Abstract: A technique for communicating a change in bit rates that dependent transponders should each transfer. In one implementation, an upstream transponder outputs a specific frequency communications signal to a downstream transponders. The downstream transponder reacts to receipt of the specific bit rate by requesting new bit rate window information. The upstream transponder communicates such new bit rate window. Thereafter both the upstream and downstream transponders transfer payloads of signals having bit rates within the programmed bit rate windows.

Abstract: A technique to identify a response cell in a ranging grant procedure is disclosed herein. The format of the response cell reduces the probability of erroneous response cell detection. The response cell is a conventional ATM cell whose payload includes multiple cell delineation bytes (CDBs).

Abstract: The present invention includes a system that determines a threshold to distinguish between binary signals. The system includes a bit wise threshold determination device coupled to receive an input signal and that delays the input signal, averages the input signal and the delayed input signal, and outputs the average to an output node. The average represents a threshold value. This system can be used in any system that must determine a threshold between binary values.

Abstract: An optical add/drop filter for wavelength division multiplexed systems and construction methods are disclosed. The add/drop filter includes a first ferrule having a first pre-formed opening for receiving a first optical fiber; an interference filter oriented to pass a first set of wavelengths along the first optical fiber and reflect a second set of wavelengths; and, a second ferrule having a second pre-formed opening for receiving the second optical fiber, and the reflected second set of wavelengths.

Abstract: A compact multiwavelength transmitter module for multimode fiber optic ribbon cable, which couples light from an M×N array of emitters onto N fibers, where the M wavelength may be distributed across two or more vertical-cavity surface-emitting laser (VCSEL) chips, and combining emitters and multiplexer into a compact package that is compatible with placement on a printed circuit board. A key feature is bringing together two emitter arrays fabricated on different substrates—each array designed for a different wavelength—into close physical proximity. Another key feature is to compactly and efficiently combine the light from two or more clusters of optical emitters, each in a different wavelength band, into a fiber ribbon.

Abstract: As the performance of individual elements within parallel processing systems increases, increased communication capability between distributed processor and memory elements is required. There is great interest in using fiber optics to improve interconnect communication beyond that attainable using electronic technology. Several groups have considered WDM, star-coupled optical interconnects. The invention uses a fiber optic transceiver to provide low latency, high bandwidth channels for such interconnects using a robust multimode fiber technology. Instruction-level simulation is used to quantify the bandwidth, latency, and concurrency required for such interconnects to scale to 256 nodes, each operating at 1 GFLOPS performance. Performance scales have been shown to ≈100 GFLOPS for scientific application kernels using a small number of wavelengths (8 to 32), only one wavelength received per node, and achievable optoelectronic bandwidth and latency.

Abstract: A highly heat conductive layer is combined with or placed in the vicinity of the optical waveguide region of active semiconductor components. The thermally conductive layer enhances the conduction of heat away from the active region, which is where the heat is generated in active semiconductor components. This layer is placed so close to the optical region that it must also function as a waveguide and causes the active region to be nearly the same temperature as the ambient or heat sink. However, the semiconductor material itself should be as temperature insensitive as possible and therefore the invention combines a highly thermally conductive dielectric layer with improved semiconductor materials to achieve an overall package that offers improved thermal performance. The highly thermally conductive layer serves two basic functions. First, it provides a lower index material than the semiconductor device so that certain kinds of optical waveguides may be formed, e.g., a ridge waveguide.

Abstract: Micromachining of bulk silicon utilizing the parallel etching characteristics of bulk silicon and integrating the parallel etch planes of silicon with silicon wafer bonding and impurity doping, enables the fabrication of on-chip optics with in situ aligned etched grooves for optical fibers, micro-lenses, photodiodes, and laser diodes. Other optical components that can be microfabricated and integrated include semi-transparent beam splitters, micro-optical scanners, pinholes, optical gratings, micro-optical filters, etc. Micromachining of bulk silicon utilizing the parallel etching characteristics thereof can be utilized to develop miniaturization of bio-instrumentation such as wavelength monitoring by fluorescence spectrometers, and other miniaturized optical systems such as Fabry-Perot interferometry for filtering of wavelengths, tunable cavity lasers, micro-holography modules, and wavelength splitters for optical communication systems.

Abstract: An optical method for separating and routing local and express channel data comprises interconnecting the nodes in a network with fiber optic cables. A single fiber optic cable carries both express channel traffic and local channel traffic, e.g., in a massively parallel processor (MPP) network. Express channel traffic is placed on, or filtered from, the fiber optic cable at a light frequency or a color different from that of the local channel traffic. The express channel traffic is thus placed on a light carrier that skips over the local intermediate nodes one-by-one by reflecting off of selective mirrors placed at each local node. The local-channel-traffic light carriers pass through the selective mirrors and are not reflected. A single fiber optic cable can thus be threaded throughout a three-dimensional matrix of nodes with the x,y,z directions of propagation encoded by the color of the respective light carriers for both local and express channel traffic.

Abstract: A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed.

Abstract: The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division-multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required.

Abstract: A low-noise optical amplifier solves crosstalk problems in optical amplifiers by using an optical cavity oriented off-axis (e.g. perpendicular) to the direction of a signal amplified by the gain medium of the optical amplifier. Several devices are used to suppress parasitic lasing of these types of structures. The parasitic lasing causes the gain of these structures to be practically unusable. The lasing cavity is operated above threshold and the gain of the laser is clamped to overcome the losses of the cavity. Any increase in pumping causes the lasing power to increase. The clamping action of the gain greatly reduces crosstalk due to gain saturation for the amplified signal beam. It also reduces other nonlinearities associated with the gain medium such as four-wave mixing induced crosstalk. This clamping action can occur for a bandwidth defined by the speed of the laser cavity. The lasing field also reduces the response time of the gain medium.

Abstract: A polarization diversity receiver comprising a lower optical waveguide and an upper waveguide formed thereover in the area of the receiver. A rib formed in the lower waveguide away from the receiver directs light along an optical axis in the receiver. A metal layer deposited over the upper waveguide preferentially couples light of the TE-mode from the lower to the upper waveguide, where it is detected by a p--i--n photo-diode. A second p--i--n photo-diode is formed on the optical axis a distance away from the first photo-diode. The intervening region acts as a coupling region to couple the remaining TM-mode radiation from the lower to the upper waveguide, where it is detected by the second photo-diode.

Abstract: An impedance-matched semiconductor detector formed on a portion of a waveguide. The waveguiding layer of the waveguide has one refractive index and the light absorbing layer of the detector has another refractive index. An impedance matching layer is formed between the waveguiding layer and the light absorbing layer and has a refractive index intermediate between those of the waveguiding layer and the light absorbing layer.

Abstract: An integrated waveguide/detector optical device is fabricated on a semiconductor substrate whose surface includes a step region. Guiding and absorbing layers are grown on the surface in sequence overlying the step region. This is done in a single epitaxial growth cycle. The absorbing layer is patterned to form a non-planar detector that overlies the guiding layer in the step region. Due to bending of the guiding layer in the step region, a strong coupling exists between the overlying detector and light propagating in the guiding layer. Easily fabricated integrated devices having short-length (high-speed) photodetectors are thereby made feasible.

Abstract: A low loss optical waveguide modulator, an essential component of opto-electronic integrated circuits which can combine optical and electronic devices on a single chip optical communication systems is described. The modulator in our embodiment consists of a sequence of epitaxial layers on a single crystal substrate consisting of a n.sup.+ -GaAs substrate, a n.sup.+ -GaAs buffer layer, a n-Al.sub.0.05 Ga.sub.0.95 As electrode layer, an effective i-Al.sub.0.25 Ga.sub.0.75 As confinement layer, an i-GaAs guiding layer, an effective i-Al.sub.0.25 Ga.sub.0.75 As confinement layer, a p-Al.sub.0.25 Ga.sub.0.75 As electrode layer and a p.sup.+ -GaAs cap layer. The layers have an index of refraction profile such that the index of refraction of the confinement layers are substantially less than the index of refraction of the guiding layer and the index of refraction of the first electrode layer is substantially greater than the index of refraction of the first confinement layer.

Abstract: A far field optical scanning system comprising a coherent light source, a waveguide array phase retardation means and a far field optical detector is characterized by a waveguide array having a linearly increasing spacing between adjacent parallel array elements so as to minimize the production of unwanted sidelobes.