Abstract:
A collimated-beam photonics package wherein the plurality of optical fibers and imaging devices are held in a parallel spaced array in a first holder and a plurality of surface-normal optic devices are held in a corresponding spaced array in a second holder. The first and second holders have complementary exterior features so that the first and second holders are securable to each other with the respective arrays being registered one with the other.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to packaging for collimated-beam optical devices and, more particularly, to an improved package for a plurality of such devices wherein ease of alignment is effected. 
     Many opto-electronic and opto-mechanical devices are packaged with the active element in the collimated-beam plane (i.e., Fourier-plane). This means that light from an input fiber, typically single mode, is collimated by a lens and illuminates a device at a small angle with respect to the surface normal of the device. The device acts upon the light, for example, by attenuating, filtering, tilting, etc. Then the reflected output signal is directed through a lens and focused into a separate output fiber, also typically single mode. It is known to package the input/output fiber pair, lens and device in a single cylindrically shaped package. However, each such package only holds a single device and its associated fibers. Where multiple devices and input/output fibers are utilized, multiple alignments are then required. It would be desirable to provide a package holding multiple devices and input/output fibers which greatly reduces the number of required alignments. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a collimated-beam photonics package comprising a plurality of optical fibers and a plurality of imaging devices. A first holder is arranged to hold end segments of the plurality of optical fibers in a parallel spaced array and to hold the plurality of imaging devices with one or more optical fibers in alignment with each of the plurality of imaging devices. A plurality of surface-normal optic devices are also provided, along with a second holder arranged to hold the plurality of optic devices in a spaced array corresponding to the parallel spaced array of the plurality of optical fibers. The first and second holders can be formed with complementary exterior features so that the first and second holders are securable one to the other with each imaging device in optical communication with a respective optic device. 
     In accordance with an aspect of this invention, the first holder holds the optical fiber end segments in a linear array. 
     In accordance with another aspect of this invention, the first holder comprises at least one silicon V-groove array. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing will be more readily apparent upon reading the following description in conjunction with the drawings in which like elements in different figures thereof are identified by the same reference numeral and wherein: 
     FIG. 1 is a cross sectional view of a prior art cylindrical collimated-beam package for a single optic device; 
     FIG. 2 is an exploded perspective view of a prior art silicon V-groove holder for multiple fibers and lenses; 
     FIG. 3 is a simplified cross sectional view schematically illustrating a first embodiment of a package according to the present invention; 
     FIG. 4 is a simplified cross sectional view schematically illustrating a second embodiment of a package according to the present invention; 
     FIG. 5 is a simplified perspective view schematically illustrating an embodiment of first and second holders according to the present invention, showing the complementary exterior features; 
     FIGS. 6A and 6B are simplified side and plan views, respectively, of a membrane tilt-mirror switch which may be used as an optic device in the package according to the present invention; and 
     FIG. 7 is a simplified side view showing a membrane tilt-mirror switch used as a 1×2 switch. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, a prior art cylindrical collimated-beam single optic device includes a ceramic ferrule  10  holding an input fiber  12  and an output fiber  14 . An imaging device, illustratively a gradient index (GRIN) lens  16  is held within another ceramic ferrule  18 . A surface-normal optic device  20 , coupled to electrical wires  22 ,  24 , is mounted to a cylindrical ceramic substrate  26 . A ceramic sleeve  28  holds the ferrules  10 ,  18 . After the fibers  12 ,  14 , the lens  16  and the device  20  have been actively aligned, the two parts are permanently joined by laser welding. 
     FIG. 2 illustrates the use of silicon V-groove substrates for holding a plurality of optical fibers in alignment with respective imaging devices. Such a package is manufactured by ACT MicroDevices, Inc., of Radford, Va., and includes a pair of opposed V-groove chips  30 ,  32  for holding therebetween optical fibers  34  and lenses  36 . Although FIG. 2 only illustrates a single optical fiber  34  associated with the lens  36 , where multiple fibers are associated with each lens the V-grooves would be configured to have a large groove at one end for accommodating the lens and a plurality of smaller parallel grooves “behind” the large groove for accommodating the plurality of fibers. 
     The applicant has realized that by utilizing a holder of the type shown in FIG. 2, the number of alignments required for multiple collimated-beam photonics packages is reduced. The advantage of using silicon V-groove alignment for multiple devices is that instead of a single device, a linear array of devices can be used. If the mechanical tolerances are sufficiently tight, then it is only necessary to perform active alignment using one or two devices (e.g., the first and last elements in the array) to obtain alignment of all devices. 
     FIG. 3 illustrates this concept. A silicon V-groove chip  38  is shown holding four gradient index lenses  40 ,  42 ,  44  and  46 , each associated with a respective pair of fibers  40 - 1 ,  40 - 2 ;  42 - 1 ,  42 - 2 ;  44 - 1 ,  44 - 2 ; and  46 - 1 ,  46 - 2 . Associated with each of the lenses  40 ,  42 ,  44 ,  46 , is a respective optic device  48 ,  50 ,  52 ,  54 , each mounted to a silicon chip  56  which is oriented at right angles to the silicon V-groove arrays used to hold the fibers and lenses. An important advantage of this packaging arrangement is that planar microlenses can be held, polished and coated in a linear array. In addition to making it possible to do this on multiple lenses at once, it allows the lenses to be held with a greater accuracy than a single lens could be held, therefore improving fabrication tolerances. Further, by insuring that the lenses  40  and  46  are in respective alignment with the devices  48 ,  54 , this insures that the intermediate lenses and devices are also in alignment. FIG. 3 is illustrative of the use of reflective devices  48 ,  50 ,  52 ,  54 . If, instead, transmissive devices are utilized, a packaging arrangement as shown in FIG. 4 would be used. Finally, if the devices are designed to stand at right angles to their substrate, the device substrate can be parallel to (or the same piece as) the V-groove array. 
     FIG. 5 illustrates complementary exterior features on the holders for the fibers and the optic devices which maintains the holders in rough alignment until an active alignment can be effected. Thus, the holder for the fibers  58  and lenses (not shown in FIG. 5) includes a silicon V-groove holder  60 , of the type shown in FIG. 2, and provided with strain relief  62  for the fibers  58 . For illustrative purposes, there are four sets of fibers and lenses. Accordingly, there are four optic devices  64  mounted to a silicon substrate  66 . Electrical contact pads  68  are provided on the substrate  66  for electrical connection to the devices  64 . (It is noted that the illustrated number of electrical connections is not intended to be limiting.) The holder  60  is of rectilinear configuration with a planar mating face. The substrate  66  is formed with a plurality of pedestals  70 , all of the same height, which height is greater than the height of the optic devices  64 . Also part of the substrate  66  is an L-shaped block  72 . The block  72  has a greater height than the pedestals  70 . Since the holder  60  is rectilinear, the surfaces  74 ,  76  of the block  72  are configured complemental to lateral surfaces of the holder  60 . Thus, the holder  60  can be placed up against the surfaces  74 ,  76  with its planar front mating face abutting the pedestals  70  so that the lenses are in a predetermined alignment with respective ones of the optic devices  64 . Final active alignment can then be made and the holder  60  secured to the substrate  66 . 
     FIGS. 6A and 6B show an illustrative optic device that may be utilized for each of the optic devices  64  (FIG.  5 ). The illustrated optic device is known as a membrane tilt-mirror switch. Such a device is disclosed, for example, in U.S. patent application Ser. No. 09/271,577, filed Mar. 28, 1999, now U.S. Pat. No. 6,178,033 and assigned to the assignee of the present invention. The device  64  includes a substrate  78  which is grounded and is formed with a cavity  80 . A flexible membrane  82  extends across the cavity  80  and has deposited thereon three areas of gold  84 ,  86 ,  88 . The outer areas  84 ,  86  are used as electrodes and the central area  86  is used as a mirror. Depending upon the voltages applied to the electrodes  84 ,  88 , the central mirror  86  is caused to tilt either one way or the other. When used with an input optical fiber and one output optical fiber as an add/drop switch, a voltage is selectively applied to only the electrode  84 . FIG. 7 schematically depicts the use of such an optic device as a 1×2 switch where there is one input optical fiber  90  and two output optical fibers  92 ,  94 . In this case, voltages are selectively applied to either of the electrodes  84 ,  88  to tilt the mirror  86  either one way or the other so that the beam from the input fiber  90  is directed to a selected one of the output fibers  92 ,  94 . 
     Accordingly, there has been disclosed an improved collimated-beam photonics package which minimizes the required active alignment. While illustrative embodiments of the present invention have been disclosed herein, it will be appreciated by those skilled in the art that various adaptations and modifications to the disclosed embodiments are possible and it is intended that this invention be limited only by the scope of the appended claims.