Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2000-03-28
2002-12-10
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S053000
Reexamination Certificate
active
06491446
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the interconnection of optical devices and optical media, and more particularly to a method of passive self-alignment of an array of active optical devices (e.g., laser drivers and photodetectors) to a corresponding array of optical fibers. The method also allows for the integration of other electronic components, such as amplifier drivers, in the interconnection.
2. Description of Related Art
Optical fibers have replaced copper wire in recent years as the preferred medium for carrying telecommunications and data signals, due to the high efficiency of optical data transmission. As with copper wire, it is necessary to provide for the interconnection of optical fibers, during installation, repair or replacement of the fibers, and to terminate the fibers onto active optical devices.
Optical devices include, for example, optical sensors (photoelectric diodes or photodetectors) and light sources (typically solid-state devices, such as light-emitting diodes (LEDs) or laser diodes). The termination of an optical fiber may be indirect, i.e., the fiber may be connected to some other (passive) optical device such as a beam splitter or polarizer, before the light beam is directed to the active optical device.
There are generally two kinds of optical interconnection devices, splices and connectors. The term “splice”, usually refers to a device which provides a permanent connection between a pair of optical fibers (i.e., a connection that is not intended to be removable). Many fiber optic splices employ plate elements having fiber-receiving V-shaped grooves, with means provided for clamping the terminal ends of a pair of fibers in a common groove. Some of these devices are designed to interconnect a plurality of pairs of fibers; see, e.g., U.S. Pat. No. 5,151,964.
The term “connector,” in contrast, usually refers to a device which may be engaged and disengaged repeatedly, often between different plugs and receptacles. Connectors also can be used to removably interconnect a plurality of pairs of fibers; see, e.g., U.S. Pat. No. 5,381,498. The present invention is generally related to such devices, although the term “connector” should not be construed in a limiting sense, since the present invention may inherently provide a permanent, as well as temporary connection/termination.
There are two primary types of commercially available fiber optic connectors, namely, ferrule connectors and bionic connectors. Ferrule connectors use a ferrule plug, typically ceramic, having a central bore which receives a single optical fiber. Bionic connectors use a plug in the shape of a truncated cone. Both connectors usually combine a pair of plugs fitting into a common socket or receptacle to provide a completed connection. The prior art includes hybrid ferrule connector/splices, such as those shown in U.S. Pat. Nos. 4,986,626 and 5,159,655.
One area which has not been adequately addressed by the prior art, however, is the interconnection, or termination, of an array of optical fibers to a corresponding array of active optical devices. Since the plugs of ferrule and bionic connectors receive only a single fiber, a relatively large bank of such connectors must be provided to terminate several fibers. One drawback with multifiber connectors is the poor interconnection densities that are achieved. While some ferrule designs have densities around 2 connections per square centimeter, this may be compared to densities of 4 connections or more per square centimeter in some copper wire connectors, such as an RJ45 connector. Some nonferrule designs provide slightly improved densities, such as that described in U.S. Pat. No. 4,045,121, but that connector has far too many parts and is not easily installed. A simpler multifiber connector is depicted in European Patent Application No. 514,722 (commonly referred to as an “MT” connector).
Fiber alignment is also a problem when terminating an array of fibers at respective optical devices. Each fiber must not only be properly aligned transversely, i.e., with the fiber tip precisely located at the emitter or receiver of the active device, but must further be positioned in the proper angular orientation to ensure that the light beam exits/enters the fiber in an optimum direction with respect to the device. Any air gap between the endface of an optical fiber and the optical surface of a respective active device should also be minimized in order to reduce transmission losses across the interface. Accurate alignment of fibers with active devices is thus a tedious and time-consuming process.
In order to discover the best position/orient ation, active alignment techniques detect actual transmission of optical signals across the device-fiber interface. For optical sensors, active alignment is accomplished by transmitting a signal through the fiber to the sensor, and then monitoring the sensor output while moving the terminal end of the fiber, or other alignment element. The signal can be fed into the other (distal) end of the fiber, or injected at an intermediate point using a “clip-on” instrument that creates a microbend in the fiber at the injection point.
For light sources, active alignment is accomplished by powering up the device, and then monitoring the signal that flows though the fiber while moving the terminal end of the fiber or other alignment element. The signal can be monitored by sensing the output at the distal end of the fiber, or by picking the signal off at an intermediate point using a clip-on instrument. For either type of optical device (transmitter or receiver), active alignment thus requires extensive instrumentation.
Another problem in terminating optical fibers relates to the wide dissimilarities in the myriad connector styles. Because of the different sizes and geometries of connector bodies, ferrules, and other components, any technique adapted for use with one particular connector is generally incompatible with other connector designs. Special adapters kits or jumper cables may be necessary to achieve compatibility.
In light of the foregoing, it would be desirable to devise an improved method of terminating an array of optical fibers to an array of optical devices, which allows for the passive self-alignment of the device array to the optical fiber array. It would be further advantageous if the method accommodated higher interconnection densities, and were generally usable with any commercially available fiber optic connector.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide an improved method of interconnecting or terminating a plurality of optical fibers with a plurality of respective active optical devices.
It is another object of the present invention to provide such a method that allows for the passive selfalignment of the optical fibers to the optical devices.
It is yet another object of the present invention to provide highly integrated, low profile fiber optic array transmitters and receivers for ultra-high bandwidth data distribution and communication.
A further object of this approach is to establish a precisely defined interface, with respects to physical separation, between the active (photonic) device apertures and the plurality optical fiber termination. The interface permits a precise uniform physical separation of less than 0.15 mm to be achieved across all emitter and/or detector apertures without physically bonding via an adhesive to the optical fiber connector termination. This reduces the dependency on requiring narrow beam divergence emitters and reduces loss in the detector to fiber termination due to bean divergence.
Still another object is the increase in design flexibility by allowing the optical (emitter/detector) to electrical interface assembly to be pre-fabricated and subsequently inserted into the desired package housing of choice. This eliminates the need for customization when used with commercial optical multi-fiber connectors (ferrules).
Yet another objective is the protective laminate in
Bovernick Rodney
Bowen Glenn W.
Hogan Patrick M.
Lockheed Martin Corporation
Pak Sung
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