WO2001031377A1

WO2001031377A1 - System and methods for packaging and routing optical fiber

Info

Publication number: WO2001031377A1
Application number: PCT/US2000/026493
Authority: WO
Inventors: Adam Richter; Reginald A. Saunders
Original assignee: Corning Incorporated
Priority date: 1999-10-27
Filing date: 2000-09-26
Publication date: 2001-05-03

Abstract

A system for routing and packaging optical fiber leads includes a platform (16) having a base (18), from which projects upward a set of convex guides (21-30), the outer surfaces of the convex guides (21-30) defining a tension loop for routing an optical fiber lead extending from a first optical component mounted proximate to a convex guide, the first optical component lead being held in position against the convex guides (21-30) in the convex loop. A set of concave guides (31-34) also projects upward from the base, the inner surfaces of the concave guides (31-34) defining a passive loop for routing an optical fiber lead from a second optical component mounted proximate to the concave guides (31-34), the second optical component lead tending to expand outward towards the inner surfaces of the concave guides (31-34). The tension loop and the passive loop are positioned relative to each other.

Description

SYSTEM AND METHODS FOR PACKAGING AND ROUTING OPTICAL FIBER

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to improvements in optical signal processing devices, and particularly to advantageous aspects of a system and methods for packaging and routing optical fiber within an optical signal processing device.

Description of the Prior Art

Devices for performing signal processing on an optical signal, such as optical amplifiers and filters, typically include a number of discrete optical components that are mounted into fixtures on a platform and are interconnected by optical fiber leads that are spliced together. The splicing together of these optical leads often results in long loops of optical fiber that must be routed and packaged within the device in a manner that prevents damage to the fiber and minimizes macrobend loss. Macrobend loss is attenuation or loss of light that occurs when light radiates away from the optical fiber due to a too small radius of curvature. In one method, loops of optical fiber within an optical device are routed and packaged by means of a number of curved guides that are mounted to the device platform in a predetermined configuration in relation to the fixtures used to mount the optical components into the device. Optical fiber is wound tangentially around the exterior surfaces of these curved guides, which have a sufficiently large radius to prevent macrobend loss, for example, approximately 16mm for 100 kpsi fiber. The fiber is held in place around the curved guides by tension in the fiber.

Although the currently used method has proved satisfactory for many optical devices, new optical devices are being developed that have created the need to develop more compact packaging methods. Some of these new devices contain optical components that are significantly larger than traditional optical components, having three or potentially more ports on each side. Further, these ports may not be symmetrically located. In order to achieve as compact a device as possible, there is a need for an improved fiber routing and packaging systems that can accommodate these new, oversized components.

SUMMARY OF THE INVENTION One aspect of the invention provides a system for routing and packaging optical fiber leads. The system includes a platform having a base, from which projects upward a set of convex guides, the curved outer surfaces of the convex guides defining a tension loop for routing an optical fiber lead extending from a first optical component mounted proximate to a convex guide, the first optical component lead being held in position against the outer surfaces of the convex guides by tension in the optical fiber lead. A set of concave guides also projects upward from the base, the curved inner surfaces of the concave guides defining a passive loop for routing an optical fiber lead from a second optical component mounted proximate to the concave guides, the second optical component lead tending to expand outward towards the inner surfaces of the concave guides. The tension loop and the passive loop are positioned relative to each other such that a first component lead routed in the tension loop can be spliced to a second component lead routed in the passive loop. Additional features and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a perspective view of a wavelength division multiplexer, the leads of which are to be routed and packaged in accordance with the present invention.

Fig. 2 shows a perspective view of a platform according to one aspect of the present invention.

Figs. 3 through 6 show perspective views of the platform shown in Fig. 2 in various stages of assembly.

Fig. 7A shows a plan view of the platform shown in Figs. 2-6 mounted into a housing.

Fig. 7B shows a cross section of the assembly shown in Fig. 7A through the plane B-B. Fig. 8 shows a perspective view of a foam insert for use in the assembly shown in

Figs. 7A and 7B.

Fig. 9 shows a flowchart of a method according to the present invention.

DETAILED DESCRIPTION The present invention now will be described more fully with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. However, the described invention may be embodied in various forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these representative embodiments are described in detail so that this disclosure will be thorough and complete, and will fully convey the structure, operation, functionality and potential scope of applicability of the invention to those skilled in the art.

Optical signal processing devices are typically constructed from discrete optical components that are mounted onto a motherboard or other platform. Each optical component can have two or more optical fiber leads for connection to other optical components. Because optical fiber is easily damaged and difficult to splice, the optical component leads are typically quite lengthy, i.e., several times the length of the component. The length of the component leads allows numerous attempts to be made to splice the leads together. If a splice proves to be unsatisfactory, it can be broken out, and the optical component leads can be trimmed back for another attempt.

Because of the length of the component leads, the interconnection of all of the optical components in a device results in several large loops of optical fiber. As these loops of optical fiber are easily damaged, it is desirable to route and package these loops within the device such that they are out of harm's way. The routing and packaging function is complicated by two design considerations. First, it is desirable for the final optical device to be as compact as possible. Second, however, optical fiber cannot be bent or curved too tightly. A curve in an optical fiber falling below a critical radius may result in unacceptable "macrobend" losses.

In one system according to the prior art, the loops of optical fiber resulting from splices are routed and packaged through the use of a number of curved optical fiber guides having convex outer guide surfaces. The optical fiber guides have a radius sufficiently large to prevent macrobend losses when optical fiber is wound around the outer surfaces of the guides. Each loop of optical fiber wound around the fiber guides is actively held in a position by tension in the fiber loop. The use of a tensioned approach has proven to be satisfactory, particularly where the optical components being spliced together are relatively small in size. However, as optical components increase in size and complexity, the use of a tensioned approach for certain mounting arrangements may result in an overall package size that is larger than desired. For example, Fig. 1 shows a perspective view of a wavelength division multiplexer

(WDM) 10 that is currently being used as a component in optical devices. The WDM package 12 has a relatively large size and has six optical fiber leads 14 that are asymmetrically located on either end of package 12. In addition, the underside of the WDM package 12 includes four taps 15 at the corners of the package that, as discussed below, are used in installing the WDM into an optical device.

In certain optical devices, it is necessary to mount both the WDM 10 and several smaller components onto a platform and then to splice the WDM optical leads 14 and the leads of other components together, as required by the device to be formed from these components. Again, the resulting loops of optical fiber must be routed and packaged to prevent damage to the fiber.

However, it has been found that if a purely convex, tension-based routing and packaging system, such as the one discussed above, is used, the size of the WDM package 12 and the asymmetrical location of the WDM leads 14 results in an optical device that may be larger than is desirable. This is because if a tension-based system is used, the platform upon which the WDM package 12 is mounted must be significantly larger than the package itself in order to provide room for the fiber guides, and in order to provide the fiber leads with a sufficient radius to prevent macrobend losses. In particular, in a tension- based system each WDM fiber lead 14 would typically require separate fiber guides located tangentially to each lead. Because of the closeness of some of the WDM leads 14 to each other, and because of the asymmetrical location of the leads 14 on either side of the WDM package 12, the use of separate, tension-based fiber guides for each lead would be cumbersome and require a significant amount of space within the device being assembled. The present invention is based on the tendency of a length of optical fiber, when curved, to open up, or expand, when the fiber is not constrained. Thus, according to one aspect of the present invention, optical fiber can be routed and packaged within an optical device in such a way that the fiber is loosely wrapped onto a platform and then allowed to expand to a predetermined minimum diameter within a loop defined by the inner surfaces of a set of concave fiber guides. This is particularly advantageous when packaging components with multiple fiber port configurations, such as the WDM shown in Fig. 1. Further, as discussed below, the component fiber can be routed to merge into a traditional routing scheme. This allows the fibers to be spliced together before exiting the device for the customer's use. Thus, the present invention allows a device containing heterogeneous components, such as the WDM, to be optimized in order to achieve a smaller size than would result from the use of traditional routing and packaging techniques.

Fig. 2 shows a perspective view of a first embodiment of a fiber routing and packaging platform 16 according to the present invention. In this embodiment, the platform 16 is a single piece of machined aluminum. However, if desired, it would also be within the spirit of the invention to manufacture the platform 16 out of separate components and from other suitable materials. The platform includes a flat base 18. Projecting upward from the base are three types of fiber guides: ten convex fiber guides 21-30, four concave guides 31-34, and six channels 35-40 leading to the exterior of the platform 16. The platform 16 further includes a substantially flat central section 42 onto which optical components are mounted. The central section 42 includes first and second V-shaped grooves 44 and 46 for receiving cylindrical optical components. A WDM, such as the one shown in Fig. 4, is mounted between the two V-shaped grooves 44 and 46. In addition, as described further below, additional component holders are mounted onto the central section 42 outside of the two V-shaped grooves 44 and 46.

The concave fiber guides 31-34 are used to route and package the leads of a WDM mounted between the V-shaped grooves 44 and 46. As shown in Fig. 2, there are defined two openings 48 and 50, between guides 22 and 23 and guides 27 and 28, respectively. The fiber optic leads of the WDM are then routed through these openings 48 and 50 and then along the loop defined by the interior surfaces of concave guides 31-34 around the inner perimeter of the platform 16. Because of the above-described physical properties of optical fiber, fiber leads routed in this manner will tend to open up, causing the fiber to be gently urged towards the interior surfaces of the concave guides 31-34. These leads can then be wound around the interior surfaces of the concave guides as many times as desired before being routed "inside" to the convex guides 21-30. Thus, a single set of four concave guides 31-34 can be used to route and package all of the leads from the WDM, even though the WDM has multiple leads that are asymmetrically located on either side of the WDM. The ten convex fiber guides 21-30, which are arranged in five pairs, 21/26, 22/27, 23/28, 24/29, and 25/30, are used to route and package the leads of the remaining optical components. Each of these components is mounted between a pair of convex guides with its fiber leads extending tangentially around the curved outer surfaces of its respective pair of convex guides. Finally, channels 35-40 provide paths for routing leads to the exterior of the device. As discussed above, the platform 16 includes upper and lower V-shaped grooves 44 and 46, which, as illustrated in Figs. 3-6 and discussed below, are dimensioned to receive cylindrical optical components. The upper groove 44 is located between guides 22 and 27. Thus, a component mounted into the upper groove 44 is aligned such that its optical fiber leads can be guided around guides 22 and 27. Similarly, the lower groove 46 is located between guides 24 and 29 such that the optical fiber leads of a component mounted into the lower groove 46 can be guided around guides 24 and 29. Finally, the platform 16 includes a number of mounting holes, including four holes 51-54 that, as illustrated in Fig. 6 and discussed below, are used to receive dowel pins that are used to position the WDM. Figs. 3 through 6 show further details of how various optical components are loaded into the platform 16 shown in Fig. 2. As shown in Fig. 3, a WDM 56, such as the one shown in Fig. 4, fits into the center section 42 of the platform 34 between grooves 44 and 46 such that the WDM leads (not shown) extend on the left side through opening 48 between guides 22 and 23, and on the right side through opening 50 between guides 27 and 28. The WDM 56 is positioned on the platform 16 by dowel pins that are inserted into holes 51-54 (shown in Fig. 2) on the platform and into the taps 15 (shown in Fig. 1) on the underside of the WDM 56. The dowel pins are illustrated in Fig. 6, discussed below.

As shown in Fig. 4, a pair of cylindrical optical components 58 and 60 are mounted in the V-shaped grooves 44 and 46 on either side of the WDM 56. The smaller of the two components is a tap 58, and the larger component is a circulator 60. The tap 58 is mounted between convex fiber guides 22 and 27. The circulator 60 is mounted between convex fiber guides 24 and 29.

As shown in Fig. 5, a pair of brackets 62 are mounted on the outside of the tap 58 and the circulator 50. Each bracket 62 includes a base 64, a middle shelf member 66 and an upper shelf member 68. This allows a pair of optical components to be held by each bracket 62, a first component between the base 64 and the middle shelf member 66, and a second component between the middle shelf member 66 and the upper shelf member 68. As shown in Fig. 7B, discussed below, the brackets 62 are used to hold gratings 82, each of which has a rectangular profile that fits closely inside the brackets. Fig. 6 shows a perspective view of the platform 16 with the WDM 56 shown in

Figs. 3-5 removed for purposes of illustration. In particular, Fig. 6 illustrates the placement of four dowel pins 71-74 in mounting holes 51-54. As discussed above, the dowel pins 71- 74 fit into receiving tap holes on the underside of the WDM 56.

For the purposes of discussion, Figs. 3 through 5 show the WDM 56 being installed first. However, in actual use, it has been found that it is easier to install the smaller components first, perform the necessary splices, and then install the WDM 56.

Fig. 7A shows a plan view of an add-drop module 76 that incorporates the platform 16 shown in Figs. 2 through 6, mounted into a housing 78. Fig. 7B shows a cross section through the plane B-B of the add-drop module 76 shown in Fig. 7A. A number of external leads 80 extend outside of the housing 78.

As discussed above, the present invention advantageously combines two techniques for routing and packaging component leads. The smaller components, including the tap 58, the circulator 60, and the gratings 82 held in the side brackets 62 are mounted into position first, after the platform 16 has been assembled into the housing 78. The component leads are then routed and packaged around the convex guides 21-30, and are held in place by tension in the leads.

After the smaller components have been mounted and spliced, the WDM 56 is then placed into position, using the dowel pins 71-74 shown in Fig. 6. Its six leads are routed on the left side through the opening 48 between guides 22 and 23 and on the right side through the opening 50 between guides 27 and 28 into the passive loop defined by concave guides 31-34. Each lead is wound around this loop as many times as required by the length of the lead. As discussed above, the WDM leads "open up" towards the interior surfaces of the concave guides 31-34. The end of each WDM lead is then routed around a convex guide, as required, for splicing to a lead from one of the other components. After the splices have been executed, the leads are tensioned around the convex guides by hand. This tensioning is accomplished by gently pulling the convex lead by hand until the proper level of tension is achieved, and then placing a foam insert over the lead to maintain that level of tension. As shown in Fig. 7B, the foam insert 84 is wedged into position between the WDM 56 and a side bracket 62, and is held in place by lid interference. Fig. 8 shows a perspective view of a foam insert 84 that may suitably be used for this purpose. After any external leads from the optical components are routed through a channel guide 35-40, a lid 84 (shown in Fig. 7B) is affixed to the housing 78, and is hermetically sealed around its perimeter. It will be appreciated that the present invention provides a highly efficient use of space, while providing protection to the optical fiber component leads.

Fig. 9 shows a flowchart of a method 90 according to the present invention. In step 92, a first set of components is loaded into a platform, such as the one discussed above. The first set of components includes components having leads that are to be routed and packaged using convex fiber guides. These would include, for example, the smaller components described above, such as the tap, circulator, and gratings shown in Figs. 9A and 9B. Once these components have been loaded into the platform, in step 94 the leads of these components are spliced, routed, and packaged around the convex fiber guides, using a tension-based technique.

After this phase has been completed, in step 96 a second set of components is loaded into the platform. The second set of components includes components having leads that are to be routed and packaged using concave fiber guides. These would include, for example, the WDM described above. Although the optical device shown and described above has only one component having leads to be routed and packaged using concave fiber guides, it would be possible to extend the concept to include devices having two or more such components. In step 98, the leads from these components are routed around the platform in the loop defined by the concave fiber guides. In step 100, the leads that have been routed using either the convex or the concave fiber guides are spliced together, as required. Finally, in step 104, the leads that have been routed around the convex fiber guides are tensioned by hand around the convex guides, and the tension is maintained by placing a foam insert over the lead.

As discussed above, the order according to which the various optical components are loaded into the platform is not essential to practicing the present invention. Thus, it would also be possible to first load an optical component with leads to be routed and packaged using the concave fiber guides, followed by loading optical components with leads to be routed and packaged using the convex fiber guides.

While the foregoing description includes details which will enable those skilled in the art to practice the invention, it should be recognized that the description is illustrative in nature and that many modifications and variations thereof will be apparent to those skilled in the art having the benefit of these teachings. It is accordingly intended that the invention herein be defined by the claims appended hereto and that the claims be interpreted as broadly as permitted by the prior art.

Claims

We claim:

1. A platform for routing optical fiber leads, comprising: a base; a set of convex guides projecting upward from the base, the outer surfaces of the convex guides defining a tension loop for routing an optical fiber lead extending from a first optical component mounted proximate to a convex guide, the first optical component lead being held in position against the outer surfaces of the convex guides by tension in the optical fiber lead; a set of concave guides projecting upward from the base, the inner surfaces of the concave guides defining a passive loop for routing an optical fiber lead from a second optical component mounted proximate to the concave guides, the second optical component lead tending to expand outward towards the inner surfaces of the concave guides; and the tension loop and the passive loop being positioned relative to each other such that a lead from the first component can be spliced to a lead from the second component.

2. The platform of claim 1 , wherein the second component has multiple, asymmetrically located leads that are routed in the passive loop.

3. The platform of claim 1, wherein the base is rectangular in shape, and wherein the concave guides are positioned at the vertices of the rectangle with their inner surfaces facing the interior of the rectangle, such that the passive loop runs along the inner perimeter of the rectangle.

4. The platform of claim 3, wherein the convex guides are disposed in the interior of the rectangle, such that the tension loop is inside of the passive loop.

5. The platform of claim 4, wherein the second component is mounted into the center of the rectangular platform, and wherein the second component leads are routed to the passive loop through an opening between the convex guides.

6. The platform of claim 1 further including a groove located proximate to a convex guide for holding the first optical component.

7. The platform of claim 6, wherein the groove has a V-shaped profile.

8. The platform of claim 6, wherein the groove holding the first optical component abuts the second optical component.

9. The platform of claim 1, further including a channel guide projection upward from the base of the platform for guiding an optical fiber lead from the interior of the platform to the exterior of the platform.

10. The platform of claim 1, further including a foam insert that is wedged into position over the first component lead, maintaining tension in the lead around the convex guides.

11. An optical device, comprising: a housing; a platform mounted into the housing, the platform having a base; a set of convex guides projecting upward from the platform base, the outer surfaces of the convex guides defining a tension loop for routing an optical fiber lead extending from a first optical component mounted between a pair of convex guides, the lead of the first component being held in position against the outer surfaces of the convex guides by tension in the optical fiber lead; a set of concave guides projecting upward from the base, the inner surfaces of the concave guides defining a passive loop for routing an optical fiber lead from a second optical component mounted proximate to the concave guides, the component lead from the second optical component tending to expand outward towards the inner surfaces of the concave guides; and the tension loop and the passive loop being positioned relative to each other such that the lead from the first component can be spliced to the lead from the second component.

12. The optical device of claim 11, wherein the second component has multiple, asymmetrically located leads that are routed in the passive loop.

13. The optical device of claim 11 , wherein the base of the platform is rectangular in shape, and wherein the concave guides are positioned at the vertices of the rectangle with their inner surfaces facing the interior of the rectangle, such that the passive loop runs along the inner perimeter of the rectangle.

14. The optical device of claim 13, wherein the convex guides are disposed in the interior of the rectangle, such that the tension loop is inside of the passive loop.

15. The platform of claim 14, wherein the second component is mounted into the center of the rectangular platform, and wherein the lead from the second component is routed to the passive loop through an opening between the convex guides.

16. A method for routing optical fiber in an optical device, comprising the following steps: (a) loading first optical component into a platform having a base from which projects upwards a set of convex guides, the outer surfaces of which define a tension loop, and a set of concave guides, the inner surfaces of which define a passive loop;

(b) routing a lead from the first optical component in the tension loop; (c) loading a second optical component into the platform;

(d) routing a lead from the second optical component in the passive loop; and

(e) splicing the lead from the first optical component to the lead from the second optical component.

17. The method of claim 16, further including the following step (f) performed after step (e):

(f) tensioning the lead from the first optical component by hand and placing a foam insert over the convex lead to maintain the tension in the lead.