Showing papers on "Optical switch published in 1988"

Nonlinear-optical loop mirror

Abstract: A nonlinear device for ultrafast processing is proposed. This device is based on the nonlinear propagation in a waveguide loop formed by connecting the output ports of a conventional coupler. The device is shown to have potentially useful characteristics for unequal coupling ratios and has the ability to operate on entire pulses when soliton effects are included.

Semiconductor laser optical amplifiers for use in future fiber systems

Abstract: The application of semiconductor laser amplifiers to long-wavelength optical fiber systems is discussed. The basic equations defining laser amplifier characteristics are presented together with experimental results. Linear and nonlinear modes of operation are considered; the former includes use as an optical gain block, a linear repeater, and a preamplifier, while the latter includes use as a bistable element, an electrically controlled optical switch, and an injection-locked amplifier. >

Silica-based single-mode waveguides on silicon and their application to guided-wave optical interferometers

Abstract: Low-loss silica-based single-mode waveguides and directional couplers are fabricated on silicon substrates. Their application to Mach-Zehnder interferometer type guided-wave devices is demonstrated. Optical switches or tunable optical couplers are fabricated using the thermooptic effect. Asymmetrical Mach-Zehnder interferometers are successfully applied to multi/demultiplexers for optical FDM transmission systems. >

Optical time-division multiplexing for very high bit-rate transmission

Abstract: Optical time-division multiplexing (OTDM) extends and expands the well-known techniques of electrical time-division multiplexing into the optical domain. In OTDM, optical data streams are constructed by time-multiplexing a number of lower-bit-rate optical streams. Opportunities for very high-speed transmission and switching are created by removing limitations set by the restricted bandwidth of electronics and by capitalizing on the inherent high-speed characteristics of optical devices. An overview of recent work in optical time-division multiplexing and demultiplexing is presented. Design considerations affecting system architecture are described. Emphasis on the factors that limit system performance, such as crosstalk between multiplexed channels. Examples of very high bit-rate optical time-division multiplexed system experiments using short pulses from mode-locked semiconductor lasers and high-speed Ti:LiNbO/sub 3/ waveguide switch/modulators are presented. >

Symmetric self‐electro‐optic effect device: Optical set‐reset latch

Abstract: We demonstrate an integrated symmetric self‐electro‐optic effect device consisting of two quantum well p‐i‐n diodes electrically connected in series. The device acts as a bistable optical memory element with individual set (S) and reset (R) inputs and complementary outputs (optical S‐R latch). The switching point is determined by the ratio of the two inputs, making the device insensitive to optical power supply fluctuations when both power beams are derived from the same source. The device also shows time‐sequential gain, in that the state can be set using low‐power beams and read out with subsequent high‐power beams. The device showed bistability for voltages greater than 3 V, incident optical switching energy densities of ∼16 fJ/μm2, and was tested to a switching time of 40 ns.

Double heterostructure optoelectronic switch as a dynamic memory with low-power consumption

Abstract: A pnn double heterostructure optoelectronic switch with dual extractor electrodes was dynamically operated as an optical memory with the resulting achievement of 20 μW holding power. This value represents a reduction in holding power of about three orders of magnitude as compared to that of conventional light‐emitting optical bistable devices. Complete operation, involving optical writing, regeneration, and high‐speed erasing of written data through a dual extractor‐electrodes configuration, was carried out with a simple driving scheme.

Crossover networks and their optical implementation

Abstract: Crossover networks are introduced as a new type of interconnection network for applications in optical computing, optical switching, and signal processing. Crossover networks belong to the class of multistage interconnection network. Two variations are presented, the half-crossover network and the full crossover network. An optical system which implements both networks is proposed and demonstrated. Crossover networks can be implemented using the full space-bandwidth product of the optical system with minimal loss of light. It is shown that crossover networks are isomorphic to other multistage networks such as the Banyan and perfect shuffle.

Optical implementation of the Hopfield model for two-dimensional associative memory

Abstract: Optical implementation of Hopfield's neural network model [Proc. Natl. Acad. Sci. USA 79, 2554 (1982)] for two-dimensional associative memory is discussed. Two-state neuron elements are represented by a twisted nematic liquid-crystal optical switch array, and three-dimensional holographic interconnections are realized with these elements. Unipolar connections, created by adding a constant to bipolar interconnections and compensating them with an input-dependent thresholding operation, are realized. The 16- (4 x 4) neuron system model acts as a content-addressable associative memory with error-correction capability.

A wavelength routing approach to optical communications networks

Abstract: A class of wavelength-routing optical networks is described on the basis of the interconnection of wavelength multiplexed channels. Unlike previously described optical network structures, these networks allow the reuse of wavelengths in different transmission sections and this leads to fewer wavelengths being needed. A choice of structures using a common set of components leads to the opportunity to design a network according to the geographical distribution of the switching nodes. The structures provide for a set of point-to-point interconnections and, with modest numbers of wavelengths, full interconnection between the optoelectronic nodes is possible at the optical level. In bypassing intermediate electronic stages the networks appear to offer good reliability characteristics. Providing the components in an initial network are designed to utilize bandwidth efficiently, the networks could be upgraded to incorporate more channels, optical switching, and other forms of optical processing at the optical nodes. >

Liquid crystal light valve showing an improved display contrast

Abstract: An optically-addressed liquid crystal light valve comprises a transparent insulating substrate having either one-dimensional or two-dimensional arrays of optical switching elements thereon which can perform switching with an incident light, another opposing transparent substrate having transparent electrodes and a liquid crystal sandwiched therebetween. Each of the light switching elements comprises a photo-detector circuit and a thin-film-transistor (TFT) drive circuit. The photo-detector circuit comprises a serially connected photodiode and a passive element such as capacitor or resistor. The TFT drive circuit receives as input the voltage produced from the photo-detector circuit, while the output voltage from the TFT drive circuit is applied to one pixel electrode for the liquid crystal.

Semiconductor circuit with low power consumption having emitter-coupled logic or differential amplifier

Abstract: An ECL circuit wherein a current switch and an emitter follower are coupled, is so constructed that, in a standby mode, the current switch has its current cut off or rendered smaller than in an operating mode In addition, the ECL circuit comprises means for decoupling a load resistance of the current switch and a base of the emitter follower in the case of cutting off the current of the current switch, or means for increasing the load resistance of the current switch in the case of rendering the current of the current switch smaller The semiconductor circuit of the present invention can reduce the power consumption of the ECL circuit and can suppress fluctuations in the voltage levels of the outputs of the ECL circuit

HYPASS: an optoelectronic hybrid packet switching system

Abstract: An architecture is presented for an optoelectronic hybrid packet switching system (HYPASS) for the distribution of multiple-bit-rate broadband services. HYPASS is based on an input-buffered/output-controlled arbitration protocol. The internal routing and interconnection utilizes a passive optical transport network with wavelength-tunable laser transmitters and fixed wavelength receivers. The single-stage multiwavelength optical interconnect provides an internally nonblocking network for large throughput routing of the bit-serial optical signals. An internal optical control network, with fixed-wavelength trouble receivers, sends output port information to the input nodes for arbitration and control. Packet buffer storage and control processing is performed by word-parallel electronic circuitry. The characteristics and device requirements for this design are presented along with results of a performance analysis of the arbitration and control protocol. >

Multi-gigabit-per-second silicon bipolar ICs for future optical-fiber transmission systems

Abstract: Basic silicon bipolar ICs for use in systems operations at bit rates of about 2.5 Gb/s are described. Examples are multiplexers, demultiplexers, amplifiers, decision circuits, etc. It is shown that the speed requirements can be met (for nearly all circuits) by today's standard technologies, provided that appropriate circuit concepts are used and the circuits are designed carefully. Applying today's advanced bipolar technologies with self-aligning polysilicon processes, bit rates well above 10 Gb/s are achievable in several cases. >

Ultrafast all-optical switching utilizing the optical Kerr effect in polarization-maintaining single-mode fibers

Abstract: An ultrafast all-optical switching scheme utilizing the optical Kerr effect in two birefringent fibers concatenated with each fast axis crossed is proposed Stable optical Kerr modulation and all-optical demultiplexing of an ultrashort (30 ps) optical pulse train at 197 GHz from a gain-switched distributed-feedback laser diode (DFB LD) have been sufficiently demonstrated using CW mode-locking Nd:YAG laser pulses as a pump Switching speed and required pump powers are studied in terms of fiber bandwidth due to fiber birefringence, and combined effects of chromatic and polarization dispersions on Kerr modulation profiles By utilizing the optical Kerr modulation properties in the presence of dispersions, the nondiagonal yx component of the nonlinear refractive index is also determined to be 034 relative to the diagonal component xx The intrinsic stability and ultimate switching capabilities are discussed >

Femtosecond optical pulse amplification

Abstract: A number of techniques have been developed for amplification of optical pulses of approximately 100-fs duration. These amplifiers span a wide range of operating parameters from kilowatt to gigawatt peak powers and from 10 Hz to megahertz repetition rates. Amplification of femtosecond pulses has also been demonstrated at several wavelengths including visible, near-infrared, and ultraviolet regions. Several problems arise when amplifying short optical pulses to very high intensities. The problems are discussed and the state of the art of femtosecond optical pulse amplification is reviewed. >

A photonic knockout switch for high-speed packet networks

Abstract: A high-performance packet switch is discussed which uses a photonic interconnect fabric to route very-wideband data packets from input to output. Packet contention is accomplished using a much slower electronic controller, based on the knockout principle operating in parallel with the optical interconnect. Specifically, the use of a wavelength-division-multiplex fabric whereby high-speed (2-4 Gb/s) packets are regenerated before modulating a single-frequency laser at each switch input. The optical signals from various inputs are summed in a star coupler and then broadcast to the different coupler outputs. Each coupler is equipped with a small number (L) of tunable receivers arranged in a parallel manner, each preceded by a power splitter so that up to L simultaneous packets can be received by each output. The L packets so received are stored in an L-input one-output first-in first-out (FIFO) buffer so that the FIFO packet sequence is always guaranteed. Not only does this architecture achieve the best delay-throughput performance, but, remarkably, modularity is such that the optical complexity grows linearly with the number of switch ports./. >

An Optically Controlled Closing and Opening Semiconductor Switch

Abstract: A concept for a bulk semiconductor switch is presented, where the conductivity is increased and reduced, respectively, through illumination with light of different wavelengths. The increase in conductivity is accomplished by electron ionization from deep centers and generation of bound holes. The reduction of conductivity is obtained by hole ionization from the excited centers and subsequent recombination of free electrons and holes. The transient behavior of electron and hole density in a high power semiconductor (GaAs:Cu) switch is computed by means of a rate equation model. Changes in conductivity by five orders of magnitude can be obtained.

Waveguide electrooptic switch arrays

Abstract: A review is presented of electrooptic waveguide switch arrays with strong emphasis on those based on titanium-diffused lithium niobate waveguides. Crosspoint and array design considerations and performance are discussed as are waveguide technology limits. Switch array demonstrations are reviewed. Experimental demonstrations of switch arrays are described and particular parameters of the array, including insertion loss, crosstalk, and switching voltage achieved by several laboratories, are discussed and compared. Results of high-speed switch arrays are also described. >

Tunable optical-wavelength conversion using an optically-triggerable multielectrode distributed feedback laser diode

Abstract: Tunable optical-wavelength conversion with tunability greater than 5 AA using a multielectrode distributed-feedback laser diode (DFB LD) with a saturable absorber is discussed. This device is not dependent on input polarization and can operate at up to 500 MHz. Preliminary results of an optical switching experiment using the tunable wavelength converter and optical narrowband filter with a DFB LD amplifier are also reported. >

Picosecond all‐optical switching in single‐mode GaAs/AlGaAs strip‐loaded nonlinear directional couplers

Abstract: Room‐temperature all‐optical switching has been achieved in single‐mode strip‐loaded nonlinear directional couplers with a GaAs/AlGaAs multiple quantum well guiding layer. For low input intensities nearly complete (1:3–1:5) cross coupling occurs, while at high input intensities switching occurs so that most (>3:1) of the light stays in the input guide. The effects of carrier diffusion are minimized by the use of picosecond pulses. The response time and the recovery time of the nonlinear directional couplers are measured with pump‐probe experiments, and the origin of the nonlinearity is attributed to fast electronic effects.

Hybrid optical and electronic packet switch

Abstract: A switch for receiving packets on optical fiber input trunks and for switching the packets to appropriate optical fiber output trunks is disclosed. The packet switch is a hybrid switch comprising both optical and electronic devices and specifically comprises and electronic input buffer, an optical transport network and an optical control network. The optical transport network prevents internal collisions within the switch and the optical control network prevents external collisions of packets. The packet switch exploits the inherent properties of optical and electronic devices for the specific functions they are best suited for.

Fiber-Optic Crossbar Switch With Broadcast Capability

Abstract: An all-optical fiber-optic crossbar switch capable of interconnecting N input fibers to M output fibers with an arbitrary interconnect pattern has been constructed. The switch can use any 1-D or 2-D spatial light modulator capable of realizing N X M pixels and can be configured for permutations, full or partial broadcast, or "wired-oring" of several inputs to a given output. Values of N and M achievable depend on the light efficiency of the switch components and the data rate. A 4X4 switch has been built; in a computer switching environment, the approach is capable of realizing a 16 X16 switch at 1 Gb/s and a 32 X32 switch at >100 Mb/s. The development of the switch has included construction of both a PLZT switch array and a magneto-optic switch array. We report on the investigations of both technologies. Reconfiguration times in the range of a few microseconds to a few tens of microseconds are of interest. A reconfiguration time shorter than 20 ps was actually achieved.

Optical distribution of transmitter signals and antenna returns in a phased array radar system

Abstract: The invention relates to the distribution of radio frequency signals using optical fibers between a centrally located radar transmitter/receiver and remotely located transmit/receive modules associated with the elements of an active phased array. The invention avoids the need for remotely located lasers, by using the optical carrier generated at the central location for both transmission, when it is modulated by the transmitter and supplied to each T/R module over an optical path; and for reception, when it is supplied to each T/R module unmodulated. An optical switch and an optical modulator in the T/R module permit the antenna return to be converted to an optical format for supply over a second optical path to the central receiver. The arrangement may be further simplified by selecting a simple optical device to perform both the optical switching and optical modulation function in each T/R module.

Fiber optic switch

Abstract: Two fixed input optical fibers may be aligned with two movable output optical fibers. The two output fibers are moved by exchanging the positions so that either output fiber may be optically aligned with either input fiber. In another optical switch either one of two movable fibers may be optically aligned with either one of two fixed fibers by rotating the movable member. In yet another optical switch a movable fiber may be aligned with one of a number of fixed optical fibers by rotating the movable member using a stepping motor. The angular positions of the fixed fibers are such that the input fiber is optically aligned with any one of the fibers by rotating the input fiber by a number of steps of the stepping motor.

Semiconductor laser device

Abstract: PURPOSE:To prevent the variation of output frequency based on frequency modulation by controlling the temperature of a semiconductor laser at a fixed value while stopping or weakening a vibration signal which is minutely vibrating laser driving currents only for a preset period CONSTITUTION:The temperature of a laser diode 11 for a semiconductor laser device is stabilized by a temperature controller 31, and output beams 35, frequency of which is stabilized by stabilizing the temperature, is inputted to a spectroscope 32 A pump optical output and a probe optical output are inputted to photodiodes 16, 17 from the spectroscope 32 A variation component except the variation of oscillation frequency from the laser diode 11 is removed by a divider 15, and inputted to a drive circuit 34 Output beams 35 passing through an optical switch 48 by a half mirror 35a are synchronized with an output from a modulation control circuit 46 stopping or weakening a vibration signal fed to the circuit 34 from a signal source 38 only for a desired period and pass, thus acquiring wavelength stabilizing output beams

Photonic switching modules designed with laser-diode amplifiers

Abstract: Photonic switching elements are designed from semiconductor optical amplifiers and passive couplers with fiber-to-fiber unity gain and low crosstalk. Designs for a 2*2 and an asymmetric 2*3 element, and several designs for 4*4 elements, are presented. While most amplifier analyses have stressed the importance of ultralow facet reflectivities for high-gain operation, with protection against external reflections with optical isolators, modest facet reflectivities are satisfactory for these elements. It is also shown that substantial amounts of external reflection can be tolerated. The various architectures are compared according to amplifier count, blocking characteristic, broadcast potential, noise power (amplified spontaneous emission), and fault tolerance. >

Optical switch matrix

Abstract: An optical switch matrix for selecting an optical propagation route between input ports and output ports by electric control. A first directional coupler is disposed on the input port side of a crosspoint of the matrix. A second directional coupler is disposed on the output port side of the crosspoint. A corner reflector is formed at a joint of the first and second directional coupler.

Modulation-instability-based fiber interferometer switch near 1.5 microm.

Abstract: We demonstrate a modulation-instability-based fiber interferometer switch, an ultrafast all-optical fiber switch operating near 1.5-microm wavelength with more than 40dB of small-signal gain. Switching is accomplished.by seeding the modulation instability in one arm of a Mach-Zehnder interferometer, thus destroying its balance. Computer simulations, which include the effects of Raman self-frequency shifts, suggest that as much as 74% of the power input to the interferometer can be transferred to its (initially nulled) output arm when cw pumps are used. Even with an 80% loss at the output analyzer, we have gated 184 mW of power from a color-center laser using only 4.4 microW from a semiconductor laser.

Nonblocking photonic switch networks

Abstract: A practical algorithm is described, with examples, for deciding whether or not a given network of 2*2 photonic switches is truly unblocking. Nonblocking photonic networks with specific additional properties, e.g. planarity, short path length, are also discussed, and specific networks, which have advantages over the square networks so far fabricated, are described. It is also shown that a correspondence can be set up between classical switch networks and networks of 2*2 switches, so that the classical results on blocking can be carried over to these networks. >

Optical switch having birefringent element

Abstract: An electrically controlled optical switch employs an electro-optical crystal of the kind exhibiting birefringence in each of two different light paths when the crystal is disposed in orthogonally oriented electric fields, with each light path being sensitive to a different one of the two electric fields and each path having its own set of fast and slow axes. A crystal of bismuth germanium oxide has those properties. Electrodes are provided for separately establishing each of the two electric fields and control circuitry allows only one field at a time to be established. Polarizers are situated at opposite ends of the electro-optical crystal in alignment with each of the two paths. Adjacent one end of the crystal are disposed a beam splitter and a right angle prism. The prism is arranged to receive some of the light entering the beam splitter and reflect that light along one of the paths of the crystal while another portion of the entering light proceeds through the beam splitter into the other path of the crystal. The polarizers block the light in one path while enabling light to emerge from the other path.