HK1083370A - Bending an optical fiber into a backplane - Google Patents

Description

Bending optical fibers into a backplane

Technical Field

The present invention relates generally to the field of opto-electronic printed circuit boards. More particularly, the present invention relates to integrating a fiber management system (fiber management system) into the board face of a printed circuit board via a right angle bend fixture.

Background

Optical fibers used in common telecommunications and other applications are based on Snell's law and the principle of total internal reflection. Each fiber consists of a central core and an outer layer known as a cladding. By making the refractive index (n) of the core higher than that of the cladding, light will be totally internally reflected without passing through the core and being lost.

Fiber optic connectors can be implemented using a device known as a ferrule. The apparatus supports and aligns the optical fibers so that one optical fiber can be precisely connected to another optical fiber at the time of connection. In the case of single mode fiber optic connectors, the ferrule is a cylindrical member, typically made of ceramic, which holds the fiber in its center with the aid of a cured epoxy. The ends of the optical fiber and ferrule are polished to produce an optically smooth and substantially flat surface and to bring the aligned optical fiber as close to the center of the ferrule assembly as possible. When two split ferrules (Keyed fibers) are aligned end-to-end using a mechanical connector, optical coupling occurs between the two optical fibers, thereby making an optical connection. To reduce unwanted reflections, the attachment surfaces of the ferrules are typically not orthogonal.

Most fiber optic connectors employ a ferrule that is generally rectangular in shape and has slots or holes to enable precise alignment of multiple optical fibers. The fibers were supported individually or in parallel rows with centers spaced 250 microns apart.

It is desirable to connect the optical fibers/fiber arrays to the printed circuit board such that the optical fibers/fiber arrays are placed along the board surface and bent into the board such that they are at right angles to the board surface. Optical fibers used in common telecommunications and other applications have limited right angle bending capabilities due to their physical construction. Physically bending the fiber at a right angle may result in strain, resulting in fiber material fracture and structural misadjustment. Repeatedly bending the fiber in this manner exacerbates the risk of failure.

What is needed, therefore, is a method of sharply bending an optical fiber or array of optical fibers into a printed circuit board that is stable and prevents repeated bending.

Summary of The Invention

It is an object of the present invention to bend optical fibers for connection to a backplane/circuit group.

It is another object of the present invention to use a molding to hold and guide the array of optical fibers to effectively bend the fibers into the backplane, the molding being shaped and dimensioned to minimize the stresses experienced by the fibers and to maximize the bend radius of the fibers.

It is a further object of the present invention to provide a right angle bend mount that is easily mounted to a printed circuit board.

It is a further object of this invention to provide such a quarter bend fastener with an easily lockable V-shaped channel member.

It is a further object of this invention to provide such a quarter bend fastener which is self-locating for installation in a base plate.

Brief description of the drawings

Other objects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.

Figure 1 shows an exploded perspective view of a right angle fixture in accordance with an embodiment of the present invention.

FIG. 2 shows a perspective view of the right angle fixture of FIG. 1 with the fiber array mounted in the fixture and the fixture embedded in a backplane.

FIG. 3 shows a cross-sectional view of the right angle fixture of FIG. 1 with the array of optical fibers mounted in the fixture and the fixture embedded in a substrate.

Figure 4 is a top view of the right angle fixture of figure 1.

Description of The Preferred Embodiment

The present invention relates to an opto-electronic backplane system employing optical fibers. The present invention is applicable to any optical fiber (single mode, multimode, polymeric) that can be physically made with a small bend radius with acceptable loss. The type of application (i.e., the frequency range employed) depends in part on the losses within the system. The system is most suitable for optical fibers with small bending radii. An exemplary embodiment of the present invention is a right angle bend fixture for bending an optical fiber into a board surface of a circuit board. The quarter-turn fastener includes a base and a cover pivotally connected to the base via a hinge. The first pair of opposing faces of the base and cover form a clamp that is located adjacent the hinge. The clamp securely clamps the ferrule portion of the optical fiber when the base and cover are brought together. A second pair of opposing faces of the base and cover form another clamp. The other clamp fixedly clamps the non-ferrule portion of the optical fiber when the base and cover are brought together. When the base and the cover are fixed together so that they are in a closed state, the ferrule portion is made at a right angle with respect to the clamped non-ferrule portion. When the base and cover are brought together, the bent portion of the optical fiber is located between the ferrule portion and the clamped non-ferrule portion, and the bent portion is located in an unclamped gap between the base and cover.

According to one exemplary embodiment, the fiber control system (or "FMS") terminates in a ferrule (single or column). The exemplary embodiment shown employs an array of "MT" connectors. The type of fiber employed in an FMS will also depend in part on the losses in the system, and the fiber will be bent to a radius of about 8-10 mm. Fibers with higher refractive index or dopant difference are useful for keeping losses low.

Referring to fig. 1, the MT connector (shown in phantom) is shown mounted in a right angle fixture (molding) 100. The fixture 100 guides and holds the optical fiber of the FMS in place to prevent signal distortion. The fixing member 100 is shaped in such a manner that it can be locked and fixed in the base plate 200. Referring to fig. 2, there is shown a perspective view of the right angle fixture 100 of fig. 1, with the array of optical fibers assembled within the fixture 100 and the fixture 100 embedded in a base 200. The MT fiber array is indicated by a dotted line.

Referring to fig. 3, there is shown a cross-sectional view of the right angle fixture 100 of fig. 2, with the array of optical fibers assembled within the fixture 100 and the fixture 100 embedded in the base 200. A silicon V-groove member 110 helps to hold the MT fiber array 50 in place. A gap 120 is formed in the fixture 100, the gap 120 providing additional space to allow for some variation in bending of the optical fiber array 50 within the fixture 100. The snap 130 holds the fastener 100 in a closed position.

Referring to fig. 4, a top view of the right angle fixture 100 of fig. 2 is shown.

The above-described manufacturing method of how to align and mount fiber optic connectors/fiber array connectors into a backplane is believed to be novel and, due to the simplicity of the method, can be effective in reducing costs. The components used in the exemplary embodiments are either readily available or easy to manufacture. The main component is a molded fixture for PCB assembly.

The exemplary embodiment expresses the idea that a conventional backplane, which is actually integrated with the fiber control system, is different.

One advantage of using the PCB manufacturing method of the exemplary embodiment is that in the event of a circuit defect due to a manufacturing failure, the expensive optical circuit assembly does not need to be discarded/scrapped. The system is modular, and the components can be replaced or stored during the manufacturing process, thereby saving money. The present invention has been described in terms of exemplary embodiments, but it will be appreciated that various changes and modifications can be made to the embodiments without departing from the scope of the invention.

Claims (2)

1. A right angle bend fixture for bending an optical fiber into a board surface of a circuit board, the right angle bend fixture comprising:

a base;

a cover pivotally connected to the base via a hinge;

a first clamp formed by a first pair of opposing faces of the base and the cover, the first pair of opposing faces being located near the hinge, the first clamp being adapted to fixedly clamp the ferrule portion of the optical fiber when the base and the cover are secured together in a closed state;

a second clamp formed by a second pair of opposing faces of the base and the cover, the second clamp adapted to fixedly clamp the non-ferrule portion of the optical fiber when the base and the cover are secured together in a closed state;

wherein the ferrule portion is held at a right angle relative to the clamped non-ferrule portion when the base and cover are secured together in a closed condition.

2. The right angle bend fixture of claim 1, wherein a bend of the optical fiber between the ferrule portion and the clamped non-ferrule portion is located within an undamped gap between the base and the cover when the base and the cover are secured together in a closed state.