Abstract:
A package for an optical device comprising two mating sections, each section including a rigid outer protective shell and a resilient inner body. The package is easily clamped together using snap clips, which are integral with the rigid outer protective shells. Preferably, strain relief is provided integrated on each end of the resilient bodies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority from previously filed U.S. patent application Ser. No. 60/224,024 filed Aug. 10, 2000. 
    
    
     TECHNICAL FIELD 
     The present application relates to optical device packages, and in particular to a package for enclosing a wavelength division multiplexing (WDM) coupler. 
     BACKGROUND OF THE INVENTION 
     Optical devices, such as WDM couplers, require special packaging for protecting the devices from mechanical, as well as thermal, stresses. Much of the difficulty in designing a suitable package arises from the fact that the optical devices are comprised of several elements with different diameters that have been fixed, e.g. glued, together. Moreover, no two devices are identical, because during assembly the elements are individually adjusted to obtain the highest possible optical coupling. 
     Conventional packages for optical devices include a rigid outer housing surrounding a rigid insert, into which the optical device is mounted and fixed. To avoid thermally induced stress, the insert is made up of a material that has thermal-expansion characteristics that are similar to those of the optical device. After the optical device is fixed to the insert, the rigid outer housing is glued or otherwise sealed together over the insert. Alternatively, if the outer housing is a rigid cylindrical sleeve, it is slipped over the optical device with the insert, and then sealed at each end. If strain relief is required, it is usually provided by mounting resilient tubes over the fibers prior to assembly, and fixing them in position during assembly. All of the aforementioned packages require several labor intensive assembly steps, while providing only limited protection. Moreover, if strain relief is required, the tubes must by positioned on the fiber before the optical device is assembled, adding to the complexity of the assembly process. 
     An object of the present invention is to provide an optical device package that overcomes the shortcomings of the prior art, and provides increased protection to the enclosed optical device. Another object of the present invention is to provide an optical device package that can be assembled quickly and easily without the need for labor intensive steps. Another object of the present invention is to provide a package with integrated strain relief. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention relates to a package for an optical device of the type comprising a plurality of elements including a first element that is not coaxial with a second element, the package comprising: 
     base means having a first resilient inner section, and a first protective outer section, said first resilient inner section having a first raised portion for engaging the first element of the optical device; 
     cover means having a second resilient inner section, and a second protective outer section, said second resilient inner section having a second raised portion for engaging the first element; and 
     clamping means for securing the base means to the cover means, whereby the first element is held between the first and second raised portions. 
     Another aspect of the present invention relates to a package for a device of the type comprising wires or fibers extending therefrom, the package comprising: 
     base means having a first resilient section at one end thereof including a first strain relief means; 
     cover means having a second resilient inner section at one end thereof including a second strain relief means; and 
     clamping means for securing the base means to the cover means, whereby the first and second strain relief means form an annular strain relief member with a bore that gradually increases in diameter from an inner end proximate the device to an outer end remote from the device; 
     wherein the first strain relief means includes first mating surfaces, each extending from an inner edge at the bore to an outer edge at an outer surface thereof; wherein the second strain relief means includes second mating surfaces, complementary with the first mating surfaces, extending from an inner edge at the bore to an outer edge at an outer surface thereof; and wherein the inner edges of the first and second mating surfaces define a line, at least a portion of which is arcuate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein: 
     FIG. 1 is a perspective view of a first embodiment of the optical device package according to the present invention; 
     FIG. 2 is an exploded view of the optical device package of FIG. 1; 
     FIG. 3 is a side view of a base of the optical device package of FIGS. 1 and 2; 
     FIG. 4 is a plan view of the base of FIG. 3; 
     FIG. 5 is an end view of the base of FIGS. 3 and 4; 
     FIG. 6 is a plan view of a cover of the optical device package of FIGS. 1 and 2; 
     FIG. 7 is a side view of the cover of FIG. 6; 
     FIG. 8 is an end view of the cover of FIGS. 6 and 7; 
     FIG. 9 is an exploded end view from one end of the optical device package of FIGS. 1 and 2; 
     FIG. 10 is an end view from the other end of the optical device package of FIGS. 1 and 2; 
     FIG. 11 is a perspective view of a second embodiment of the optical device package according to the present invention; 
     FIG. 12 is an exploded view of the optical device package of FIG. 11; 
     FIG. 13 is a side view of a base of the optical device package of FIGS. 11 and 12; 
     FIG. 14 is a plan view of the base of FIG. 13; 
     FIG. 15 is an end view of the base of FIGS. 13 and 14; 
     FIG. 16 is a side view of a cover of the optical device package of FIGS. 11 and 12; 
     FIG. 17 is a plan view of the cover of FIG. 16; 
     FIG. 18 is an end view of the cover of FIGS. 16 and 17; 
     FIG. 19 is a plan view of a reinforcing sleeve of the optical device package of FIGS. 11 and 12; 
     FIG. 20 is a side view of the reinforcing sleeve of FIG. 19; and 
     FIG. 21 is an end view of the reinforcing sleeve of FIGS.  19  and  20 . 
    
    
     DETAILED DESCRIPTION 
     The first embodiment of the optical device package according to the present invention, which is illustrated in FIG. 1 to  10 , includes a base member  1  and a cover member  2  for encasing an optical device  3 . The optical device package may also include a reinforcing sleeve  4  for extra protection. The optical device package can be adapted to enclose any optical device, but is particularly useful with optical devices that include several elements with different diameters that have been fixed together non-concentrically. The optical device illustrated in FIG. 1 is a wavelength division multiplexing (WDM) coupler, which includes a single bore ferrule  5  encasing one end of an optical fiber  6 , a first graded index (GRIN) lens  7 , a WDM filter  8 , a second GRIN lens  9 , and a double bore ferrule  11  encasing one end of each fiber  12  and  13 . What is evident from the drawing is that the GRIN lenses  7  and  9  have smaller diameters than the ferrule tubes  5  and  11 ; however, what is less evident is that many of the elements do not share the same longitudinal axis. During the optical alignment process it is necessary to slightly misalign some of the elements to maximize optical coupling between the fibers  6 ,  12  and  13 . 
     With reference to FIGS. 3,  4  and  5 , the base member  1  includes a hard protective outer shell  16  and a resilient inner body  17 . With reference to FIGS. 6,  7  and  8 , the cover member  2  includes a hard protective outer shell  18  and a resilient inner body  19 . The outer shells  16  and  18  protect the optical device  3  from stresses originating externally, while the inner bodies  17  and  19  provide a cushion for the optical device  3  in the event the outer shells  16  and  18  are not sufficiently strong to mitigate all of the external stress. The outer shells  16  and  18  and the resilient inner bodies  17  and  19  can be manufactured separately out of different types of plastic, or any other suitable material, and assembled manually. However, for the preferred embodiment, the base member  1  and the cover member  2  are manufactured using a multi-shot or insert injection molding technique, which results in the hard plastic shells  16  and  18  substantially covering the resilient bodies  17  and  19 , respectively. Holes  21  (see FIGS. 2,  3  and  7 ), which extend through the outer shells  16  and  18 , receive projections  22  extending contiguously from the inner bodies  17  and  19 . The holes  21  and the projections  22  eliminate the need for a separate adhesive between the outer shells  16  and  18  and the inner bodies  17  and  19 , respectively, although one can be applied for extra strength. 
     The majority of the inner bodies  17  and  19  are custom sized to loosely receive the optical device  3 , i.e. big enough to allow free movement of the majority of the optical device  3 , but small enough to provide the optical device  3  with a sufficient cushion in the event the device undergoes stress. However, one or more sets of raised portions, such as U-shaped raised portions  23  and  24 , are provided to frictionally engage at least one of the elements of the optical device  3 . In the illustrated embodiment the raised portions  23  and  24  are adapted to clamp the second lens  9  therein. The entire optical device  3  can not be similarly engaged because all of the elements of the optical device are not aligned nor are any two optical devices assembled identically. When two or more different elements of the optical device are consistently positioned relative to each other, two or more sets of raised portions can be provided, which engage the different elements, See FIGS. 11-21. Preferably, the base member  1  defines over half of the entire package, and ideally approximately two thirds thereof. Accordingly, the raised portion  23  in the base member  1  is able to securely clamp the corresponding optical element to stabilize the optical device  3  during assembly. 
     If the optical device  3  becomes disengaged from the raised portions  23  and  24  due to a pulling force on one of the fibers, shoulders  26  and  27  are provided at each end of the inner bodies  17  and  19 , respectively, to abut the ends of the optical device  3 . The shoulders  26  and  27  provide a resilient annular stop for the optical device  3 , thereby preventing the optical device  3  from leaving the package, while absorbing a certain amount of the pulling force. 
     Each end of the inner bodies  17  and  19  also includes a gradually narrowing neck portion formed by mating neck portions  28  and  29  on the inner bodies  17  and  19 , respectively. The mating neck portions  28  and  29  are adapted to receive the optical fibers  6 ,  12  and  13 , and align them proximate the longitudinal axis of the device. In the preferred embodiment, in which the base member  1  forms a greater percentage of the overall circumference of the package than the cover member  2 , the neck portion  28  forms a channel for receiving the optical fibers, while the neck portion  29  includes an elongated projection for closing the open end of the channel. Accordingly, the neck portion  28  protects the fibers during assembly by preventing them from being trapped out of position between the base  2  and cover  1 . The neck portions  28  and  29  are sized to receive the required number of fibers, e.g. 1 or 2, in any possible alignment, e.g. adjacent or superposed. 
     Integrated strain relief elements  31  and  32  are provided at each end of the inner bodies  17  and  19 , respectively, to protect the portion of the fibers exiting the package from damage caused by bending. The strain relief elements  31  and  32  form an annular strain relief member with a central bore  33 , which gradually increases in size from its inner end proximate the optical device  3  to the outer free end thereof. The term central bore is not meant to be limited to a bore in the geometric center of the strain relief member, but rather anywhere inside the periphery thereof. In fact, improved strain relief may be obtained from a bore not positioned in the geometric center of the strain relief member The mating surfaces  36  and  37  of the strain relief elements  31  and  32 , respectively, are specially designed to include a difficult path for the optical fibers, which prevents the optical fibers from slipping between the strain relief elements  31  and  32  into contact with the outer shells  17  and  19 . There are two aspects that combine to create the difficult path: the first aspect is the shape of the mating surfaces  36  and  37  at the inner wall  38 , and the second aspect is the direction in which the mating surfaces  36  and  37  extend from the inner wall  38 . At the inner wall  38 , the mating surfaces  36  and  37  define an arcuate or a circuitous path, thereby making it extremely difficult for a fiber extending outwardly from one end of the package to work its way therebetween. Moreover, the mating surfaces  36  and  37  do not extend radially through the wall of the strain relief member, rather at an angle therethrough, making it even more difficult for a fiber to work its way out, because any bending force on the fiber will be transferred radially to the inner wall  38 . 
     A plurality of C-shaped hook arms  41 , extending from the outer shell  18 , are provided as part of a plurality of snap clips for fastening the cover member  2  to the base member  1 . The arms  41  are received in corresponding recesses  42  in the outer shell  16 . Each arm  41  includes a detent  43  with a cam surface  44  (See FIGS.  8  and  9 ). Each snap clip also includes a corresponding cam surface  46  on a detent  47  (See FIGS. 2,  3  and  4 ), which extends into each recess  42 . During assembly, the corresponding cam surfaces  44  and  46  enable the detents  43  to pass over the detents  47 , and lock into place therebehind. The snap clips lock the cover member  2  to the base member  1 , while squeezing the inner resilient bodies together along their mating longitudinal seams forming a seal. 
     The reinforcing sleeve  4  is provided when extra protection is required. Detents  51  are punched from the walls of the reinforcing sleeve  4  for frictionally engaging one of the outer shells  16  or  18 . 
     With reference to FIGS. 11 to  21 , a second embodiment of the present invention includes a base member  61  and a cover member  62 . The cover member  62  comprises a resilient inner body  63 , and a hard outer shell  64 , which are assembled separately. Preferably, the inner body  63  is a resilent plastic, while the outer shell  64  is metal. Projections  66 , extending from the inner body  63 , are received in holes  67 , extending through the outer shell  64 , for preventing relative movement between the inner body  63  and the outer shell  64 . The base member  61  comprises a resilient inner body  65  and a hard outer shell  70 . Preferably, the base member  61  is manufactured using the multi-shot or insert molding techniques mentioned above. 
     In this embodiment the package protects an optical member  68 , which includes a first lens (not shown) mounted in a first sleeve  69 , and a second lens (not shown) mounted along with a WDM filter (not shown) in a second sleeve  71 . A single fiber tube  72  is mounted in a third sleeve  73 , which is attached to one end of the first sleeve  69 . The single fiber tube encases one end of an optical fiber  74 . A double bore tube  76  is mounted in a fourth sleeve  77 , which is attached to one end of the second sleeve  71 . The double bore tube  76  encases one end of optical fibers  78  and  79 . 
     In optical element  68 , the relative positions of the third and fourth sleeves  73  and  77  are substantially fixed, whereby two sets of raised portions  81  and  82  (See FIG. 14) are provided on the inner body  65  to hold the third and fourth sleeves  73  and  77 , respectively, while the remaining elements remain floating. Each set of raised portions  81  and  82  comprises two longitudinally extending raised portions. With reference to FIG. 17, the inner body  63  of the cover member  62  includes laterally extending raised portions  83  and  84 , which co-operate with the sets of raised portions  81  and  82 , respectively, to hold the optical element  68  therebetween. 
     As in the aforementioned embodiment, shoulders  86  formed in the inner body  65  co-operates with shoulders  87  formed in the inner body  63  to prevent the optical device  68  from being pulled from the package. Similarly, neck portions  88  in the inner body  65  co-operates with neck portions  89  in the inner body  63  to guide and protect the fibers  74 ,  78  and  79  during assembly. 
     Integrated strain relief portions  91  of the inner body  65  engage integrated strain relief portions  92  of the inner body  63 . The strain relief portions  91  and  92  are identical to the above identified strain relief portions  31  and  32 , respectively. 
     Snap clips for holding the package together are comprised of U-shaped hook arms  93  extend downwardly from the outer shell  64  for engaging detents  94 , which extend outwardly from the outer shell  70 . The detents  94  are provided with a cam surface, which enables the arms  93  to pass over the detents  94  and lock therebehind. Locking fingers  96  extend downwardly from the outer shell  64  into the space defined by the arms  93  for engaging the top of the detents  94 , thereby preventing any relative movement between the outer shells  64  and  70 .