Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-05-26
2001-04-10
Bovernick, Rodney (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S089000, C385S093000
Reexamination Certificate
active
06213651
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to light bending devices. More particularly, the invention relates to fiber optic modules.
BACKGROUND OF THE INVENTION
Fiber optic modules interface optical fibers to electronic circuitry transducing communication by light or photons with communication by electrical signals. A fiber optic module may be a fiber optic receiver, transmitter or transceiver including both receive and transmit functions. The fiber optic receiver, transmitter and transceiver each have optical elements (OE) and electrical elements (EE). The fiber optic transmitter OE includes an emitter (such as a semiconductor LED or Laser) mounted in a package and an optical coupling element for coupling light or photons from the OE into the optical fiber. The type of semiconductor laser (light amplification by stimulated emission of radiation) may be a vertical cavity surface emitting laser (VCSEL). The fiber optic receiver OE includes a photodetector (such as a photodiode) mounted in a package and an optical coupling element for coupling light or photons from the optical fiber into the photodetector. The EE for each includes integrated circuits and passive elements mounted on a substrate such as a printed circuit board (PCB) or ceramic. The OE and EE are connected electrically at the emitter and photodetector.
Because of the high transmission frequencies utilized in fiber optic communication, crosstalk between receive and transmit signals is of concern. Additionally, electromagnetic interference (EMI) is of concern due to the high frequency of operation of the fiber optic modules. In order to reduce EMI, shielding of the electrical components is required which is usually accomplished by attaching a metal shield to the substrate of the fiber optic module and connecting it to ground. In order to avoid electronic crosstalk and EMI, the fiber optic transceiver usually employs separate components and separate shielding of fiber optic receiver and fiber optic transmitter components. In order to avoid optical crosstalk where light or photons can interfere between communication channels, the fiber optic transceiver usually employs separate optical elements for coupling light or photons into and out of the optical fiber for fiber optic receiver and fiber optic transmitter. Using separate optical elements requires additional components and increases the costs of fiber optic transceivers. It is desirable to reduce the component count of fiber optic transceivers such that they are less expensive to manufacture.
The form factor or size of the fiber optic module is of concern. Previously, the fiber optic transceiver, receiver, and transmitter utilized horizontal boards or substrates which mounted parallel with a system printed circuit board utilized significant footprint or board space. The horizontal boards provided nearly zero optical crosstalk and minimal electronic crosstalk when properly shielded. However, the horizontal boards, parallel to the system printed circuit board, required large spacing between optical fiber connectors to make the connection to the optical fibers. While this may have been satisfactory for early systems using minimal fiber optic communication, the trend is towards greater usage of fiber optic communication requiring improved connectivity and smaller optical fiber connectors to more densely pack them on a system printed circuit board. Thus, it is desirable to minimize the size of system printed circuit boards (PCBs) and accordingly it is desirable to reduce the footprint of the fiber optic module which will attach to such system PCBs. Additionally, the desire for tighter interconnect leads of fiber optic cables, restricts the size of the OE's. For example, in the common implementation using TO header and can, the header dimension of the interconnect lead is normally 5.6 mm. In small form factor optical modules, such as the MT family, the two optical fibers are separated by a distance of only 0.75 mm. This severely restricts the method of coupling light or photons from the OE into and out of fiber optic cables.
BRIEF SUMMARY OF THE INVENTION
Briefly, the present invention includes a method, apparatus and system for method and apparatus for vertical board construction of fiber optic transmitters, receivers and transceivers as described in the claims. Fiber optic transmitter and receiver electrical elements are implemented on two separate substantially parallel boards in a fiber optic module. The parallel boards are mount substantially perpendicular to the base of the fiber optic module and the system printed circuit board to which it attaches, to reduce the footprint of the fiber optic module. In one embodiment, bending light or photons through ninety degrees, the light transmitter (a packaged type of emitter) and a light receiver (a packaged type of photodetector) are each mounted substantially perpendicular to the transmit and receive boards respectively such that their active areas are nearly facing each other but offset. A single optical block implements lenses and reflecting surfaces to minimize manufacturing costs. The light receiver and light transmitter are mounted offset from each other in the optical block in order to avoid optical cross talk. In a second embodiment, the light transmitter (emitter) and the light receiver (photodetector) are each mounted substantially parallel with the transmit and receive boards respectively and the connection to the optical fibers. The separate and substantially parallel receive and transmit boards are provided with ground planes on back sides in order to minimize electrical cross talk. A module outer shielded housing, manufactured out of metal or metal plated plastic, provides further shielding for EMI. The substantially parallel boards may be extended to support multiple channels or multiple parallel fibers such as in a ribbon optical fiber cable. Manufacturing steps of the boards for the fiber optic module are disclosed to provide reduced manufacturing costs.
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patent
Jiang Wenbin
Wei Cheng Ping
Blakely , Sokoloff, Taylor & Zafman LLP
Bovernick Rodney
E20 Communications Inc.
Stahl Michael J.
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