from the center  341  of the core portion  330  to the exposed longitudinal surface portion  334 . The distance D may be best shown in  FIGS. 6  (enlarged for clarity) and  8 A- 8 C. The widths W 2  and W 1  of the core and cladding portions  330 ,  332  of the rectangular shaped longitudinal surface portion  334  may decrease as the distance D increases and may be minimized when D is equal to the radius of the core portion  330 . The maximum widths W 2  and W 1  of the core and cladding portions  330 ,  332  of the rectangular shaped exposed longitudinal surface portion  334  may be equal or substantially equal to the core and cladding diameters d 1  and d 0  when the distance D is at or substantially equal to zero. 
     The axial cross-section throughout contact portion  335  may change when the distance D is varied, as shown in  FIGS. 8A-8C . The shape of core portion  330  exposed on longitudinal outer surface portion  334  in  FIGS. 8A-8C  may be rectangular, as shown in  FIG. 4 . The length of the rectangular exposed core portion  330  may be equal to distance L 1 . The width W 2  of the exposed core portion  330  may vary inversely with the distance D. A large distance D may result in a relatively small width W 2  of exposed core portion  330 . A small distance D may result in a relatively large width W 2  of exposed core portion  330 .  FIG. 8A  shows the axial cross section of contact portion  335  when the distance D is equal or substantially equal to the radius of core portion  330 . The amount of core portion  330  exposed on longitudinal outer surface portion  334  may be minimized when the distance D is equal or substantially equal to the radius of core portion  330 .  FIG. 8B  shows the axial cross section of contact portion  335  when the distance D is less than the radius of core portion  330  but greater than zero. The amount of core portion  330  exposed on longitudinal outer surface portion  334  in  FIG. 8B  may be similar to the core portion  330  shown in  FIG. 4 .  FIG. 8C  shows the axial cross section of contact portion  335  when the distance D is at or substantially equal to zero. The width W 2  of core portion  330  exposed on longitudinal outer surface portion  334  in  FIG. 8C  may be equal the diameter d 0  of core portion  330 . The amount of the core portion  330  exposed on longitudinal outer surface portion  334  may be maximized when the distance D is at or substantially equal to zero, as shown in  FIG. 8C . As shown in  FIGS. 8A-8C , the core portion  330  may form a semi-circular structure throughout length L 1 . 
     The distance D may vary anywhere from zero to the radius of core portion  330 . A negative value of the distance D may indicate that more than half of the core portion  330  has been removed. For example, the distance D may be selected in order to minimize loss as the optical signal transitions through the second end  339  of longitudinal outer surface portion  334 . For example, if the radius of core portion  330  is 4.15 μm, the distance D may be 2.15 μm+/−0.2 μm. Additionally or alternatively, the distance D may be determined based on a percentage or ratio of the radius of core portion  330 , such as for example, D equals approximately 52% (+/−5%) of the radius of core portion  330 . Accordingly, the distance D may be within 47% to 57% of the radius of core portion  330 . 
     The relationship between the amount of core portion  330  exposed on longitudinal outer surface portion  334  may vary based on the axial cross section of core portion  330 . A circular axial cross section is shown for core portion  330  in these figures, however any axial cross section shape may be used. For example, if the axial cross section of core portion  330  was rectangular, the amount of core portion  330  exposed on longitudinal outer surface portion  334  may not vary based on the distance D. In addition, the composition of the core and cladding portions  330 ,  332  making up the axial cross-sections may vary as the distance D varies. For example, some axial cross-sections may include only the cladding portion  332  if longitudinal outer surface portion  334  is located at the top of core portion  330 . Other axial cross-sections may include both the core portion  330  and the cladding portion  332 , as exemplified in the axial cross-section shown in  FIGS. 6 and 8A-8C . 
     The outer surface of the optical coupler  300  may also include a third exposed surface portion  337  that includes both the core portion  330  and the cladding portion  332 . The third exposed surface portion  337  may be separated from the longitudinal exposed surface portion  334  by a uniform portion  338  of the optical coupler  300 . Similar to the longitudinal exposed surface portion  334  and the transverse outer surface portion  340 , the third exposed surface portion  337  may expose the core portion  330  to outer surroundings of the optical coupler  300 . Also, over the third exposed surface portion  337 , the core and cladding portions  330 ,  332  may be flush or co-planar with each other so that the third exposed surface portion  337  is a substantially smooth or flat, planar surface. As shown in  FIG. 5 , each of the core and cladding portions  330 ,  332  over the third exposed surface portion  337  may be circularly shaped and have diameters that are equal or substantially equal to the core and cladding diameters d 1  and d 0 , respectively. 
     The outer surface of the optical coupler  300  may further include another surface portion  336 , which may be an unexposed surface portion. The unexposed surface portion  336  may only include the cladding portion  332  and/or may not include the core portion  330 . That is, over the unexposed surface portion  336 , the cladding portion  332  may cover the core portion  330  or prevent the core portion  330  from being exposed to the outer surroundings of the optical coupler  300 . Additionally, the unexposed surface portion  336  of the outer surface may have a shape, such as a rounded shape, that conforms to or tracks an outer surface of a cladding of an optical fiber. 
     As shown in  FIG. 3 , the contact portion  335  of the optical coupler  300  may longitudinally extend a first length L 1  from the first end  331  to a second end  339 . The lengths of the core and cladding portions  330 ,  332  of the rectangular shaped longitudinal surface portion  334  may be equal to the first length L 1 . Throughout the longitudinal first length L 1 , an axial cross-section perpendicular to the longitudinal axis may remain constant in height, cross-sectional shape, and compositional makeup of the core and cladding portions  330 ,  332  because the longitudinal outer surface portion  334  may be parallel to a longitudinal axis of the optical coupler  300 . 
     The optical coupler  300  may further include a uniform portion  338  connected to and/or formed integral to the contact portion  335 . The uniform portion  338  may have a uniform axial cross-section over a longitudinal length L 2 , from the second end  333  of the optical coupler  300  to the second end  339  of the longitudinal surface portion  334 , where the uniform portion  338  is connected to the contact portion  335 .  FIGS. 5 and 7  show the axial cross section of the optical coupler  300  being uniform over the longitudinal length L 2 . 
     As previously described, the optical coupler  300  may be formed from and/or be a part of an optical fiber. To illustrate,  FIG. 9  shows a cross-sectional side view of a fiber end  900  of an optical fiber. Dotted lines  902  and  903  in  FIG. 9  divide the end  900  into a first portion  904  and a second portion  906 . The first portion  904  is shown using solid lines to denote the portion of the optical fiber used for the optical coupler  300  shown in  FIGS. 3-8 . The second portion  906  is shown using dotted lines to denote a remaining, unwanted portion that may not be used for the optical coupler  300 . Dotted line  902  may represent a cutting line parallel or substantially parallel to a longitudinal axis of the optical coupler  300  along which a first cut in the fiber optic structure may be made. Dotted line  903  may represent a cutting line perpendicular or substantially perpendicular to the longitudinal axis of the optical coupler  300  along which a second cut in the fiber optic structure may be made. As shown in  FIG. 9 , the dotted line  902  dividing the first and second portions  904 ,  906  may extend through core and cladding portions  908 ,  910  of the optical fiber from a first end  912  to a second opposing end  914  at the angle that is parallel or substantially parallel to the longitudinal axis of the optical fiber end  900 . Dotted line  903  may extend from dotted line  902  to an exterior surface of the optical fiber and may extend through core and cladding portions  908 ,  910  of the optical fiber. An example process of making the optical coupler, including removal of the second unwanted portion  906  from the first portion  904  used for the optical coupler is described in further detail below. Longitudinal outer surface portion  334  and transverse outer surface portion  340  may be created by cutting optical coupler  300  along dotted lines  902  and  903 . Executing a cut that is parallel or substantially parallel to a longitudinal axis of the optical coupler  300  may reduce the complexity of manufacturing and/or be less costly to manufacture than a cut made at an angle relative to a longitudinal axis of the optical coupler  300 . 
     After the second, unwanted portion  906  is removed from the first portion  904 , the optical coupler  300  having the four outer surface portions  334 ,  336 ,  337 , and  340  shown in  FIG. 3  may result. Further portions of the optical coupler  300  may be removed to form various alternative embodiments of the optical coupler  300 . In particular, portions beginning from the first end  331  and/or the second end  333  of the optical coupler  300  may be removed, which may reduce an overall size of the optical coupler  300 , including a reduction in the overall length L 0  of the optical coupler  300  and/or the first and second lengths L 1  and L 2  associated with the contact portion  335  and the longitudinal surface portion  334 ; modify shapes, sizes and core and cladding compositional makeup of the longitudinal surface portion  334  and/or third exposed surface portion  337 ; modify orientations of the longitudinal surface portion  334 , the transverse outer surface portion  340 , and the third exposed surface portion  337  relative to each other; and/or form additional outer surface portions. Other modifications to the optical coupler  300  may result when the further portions of the optical coupler are removed. 
     Looking at  FIG. 3  in particular, to remove a first further portion of the optical coupler  300  beginning from the first end  331 , a first point or position along the longitudinal surface portion  334  from the first end  331  may be determined. The first position may be within a range of possible positions that extends along the longitudinal surface portion  334  between the first end  331  of the optical coupler  300  and the second end  339  of the contact portion  335 . After the first position in the range is determined, the first further portion to be removed may be defined by a line segment extending from the first position perpendicular to the longitudinal surface portion  334  to a second point or position on the unexposed surface portion  336 . The first further portion of the optical coupler  300  defined by the line segment may then be removed, which may form a fifth outer surface portion adjacent to the longitudinal surface portion  334  and the unexposed surface portion  336 . In some example configurations, the line segment may extend at an angle not perpendicular to the longitudinal surface portion  334 , so that the fifth outer surface portion, in turn, may be oriented at an angle to the longitudinal surface portion  334 . 
     In addition or alternatively, a second further portion may be removed from the optical coupler  300  beginning from the second end  333 . The second further portion of the optical coupler  300  that may be removed may include all or some of the uniform portion  338 . In addition or alternatively, a second point or position along the longitudinal surface portion  334  may be determined to remove all or some of the second further portion. The second position may be within a range of possible positions that extends along the longitudinal surface portion  334  between the second end  339  of the longitudinal surface portion  334  and the first end  331  of the contact portion of  335 . After the second position in the range is determined, the second further portion to be removed may be defined by a line segment extending from the second position to the unexposed surface portion  336 . The second further portion of the optical coupler  300  defined by the line segment may then be removed. When the second further portion is removed, the orientation of the third exposed surface portion  337  may be changed such that the third exposed surface portion  337  is adjacent to the longitudinal surface portion  334  at the second position along the longitudinal surface portion  334 . In some example configurations, the line segment may extend perpendicular to the longitudinal surface portion  334 , so that the orientation of the third exposed surface portion  337  is perpendicular to the longitudinal surface portion  334 . 
     The axial cross-sectional shape and the compositional makeup of the core and cladding portions  330 ,  332  at the third exposed surface portion  337  may vary; depending on how much of the second further portion is removed. For example, if only the uniform portion  338  of the optical coupler  300  is removed, the axial cross-section of the optical coupler  300  may be fully rounded, such as completely circular, as shown in  FIGS. 5 and 7 . Alternatively, if more of the second further portion than the uniform portion  338  is to be removed and the second position along the longitudinal surface portion  334  is determined, then the axial cross-section of the optical coupler  300  over the third exposed surface portion  337  may be partially rounded or semi-circular, as a part of the axial cross-sectional shape will include the flat, planar surface of the longitudinal surface portion  334 . 
       FIGS. 10-15  show cross-sectional side views taken along a central axis and corresponding cross-sectional axial views of various example alternative configurations of the optical coupler  300  when various amounts of a first further portion and/or a second further portion are removed from the optical coupler  300 .  FIGS. 10-13  show alternative example optical couplers when different amounts of a second further portion, beginning from the second end  333 , are removed.  FIGS. 14-15  show an alternative example optical coupler when an amount of a first further portion, beginning from the first end  331 , is removed. In all of these alternative embodiments, the core and cladding portions are exposed on a longitudinal outer surface portion  334  that may extend in a longitudinal direction of the optical coupler  300 . 
     The alternative example optical coupler  1000  shown in  FIGS. 10 and 11  may be formed from the optical coupler  300  when a part of the uniform portion  338  may be removed, which may modify the third exposed surface portion  337  to form an alternative third exposed surface portion  1037 . The third exposed surface portion  1037  may be adjacent and oriented perpendicular to a longitudinal surface portion  1034 , which may extend in a longitudinal direction of the optical coupler. Also, an axial cross-sectional shape of the optical coupler  1000  at the third exposed portion  1037  may be completely round, such as elliptical or circular, as shown in  FIG. 11 . 
     The alternative example optical coupler  1200  shown in  FIGS. 12 and 13  may be similar to the alternative optical coupler  1000 , except that additional material may be removed from the optical coupler  1000 . In particular, in view of  FIGS. 10 and 12 , a position  1239  along the longitudinal surface portion  1034  may be determined, and a corresponding portion may be removed from the optical coupler  1000  to form a third exposed surface portion  1237  and a longitudinal surface portion  1234  of the optical coupler  1200  shown in  FIGS. 12 and 13 . Optical coupler  1200  may not include a transverse outer surface portion, as shown in  FIG. 12 , if the entire uniform portion  338  is removed. Also, the optical coupler  1200  at the second exposed surface portion  1237  may have a semi-circular axial cross-section, as shown in  FIG. 13 , as the flat, planar surface of the longitudinal surface portion  1234  may be part of the axial cross-section. 
       FIGS. 14-15  show another alternative example optical coupler  1400  when an amount of a portion of the optical coupler  300 , beginning from the first end  331 , is removed. The optical coupler  1400  is configured to have third exposed surface portions  1437  configured similarly to the third exposed surface portion  1037  of the optical coupler  1000  shown in  FIGS. 10 and 11 . However, other configurations for the third exposed surface portions  1437 , such as those for the example optical couplers  300  or  1200 , may be alternatively used. 
     With reference to  FIGS. 3 and 14 , the alternative example optical coupler  1400  may be formed from a determined point or position  1444  along the longitudinal surface portion  334  in between the first end  331  and second end  339  of the longitudinal surface portion  334  to form a longitudinal surface  1434  and a fourth surface portion  1443  of an outer surface of the optical coupler  1400 . The fourth surface portion  1443  may be adjacent to the longitudinal surface portion  1434  and oppose the exposed surface portion  1437 , in which the optical coupler  1400  may longitudinally extend from the fourth surface portion  1443  to the third exposed surface portion  1437 . The fourth surface portion  1443  may be separated from the transverse outer surface portion  1440  by the longitudinal surface  1434 . Additionally, as shown in  FIG. 14 , the fourth surface portion  1443  may be oriented perpendicular to the longitudinal surface portion  1434 , although other orientations are possible. As shown in  FIG. 14 , the fourth surface portion  1443 , the transverse outer surface portion  1440 , and the third exposed surface portion  1437  may be oriented perpendicular or substantially perpendicular to the longitudinal surface portion  1434 , and as such, may be oriented parallel or substantially parallel to each other. As shown in  FIG. 15 , an axial cross section of the optical coupler  1400  at the fourth surface portion  1443  may be semi-circular. Also, because the position  1444  was in between the ends  331  and  339  of the optical coupler  300 , the compositional makeup of the fourth surface portion  1443  may include both a cladding portion  1432  and a core portion  1430 , as shown in  FIG. 15 . 
     The various optical couplers shown in  FIGS. 3-15  are non-limiting examples of optical couplers that may be formed from a fiber optic structure having a longitudinal surface that extends in a longitudinal direction of the optical coupler. Other optical couplers, including optical couplers having different combinations of the features shown in  FIGS. 3-15 , may be formed in accordance with the above description. 
     A longitudinal exposed surface portion of an optical coupler, such as those shown in  FIGS. 3-15 , may be positioned and oriented relative to an optical waveguide to optically couple the optical coupler with the optical waveguide. In particular, the optical coupler may be positioned over the optical waveguide such that the longitudinal exposed surface portion faces and is substantially parallel to the core of the optical waveguide. Additionally, the third exposed surface portion of the optical coupler, such as those shown in  FIGS. 3-15 , may be used to optically couple the optical coupler with a single-core optical fiber. In particular, the third exposed surface portion may face and be butt coupled with an end of the optical fiber. 
       FIG. 16  shows a partial cross-sectional side view of an optical system that includes an optical coupler  1600  optically coupled with an optical waveguide of an IC front end  1602  of an optical IC  1604  and a fiber end  1606  of an optical fiber  1608 . The optical coupler  1600  shown in  FIG. 16  has the configuration of the example optical coupler  1000  shown in  FIG. 10 , although other optical couplers configured in accordance with those shown and described above with reference to  FIGS. 3-15  may be used. 
     The IC front end  1602  of the optical IC  1604  may be a generally planar structure that includes one or more planar layers disposed and/or deposited on top of one another. The planar layers may include a top layer  1668  that includes at least a core of the optical waveguide with which the optical coupler  1600  may be optically coupled. The top layer  1668  may be disposed on a top surface  1612  of the other or non-top layers of the planar structure. The other or non-top layers may be generally referred to as the substrate or substrate layers  1614 . 
     The layers of the front end  1602  of the optical IC may be configured in accordance with one of various material technologies or systems used for optical waveguides and optical integrated circuits. In some example configurations, the layers may be configured in accordance with silicon on insulator (SOI), which may be formed using complementary metal-oxide-semiconductor (CMOS) fabrication techniques or SOITEC Smart Cut™ process. 
     In accordance with SOI, the layers of the IC front end  1602  may include a first, base layer  1660  and a second, buried oxide (BOX) layer  1662  disposed on a top planar surface  1664  of the base layer  1660 . The base layer  1660  may be made of silicon (Si), and the BOX layer  1662  may be made of an oxide material, such as silicon dioxide (SiO 2 ). For purposes of the present description, the base and BOX layers  1660 ,  1662  may be referred to as the substrate layers  1614  when the IC front end  1602  is configured for SOI. The top layer  1668  may be disposed on a top surface  1612  of the BOX layer  1662 . The top layer  1668  may include the core of the optical waveguide, which in accordance with SOI, may be an etched layer of silicon that is disposed on the top surface  1612  of the BOX layer  1662 . 
     To integrate the optical coupler  1600  with the IC front end  1602 , the optical coupler  1600  may be positioned over the top layer  1668 . In particular, a longitudinal surface portion  1634  of the optical coupler  1600  may face and be disposed on a top surface  1666  of the top layer  1668 . When the longitudinal surface portion  1634  is disposed on the top surface  1666  as shown in  FIG. 16 , the optical coupler  1600  may be optically coupled with the optical waveguide. 
     The core of the optical waveguide may be included as a sub-layer or portion of the top layer  1668 . In addition to the core, the top layer  1668  may include an adhesive sub-layer or portion and/or a cladding sub-layer or portion. The adhesive portion may be used to affix the optical coupler  1600  to the IC front end  1602 . The adhesive portion may include an epoxy, such as an optically transparent epoxy, or other type of adhesive material. The cladding portion may be an additional component of the optical waveguide structure that at least partially surrounds or encases the core to confine optical signals to the core as they propagate along the waveguide path. 
       FIGS. 17A-17G  show cross-sections of the optical system of  FIG. 16  along the line  17 - 17 , illustrating various example configurations of the top layer  1668 . All of the configurations include a core  1710  of the top layer  1668  disposed on the top surface  1612  of the BOX layer  1662 .  FIGS. 17A-17G  illustrate various ways in which adhesive and/or cladding portions may be integrated with the core to form an optical waveguide and affix the optical coupler  1600  to the top layer  1668 . 
     In one example configuration of the top layer  1668  shown in  FIG. 17A , a top layer  1668 A may include an adhesive portion  1770 A that is disposed around longitudinally extending sides  1772 ,  1774  and a top surface  1776  of the core  1710 . The longitudinal surface portion  1634  may be disposed on and be in contact with a top surface  1766 A, which may include only the adhesive portion  1770 A. Additionally, as shown in  FIG. 17A , the adhesive portion  1770 A may separate a core portion  1630  of the optical coupler  1600  and the top surface  1776  of the core  1710 . 
     In another example configuration of the top layer  1668  shown in  FIG. 17B , a top layer  1668 B may include an adhesive portion  1770 B that is disposed around or adjacent to the sides  1772 ,  1774  but not the top surface  1776  of the core  1710 . In this way, the top surface  1766 B may include both the core and adhesive portion. When the optical coupler  1600  is disposed on the top layer  1668 B, the core portion  1630  may be in direct contact with the top surface  1776  of the core  1710 , and the adhesive portion  1770 B on both sides  1772 ,  1774  of the core  1710  may affix the optical coupler  1600  to the top layer  1668 B. 
     In another example configuration of the top layer  1668  shown in  FIG. 17C , an adhesive portion  1770 C of a top layer  1668 C may be adjacent to the sides  1772 ,  1774 , and may also extend into and/or at least one trench, such as a pair of trenches  1778 C,  1780 C that may be formed in the BOX layer  1662 . The trenches  1778 C,  1780 C may be formed in the BOX layer  1662  and filled or added with adhesive material to provide an extra thickness or increased bond line for the adhesive portion, which in turn may enhance the adhesive bond between the top layer  1668 C and the optical coupler  1600 . The trenches  1778 C,  1780 C may longitudinally extend parallel or substantially parallel with the sides  1772 ,  1774  of the core  1710  over at least a part of the length of the top layer  1668 C over which the optical coupler  1600  may be disposed. Also,  FIG. 17C  shows the trenches  1778 C,  1780 C extending partially through the BOX layer  1662 . In alternative configurations, the trenches  1778 C,  1780 C may extend completely through the BOX layer  1662  and/or into the base layer  1660 . The trenches  1778 C,  1780 C may be located a sufficient lateral distance from core  1710  to prevent interference with the optical mode. Additionally, the trenches  1778 C,  1780 C may be formed using planar lithography and etching techniques. One example etching technique used to form the trenches  1778 C,  1780 C may be deep reactive ion etching (DRIE), although other etching techniques may be used. 
     In another example configuration of the top layer  1668  shown in  FIG. 17D , a top layer  1668 D may include a cladding  1782 D surrounding and/or adjacent to the sides  1772 ,  1774  and the top surface  1776  of the core  1710 . An adhesive portion  1770 D may be applied to a top surface  1784 D of the cladding  1782 D. In this way, the adhesive portion  1770 D may be included as a top sub-layer of the top layer  1668 D. The longitudinal surface portion  1634  may be disposed on the adhesive portion  1770 D to be affixed to the IC front end  1602 . For the example configuration shown in  FIG. 17D , the core  1710  may be separated from the core portion  1630  of the optical coupler  1600  by both the adhesive layer  1770 D and the cladding  1782 D of the top layer  1668 D. 
     In another example configuration of the top layer  1668  shown in  FIG. 17E , a cladding  1782 E of a top layer  1668 E may be disposed around and/or be adjacent the sides  1772 ,  1774  of the core, and a top surface  1784 E of the cladding  1782 E may be co-planar or substantially co-planar with the top surface  1776  of the core  1710 . Similar to the configuration shown in  FIG. 17D , an adhesive portion  1770 E may be included as a top sub-layer of the top layer  1668 E and disposed over the top surfaces  1776 ,  1784 E of the core  1710  and cladding  1782 E, respectively. The longitudinal exposed surface portion  1634  may be disposed on  1770 E to be affixed to the IC front end  1602 . 
     In another example configuration of the top layer  1668  shown in  FIG. 17F , a top layer  1668 F may include trenches  1778 F and  1780 F that may be formed in a cladding  1782 F and extend into the BOX layer  1662 . The trenches  1778 F,  1780 F may be filled with adhesive  1770 F to affix the longitudinal surface portion  1634  of the optical coupler  1600  to a IC front end  1602 . As shown in  FIG. 17F , the trenches  1778 F,  1780 F may extend completely through the cladding  1782 F, from the top surface  1784 F of the cladding and partially through the BOX layer  1662 . In alternative example configuration, the trenches  1778 F,  1780 F may extend only partially through the cladding  1782 F. Alternatively, the trenches  1778 F,  1780 F may extend completely through both the cladding  1782 F and the BOX layer  1662  and/or into the base layer  1660 . The trenches  1778 F,  1780 F may be located a sufficient lateral distance from core  1710  to prevent interference with the optical mode. The trenches  1778 F,  1780 F may be formed using planar lithography and etching techniques, such as DRIE, as previously mentioned. In addition or alternatively, one or more cutting techniques may be used to cut through the cladding  1782 F to form at least the portions of the trenches  1778 F,  1780 F that extend through the cladding  1782 F. Additionally, the top layer  1668 F is shown to include trenches  1778 F,  1780 F for a core/cladding configuration where the cladding  1782 F surrounds the sides  1772 ,  1774  and the top surface  1776  of the core  1710 . In this way, the top surface  1766 F of the top layer  1668 F, may include both the top layer  1784 F and an adhesive portion  1770 F filled in the trenches  1778 F,  1780 F. 
     In another example configuration of the top layer  1668  shown in  FIG. 17G , trenches  1778 G,  1780 G filled with adhesive material may be used for a core/cladding configuration where a top surface  1784 G of cladding  1782 G is co-planar with the top surface  1776  of the core  1710 , and the cladding  1782 G does not surround the top surface  1776  of the core  1710 . For this example configuration, the top surface  1766 G of the top layer  1668 G may include core, cladding, and adhesive portions that are flush or co-planar with each other. As shown in  FIG. 17G , the core portion  1630  of the optical coupler  1600  may be in direct contact with the core  1710 . 
     The example configurations of the top layer  1668 F and  1668 G are shown using trenches instead of a top adhesive sub-layer to affix the optical coupler  1600  to the IC front end  1602 . In alternative configurations, the trenches may be used in combination with a top adhesive sub-layer, such as the top adhesive sub-layers  1770 D and  1770 E used for the configurations shown in  FIGS. 17D  and E. The combination of the trenches and the top adhesive sub-layer may be used for the core/cladding configuration where the cladding surrounds the top surface  1776  of the core  1710  and/or for the core/cladding configuration where the top surface of the cladding is co-planar with the top surface  1776  of the core  1710   
     The cross-sections shown in  FIGS. 17A-17G  are non-limiting example configurations of a top layer  1768  for the IC front end  1602  that includes a core of an optical waveguide in combination with various configurations of an adhesive portion used to affix the optical coupler  1600  to the IC front end  1602  and an optional cladding portion. Other configurations or combinations of the configurations of the top layer  1768  shown in  FIGS. 17A-17G  may be possible. 
     Additionally,  FIGS. 17A-17G  show the core  1710  as a single-layer structure. However, in alternative configurations, the core  1710  may be a multi-layer structure, such as a double-layer structure. For example, the core may be formed by a partial etching, instead of a complete etching, of a silicon layer disposed on the top surface  1612  of the BOX layer  1662 . A thinner layer of silicon formed from the partial etch may remain disposed over the BOX layer  1662 , which may be the first layer, and the core forming the waveguide path may be the second layer. In another alternative configuration, the core may include a ribbed structure disposed on a base layer, which may be a nanotaper or uniform waveguide portion determining the waveguide path. The ribbed and base layers may be made of the same or different materials, such as silicon and polycrystalline (polysilicon) or silicon nitride (Si 3 N 4 ), as examples. 
     In addition, as shown in  FIGS. 17A-17G , when the optical coupler  1600  is positioned over the core  1710 , the core portion  1630  of the optical coupler  1600  may be axially aligned with the core  1710 . 
     Further, when positioned over the core  1710 , the longitudinal surface portion  1634 , including the core portion  1630  of the longitudinal surface portion, may be longitudinally aligned with a nanotaper portion of the core  1710 .  FIG. 18  shows an exploded view of the optical system shown in  FIG. 16 , with the optical coupler  1600  and the IC front end  1602  rotated ninety degrees, so that the surfaces of the optical coupler  1600  and the IC front end  1602  that face each other (i.e., the longitudinal surface portion  1634  and the top surface  1776  of the core  1710 ) are shown. The core  1710  may include a nanotaper  1816  connected to uniform waveguide portion  1822 , which may be similar to the nanotaper  116  and uniform waveguide portion  122  shown in  FIG. 1 . The nanotaper  1816  may extend a longitudinal length and increase in width over the longitudinal length from a first end  1818  to a second end  1820 . 
     Nanotaper  1816  may increase in width in multiple segments, such as two linear segments as shown in  FIG. 18 . The first segment  1815  may increase the width of nanotaper  1816  relatively gradually over length L 3 . The second segment  1817  may increase the width of nanotaper  1816  relatively rapidly over length L 4 . The number of segments may vary from one segment to multiple segments. The profile of each segment may be linear or non-linear. Linear segments may be used in conjunction with non-linear segments. The length of each segment and/or the combined length of all segments in nanotaper  1816  may vary based on, for example, the length or width of the longitudinal surface portion  334  of optical coupler  300 , the length or width of the core portion  330  of optical coupler  300 , the distance D of the core portion  330  of optical coupler  300 , the mode of optical signals received from or sent to optical fiber  108 , the waveguide mode of the optical signals in the optical waveguide structure, and the amount of energy loss that that can be tolerated as the optical signals propagate through the nanotaper  1816 . To achieve or ensure minimal energy loss, the length of the nanotaper  1816  and/or segments  1815 ,  1817  may be sufficient to cause or enable single modal propagation of the optical signals through the nanotaper  1816  and optical coupler  1600  with minimal or no coupling of optical energy to other optical modes or radiation modes. Nanotaper  1816  and optical coupler  1600  may form an adiabatic coupling system. The optical energy in the optical mode of uniform waveguide portion  1822  may gradually transform into the optical mode of the combined nanotaper  1816  and optical coupler  1600 . As the nanotaper  1816  decreases in width, the optical energy may be more and more confined in core portion  1630  of the longitudinal surface portion  1634 . The optical energy may enter the full core portion  1630  at the second end  1639  of the longitudinal surface portion  1634  and finally exit into the core portion  1624  of the optical fiber  1608 . The length of the nanotaper  1816  and/or segments  1815 ,  1817  may be significantly greater than the wavelengths of the optical signals, and the closer in effective index the modes are, the longer the length may be. In some cases the length may be at least ten times greater than the wavelengths. 
     The increase in width of nanotaper  1816  in the second segment  1817  may be determined by the width of uniform waveguide portion  1822 . The length L 4  of second segment  1817  may be relatively smaller than the length L 3  of first segment  1815 . The length L 4  of second segment  1817  may remain relatively constant, whereas the length L 3  of first segment  1815  may be varied to achieve a desired coupling efficiency. For example,  FIG. 18A  shows the coupling efficiency based on various lengths L 3  of first segment  1815  ranging from 15 μm to 1000 μm. In  FIG. 18A , the coupling efficiency was calculated based on a distance D of 2.15 μm, length L 4  of second segment  1817  of 5 μm, width of uniform waveguide portion  1822  of 0.45 μm, width of second segment  1817  at second end  1820  of 0.45 μm, width of second segment  1817  at its narrow end of 0.2 μm, and width of first segment  1815  at first end  1818  of 0.12 μm. As shown in  FIG. 18A , the coupling efficiency generally increases as length L 3  of first segment  1815  increases. 
     The length of the nanotaper  1816  and/or segments  1815 ,  1817  and the distance D of the core portion  330  may be selected to maximize coupling efficiency between the optical IC  104  and optical fiber  108 . For example, a larger distance D of core portion  330  may require a longer nanotaper  1816  in order to achieve a desired coupling efficiency. A relatively large distance D of core portion  330 , such as at or near the radius of core portion  330 , may require the length of nanotaper  1816  to be so large that the resultant optical coupler is impractical to use or manufacture. The distance D of core portion  330  may need to be balanced with the length of nanotaper  1816  in order to achieve a desired coupling efficiency and a practical optical coupler. 
     In some example configurations, when the optical coupler  1600  is positioned over the nanotaper  1816 , the optical coupler  1600  and the nanotaper  1816  may form an adiabatic system or a combined adiabatic optical structure. Some or all of the dimensions and/or material properties of the optical coupler  1600  and/or the core  1710 , including the nanotaper  1816 , may depend on each other or chosen relative to each other. Further, the dimensions and/or properties may be determined in accordance with optical criteria. For example, the width of the nanotaper  1816  at the larger-width end  1820 , the shorter-width end  1818  and the profile of the tapering between the two ends  1818 ,  1820  may be chosen such that an effective index of the mode at the larger-width end  1820  of the nanotaper  1816  may be greater than the index of the core portion  1630  at the first end  1631 , such that the mode is predominantly confined in the nanotaper  1816  of the optical waveguide of the IC front end  1602 . Additionally, the width of the nanotaper  1816  at the smaller-width end  1818  may be determined such that the effective index of an overall mode of the nanotaper  1816  and the optical coupler  1600  combined adiabatically decreases to a value that may be less than the index of the core portion  1630 , but greater than the index of the cladding portion  1632 . In this way, the optical mode may be predominantly confined in the core portion  1630  of the optical coupler  1600  at the shorter-width end  1818  of the nanotaper  1816 . 
     In accordance with the above optical criteria, the relative lengths of the optical coupler  1600  and the nanotaper  1816  may be determined. In some example configurations, the lengths of the longitudinal surface portion  1634  and the nanotaper  1816  may be the same or substantially the same, as shown in  FIG. 18 . In alternative example configurations, the lengths may be different. In some example configurations, the maximum length of the core portion  1630  of the longitudinal surface portion  1634  may be the same, different, and/or generally determined relative to length of the nanotaper  1816 , regardless of the overall length of the longitudinal surface portion  1634 . This may be particularly applicable for configurations of the optical coupler  1600  where the maximum length of the core portion  1630  over the longitudinal surface portion  1634  may be different than the overall length of the longitudinal surface portion  1634 . 
     In addition to the lengths of the optical coupler  1600  and the nanotaper  1816  being determined relative to each other, the optical coupler  1600  may be longitudinally aligned relative to the nanotaper  1816 . Where the overall length of the longitudinal surface portion  1634  is the same or substantially the same as the length of the nanotaper  1816 , the first end  1631  where the fourth surface portion  1640  is disposed may be aligned with the larger-width end  1820  of the nanotaper  1816 , and the second end  1639  may be aligned with the smaller-width end  1818  of the nanotaper  1816 . Alternatively, the longitudinal alignment between the nanotaper  1816  and the optical coupler  1600  may be relative to the length of the core portion  1630  over the longitudinal surface portion  1634 . 
     In alternative configurations where the length of the longitudinal surface portion  1634  and/or the maximum length of the core portion  1630  is different than the length of the nanotaper  1816 , longitudinal alignment may be relative to one of the ends  1818 ,  1820  of the nanotaper  1816 , but not the other. For example, the second end  1639  of the longitudinal surface portion may be aligned with the shorter-width end  1818  of the nanotaper  1816 . The first end  1631  may be disposed relative to the large-width end  1820  depending on the respective lengths of the longitudinal surface portion  1634  and the nanotaper  1816 . For example, if the longitudinal surface portion  1634  is longer than the nanotaper  18416 , then the first end  1631  may extend beyond the larger-width end  1820  of the nanotaper  1816  and be positioned over the uniform waveguide portion  1822 . Alternatively, if the longitudinal surface portion  1634  is shorter than the nanotaper  1816 , then the first end  1631  may be positioned over the nanotaper  1816  before the nanotaper  1816  is finished inversely tapering. In still other alternative configurations where the lengths are different, longitudinal alignment may be relative to the larger-width end  1820  instead of the shorter-width end  1818 . 
     For some example manufacturing processes, the optical coupler  1600  may be axially and/or longitudinally aligned with the nanotaper  1816  passively by defining lithographically defined features on the optical IC  1604 . A vision based system may be used to place the optical coupler  1600  over the IC front end  1602  aligned to the core  1710  relative to these lithographically defined features. 
     Referring to  FIGS. 16 and 18 , the optical system may also include an optical fiber support structure  1650  that is configured to receive the fiber end  1606  and uniform portion  338  of optical coupler  300  and position and support the fiber end  1606  in an optimally aligned position so that a core portion  1624  of the fiber end  1606  is in optimal axial alignment with the core portion  1630  of optical coupler  1600  at the second end  1637  to achieve optimum coupling between the optical fiber  1608  and the optical coupler  1600 . 
     As shown in  FIG. 16 , the fiber end  1606  may abut or be butt coupled to the second end  1637  of the optical coupler  1600  to optically couple the fiber end  1606  with the second exposed surface portion  1637  of the optical coupler  1600 . When positioned in the support structure  1650 , the fiber end  1606  may be butt coupled with the second end  1637  of the optical coupler  1600  in an optimally aligned position relative to the optical coupler  1600  to achieve optimum coupling between the two optical structures. 
       FIG. 19  shows a cross-sectional axial view of the optical system taken along line  19 - 19 . The support structure  1650  may include a channel  1902  formed in a body  1904  of the support structure  1650 . The channel  1902  may be configured to receive, position, and support the fiber end  1606  in the optimally aligned position. In the example configuration shown in  FIG. 19 , the channel  1902  may be a V-groove or V-groove type channel. The V-groove  1902  may be formed using planar lithography techniques and etching, such as potassium hydroxide (KOH) etching. That is, planar lithography techniques and etching may be used to form a channel to hold the optical fiber  1608  to passively align the fiber end  1606  with the optical coupler  1600  and the optical waveguide path to achieve optimum alignment and coupling. 
     A size of the V-groove  1902  may be determined by an angle φ, which may depend on the material properties of the material making up the body  1904 . In some example configurations, the body  1904  may be made of silicon, and the angle φ may be about 70 degrees, which may depend on the crystalline structure of the silicon. Other materials and or angles of the V-groove  1902  are possible. Also, alternative example configurations may include different types of channels other than V-grooves, such as U-shaped channels, rectangular shaped channels, or trapezoidal shaped channels. These different types of channels or shaped channels may depend on the material making up the body  1904  and/or the type of process used to make the channel  1902 . Various configurations are possible. 
       FIG. 20  shows a cross-sectional axial view of the optical system taken along line  20 - 20 . Channel  1902  in support structure  1650  may be configured to receive, position, and support the uniform portion  1638  of optical coupler  1600  in the optimally aligned position. 
     Referring back to  FIG. 16 , for some example configurations, the support structure  1650  may be part of or integrated with the substrate  1614  of the optical IC  1604 . For example, the support structure  1650  may be part of and made of the same material as a base layer  1660  of the substrate  1614 . In alternative example configurations, the support structure  1650  may be a component of the optical system that is separate from and/or external to the substrate  1614 , and that may be positioned adjacent to or near the substrate  1614  in the optical system. Various configurations are possible. 
     In sum, when the core portion  1630  of the optical coupler  1600  is positioned and aligned with core  1710  of the nanotaper  1816 , and the fiber end  1606  of the optical fiber  1608  is positioned in the channel  1902  ( FIG. 19 ), the optical coupler  1600  may optically couple the waveguide path formed by the core  1710  with the optical fiber  1608  with optimum coupling efficiency. In this way, optical signals being communicated between the optical IC  1604  and the optical fiber  1608  may transition between the waveguide mode and optical fiber modes with minimum loss and/or maximum coupling efficiency. 
     The optical system shown in  FIGS. 16-20  is not limited to including all of the optical coupler  1600 , the optical IC  1604 , and the optical fiber  1608 . Some configurations of the optical system may include the optical IC  1604  and the optical coupler  1600 , but may not include the optical fiber  1608 . Alternatively, the optical system may include the optical coupler  1600  and the optical IC  1604  without the support structure  1650 , and the support structure  1650  may be considered a component that is separate to the optical system. In still other example alternative configurations, the optical system may include the IC front end  1602  without other portions of the optical IC  1604 . For example, the IC front end  1602  may be a standalone component that is considered separate from other optical IC portions. The standalone IC front end  1602  may be integrated with the optical coupler  1600 , and together, the IC front end  1602  and the optical coupler  1600  may be used or implemented with one or more optical integrated circuits. Various configurations or combinations of configurations of the optical system are possible. 
     In addition, the optical system shown and described with reference to  FIGS. 16-20  is described for optical ICs using SOI. The components and features of the optical system may be equally or similarly applicable to optical ICs that use material technologies other than SOI or that use other types of semiconductor materials, such as Germanium (Ge) or compound semiconductor materials, such as Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (Al x Ga x As), Indium Phosphide (InP), Indium Gallium Arsenide (In x Ga 1-x As), Indium Gallium Arsenide Phosphide (In x Ga 1-x As y P 1-y ), Indium Aluminum Arsenide (In x Al 1-x As), Indium Aluminum Gallium Arsenide (In x Al y Ga 1-x-y As), Gallium Nitride (GaN), Aluminum Gallium Nitride (Al x Ga 1-x N), Aluminum Nitride (AlN), or Gallium Antimodide (GaSb), as examples. Alternatively, the substrate  1614  and the core  1710  may be made of one or more polymers or polymer materials. Other materials or configurations of materials are possible. 
     For some example configurations, the optical coupler may be disposed or positioned within a housing for manufacturability or support.  FIGS. 21-22  show various views of the optical coupler  1600  positioned in an example housing  2100 . In alternative embodiments, other example optical couplers, including those previously shown and described with reference to  FIGS. 3-20 , may be similarly positioned within the example housing  2100 . 
     The housing  2100  may include a body  2102  and a channel  2104  extending in the body  2102  from a first end  2106  to a second, opposing end  2108 . The optical coupler  1600  may be positioned in the channel  2104 . The channel  2104  may have a height or depth that does not increase or decrease. Alternatively, the channel  2104  may have a height or depth that increases in accordance with the diameter of optical coupler  1600 . When the optical coupler  1600  is positioned in the channel  2104  of the housing  2100 , a base surface  2114  of the body  2102  may be coplanar or substantially coplanar with the longitudinal surface portion  1634  of the outer surface of the optical coupler  1600 . The coplanar surfaces  1634 ,  2114  may be suitable for mounting and affixing the optical coupler  1600  with the housing  2100  to a top layer of an optical IC. 
     For the example housing  2100 , the body  2102  may be made of a material that is the same or similar to the fiber optic materials used for the core portion  1630  or the cladding portion  1632  of the optical coupler  1600 . An example material may be glass. When glass is the material used for the body  2102 , a cutting procedure in which a cutting mechanism, such as a saw cutting into the body  2102 , may be a suitable removal procedure to remove material from the body to form the channel  2104 . In alternative configurations, an etching process may be used to remove the glass material from the body to form the channel  2104 . 
     The cutting procedure, or the removal procedure generally, may determine the cross-sectional shape for the channel  2104 . As shown in  FIG. 22 , the channel  2104  may have a generally rectangular cross-sectional shape, which may be defined or determined by inner walls  2110 ,  2112 , and  2114 . Cross-sectional shapes other than rectangular, such as U-shaped or trapezoidal shapes, may be formed, depending on the cutting mechanism and/or the material used for the body  2102 . For example, in alternative example embodiments, the body  2102  may be made of a material, such as silicon, in which etching and planar lithography techniques may be used to form the channel  2104 . For these alternative embodiments, the channel  2104  may be a V-groove, similar to the V-groove  1902  shown in  FIG. 19 . 
     As shown in  FIG. 21 , the length of the housing  2100  from the first end  2106  to the second end  2108  may be the same or substantially the same as the length of the optical coupler  1600  from the first end  1631  to the second end  1637 . Alternatively, the lengths may be different and in some example configurations, the optical coupler  1600  may extend beyond the ends  2106 ,  2108  of the housing  2100 , depending on the process used to manufacture the optical coupler  1600  and the housing  2100 . 
       FIGS. 23-24  show various views of the optical coupler  1600  positioned in an alternative example housing  2300  that includes a body  2302  and a channel  2304  extending in the body  2302  from a first end  2306  to a second end  2308 . The alternative example housing  2300  may be made of a material in which etching and planar lithography techniques may be a suitable removal process to form the channel  2304 , such as silicon. 
     In the example configuration shown in  FIGS. 23-24 , the channel  2304  may be formed as a V-groove extending in the body  2302  of the housing  2300 , which may be similar to the V-groove  1902  shown in  FIG. 19 . The V-groove  2304  may be formed using etching and planar lithography techniques. The V-groove channel  2304  may be defined or determined by inner walls  2310 ,  2312  of the body  2302 . The V-groove  2304  may also be defined or determined by an angle δ formed by an intersection of the two inner walls  2310 ,  2312 , such as at a point or corner  2316 , although other shaped intersections are possible depending on the etching and lithography techniques used. Also, the angle δ may depend on the material properties of the material making up the body  2302 . In some example configurations, the body  2302  may be made of silicon, and the angle δ may be about 70 degrees, which may depend on the crystalline structure of the silicon, as previously described. 
     As shown in  FIGS. 23-24 , when the optical coupler  1600  is positioned in the housing  2300 , the base surface  2314  may be coplanar or substantially coplanar with the longitudinal surface portion  1634  of the outer surface of the optical coupler  1600 . So that the longitudinal surface portion  1634  and the base surface  2314  may be flush or coplanar. The angle δ of the V-groove  2304  may remain constant over the length. 
     As shown by the cross-sectional views in  FIG. 24 , the height of the V-groove  2304  may be determined or defined as a distance extending from a point or position coplanar with the base surface  2314  to the intersection  2316  of the inner walls  2310 ,  2312 . The height may remain constant over the length of the housing  2300  in accordance with height of the optical coupler  1600 . 
     For some configurations, the example housing  2100  made of glass (i.e., a material that is the same or similar to the fiber optic materials used for optical coupler  1600 ) may be preferred over the example housing  2300  made of silicon (i.e., a material different than the fiber optic materials used for the optical coupler  1600 ). In particular, when the materials are the same or similar, an optical fiber may be integrated with the housing before the optical coupler is formed from the optical fiber. For example, the optical fiber may be positioned in a channel of uniform height in the glass housing. Once the optical fiber and the housing are integral components, any removal processes performed on the optical fiber to form the optical coupler may similarly and simultaneously be formed on the housing. As a result, the longitudinal surface portion of the optical coupler and the base surface of the glass housing may be more co-planar with each other. In contrast, when silicon is used, removal processes performed on an optical fiber to form the optical coupler may not be used to remove silicon. Instead, a channel, such as a V-groove, may be formed, and the optical fiber may be positioned in the V-groove. A portion of the optical fiber may protrude or extend beyond the V-groove, and this portion may be removed to form the optical coupler. The resulting co-planar longitudinal surface portion and the base surface of the silicon housing may not be as co-planar or smooth as where a glass housing is used. 
       FIGS. 21-24  show the optical coupler  1600  positioned in the example housings  2100 ,  2300  in isolation. However, the optical coupler  1600  positioned in the housing  2100  or the housing  2300  may be used or implemented together in an optical system, such as the optical system shown in  FIGS. 16-20 . For example, the optical coupler  1600  positioned in the housing  2100  or the housing  2300  may be positioned over and affixed to the top layer  1668 , as previously described. 
     The above description with reference to  FIGS. 3-24  describes an optical coupler that is configured to optically couple an optical fiber with a single fiber optic core with a single waveguide path of an optical IC. Alternative optical systems may include a plurality or an array of optical waveguide paths that may communicate optical signals to a plurality or an array of optical fibers. 
       FIG. 25  shows a cross-sectional view of an example optical system that includes a plurality of waveguide paths  2510 A,  2510 B,  2510 C disposed on a BOX layer  2512  of a substrate  2514 .  FIG. 25  shows three waveguide paths  2510 A-C, although any number of optical waveguide paths may be included. A plurality of optical couplers  2500 A- 2500 C, which may be configured in accordance with the example optical couplers shown in  FIGS. 3-20 , may be used to optically couple the plurality of waveguide paths  2510 A- 2510 C with a plurality of optical fibers (not shown). Each of the optical couplers  2500 A- 2500 C may be disposed over and aligned with one of the optical waveguide paths  2510 A- 2510 C. In addition, as shown in  FIG. 25 , a support structure  2550  may include a plurality of channels  2502 A- 2502 C to receive the plurality of optical fibers and passively align the plurality of optical fibers with the plurality of optical couplers  2500 A- 2500 C. The channels  2502 A- 2502 C, which may be V-grooves as shown in  FIG. 19 , may be formed using planar lithography and etching techniques, as previously described. The V-grooves  2502 A- 2502 C may be separated by a pitch, which may be defined and/or supported by the etching and planar lithography techniques used to form the V-grooves. 
       FIG. 26  shows a cross-sectional view of another example optical system that includes a plurality of optical couplers  2600 A- 2600 C, which may be configured in accordance with the optical couplers shown in  FIGS. 3-20 . The optical system shown in  FIG. 26  is similar to the optical system shown in  FIG. 25 , and further includes a housing  2601  configured to house the plurality of optical couplers  2600 A- 2600 C. The housing  2601  may be configured and/or formed similarly to the example housing  2100  shown in  FIGS. 21-22 , or the example housing  2300  shown in  FIGS. 23-24 . The housing  2601  includes a body  2602  and a plurality of channels  2604 A- 2604 C configured to house the plurality of optical couplers  2600 A- 2600 C. As shown in  FIG. 26 , the housing  2601  may include a single integrated body  2602 . In alternative example configurations, the housing  2601  may include a plurality of separate bodies, each configured with one or more channels to house one or more optical couplers. Various configurations are possible. 
     The optical couplers  2500 A-C,  2600 A-C shown in  FIGS. 25-26  may be used to optically couple a plurality of optical waveguide paths of an optical IC with a plurality of single core optical fibers. In other systems, the optical couplers  2500 A-C,  2600 A-C may be used to optically couple a plurality of optical waveguide paths of an optical IC with a single optical fiber that includes multiple cores (i.e., a multi-core optical fiber). Each of the optical couplers  2500 A-C or  2600 A-C may be configured to optically couple one core of the multi-core optical fiber with one of the optical waveguide paths of the optical IC. To illustrate,  FIG. 26A  shows a top view of the example optical system shown in  FIG. 26 , and further shows a fiber end  2606  of a multi-core optical fiber  2608  positioned in a support structure  2650  and butt coupled to the optical couplers  2600 A- 2600 C (shown as dotted lines). The multi-core optical fiber  2608  is shown as including three cores  2624 A,  2624 B, and  2624 C encased or embedded in a single cladding  2626 . Each of the cores  2624 A- 2624 C may be optically coupled to one of the optical couplers  2600 A- 2600 C. In particular, as shown in  FIG. 26A , the first core  2624 A is optically coupled to the first optical coupler  2600 A, the second core  2624 B is optically coupled to the second optical coupler  2600 B, and the third core  2624 C is optically coupled to the third optical coupler  2600 C. 
     The present description also describes example methods of manufacturing an optical coupler with a housing and optically coupling the optical coupler with an optical waveguide path and an optical fiber.  FIG. 27  shows a flow chart of an example method  2700  of manufacturing an optical coupler with a housing having a uniform depth channel. At block  2702 , a channel with a uniform or substantially uniform depth may be formed in a slab to create the housing. The channel may be formed using various processes, depending on the material used for the housing. Example processes may include cutting or etching. For example, where glass is used, the channel may be formed using a cutting process, in which a saw or other cutting mechanism may be used to cut into the glass slab to form the channel. Alternatively, etching techniques may be used. As another example, where silicon is used as the material for the housing, the channel may be formed through planar lithography and etching techniques. The channel may be formed to have a uniform depth between opposing ends of the formed channel. In some examples, the depth of the channel may be the same or substantially the same as a size or diameter of an optical fiber used to make the optical coupler. 
     At block  2704 , after the channel is formed in the slab, a portion, such as an end, of an optical fiber may be positioned in the channel. Also, at block  2704 , the portion of the optical fiber may be secured in the channel by applying an adhesive material, such as an epoxy, which may affix the portion of the optical fiber positioned in the channel to inner walls of the slab defining the channel. When affixed to the inner walls of the slab, the slab and the optical fiber may form a combined or integrated structure. 
     At block  2706 , one or more removal processes may be performed on the optical fiber positioned in the channel to form the optical coupler positioned in the housing. For example, a first removal process may remove a first portion of the optical fiber and the housing from a second portion of the optical fiber with a first cut that is parallel or substantially parallel to a longitudinal axis of the optical fiber and a second cut that is perpendicular or substantially perpendicular to a longitudinal axis of the optical fiber. The second portion may be used for the optical coupler. After the first removal process is performed, an outer surface that includes a longitudinal exposed surface portion and a second exposed surface portion may be formed. Both exposed portions may include core and cladding portions of the optical fiber. One or more additional removal processes may be performed to remove further additional portions from the second portion formed from the first removal process. The additional removal processes may be performed to form an overall shape or size of the optical coupler and the housing. In particular, the additional removal processes may modify or reduce a length of the longitudinal surface portion and/or modify an orientation of the third exposed surface portion relative to the longitudinal exposed surface portion. 
     Various techniques may be used to perform the removal processes, including polishing, cleaving (e.g., laser cleaving), slicing, grinding, or combinations thereof. For example, a relatively large amount of the slab and the optical fiber may be removed using cleaving techniques, and a remaining relatively small amount of the housing and the optical fiber (e.g., 4-5 μm) may be removed using polishing techniques. Other techniques, currently known or later developed, may be used during the removal processes. Also, where the housing is made of glass or other similar material as the materials of the optical fiber, the various techniques or processes used to remove portions of the optical fiber to form the optical coupler—such as cleaving, slicing, grinding, polishing etc.—may also be used to remove portions of the housing. In this way, any removal processes performed on the optical fiber may simultaneously be performed on the housing, which may yield a substantially uniform or smooth overall surface between the longitudinal surface portion of the optical coupler and a base surface portion of the housing. 
     Additional or further manufacturing processes may be performed to optically couple the optical coupler and housing with a waveguide path of an optical IC. For example, at block  2708 , the optical coupler and the housing may be positioned over and/or affixed to a front end of the optical IC. In particular, the optical coupler may be positioned over and/or aligned with a nanotaper portion of an optical waveguide path at a front end of the optical waveguide path. For some examples, the optical coupler may be axially and/or longitudinally aligned with the nanotaper passively by implementing lithographically defined features on the optical IC. A vision based system may be used to place the optical coupler over the IC front end aligned to the nanotaper relative to these lithographically defined features. 
     Also, at block  2708  the optical coupler and housing may be affixed to the optical IC. To affix the optical coupler to the optical IC, one or more optically transparent adhesive portions may be applied to a top layer of the optical IC. In some examples, the adhesive portion may be a top sub-layer that may be added or applied over a core of the optical waveguide. In addition or alternatively, the adhesive portion may be applied by filling trenches extending longitudinally along sides of the core. The trenches may be formed using various etching techniques, such as KOH or DRIE as examples. After the trenches are formed, the trenches may be filled with the adhesive material. 
     Still further or additional processes may be performed to optically couple the optical coupler with a fiber end of an optical fiber. For example, at block  2710 , a channel may be formed in a substrate or support structure portion of the optical IC. The channel may be formed using various techniques such as planar lithography and etching. The channel may be aligned with an optical waveguide path of the optical IC. Also, at block  2710 , after the channel is formed, the fiber end of the optical fiber may be positioned in the channel. When positioned in the channel, the fiber end may be butt coupled with the third exposed surface portion of the optical coupler. 
       FIG. 28  shows a flow chart of another example method  2800  of manufacturing an optical coupler with a housing made of an etchable material, such as silicon. At block  2802 , a channel may be formed in a slab to create the housing. The channel may be a V-groove trench that is formed using planar lithography and etching techniques. The V-groove trench may be etched to have a height or depth corresponding to a height of the optical coupler to be formed, which may depend on the distance D. The height or depth of the V-groove trench may be varied by increasing the width of a mask layer defining the V-groove trench along its length during the lithography and/or etching processes. 
     At block  2804 , after the channel is formed in the slab and the housing is created, a portion of an optical fiber may be inserted and positioned at a desired position in the V-groove. The optical fiber may be positioned in the V-groove trench such that some core material is in the V-groove at both ends of the housing. Also, at block  2804 , once the optical fiber is positioned in the desired position, an epoxy or other adhesive material may be applied within the V-groove around the optical fiber to affix the optical fiber to the housing. 
     When the optical fiber is in the desired position, only a portion of the optical fiber may be within or inside the V-groove, and a remaining portion may be located outside of the V-groove (and the housing generally). At block  2806 , at least some of the remaining, outside portion may be removed or detached from the portion of the optical fiber in the V-groove. The outside portion may be removed such that after the outside portion is removed, the portion of optical fiber inside the V-groove trench has a flat and/or polished surface that includes both the core and cladding portions of the optical fiber. The flat and/or polished surface may be flush or substantially even with a base surface of the housing. Various techniques may be used to remove the outside portion, including polishing, cleaving (e.g., laser cleaving), slicing, grinding, or combinations thereof. For example, a relatively large amount of the outside portion may be removed using cleaving techniques, and a remaining relative small amount of the outside portion (e.g., 4-5 μm) may be removed using polishing techniques. Other techniques, currently known or later developed, may be used during the removal process. After the removal process is performed at block  2806 , an optical coupler made of an optical fiber structure with a constant height and that has a flat, polished surface exposing the core of the optical fiber may be created. 
     After the flat surface is formed, other portions of the outside portion may still remain. For some configurations, all of the remaining portions may be removed as well using all or some of the removal techniques or processes described above. For other configurations, at least some of the remaining portions may be kept attached to the optical fiber portion in the V-groove. 
     After the flat surface is formed and other portions of the outside portion are optionally removed, further or additional acts may be performed to optically couple the optical coupler positioned in the housing with an optical waveguide path of an optical IC and a fiber end of an optical fiber, as described above. 
     The above-described methods  2700  and  2800  are described for making a single optical coupler disposed in a single channel. Similar processing techniques may be used to make a plurality of optical couplers disposed in a plurality of channels of a housing. 
     Various embodiments described herein can be used alone or in combination with one another. The foregoing detailed description has described only a few of the many possible implementations of the present invention. For this reason, this detailed description is intended by way of illustration, and not by way of limitation.