Abstract:
An apparatus having multiple fiber terminated optical ports uses optical components such as isolators, reflectors, mirrors, and prisms to steer a beam of light to an optical port. The steered beam of light is approximately parallel to the main axis and has a small lateral offset. The optical components may be part of an integrated component or discrete. The apparatus may have multiple input fiber terminated optical ports and multiple output fiber terminated optical ports. The apparatus is especially amenable to planar packaging of optical components.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to the field of fiber optics, and specifically to an apparatus and method for providing multiple fiber terminated optical ports.  
         BACKGROUND  
         [0002]    To meet the demand for increasing bit rates and circuit complexity, data communication systems require high density interconnections with high data throughput and low crosstalk. Meeting this demand often requires implementing parallel systems with more precise coupling and alignment techniques. Thus, automated assembly and circuit packaging play an increasingly more important role in the design process of data communication systems.  
           [0003]    Packaging costs typically dominate the cost of optoelectronic modules in data communication systems. Many factors contribute to packaging costs. These factors include coupling efficiency, insertion loss, gain, noise, environmental requirements, thermal characteristics, power consumption, alignment tolerances, and the form factor such as planar package (flat), and cylindrical package. The form factor impacts component design and the automated assembly strategy.  
           [0004]    Cylindrical packaging requires the optical components to be co-axial. Optical components must be precisely aligned to prevent components being off the main optical axis. Also, the addition of optical components and the types of optical components are limited in cylindrical packaging. Optical components which are very lossy are not appropriate for cylindrical packaging because a signal with adequate signal strength does not pass through to the next component. The use of components such as photodetectors must be carefully considered, because photodetectors typically do not allow an optical signal to pass through. Furthermore, component density is limited in a cylindrical module because each optical component is positioned along a main optical axis.  
           [0005]    Assembly of cylindrical modules often requires that individual components be optically coupled by optical fiber. This typically requires fusion splicing of the optical fiber at various locations in the cylindrical module. Fusion splicing during the assembly process is time consuming and costly, and also contributes to insertion loss. Thus a need exists for a package which overcomes the above disadvantages.  
         SUMMARY OF THE INVENTION  
         [0006]    A compact in-line multifunction apparatus includes multiple fiber terminated optical ports. The apparatus comprises at least one input port for receiving at least one beam of input optical energy. The input port produces at least one beam of received optical energy. The apparatus further comprises at least one optical component which receives the optical energy and produces at least two beams of optical energy. At least one of the two beams is not co-axial with the received optical energy. The apparatus also comprises an output port for receiving at least one of the beams of directed optical energy and for producing at least one beam of output optical energy. None of the beams of output optical energy need be co-axial with the beam of input optical energy.  
           [0007]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The invention is best understood from the following detailed description when read in connection with the accompanying drawing. The various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures:  
         [0009]    [0009]FIG. 1 is plan view of an exemplary embodiment of the invention with multiple fiber terminated optical ports;  
         [0010]    [0010]FIG. 2 is an exemplary embodiment of the invention using a prism to direct optical energy;  
         [0011]    [0011]FIG. 3 is an exploded view of an optical component assembly having multiple fiber terminated optical ports in accordance with an exemplary embodiment of the present invention; and  
         [0012]    [0012]FIG. 4 is a flow diagram describing an exemplary process to produce beams of optical energy in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Referring now to the drawings, wherein like reference numbers refer to like elements throughout, FIG. 1 is plan view of an exemplary embodiment of the invention with multiple fiber terminated optical ports. FIG. 1 illustrates multiple optical fibers  2 ,  4 ,  22 ,  19 , and  15 ; input port  6 ; multiple output ports  8  and  10 ; optical component region  24 ; and optical components  14 ,  16 ,  18 , and  17 .  
         [0014]    In FIG. 1, input optical fibers  2  and  4  receive multiple beams of optical energy. Two input optical fibers are shown for illustrative purposes. The number of input optical fibers may be more or less than two. The source of the multiple beams of optical energy (not shown in FIG. 1) may be any source, for example, lasers, injection laser diodes (ILDs), or light emitting diodes (LEDs). The wavelength of the beams of optical energy may or may not be in the range of visible light. Each of the multiple sources need not be of the same type.  
         [0015]    Output optical fibers  22 ,  19 , and  15  produce beams of output optical energy. It is envisioned that the number of output optical fibers may differ from the number of output optical fibers shown in FIG. 1. The characteristics of each beam of output optical energy may differ. For example, the beams of optical energy within optical fibers  22 ,  19 , and  15  my differ in frequency, phase, wavelength, polarization and/or intensity. The characteristic differences are due, in part, to the types of optical components retained in region  24 . In an exemplary embodiment of the invention, the beams of output optical energy are approximately parallel. Approximately parallel beams of output optical energy facilitate system design by allowing efficient placement of adjacent packages.  
         [0016]    Input port  6  couples the input optical fibers  2  and  4  to optical component region  24 . Output port  8  couples output optical fibers  22  and  19  to optical component region  24 , and output port  10  couples output optical fiber  15  to optical component region  24 . Input port  6  and output ports  8  and  10 , may be any coupling device, or combination of coupling devices. In an exemplary embodiment of the invention, the input and output ports comprise collimated lens assemblies. Each collimated lens assembly may comprise combinations of several components, such as lenses, filters, ferrules, and wavelength division multiplexers (WDMs).  
         [0017]    Region  24  may have positioned therein any combination of optical components. Examples of optical components which may be retained in region  24  include lenses, reflectors, isolators, taps, and WDMs. In an exemplary embodiment of the invention, element  14  is an isolator, elements  18  and  17  are reflectors, and element  16  is a tap. Elements  16 ,  18  and  17  perform the functions of filtering and routing optical energy. These functions may also be accomplished with a prism.  
         [0018]    [0018]FIG. 2 is an exemplary embodiment of the invention using a prism to direct optical energy. In FIG. 2, prism  29  filters and directs optical energy to optical fibers  22 ,  19 , and  15 . In an exemplary embodiment of the invention, prism  29  comprises an anti-reflective coating on a portion of its outer surfaces,  30  and  32 , and a reflective coating, such as a mirror, on a portion of its inner surface  33 . Surface area  35  comprises a tap coating, which allows a portion of optical energy to be reflected and also allows a portion of optical energy to pass through the surface. Optical energy transmitted through isolator  14  enters prism  29  through surface  30 . This optical energy is coupled to surface area  35  which passes a portion of the optical energy to optical fibers  22  and  19 , and reflects a portion of the optical energy to surface  33 . Surface area  33  reflects optical energy toward optical fiber  15 . This optical energy is coupled to optical fiber  15  through surface area  32 .  
         [0019]    [0019]FIG. 3 is an exploded view of an optical component assembly having multiple fiber terminated optical ports in accordance with an exemplary embodiment of the present invention. Optical fibers  36  and  38  are attached to collimated lens assembly  50 . Collimated lens assemblies are used to optically couple energy between optical fibers and optical components. As shown in FIG. 3, collimated lens assemblies  50 ,  51 , and  53  optically couple energy between optical fibers and components  54  and  56  positioned in region  24 , through windows  26  and  28 .  
         [0020]    Collimated lens assemblies may comprise combinations of several components, such as lenses, filters, ferrules, and wavelength division multiplexers (WDMs). Exemplary collimated lens assembly  50  comprises a ferrule  44 , a lens  46 , and an optical filter  34 . Ferrule  44  is a cylindrical device having apertures sized to fit optical fibers  36  and  38 . Optical fibers  36  and  38  are mounted in ferrule  44 . Ferrule  44  centers and aligns optical fibers  36  and  38 . Optical fibers  36  and  38  are terminated within ferrule  44 . Typically, cylindrical ferrules are limited to housing no more than two optical fibers because of the strict tolerances associated with transferring optical energy between a pair of optical fibers. Lens  46  focuses optical energy.  
         [0021]    Lens  46  may comprise any suitable lens, such as a gradient radial index (hereinafter GRIN) lens, a molded aspheric lens, or a ground spherical lens. In the exemplary embodiment shown in FIG. 3, lens  46  is a GRIN lens. Note that collimated lens assemblies  50  and  51  each comprise filter  34  attached to the lens of the collimated lens assembly. Filter  34  is optional. Note that collimated lens assembly  53  does not comprise a filter. Depending upon system requirements, other optical components (e.g., WDM) may be positioned between the lens of the collimated lens assembly and the window.  
         [0022]    Collimated lens assembly  50  is attached to window  26  and collimated lens assemblies  51  and  53  are attached to window  28 . The attachment of collimated lens assembly  50  with window  26  and collimated lens assemblies  51  and  53  with window  28 , may be by any appropriate means, such as through the use of an adhesive (e.g., optical quality heat cured epoxy MH77A). Adhesively attaching the collimated lens assemblies to the windows does not require sustained localized heating, in contrast to soldering and laser welding. Therefore components are not as susceptible to heat damage. Also, because adhesively attaching the collimated lens assemblies to the window does not require access by a laser welder, more collimated lens assemblies can be adhered to the window. Furthermore, windows  26  and  28  may be adjusted in size to accommodate any number of collimated lens assemblies and therefore, more optical fibers. Additionally, the curing process associated with adhesively attaching the collimated lens assemblies to the windows does not misalign the components to the same degree as does post weld shift. Thus the alignment procedure associated with adhesively attaching collimated lens assemblies to the windows is less time consuming and more easily accomplished than the alignment process associated with laser welding.  
         [0023]    Optical fibers  36  and  38  are axially positioned within bend limiter tubing  40 . Bend limiter tubing  40  is a hollow, generally cylindrical sleeve through which optical fibers  36  and  38  are positioned to limit the bending of the optical fibers. In an exemplary embodiment of the invention, optical fibers  36  and  38  are attached to the inner surface of bend limiter tubing  40  with a filler material. The filler material may comprise, for example, a commercially available pliable adhesive (e.g., silicone). Attaching optical fibers  36  and  38  to the inner surface of bend limiter tubing  40  facilitates the automated assembly process by reducing the motion of optical fibers  36  and  38 . The filler material reduces axial motion of optical fibers  36  and  38  in the directions indicated by arrow  48 . Axial motion may be caused by mechanical strain applied to optical fibers  36  and  38  during the assembly process. Axial motion may also be caused by expansion and contraction of optical fibers  36  and  38 , and/or other components, due to thermal variation. Excessive axial motion may cause optical fibers  36  and  38  to bend and ultimately sustain damage. The filler material also reduces radial motion of optical fibers  36  and  38 , thus reducing the possibility of any damage due to radial motion.  
         [0024]    Support member  42  provides support for bend limiter tubing  40  and optical fibers  36  and  38 . In an exemplary embodiment of the invention, optical fibers  36  and  38  are rigidly attached to collimated lens assembly  50 . This rigid attachment also contributes to the bending of optical fibers  36  and  38  when subjected to axial motion. The support provided by support member  42  reduces bending of optical fibers  36  and  38 , and reduces the possibility of optical fibers  36  and  38  becoming detached from collimated lens assembly  50 . In an exemplary embodiment of the invention, bend limiter tubing  40  is attached to support member  42 . Attachment of bend limiter tubing  40  to support member  42  may be achieved through the use of, for example, an adhesive such as epoxy. Attachment of bend limiter tubing  40  to support member  42  facilitates the automated assembly process by reducing movement of bend limiter tubing  40 , which in turn reduces movement of optical fibers  36  and  38 .  
         [0025]    Region  24  may retain any combination of optical components. Optical components  54  and  56  represent exemplary optical components which may be retained in region  24 , examples of which include lenses, reflectors, isolators, taps, and WDMs. In the exemplary embodiment of the invention shown in FIG. 3, optical component  54  is an isolator and optical component  56  is a prism. In this embodiment, isolator  54  ensures that optical energy is directed toward optical component  56  with minimal reflection of optical energy back toward collimated lens assembly  50 . Optical energy which has interacted with isolator  54  is directed toward prism  56 . Prism  56 , apportions and routes the optical energy received from isolator  54  to collimated lens assemblies  51  and  53 .  
         [0026]    In an exemplary embodiment of the invention, prism  29  comprises an anti-reflective coating on a portion of its outer surfaces,  30  and  32 , and a reflective coating, such as a mirror, on a portion of its inner surface  33 . Surface area  35  comprises a tap coating, which allows a portion of optical energy to be reflected and also allows a portion of optical energy to pass through the surface. Optical energy transmitted through isolator  14  enters prism  29  through surface  30 . This optical energy is coupled to surface area  35  which passes a portion of the optical energy to optical fibers  22  and  19 , and reflects a portion of the optical energy to surface  33 . Surface area  33  reflects optical energy toward optical fiber  15 . This optical energy is coupled to optical fiber  15  through surface area  32 .  
         [0027]    Isolator  54  and prism  56  form a free air space optical network. Optical energy is coupled between window  26  and isolator  54 , between isolator  54  and prism  56 , and between prism  56  and window  28 , through air. A free air space optical network may not be appropriate in an environment with high ambient optical energy. In high ambient optical energy environments, it is advantageous to provide a cover, such as upper portion  52  over region  24 . Upper portion  52  also protects optical components within region  24  from damage (e.g., dust, collision, contamination) during storage, shipping, and use. Hole  70 , in upper portion  52  may remain open or be filled with material. An example of a filler material for hole  70  is a membrane comprising a wicking agent to withdraw moisture from region  24 .  
         [0028]    Upper portion  52  is positioned opposite base structure  20  and support members  42 . Upper portion  52  is attached to base structure  20  and/or support member  42 . Attachment of upper portion  52  to base structure  20  and/or support member  42  may be accomplished by any means known in the art (e.g., adhesives, press fit, or snaps). Bend limiting tubing  40  is positioned between support member  42  and upper portion  52 . Positioning bend limiting tubing  40  between support member  42  and upper portion  52  facilitates the automated assembly process by limiting movement of bend limiting tubing  40  and optical fibers  36  and  38 .  
         [0029]    Bend limiter tubing  40  is positioned around each group of optical fibers coupled to the optical component housing. Placing bend limiter tubing around all optical fibers facilitates the automated assembly process by reducing fiber motion. Support members  42  provide support for all bend limiter tubes  40 . Supporting all bend limiter tubes  40  with support member  42  facilitates the automated assembly process by reducing motion of the optical fibers and bend limiter tubing. In various embodiments of the invention, bend limiting tubing  40  is attached to support member  42  and/or upper portion  52 . Attachment of bend limiter tubing  40  to support member  42  and/or upper portion  52  may be achieved through the use of, for example, an adhesive such as epoxy, or a press fit. Attachment of bend limiter tubing  40  to support member  42  and/or upper portion  52  facilitates the automated assembly process by reducing movement of bend limiter tubing  40 , which in turn reduces movement of optical fibers  36  and  38 .  
         [0030]    It is emphasized that the embodiment of the invention shown in FIG. 3 is exemplary. FIG. 3 shows two optical fibers,  36  and  38 . FIG. 3 shows support member  42  as an integral part of base structure  20 . It is envisioned that base structure  20  and support member  42  may be separate, but rigidly attached by any appropriate means such as adhesively, snap fit, press fit, or bolted.  
         [0031]    [0031]FIG. 4 is a flow diagram describing an exemplary process to produce beams of optical energy in accordance with the present invention. The steps in FIG. 4 are described with reference to the elements in FIG. 3. In step  62 , input optical energy is provided to the input port via optical fibers  36  and  38 . The input optical energy is collimated and focused by collimated lens assembly  50  and lens  34  to produce received optical energy. The received optical energy, as described in step  64 , is directed toward optical component  54 , as described in step  66 . Isolator  54  ensures that the optical energy is directed toward optical component  56  with minimal reflection of optical energy back toward the input port. Optical energy which has interacted with optical component  54  is directed toward optical component  56 . In accordance with steps  66  and  68 , optical component  56  directs portions of the optical energy toward collimated lens assemblies  51  and  53 . The beams of output optical energy, within optical fibers  58 ,  60 , and  61 , are offset from each other and are approximately parallel with the beams of input optical energy, as described in step  72 . Further, none of the beams of output optical energy are required to be co-axial with the beam of input optical energy, which is in contrast to cylindrical optical packages.  
         [0032]    Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.