Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
2002-11-13
2004-11-02
Ullah, Akm Enayet (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S091000
Reexamination Certificate
active
06811320
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to connection assemblies for electronics and, more particularly to a fiber-optic cable system which provides a connection between a fiber optic cable and an electronic device. The system of the invention provides high precision interconnections which makes it particularly well suited for microelectronic device packages.
Because of their inherent capability of transmitting more data than any comparably sized electrical wire, fiber optic cable transmission lines have become more widely used in various electronic applications including those utilizing microelectronic components. Since fiber optic cables do not produce electromagnetic interference and are not susceptible to radio frequency interference, they have become more desirable in computer systems and avionic systems and many other types of systems in which noise interference can cause malfunction thereof. Moreover, fiber optic cable transmission systems have an additional advantage of having lower power requirements than electrical wire transmission lines of comparable data transmission capabilities. However, fiber optic cable transmission systems have the disadvantage of requiring precise alignment of their connections in order to function properly. This important disadvantage of fiber-optic cable systems has to a certain degree obviated the advantages such systems have and prevented them from more widespread use.
Current electronic packaging of devices are now confronting the problem of input and output bounding wherein the number of inputs and outputs needed is the most important factor determining the size of the device package. For example, it is now common that there are 500-700 I/O bald grid arrays in midrange personal computers. There are also higher I/O counts in high end computers as well as in data fusion or graphics applications. However, using such high pin counts has a significant drawback in that soldering the many pin connections has a certain element of risk as it takes only one failed solder joint to cause a system failure. As a result designers have investigated the use of optical interconnections between these large package devices including FPGAs, microprocessors, memory devices etc.
Current fiber-optic systems use discrete devices to convert the light pulses from the fiber-optic cable into electrical signals. The signals are then conducted to the next device using a printed circuit board to connect to high count I/O packages. The signals are then demultiplexed down to a lower data rate required by the lower speed low-power technologies. As a consequence, the I/O increases to maintain the data rate. I/O power is a significant contributor to the overall power consumption of the integrated circuit.
An optical interconnections system for electronic devices has the important advantage of enabling high data transfer between microelectronic devices. However, the development of such a system involves various problems. Such systems would require that a microelectronic package be used to mount the VCSEL transmitters and detectors as well as the fiber optic connector body onto. In addition, very precise alignment of the fiber-optic connector body and the electronic device base is required. This alignment requirement is on the order of approximately 5 to 10 microns for multimode fiber. Some applications would desire a fixed connection whereas other applications would desire a removable connection.
Prior art systems used in applying photo resistors to semiconductor wafers have utilized an alignment method. In the fabrication of the semiconductor substrates a holographic system using an infrared light is used to backlight alignment patterns on a substrate fabricated in the wafer. The substrate is transparent to the infrared light and thus can be detected by a holographic imaging and detection system to automatically align the wafer.
Some prior art approaches to providing optical communication for electronic devices involve mounting the electronic devices in a transparent substrate. Ultra-thin silicon-on-sapphire CMOS technology produces circuitry extremely well suited for optical communications functions on a transparent substrate. The silicon and sapphire process allows for flip chip bonding of optical electronic devices and to CMOS circuitry to build flipped optical chip and UTSi (FOCUTS) modules. Flip chip bonding eliminates the wire bond inductance between driving/receiving circuits and the OE devices which becomes problematic at data rates greater than 2.5 Gbps. The flip chip bonding also reduces the number of discrete chips that must be handled, packaged and aligned in the final module thereby reducing manufacturing costs. Because of the isolating substrate and the elimination of the substrate parasitic effects, the UTSI process produces high-performance CMOS circuitry requiring less power than bulk Si CMOS circuitry. In the current 0.5 micron UTSI process, modulation rates greater than 5 Gigahertz are achievable. UTSI with 0.25 micron features will be available allowing greater than 10 Gigahertz modulation. Additional byproducts of the UTSi are the availability of multi-threshold transistors in the EEPROM devices. Even with these enhancements, the standard semiconductor tools used for CMOS are also used for designing simulation fabrication packaging and testing UTSi. The fabrication process yield is comparable to bulk SI and the processed wafer cost is much less than competing high-performance technologies such as GaAs, BiCMOS and SiGe. The isolating substrate allows for mixed signal integration, as demonstrated in prior art wireless products.
Optical data communication products such as VCSELs are very cost effective due to wafer scale processing and testing and standard IC handling. Their optical properties also allow more tolerance on alignment thereby being preferable in less stringent packaging techniques. Similar cost reductions are offered by flip chip bonding OE devices to UTSi and packaging in a method compatible with electronic and fiber optic technologies.
The UTSi technology applied to optical transmitter/receiver modules allows a high degree of functional integration within the module. The non-conducting sapphire substrate of the UTSi provides a high degree of isolation between mixed signal circuits, enabling the integration of high-performance transmitters, receivers and other sensitive analog circuitry with digital circuitry. The fact that UTSi uses standard CMOS CAD tools allows easy importing of standard digital CMOS function block. Examples of key telecom blocks are digital modulation coding, your correction coding, routing, deskewing, equalization, ADC/DAC, multiplexing and demultiplexing circuitry. This integration ultimately reduces the cost and increases performance as compared to board level integration. Additionally, the UTSi process has the capability of multilevel threshold transistors and EEPROM devices. Multilevel transistors give the circuit designer added flexibility to increase performance and reduce power consumption.
EEPROM devices integrated with the drivers and logic circuitry reduces board level complexity and thereby provides another cost savings. EEPROM memory can be used for several functions including storage of trim values to equalize the drive bias on VCSEL devices across the parallel channels, hardware node address information for networking, network fault codes, error correction coefficients, initialization and training sequences for link startup.
The use of VCSELs to emit light through the UTSi substrate provides several advantages related to device packaging. Mating the fiber coupling assembly directly to the sapphire substrate creates a physically compact module. The transparent substrate enables alignment between marks on the UTSi and the fiber coupling assembly. Integration of an optical photodetector fabricated in the UTSi process for automated power control provides further advantages. The detector picks off a small percentage of the light to control the output optical power, an essential function i
Papageorge Chris
Rahll Jerry T.
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