Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-11-02
2003-09-09
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C174S261000, C174S262000, C174S266000, C361S749000, C361S760000
Reexamination Certificate
active
06617518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an enhanced flex cable, used to electrically couple a fiber optic data communications transceiver, for example, to an associated wiring board.
2. Background Information
An optical transceiver is a device that uses pulses of light to carry signals for transmitting and receiving data at very high speeds. Typically, the light pulses are converted into, or converted from, associated electrical signals using known circuitry. Such optical transceivers are often used in devices, such as computers and data communication networks, in which data must be transmitted at high rates of speed.
Optical transceivers typically use an optical transmitter, such as a light emitting diode (LED) or laser, for example, to transmit the light pulses, and/or an optical receiver, such as a photodiode chip or photo detector chip (hereinafter receiver chip), for example, to receive the light pulses. One type of optical transceiver has a subassembly including a receiver chip disposed within a transistor-outline (TO) can package. This type of optical transceiver subassembly is known as a receiver optical subassembly (hereinafter ROSA for short). Another type of optical transceiver has a subassembly that includes either an edge-emitting laser or a surface-emitting laser, such as a VCSEL, disposed within a TO can package. This type of subassembly is known as a transmitter optical subassembly (hereinafter TOSA for short). The specifics of ROSAs and TOSAs are well known to those skilled in the art. However, briefly, the TO can package is a metal housing that hermetically houses the other components of the ROSA or TOSA. The TO can package may then be disposed within a further housing, formed of a plastic for example, that is adapted to couple a ferrule or optical fiber to the receiver chip or laser.
Typically, the ROSA and TOSA are electrically coupled to a printed circuit board (also known as, and herein after referred to, as a transceiver wiring board). The transceiver wiring board includes the associated electronics for operating the receiver chip or laser. These electronics include, for example, the laser driver and control, receiver preamplifier and post amplifier, and other supporting components. In a computer system, the transceiver wiring board is typically connected to a further circuit board, for example, a motherboard. The assembly may then be positioned within a chassis, which is a frame fixed within a computer housing. The chassis serves to hold the assembly within the computer housing.
Typically, the TOSA and ROSA are electrically coupled to the transceiver wiring board using a number of relatively rigid leads. For example, the aforementioned ROSA conventionally has four leads: a power lead for supplying power to the ROSA; a single ground lead for connecting the ROSA to a ground potential; and two data leads for transmitting signals to and/or from the ROSA. The TOSA also conventionally has a number of leads for coupling the laser within the TO can to the transceiver wiring board. Each of the respective leads typically extends out of the TO can for connection to the transceiver wiring board in a known manner, and in an industry standard arrangement. For example, the ends of the respective leads may be passed into corresponding vias formed in the transceiver wiring board, and soldered in place. Alternatively, the ROSA/TOSA leads may be connected to the transceiver wiring board by soldering the leads to electrical pads on the bottom or top surface of the transceiver wiring board.
However, this manner of connecting the leads to the transceiver wiring board requires that each of the leads has a relatively long length. The long lengths have generally been deemed necessary in order to allow the ROSA/TOSA to be properly oriented relative to the transceiver wiring board, while still allowing the ROSA/TOSA to be connected thereto. That is, the leads typically extend out of a rear portion of the ROSA/TOSA and initially in a direction parallel to the surface of the transceiver wiring board. Thus, in order to connect the leads to the transceiver wiring board, the leads must also extend for a distance in a different direction, i.e., toward the transceiver wiring board. Depending on the orientation and geometry, the length of the leads may be so long as to cause the leads to disadvantageously have a relatively high impedance. As is known to those skilled in the art, a high impedance on the leads is undesirable, since this may affect the immunity of the receiver, for example, to noise present on the power supply or ground. Moreover, this configuration may subject the leads to a cross talk (i.e., undesirable coupling) effect. Thus, there is need for a way to easily and rapidly electrically couple the leads of a ROSA and/or TOSA, for example, to a transceiver wiring board, while reducing the impedance, and minimizing the cross talk effect. Furthermore, due to the industry-standard arrangement of the optical transceiver utilizing a ROSA and/or TOSA, the ROSA and/or TOSA are typically placed immediately adjacent to an edge face of the transceiver wiring board, with the ground lead typically extending from the TO can at the edge face (i.e., between the upper and lower primary surfaces of the transceiver wiring board). The transceiver wiring board is thus conventionally provided with a notch to accommodate the ground lead. However, this requires that the ground lead be provided with a relatively long length and numerous bends to allow the ground lead to pass past the notch and to allow the ground lead to be connected to the transceiver wiring board in the aforementioned manner. Alternatively, it is also known to provide a ground cage that can be connected to the ground lead and to a ground potential. For example, the ground cage can be attached and grounded to the transceiver wiring board, which may in turn be fastened to, and grounded in a known manner, to the motherboard and its ground. While this may allow the length of the ground lead to be reduced, it also requires the use of a further component (i.e., the ground cage), which increases inventory costs. Moreover, connecting the ground cage to the ground lead and to the transceiver wiring board is a labor intensive procedure.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a flex cable is used in conjunction with a so-called duplex optical transceiver. The duplex optical transceiver has a so-called electro-optic receiver optical subassembly (ROSA) positioned adjacent to a transmitter optical subassembly (TOSA). In the exemplary embodiment, the ROSA has four leads projecting from the rear surface of a respective transistor-outline (TO) can package: a power lead for supplying power to the ROSA; a ground lead for connecting the ROSA to a ground potential; and two data leads for transmitting signals to and/or from the ROSA. The TOSA may be similarly tailored, or have a different configuration. However, in the exemplary embodiment, the TOSA has three leads projecting from the rear surface of a respective TO can package: a power lead for supplying power to the TOSA; a cathode lead; and a monitor lead. However, the present invention may be used with electrical components having more or fewer leads without departing from the spirit and scope of the invention.
The exemplary flex cable is used to electrically couple the leads of the ROSA and TOSA to a transceiver wiring board. The transceiver wiring board includes the associated electronics for operating the ROSA and/or TOSA, for example the laser driver and control, receiver preamplifier and post amplifier, and other supporting components.
In accordance with industry standards, the ROSA/TOSA are placed immediately adjacent to an edge face of the transceiver wiring board. Moreover, due to industry standards, the ground lead of the ROSA, for example, extends from the TO can package in a region of the edge face of the wiring board (i.e., between the upper and lower primary surfaces of the transceiver wiring board). To accomm
Ames Stephen John
Connell, III Michael Joseph
Distad, Jr. Eugene E.
McCoy Bart Owen
Storino Salvatore Nicholas
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Cuneo Kamand
JDS Uniphase Corporaton
Patel I B
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