Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-07-07
2001-10-16
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S089000, C385S092000
Reexamination Certificate
active
06302596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optoelectronic transceivers, and more particularly to a optoelectronic transceivers fabricated to be reduced in size and manufacturing complexity.
2. Description of the Related Art
Conventional duplex fiber optic connectors, such as SC Duplex connectors, (see, for example, ANSI Fibre Channel—physical and signaling interface (FC-PH) X3.230 rev. 4.3 (1994)) achieve the required alignment tolerances by threading each optical fiber through a precision ceramic ferrule. The two ferrules of an SC connector have an outer diameter of 2.5 mm, and the resulting fiber-to-fiber spacing (or pitch) of a duplex connector is approximately 12.5 mm, i.e., the distance from ferrule face to ferrule face when in operative position in the connector. Since the outer of the fiber captured by the ferrule is only 125 &mgr;m, it should be possible to design a significantly smaller optical connector. Smaller connectors with fewer precision parts could dramatically reduce manufacturing costs.
Recently, a new class of “small form factor” (SFF) fiber optic connectors has been introduced with the goal of reducing the size of a fiber optic connector to one half of that of a standard SC Duplex connector while maintaining or reducing the cost. Such connectors are described by C. Schwantes, in “Small form factors herald the next generation of optical connectors”, Lightwave, October 1998, pp. 65-68. Several different designs have been proposed by different manufacturers, including the LC (manufactured by Lucent Technologies and others), MT-RJ (manufactured by Fujikura, Siecor and AMP and others), and VF-45 (manufactured by 3M Corp.). All connectors use the familiar RJ45 modular jack latching mechanism used in telephone cords for securing the connector.
While the smaller size of the SFF connectors is in itself an important advantage, an equally important advantage of the new SFF technology lies in the corresponding smaller size of the transceivers which mate to these connectors. The transceiver is a module including a digitally modulated laser to feed light signals into the outgoing fiber of the mating SFF connector, as well as a detector which receives light signals from the incoming fiber of that detector. The transceiver also includes the electronic chips which process these signals for both the transmitting and receiving functions, and provide connections between the module and a “master” board to which it is connected.
The smaller SFF transceiver size means that less area on the board is occupied, which permits the user to install more interconnects. A SFF Multisourcing Agreement between major manufactures of optical transceivers specifies a 13.97 mm pitch requirement between ferrules for the transceivers, a maximum length requirement for the transceivers of 31 mm, and a maximum height of 9.8 mm, which in effect permits a doubling of the port density compared with transceivers designed to mate to SC Duplex connectors.
Careful attention is needed to design a SFF transceiver to ensure full functionality while maintaining a low cost. A critical component of the transceiver is the optical subassembly (OSA) which carries out the conversion of electrical to optical signals (transmitter optical subassembly, TOSA), or optical to electrical signals (receiver optical subassembly, ROSA). The optoelectronic chips, i.e. laser (transmitter) and detector (receiver) are usually housed in metal “TO” cans furnished with a window for light transmission, so that the chips are hermetically sealed. The fabrication of an optical system which serves to align the fibers to the chips in the cans while efficiently permitting optical power transfer represents a difficult challenge in the design of all OSAs.
Therefore, a need exists for OSAs which are smaller in size and easier to manufacture. In particular, a need exists for OSAs which mate to connectors with a small, 1.25 mm diameter ferrule, e.g. the LC connector.
SUMMARY OF THE INVENTION
An optical subassembly (OSA), in accordance with the present invention, includes a housing, which may be substantially rectangular, the OSA includes a first end portion and a second end portion oppositely disposed from the first end portion. The first end portion forms a bore configured and dimensioned to receive a ferrule having an optical fiber therein. The bore is adjacent to a ferrule stop which is integrally formed in the housing. A lens is integrally formed with the housing. The lens has a planar surface and a convex surface opposite the planar surface. The planar surface of the lens is substantially parallel to and set in from the ferrule stop to prevent contact between the ferrule and the planar surface. The optical device, the lens, and the bore which accepts the ferrule are all in optical alignment.
In alternate embodiments, the optical subassembly may include an optical transmitter (which is preferably class
1
eye safe) or an optical receiver. The housing preferably includes a material transparent to wavelengths of light provided by the optical transmitter so that the housing, the lens, and the bore and cavity at opposite ends of the housing comprise one monolithic component. The optical transmitter may be a light-emitting diode chip or preferably a laser transmitter chip, and the laser of the transmitter is a vertical cavity surface emitting laser chip or an edge emitting laser chip. The optical receiver is preferably a photodiode chip or a photodiode plus pre-amplifier combination chip. The housing may include a transparent plastic material which may include polycarbonate, polyethersulfone or polyetherimide. The optical device may be bonded to the housing with an ultraviolet light curing compound. The optical device may include either a transmitter or photodiode packaged in a suitable TO can. The optical subassembly is preferably adapted for LC connectors. The ferrule stop may include a recess for receiving debris introduced into the bore. The housing may include a protrusion extending from the second end portion forming a substantially circular opening in the housing for receiving the optical device. The protrusion may include an angled external surface about the circular opening to receive a bonding compound for bonding the optical device to the housing.
A transceiver module, in accordance with the present invention includes a compliant retainer having a first end portion oppositely disposed to a second end portion. The first end portion is dimensioned and configured to receive optical connectors. A circuit board is received in the second end portion of the retainer. The circuit board connects electrically to a master circuit board, so that the master board can communicate via the optoelectronic transceiver, e.g., to another master board. The transceiver circuit board processes signals to and from the optical subassemblies. The second end portion of the retainer also includes a U shaped portion for permitting optical subassemblies to be received in the retainer. The transceiver includes a transmitter optical subassembly matable to a receiver optical subassembly. Each of the transmitter and the receiver subassemblies includes a substantially rectangular housing forming a bore configured and dimensioned to receive a ferrule having an optical fiber therein. The bore is adjacent to a ferrule stop integrally formed in the housing. A lens is integrally formed with the housing. The lens has a planar surface and a convex surface opposite the planar surface. The planar surface of the lens is substantially parallel to and set in from the ferrule stop to prevent contact between the ferrule and the planar surface.
In alternate embodiments, the ferrule stop may include a recess for receiving debris introduced into the bore. The transceiver module may further include an optical device for each of the transmitter and the receiver subassemblies in operative relationship with the bore and the lens which are optically aligned with the fiber in the ferrule. The transmitter and receiver subassemblies may be matable by
Cohen Mitchell S.
Gaio David P.
Hogan William K.
Isaacs Phillip D.
McKnite Patrick E.
Bovernick Rodney
F. Chau & Associates LLP
International Business Machines - Corporation
Pak Sung
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