Showing papers on "Optical switch published in 1996"

Micromechanical switch with insulated switch contact

Abstract: A micromechanical switch and a method of making the switch. The micromechanical switch of the invention is made by surface micromachining techniques and include an isolated contact located on the beam and separated from the main body of the beam by an insulated connector. The isolated contact provides the advantage that the current flow caused by the circuit being switched does not alter the fields or currents used to actuate the switch. Thus, the present invention allows the actuation functions to be unaffected by the signals that are being switched.

Scaling optoelectronic-VLSI circuits into the 21st century: a technology roadmap

Abstract: Technologies now exist for implementing dense surface-normal optical interconnections for silicon CMOS VLSI using hybrid integration techniques. The critical factors in determining the performance of the resulting photonic chip are the yield on the transceiver device arrays, the sensitivity and power dissipation of the receiver and transmitter circuits, and the total optical power budget available. The use of GaAs-AlGaAs multiple-quantum-well p-i-n diodes for on-chip detection and modulation is one effective means of implementing the optoelectronic transceivers. We discuss a potential roadmap for the scaling of this hybrid optoelectronic VLSI technology as CMOS linewidths shrink and the characteristics of the hybrid optoelectronic transceiver technology improve. An important general conclusion is that, unlike electrical interconnects, such dense optical interconnections directly to an electronic circuit will likely be able to scale in capacity to match the improved performance of future CMOS technology.

Bidirectional WDM optical communication systems with bidirectional optical amplifiers

Abstract: The present invention provides a bidirectional WDM optical communication system with bidirectional optical amplifiers for optically amplifying two counter-propagating WDM optical signals. The bidirectional system includes two sets of optical transmitters for respectively creating a set of west-east optical channels and a set of counter-propagating east-west optical channels. The respective channel sets are multiplexed by optical combiners and output to an optical transmission path. A bidirectional optical amplifier positioned in the optical transmission path amplifies the west-east and east-west WDM signals. In an exemplary embodiment, the amplifier includes at least two optical circulators with at least first, second, and third circulating ports. A gain block interconnects the circulators for optically amplifying the WDM signals. Bragg gratings configured to reflect either the west-east or the east-west channel band are positioned in optical paths which optically communicate with the optical circulators. The bidirectional WDM optical system further includes two receiving systems for demultiplexing the WDM signals and routing the individual optical channels to their respective receivers.

Soliton-based optical switching in waveguide arrays

Abstract: We analyze the propagation of discrete solitons in a periodic system of weakly coupled nonlinear optical waveguides, i.e., a waveguide array. Soliton reflection, transmission, and trapping, as well as coherent and incoherent interaction with a linear guided wave [which can exist owing to defect (inhomogeneous) coupling between two neighboring waveguides], are demonstrated numerically and investigated analytically with a collective-coordinate approach. Some potential schemes of controllable and steerable soliton-based optical switching in nonlinear waveguide arrays are discussed. For the first scheme it is suggested that unstable soliton modes be used to achieve easily steerable propagation of discrete bright and dark solitons. This is to avoid mode trapping by the effective Peierls –Nabarro potential, which always appears because of the system discreteness. The other scheme is based on soliton control with the help of a linear guided wave that can be excited in an inhomogeneous array.

Single-mode waveguide microcavity for fast optical switching.

Abstract: We investigate the properties of a tunable single-mode waveguide microcavity that is well suited for frequency modulation and switching. The cavity mode has a volume of less than one cubic half-wavelength, and the resonant frequency is tuned by refractive-index modulation. We suggest using a photorefractive effect to drive the device, based on the photoionization of deep donor levels known as DX centers in compound semiconductors. Picosecond on–off switching times are achievable when two of these cavities are placed in series. The resulting switch has the advantages of being compact and requiring as little as 10 pJ of energy of operate.

Integrated optic devices using micromachined metal membranes

Abstract: Metal membranes fabricated using a surface micromachining process can be integrated with passive optical waveguides on silicon substrates to form active devices. Electrostatic actuation of a membrane into contact with a waveguide alters both the real and imaginary parts of the propagation constant of the guided mode. This effect has been used to demonstrate both on-off and routing type integrated optic switches, and has potential application to other devices such as variable attenuators and tunable Bragg filters.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fiber loop optical buffer

Abstract: Fiber loop optical buffers enable data storage for discrete time intervals and therefore appear suitable for applications in optical asynchronous transfer mode (OATM)-based networks where data are transmitted in cells of fixed length. In this paper, the feasibility and the limitations of optical data storage in a fiber loop optical buffer are studied theoretically and experimentally, A model of a fiber loop buffer, incorporating semiconductor laser amplifiers (SLA) as switching gates, is described. The two major interfering quantities are cross talk and amplified spontaneous emission of the SLA gates. To limit the impact of cross talk on the signal quality, an on/off ratio of the SLA gates of at least 30 dB is required. The paper describes the optimum operation conditions, which enable data storage for more than 100 circulations even for data rates in the range from 10 to 160 Gb/s.

16-channel optical add/drop multiplexer consisting of arrayed-waveguide gratings and double-gate switches

Abstract: An optical add/drop multiplexer that enables full access to 16 individual wavelength channels has been fabricated on the planar lightwave circuit (PLC). The device consists of four arrayed-waveguide gratings which are connected through 16 double-gate thermo-optic switches. The crosstalk characteristics of the optical switches have been improved by adopting a double-gate configuration. The on-off crosstalks from main input or add port to main output or drop port are less than -28.4 dB and the on-chip insertion losses are 7.8-10.3 dB, respectively.

Optical switching with a nonlinear photonic crystal: a numerical study.

Abstract: A nonlinear finite-difference time-domain method was used to investigate optical switching mechanisms with a nonlinear photonic crystal and with two electromagnetic pulses with different frequencies. It was found that the mechanism based on the shifting of the band edge required the detector to discriminate between the pump and the probe frequencies, whereas that based on frequency mixing did not.

Advanced optical fiber communications network

Abstract: An advanced optical fiber communications network comprises a multimode optical fiber connection (one fiber or two) from a central office to an intelligent interface device in the subscriber's premises The central office includes at least a narrowband switch and a broadband switch The narrowband switch provides voice grade telephone service routing The broadband switch provides routing for video services and may comprise an ATM switch, an optical switch or the like The intelligent interface device provides a connection to the optical fiber and performs two-way wavelength division multiplexing and demultiplexing as well as any necessary signal format conversions The network has media access control functionality and utilizes a dynamic media access control procedure The optical fiber loop to the subscriber's premises has the capacity to carry at least three different wavelengths Bandwidth on the optical fiber loop is dynamically allocated to individual services on demand, and the allocation of bandwidth includes wavelength selection as well as bit rate allocation

Optical add-drop multiplexers for WDM optical communication systems

Abstract: The present invention provides an optical add-drop multiplexer for wavelength division multiplexed optical communication systems which includes first and second optical couplers which optically communicate with each other through an optical filter. The first optical coupler includes a first input port and first and second output ports while the second optical coupler includes first and second input ports and an output port An optical path optically communicates with the first output port of the first optical coupler and with the first input port of the second optical coupler and includes an optical filter for selecting portions of a wavelength division multiplexed optical signal input to the first optical coupler. The portions of the wavelength division multiplexed signal which are not sent to an input port of the second optical coupler exit the add-drop multiplexer. An optical path communicating with the second output port of the first optical coupler includes wavelength selectors configured to select one or more optical wavelengths from the wavelength division multiplexed optical signal. Optical channels to be added are sent the second input port of the second optical coupler and combined with the "through" portion of the WDM optical signal such that the output is a new wavelength division multiplexed optical signal output by the second optical coupler.

Optical path technologies: a comparison among different cross-connect architectures

Abstract: The introduction of optical technology in the path layer of the transport network is expected to allow scalable and modular networks to be realized. In this paper, different optical cross-connect architectures, based either on space division or wavelength division switching, are analyzed. A comparative investigation is accomplished considering three issues of primary importance: cross-connect modularity, complexity, and transmission performance. In particular, the transmission performance of a generic path through the network is evaluated by upgrading a previously published analytical model, so to more accurately take into account the in-band crosstalk arising in the cross-connect.

Active optical circuit sheet or active optical circuit board, active optical connector and optical MCM, process for fabricating optical waveguide, and devices obtained thereby

Abstract: An active optical circuit sheet or active optical circuit board wherein an electro optical switch or optical modulator is driven with a voltage (SIGin) from an electronic device, the electrical signal (SIGin) is converted to an optical signal, transmitted and then converted to an electrical signal (SIGout) at an optical receiver element, and an electrical connection is formed between an optical wiring board and the electronic device for transmission of signals to another or the same electronic device, separating the electrical wiring at the electronic device end and the optical wiring at the optical wiring board end, or alternatively, SIGin and SIGout electrode pads are provided on the side of the optical wiring board on which the optical device is mounted or on the opposite side, for connection with the electronic device

Optical switching and routing system

Abstract: The present invention provides a free space optical switching and routing system utilizing a switchable grating based approach together with novel noise suppression techniques. This family of devices provides for an optical switching and routing system that is useful for interconnecting any of an input array's optical channels to any of an output array's optical channels. The incorporation of free space switched grating based routing in the present invention has several distinct advantages including compactness, a reduction in insertion loss and the number of required switching devices and control signals, and improvements in switch isolation, noise and crosstalk suppression, spurious reflections, data skew, and compactness.

Lighting control subsystem for use in system architecture for automated building

Abstract: An electrical power control system is adapted for controlling power and lighting in a building. Switch controls have either relays or triacs, controlled by microprocessors, to switch power on electrical branch circuits. An interface device 122 communicates with the switches 124,126, arranged in a multidrop configuration, with variable length data packets over serial branch circuits or data buses 142. In addition to being controlled by the interface device 122, the switch controls also have local switch actuators. The actuation of the local switch controls can be used by the interface device 122 as a control inputs to initiate other actions. Adaptive polling of switch controls is used to minimize system response time, and both transmit and receive signals are carried between the switch controls and the interface device 122 at different times on the same twisted pair wires. The interface device 122 can also communicate with a home automation system controller.

Recent progress in silica-based planar lightwave circuits on silicon

Abstract: Low-loss integrated silica waveguides on silicon allow the efficient interaction of guided-wave optical signals and are used to form a variety of planar lightwave circuits for optical branching, switching and filtering. Silica waveguides can also be used as platforms (motherboards) for hybrid optoelectronic (OE) integration. The paper reviews recent progress on silica waveguide technologies which are currently penetrating the passive component market for optical networks and providing innovative ways of packaging OE components.

High speed, high capacity ATM optical switches for future telecommunication transport networks

Abstract: This paper describes the work carried out in the RACE Project R2039 ATMOS (asynchronous transfer mode optical switching). The project is briefly illustrated, together with its main goal: to develop and assess concepts and technology suitable for optical fast packet switching. The project's technical approach consisted in the exploitation of the space and wavelength domains for fast routing and buffering: The major achievements are then reported. Four different switch architecture concepts have been proposed, investigated and developed, all based on a high speed optical routing matrix electrically controlled at lower speed. The basic optical key components and subsystems (wavelength converters, space switches and optical buffers) are described in detail, with the outstanding results obtained and the corresponding projected performance. In particular, system demonstration of wavelength conversion at 10 and 20 Gb/s has been realized, to show the usefulness of the ATMOS technology both to implement optimized high performance optical packet-switching fabrics as well as transparent optical circuit-routing nodes. Four rack-mounted, reduced size demonstrators of basic switching matrices have been designed and implemented scalable to real system sizes. The obtained good results in terms of bit error rate and hardware integration are reported, showing that ATM switches are feasible with state of-the-art optical technology.

Comparison of Sagnac and Mach-Zehnder ultrafast all-optical interferometric switches based on a semiconductor resonant optical nonlinearity.

Abstract: We present a theoretical analysis of recently demonstrated ultrafast all-optical interferometric switching devices (based on Sagnac and Mach–Zehnder interferometers) that use a large optical nonlinearity in a resonant regime. These devices achieve ∼10-ps switching windows and do not require high-energy optical control pulses. We theoretically analyze and compare one Sagnac and two Mach–Zehnder switching configurations.

Evolution of the acousto-optic wavelength routing switch

Abstract: Through the efforts of many research groups and consortia over the last several years, the acousto-optic tunable filter has evolved into a device capable of high-performance wavelength-selective optical switching and wavelength routing in dense WDM systems. The distinguishing feature of the AO switch is its ability to sustain many independent coexisting passbands, thus allowing in a simple integrated-optic device, the parallel processing capability of much more complex designs. The AOTF has also found a role in active gain equalization of optically amplified networks. In this paper, we review the design of both hybrid and fully integrated AO switches. The theory of operation is reviewed and recent advances in passband engineering are described which have made low-crosstalk, wavelength misalignment-tolerant switches to be possible. Advanced issues such as mechanisms of interchannel crosstalk and its reduction are also discussed. Both device and system issues are covered.

A modular optical cross-connect architecture with optical wavelenght switching

Abstract: An optical cross-connect node architecture interfaces plural optical fiber input and output links, each link containing plural wavelength channels. In one embodiment, the input links are connected to a single optical coupler, or alternatively, to an associated one of plural optical couplers. Pairs of tunable optical filters and optical wavelength converters are each connected to an output port of the optical coupler, or to each of the plural optical couplers, and perform wavelength channel routing and switching in the wavelength domain, i.e., without the need for any optical space switch. In other embodiments, an additional input wavelength converter is connected to each input fiber link to convert the plural wavelength channels on each link to different, non-interferring wavelengths. This prevents wavelength contention in the optical coupler to which the input wavelength converters are connected. New fiber links may be added in modular fashion without significant impact on the pre-existing optical cross-connect structure. Similarly, new wavelength channels may also be multiplexed onto existing fibers to provide wavelength modularity without having to reconfigure the node.

Noninvasive optical method for measuring internal switching and other dynamic parameters of CMOS circuits

Abstract: Intrinsic, transient optical emission from a CMOS integrated circuit is used to determine the internal switching of such a circuit including the temporal evolution of its logic states. By joining an appropriate optical microscope to a suitable, photon counting, multichannel optical detector which is capable of time resolution better than 100 psec, and a spatial resolution of better than 60 microns, full temporal information, including the relative phases of switching events, can be obtained from many devices in a circuit simultaneously. The time and spatial resolution are suitable for analyzing timing problems in present and future sub-micron-scale CMOS integrated circuits with switching speeds up to at least 10 GHz. The invention comprises a combination of an optical microscope and a detector capable of providing optical waveforms and/or spatial images of the light emitted during electrical switching by the individual devices which comprise an integrated circuit. The microscope and detector are combined such that an image of all or a portion of an integrated circuit under test is provided by the microscope to the detector. The spatial and temporal information from the detector is used to determine switching times and other dynamic information about the devices in the circuit.

Fault detection for all-optical add-drop multiplexer

Abstract: A fault detecting apparatus and method for a network node of an optical transmission system receives a wavelength division multiplexed (WDM) optical signal which includes a group of optical channels. The network node includes an optical demultiplexer, optical switch, optical multiplexer, and an optical channel add/drop device. Supervisory optical signals having a different wavelength than the wavelengths of the group of optical channels are generated and spliced with each optical channel by the optical demultiplexer. The supervisory channel optical power is tapped off at various points in the network node, such as the output optical channels of the demultiplexer, dropped optical channel outputs, output optical channels from the optical switch, and the output WDM optical signal of the multiplexer. The supervisory channels are monitored by a wavemeter for bypass lightpaths and dropped lightpaths. Added optical channels are monitored by monitoring a portion of the signal power in the added lightpath of the added optical channel. If the wavemeter detects the absence of the supervisory signal, or the portion of the added optical channel, this indicates a fault condition and the network control is notified to effect correction of the fault.

Semiconductor optical space switches

Abstract: This paper reviews the various optical space switch structures on III-V semiconductor material. Their characteristics are discussed in the context of optical transport and switching network applications exploiting wavelength division multiplexing.

Soft power switching for hot installation and removal of circuit boards in a computer system

Abstract: A soft power switch for insertion and removal of a logic unit in a system during continuing operation of the system, including a current switch for each supply voltage to the logic unit that is to be protected, each current switch having a current input connected from a corresponding system power source and a current output connected to the logic unit. The switch includes a gate drive delay connected to each current switch that provides a gate signal controlling the flow of current through each current switch, and a connector having staggered connector pins for sequenced connection of power and control signals as the logic unit is inserted or withdrawn, the soft switch responding to the sequence of control and power signals by controllably and gradually increasing or decreasing the current through the current switches as the logic unit is inserted or withdrawn.

Two-port optical wavelength circuits composed of cascaded Mach-Zehnder interferometers with point-symmetrical configurations

Abstract: Wavelength circuit characteristics are investigated systematically for a family of two-port optical wavelength circuits composed of cascaded Mach-Zehnder interferometers (MZIs) with point-symmetrical configurations. A novel design method is presented for flattening their cross-port passbands (through-port stopbands). The design principle is based on a consideration of the general relations between wavelength circuit characteristics and circuit configuration symmetries. It is shown that the role of this novel design method is complementary to that of the conventional flattening method which is used for simple wavelength-insensitive couplers (WINCs) with a single-stage MZI configuration. Various optical wavelength circuits are designed by using both the novel and conventional design principles, including fixed and tunable WINCs, a wavelength-insensitive switch (WINS), and a wavelength multi/demultiplexer with a flattened passband and stopband. Measurement results are provided for some of the designed optical circuits which were fabricated using silica-on-silicon planar lightwave circuits (PLCs).

Spatial mode filters realized with multimode interference couplers.

Abstract: Spatial mode filters based on multimode interference couplers (MMI's) that offer the possibility of splitting off antisymmetric from symmetric modes are presented, and realizations of these filters in InGaAsP/InP are demonstrated. Measured suppression of the antisymmetric first-order modes at the output for the symmetric mode is better than 18 dB. Such MMI's are useful for monolithically integrating mode filters with all-optical devices, which are controlled through an antisymmetric first-order mode. The filtering out of optical control signals is necessary for cascading all-optical devices. Another application is the improvement of on-off ratios in optical switches.

Using an asymmetric element to create a 1XN optical switch

Abstract: An architecture for a compact, 1×N optical switch. The switch package receives light from an input optical fiber (12b), which is directed over a well or gap at the bottom of which lies a micromechanical structure (10). If the structure is in an unaddressed state, the light travels into an in line output optical fiber (12a). If the structure (10) is in an addressed state, it intercepts the light and reflects it out of the plane of the input optical fiber to an offset mirror (24). The offset mirror (24) then reflects the light to one output fiber (16a, 16b). The offset mirror may have steps such that more than one optical fiber could become the output fiber, depending upon the structure's position.

Optical communication system

Abstract: A discontinuous ring is formed by separate bidirectional optical communication links, with possibly different transmission speeds, synchronous or asynchronous transmission, and ratios of working to protection channels, each linking a pair of terminals in different nodes of a communication system. To protect protection-switched traffic on a communication link from a link failure, it is routed around the ring via the protection channel of the other communication links. To this end, an optical switch is provided between the protection channel of each link and the associated terminals in each node, and is controlled differently in nodes adjacent the link failure and in nodes not adjacent the link failure to route the protection-switched traffic accordingly. Rapid protection switching is facilitated by controlling the optical switches using wavelength detectors directionally coupled to the protection channel at each node.

WDM optical communication system with remodulators and diverse optical transmitters

Abstract: A WDM optical communication system is described which is capable of placing information from incoming information-bearing optical signals onto N optical signal channels for conveyance over an optical waveguide. The optical system includes a first set of one or more optical transmitters, each of which emits an information-bearing optical signal at one or more transmission wavelengths, λ Ti . At least M optical receiving systems are provided, each receiving system configured to receive an information-bearing optical signal at a particular reception wavelength λ j , where M is a whole number greater than or equal to N and j is from 1 to M. Each receiving system includes at least one Bragg grating member for selecting the particular reception wavelength λ j . An optical waveguide optically communicates with each of the M receiving systems for transmitting a plurality of optical signals. A plurality of optical remodulators is further included for communicating with the first set of optical transmitters and the optical waveguide. Each optical remodulator is configured to receive an information-bearing optical signal at a transmission wavelength λ Ti and output an information-bearing optical signal at a reception wavelength λ j . A second set of one or more optical transmitters is also provided, each of which emitting a

Wavelength selective optical devices

Abstract: Wavelength selective devices and subsystems having various applications in the field of optical communications are disclosed. These devices and subsystems are composed of bidirectional grating assisted mode couplers (9). The high add/drop efficiency and low loss of this coupler enable low loss wavelength selective elements such as optical switches (62), amplifiers (63), routers (5), and sources to be fabricated. The grating assisted mode coupler (23) can be wavelength tuned by modifying the optical properties of the coupler interaction region. A programmable, wavelength selective router (5) composed of multiple grating assisted mode couplers is also disclosed.