Showing papers on "Optical switch published in 1992"

Fiber-Optic Communication Systems

Abstract: Preface. 1 Introduction. 1.1 Historical Perspective. 1.2 Basic Concepts. 1.3 Optical Communication Systems. 1.4 Lightwave System Components. Problems. References. 2 Optical Fibers. 2.1 Geometrical-Optics Description. 2.2 Wave Propagation. 2.3 Dispersion in Single-Mode Fibers. 2.4 Dispersion-Induced Limitations. 2.5 Fiber Losses. 2.6 Nonlinear Optical Effects. 2.7 Fiber Design and Fabrication. Problems. References. 3 Optical Transmitters. 3.1 Semiconductor Laser Physics. 3.2 Single-Mode Semiconductor Lasers. 3.3 Laser Characteristics. 3.4 Optical Signal Generation. 3.5 Light-Emitting Diodes. 3.6 Transmitter Design. Problems. References. 4 Optical Receivers. 4.1 Basic Concepts. 4.2 Common Photodetectors. 4.3 Receiver Design. 4.4 Receiver Noise. 4.5 Coherent Detection. 4.6 Receiver Sensitivity. 4.7 Sensitivity Degradation. 4.8 Receiver Performance. Problems. References. 5 Lightwave Systems. 5.1 System Architectures. 5.2 Design Guidelines. 5.3 Long-Haul Systems. 5.4 Sources of Power Penalty. 5.5 Forward Error Correction. 5.6 Computer-Aided Design. Problems. References. 6 Multichannel Systems. 6.1 WDM Lightwave Systems. 6.2 WDM Components. 6.3 System Performance Issues. 6.4 Time-Division Multiplexing. 6.5 Subcarrier Multiplexing. 6.6 Code-Division Multiplexing. Problems. References. 7 Loss Management. 7.1 Compensation of Fiber Losses. 7.2 Erbium-Doped Fiber Amplifiers. 7.3 Raman Amplifiers. 7.4 Optical Signal-To-Noise Ratio. 7.5 Electrical Signal-To-Noise Ratio. 7.6 Receiver Sensitivity and Q Factor. 7.7 Role of Dispersive and Nonlinear Effects. 7.8 Periodically Amplified Lightwave Systems. Problems. References. 8 Dispersion Management. 8.1 Dispersion Problem and Its Solution. 8.2 Dispersion-Compensating Fibers. 8.3 Fiber Bragg Gratings. 8.4 Dispersion-Equalizing Filters. 8.5 Optical Phase Conjugation. 8.6 Channels at High Bit Rates. 8.7 Electronic Dispersion Compensation. Problems. References. 9 Control of Nonlinear Effects. 9.1 Impact of Fiber Nonlinearity. 9.2 Solitons in Optical Fibers. 9.3 Dispersion-Managed Solitons. 9.4 Pseudo-linear Lightwave Systems. 9.5 Control of Intrachannel Nonlinear Effects. Problems. References. 10 Advanced Lightwave Systems. 10.1 Advanced Modulation Formats. 10.2 Demodulation Schemes. 10.3 Shot Noise and Bit-Error Rate. 10.4 Sensitivity Degradation Mechanisms. 10.5 Impact of Nonlinear Effects. 10.6 Recent Progress. 10.7 Ultimate Channel Capacity. Problems. References. 11 Optical Signal Processing. 11.1 Nonlinear Techniques and Devices. 11.2 All-Optical Flip-Flops. 11.3 Wavelength Converters. 11.4 Ultrafast Optical Switching. 11.5 Optical Regenerators. Problems. References. A System of Units. B Acronyms. C General Formula for Pulse Broadening. D Software Package.

Optical Signal Processing

Abstract: : We studied optical processing techniques to detect and track frequency hopped radio signals in a dense electromagnetic environment by using cross-spectrum of two signals obtained from antenna elements spaced by one-half an RF wavelength. We decimate the array by retaining only every Mth element and scan the cross-spectrum past the decimated array. We therefore reduce the circuit complexity, but suffer some loss in system performance because we require more photodetector bandwidth to accommodate the scanning action. An extension of the decimated array concept is to decimate the reference waveform in the heterodyne spectrum analyzer. In this case, we generate only 64 optical probes in the Fourier domain instead of the 2048 that are normally required. The advantage is that all of the optical power in the reference beam can be concentrated into the reduced number of optical probes, thereby offsetting some of the intrinsic loss in performance experienced by the cross-spectrum analyzer. (JHD)

Microelectronic module having optical and electrical interconnects

Abstract: A multichip module having high density optical and electrical interconnections between integrated circuit chips includes a substrate overlaying an array of integrated circuit chips. An optical transmitter generates a first optical beam through the substrate and an optical detector receives a second optical beam through the substrate. A hologram is positioned in the path of at least one of the first and second optical beams. An array of electrical contact pads is located on the substrate corresponding to the array of electrical contact pads on the respective integrated circuit chips. A pattern of electrical interconnection lines is located on the substrate for electrically interconnecting the integrated circuit chips. A solder bump between electrical contact pads on the substrate and on the integrated circuit chips establish electrical connections between the substrate and the integrated circuit chips, and also facilitate alignment of the integrated circuit chips with respect to the substrate. The optical transmitter and detector may be mounted on/in the substrate or on/in the integrated circuit chips. The optical transmitter and detector may also be used to provide optical connections external to the microelectronic module, using a holographic substrate to optically link modules. The substrate may also be used to establish optical alignment of the hologram to an underlying optical emitter and/or optical detector without establishing electrical connections thereto.

Method and system for routing cells in an ATM switch

Abstract: A method and a system for routing cells in an ATM switch. The switch which is input buffered, employs a multiplicity of crosspoint switch planes operating simultaneously in parallel, and whose outputs are combined by an output-buffered second stage. A traffic controlling or path assignment switching stage disposed before the crosspoint switch planes improves performance in the presence of correlated traffic. The switching stage may either control the traffic randomly or adaptively. Input concentration and output expansion functions within the switch are also disclosed. The use of an "unfair" or a predictable preference contention resolution device (CRD) in each of the crosspoint switch planes is possible in another embodiment of the invention. Advantages of the method and system include linear growth with large N in the size and complexity of both the switching circuits and the contention resolution circuits. Switch performance tends to gracefully degrade with failures in switch planes and contention resolution devices. Dense, low-cost memory with simple FIFO addressing schemes can be used to realize both the input and output buffered stages.

High performance optical wavelength shifter

Abstract: A broadband (>50 nm) wavelength shifter capable of switching multigigabit data between optical frequencies in the 1.5 μm region is presented. The device, based on gain saturation in a semiconductor optical amplifier, is tunable, has gain, and is nearly polarisation insensitive. Data degradation after wavelength shifting is negligible.

Monolithically integrated 4×4 InGaAsP/InP laser amplifier gate switch arrays

Abstract: Monolithically integrated 4×4 semiconductor laser amplifier gate switch arrays comprising 24 integrated laser amplifiers have been fabricated and evaluated. Net positive optical gain between fibres, high extinction ratio, and low crosstalk are reported.

Nonlinear Sagnac interferometer switch and its applications

Abstract: Ultrafast all-optical switching based on the optical Kerr effect in a Sagnac interferometer which consists of a dichroic polarization-maintaining fiber coupler and dispersion-shifted polarization-maintaining fiber loop is reported. This nonlinear Sagnac interferometer switch has the advantage of high stability originating from completely balanced interfering arms. In addition, because dispersion-shifted fibers were used, increases in switching power and switching time were prevented. Moreover, polarization fluctuation was completely suppressed due to the all-polarization maintaining fiber configuration. The required switching power for complete switching was measured to be 1.8 W for a 200-m-long fiber. All-optical time division demultiplexing and logic operations, including inversion and operation, using the nonlinear Sagnac interferometer switch were successfully demonstrated at 5 Gb/s. >

Method and apparatus for low power optical sensing and decoding of data

Abstract: A portable optical data reader for optically sensing and decoding data, comprising a carrier oscillator (110) for producing a carrier signal at a predetermined frequency, an optical emitter (120) electrically connected to the carrier oscillator for emitting optical radiation in an optical path to an optical data carrier at the predetermined frequency, an optical detector (140) for detect-ing the emitted optical radiation returning from the optical data carrier thereby receiving the optical data and producing a detect-ed electrical signal responsive thereto, and a double balanced demodulator (150) electrically connected to the optical detector and the carrier oscillator for combining the detected radiation signal with the carrier signal to demodulate the optical data with the optical data carrier. A method of sensing and decoding optical data comprising the steps of oscillating a carrier signal, transmit-ting the carrier signal to an optical emitter, thereby illuminating the optical emitter adjacent optical data, reflectively sensing the illumination from the optical emitter, thereby receiving the optical data, and demodulating the optical data by use of the oscillat-ing carrier signal.

Passive protected self healing ring network

Abstract: A self healing, passive protected ring network and a method of operation are disclosed. The ring network includes a plurality of active nodes interconnected by optical fibers into a working ring. The ring network also includes a passive optical fiber protection ring which interfaces with the working ring through a small number of optical switches located at each node. In the event of a failure in the optical fibers or nodes of the working ring, the optical switches are set to interconnect the protection ring to the nodes on either side of the failure and to bypass all other nodes. It is a particular advantage of the present invention that the protection ring may be installed without modifying or adding to the active electronic equipment at each node and remains unchanged when the working ring's equipment is upgraded to a higher line transmission rate.

Multiple wavelength division multiplexing signal compensation system and method using same

Abstract: A method and system for multiple WDM signal compensation compensates optical chromatic dispersion for a plurality of optical signals having predetermined frequencies and each traveling in an optical path associated with the wavelength division multiplexer that forms a multiplex optical signal from the plurality of optical signals. The invention first undercompensates the multiplex optical signal by a predetermined amount so that each of the optical signals has an associated residual optical chromatic dispersion. Then, either before or after undercompensating of the multiplexed optical signal each of the optical signals is individually compensated to remove therefrom the residual chromatic dispersion. The system and method permit simultaneous and independent control of optical dispersion at any desired wavelength, as well as selection of matching compensation for optical transmitters prior to installation. The result is an increase in the usable wavelength range of optical signals for WDM networks.

Analysis of an electron‐wave Y‐branch switch

Abstract: An electron‐wave Y‐branch switch, analogous to the integrated optics Y‐branch or digital switch, is proposed and analyzed using the beam propagation method. It is shown that this switch allows considerably wider electron velocity spectra than interferometric devices, such as the directional coupler. Furthermore, the Y‐branch switch does not require single‐mode electron waveguides.

NxN Optical crossbar switch matrix

Abstract: An optical crossbar switch matrix for use in switching optical signals from a first set of optical fibers to a second set of optical fibers, in any order, which is characterized by having a matrix of rows and columns of diffraction gratings formed in a semiconductor heterostructure. Each grating is independently biased with either a forward or reverse bias voltage to switch the grating between a reflective state and a transmissive state. The gratings are oriented at an angle relative to the rows and columns so that when the Bragg condition for the light received from an optical film is met, a portion of the light is diffracted from the row in which it is propagating into a column toward another optical fiber. The heterostructure may include optical amplifiers to restore the optical signal to its original power level. Beam expanding, collimating and focussing optics may also be integrated into the heterostructure.

Index-and-dimensional taper and its application to photonic devices

Abstract: A mode-field-converting optical channel waveguide with tapered refractive index and cross-sectional dimensions is proposed. In this waveguide, both the refractive index and cross-sectional dimensions of a core are adiabatically varied along a propagation direction in such a way that the normalized frequency V of the waveguide may be kept constant. Since radiation loss caused by waveguide imperfections is strongly dependent on the V value, the waveguide has good mode-field-converting capability without causing high radiation loss. Layer thickness and index of a core of a silica waveguide were tapered by modulating a raw material gas flow in a flame hydrolysis deposition method, and a channel width taper was formed by a photolithographical technique. In order to confirm the usefulness, taper waveguides have been used (1) to achieve good field matching between a fiber and a guided-wave optical switch, and (2) to fabricate a fiber-compatible monolithic 32*32 star coupler in a small chip. >

Experimental investigation of a free-space optical switching network by using symmetric self-electro-optic-effect devices

Abstract: A prototype digital free-space photonic switching fabric is demonstrated. It consists of three cascaded 16 x 8 arrays of symmetric self-electro-optic-effect devices that are used as logic gates that implement part of a multistage interconnection network. We discuss architecture, device tolerancing, optical system design, and optomechanical design. This optical circuit is successfully configured as a fully operational array of 32 independent 2 x 2 nodes and operates at 100 kHz.

All-optical regenerator based on nonlinear fibre Sagnac interferometer

Abstract: For the first time, all-optical regeneration using a nonlinear fibre Sagnac interferometer switch (NSIS) and pump-probe walk-off is demonstrated. In the NSIS, all-optical regeneration including timing and amplitude restoration is performed by switching clock pulses with amplified input signals. Timing restoration is evaluated by performing error-rate measurements at 5 Gbit/s. >

Ultrafast photonic ATM switch with optical output buffers

Abstract: An ultrafast photonic asynchronous transfer mode (ATM) (ULPHA) switch based on a time-division broadcast-and-select network with optical output buffers is presented. The ULPHA switch has an ultra-high throughput and excellent traffic characteristics, since it utilizes ultrashort optical pulses for cell signals and avoids cell contentions by novel optical output buffers. Feasibility studies show that an 80*80 ULPHA switch with 1-Gb/s input/output is possible by applying the present technology, and that more than 1 Tb/s is possible by making a three-stage network using such switches. As an experimental demonstration, 4-bit 40-Gb/s optical cells were generated and certain cells were selected at an output on a self-routing basis. With its high throughput and excellent traffic considerations, the ULPHA switch is a strong candidate for a future large-capacity optical switching node. >

Space division switches based on semiconductor optical amplifiers

Abstract: Multiple space-division switches based on semiconductor optical amplifiers (SOAs) can be cascaded to obtain larger switching fabrics. The authors present a general analysis of optical switching fabrics using SOAs, considering noise and saturation effects associated with amplified spontaneous emission. They find that the SOA saturation output power limits the number of switches which can be cascaded. For example, a saturation output power of 100 mW limits the size of switching fabrics to 100 64*64 switches or 200 8*8 switches if distributed gain matrix-vector multiplier (MVM) switches or Benes switches are employed. The corresponding limit for lumped gain MVM fabrics is 10 64*64 or 100 8*8. The Benes switch may be more suitable for large switch size (N>16) because it requires fewer SOAs. >

Ultrafast intrinsic optical switching in a dense medium of two-level atoms

Abstract: We performed a numerical investigation of the dynamics of the Bloch equations, extended for dense media (media having many atoms within a cubic resonance wavelength), for optical pulses whose duration is much less than an induced-dipole dephasing time. We find a signature of near dipole-dipole interaction which may provide a useful method for validating the first-principles model, for measuring the strength of the interaction, and for coherent pumping. Further, we demonstrate a new and unique optical switching mechanism which may lead to the development of important devices

Microdynamical fiber-optic switch and method of switching using same

Abstract: A microdynamical optical switch includes a piezoelectric actuator disposed on a substrate, a mirror securely mechanically coupled to the actuator, an input connection port, and a plurality of output connection ports. The actuator displaces the mirror along a mirror displacement path such that the mirror, which is oriented at a 45° angle to the path of the incident light, deflects light passing from the input connection port into an output connection port. The actuator includes a plurality of piezoelectric bars mechanically coupled together in series in a meander line geometry such that the cumulative deflection of the piezoelectric bars is used to displace the mirror. The amount of displacement of the actuator is governed by a controllable voltage source, which applies a voltage across each of the piezoelectric bars. In one embodiment the microdynamical switch has a 1×n arrangement, in which light entering through one input connection port is selectively directed to one of n output connection ports. In an alternative embodiment, the switch has a 2×2 arrangement in which light beams entering through two ports are individually selectively directed to one of two respective outlet ports.

Control unit for occupancy sensor switching of high efficiency lighting

Abstract: A control unit for switching AC powered high efficiency lighting in response to a signal from an occupancy sensor. The lighting is switched by a hybrid mechanical relay/semiconductor switch. The semiconductor switch is connected in parallel with the relay switch contacts to protect them and is controlled by a noise-insensitive zero voltage crossing detector circuit which switches the semiconductor switch only at the zero crossings of the AC power. The semiconductor switch is preferably turned on by a pulse forming circuit only for a brief period of time spanning the time when the relay is switching.

Apparatus and method for large scale ATM switching

Abstract: Apparatus and method for large scale asynchronous transfer mode (ATM) switching utilizing tunable lasers and fixed-tuned receivers are provided. The apparatus, an optical switch, includes a plurality of input modules for receiving ATM cells to be switched and a plurality of output modules for outputting the switched ATM cells. The optical switch also includes an optical transmission network for optically transmitting each ATM cell from an input module to a particular output module, and a contention resolution device in electrical communication with the plurality of input modules for selecting the ATM cells from the plurality of input modules to be switched. Preferably, each output module includes a plurality of fixed-tuned receivers and each input module includes a plurality of tunable lasers. The fixed-tuned receivers of each output module are tuned to a particular wavelength so as to pass only those ATM cells optically received from the optical transmission network at the particular wavelength. The tunable lasers are tunable to a plurality of distinct wavelengths for optically transmitting the ATM cell to the optical transmission network at the particular distinct wavelength associated with the output module to which the ATM cell is destined.

Ultrafast polarisation-independent all-optical switching using a polarisation diversity scheme in the nonlinear optical loop mirror

Abstract: Polarisation-independent 32 to 8 Gbit/s demultiplexing in the nonlinear optical loop mirror is successfully demonstrated using a novel polarisation diversity scheme in which two independent switching operations are performed along the two principal axes of a polarisation-maintaining fibre loop. The variation of the switched signal powers is measured to be less than 1 dB as the input polarisation direction is varied over 180°.

Electro-optical switch with 4 port modules with electro-optic polarization rotators

Abstract: A family of optical switches employ dielectric film polarizing beam splitters and switchable electro-optic retarder to produce 2×2 optical switches which exhibit low crosstalk characteristics while switching unpolarized or linearly polarized collimated light The switches all contain four port modules through which light enters and leaves the switch The port modules utilize polarizing beam splitters to separate incoming light into two orthogonal linearly polarized components The component beams are made parallel after which each passes through an electro-optic retarder The retarders are electrically driven so as to selectively change the polarization of either one of the two component beams, thus making the polarizations the same Other polarizing beam splitters are disposed to direct the component beams along one of two pairs of paths as determined by their common polarization The pairs of paths associated with each of the port modules are positioned and aligned in two sets of pairs, and the electro-optic retarders of the four port modules are jointly controlled electrically so that light entering the switches through any one port can be switched to selectively leave through either of two of the remaining ports The two ports not thus connected as the foregoing pair are themselves connected so that light may pass between them

Optical switching in twin-core erbium-doped fibers.

Abstract: We report the theoretical and experimental investigation of switching in a nonlinear twin-core erbium-doped fiber coupler. It is shown that switching action takes place at a power of a fraction of 1 mW. Thus it provides a practical means of fabricating an all-optical fiber switch.

Programmable optical crossbar switch

Abstract: This is crossbar switch 56 which comprises : X rows by Y columns of modular optical switches 60 each comprising X or more channel inputs and X or more channel outputs where X is greater than one ; and each of columns 1 to Y-1 of the modular optical switches 60 having 1/Xth of the channel outputs optically connected to 1/Xth of the channel inputs of each of the modular optical switches 60 in a next column. Other methods and devices are disclosed.

Integrated-optic waveguide devices and method

Abstract: It is possible to utilize changes in the complex effective refractive index caused by bringing a metal membrane in close proximity to the core of an optical waveguide to form many devices. The invention described herein provides structures and processes that do so, the structure comprising a substrate, a lower cladding, a waveguide core, a removable upper cladding which supports a metal membrane, and an electrode for deflecting said membrane. Switchable devices using this structure include, but are not limited to, polarizers, mode converters, optical switches, Bragg devices, directional couplers and channel waveguides.

Switch circuit for setting and signaling a voltage level

Abstract: A switch circuit is disclosed which both sets the voltage at an output terminal and signals that the voltage has been set The switch circuit may be implemented with a single-pole single-throw switch A voltage drop device, connected in parallel with the switch, is used to generate the output voltage levels The switch circuit is also suitable for enabling and disabling the heartbeat signal generated by a local area network transceiver and for signaling whether the heartbeat signal has been enabled by lighting a light-emitting diode

Ultrafast all-optical switching in GaAlAs integrated interferometer in 1.55 mu m spectral region

Abstract: The first observation is reported of ultrafast all-optical switching in an integrated asymmetric Mach-Zehnder inter-ferometer, using the nonresonant nonlinearity in Ga0.82Al0.18As below half the bandgap. A relative switching fraction of more than 80% has been achieved using 330 fs pulses at around 1.55 μm from a coupled-cavity mode-locked colour centre laser.

Switch inversion and polarization sensitivity of the nonlinear-optical loop mirror

Abstract: The switching characteristic of a nonlinear-optical loop mirror can be inverted by a birefringent bias element. The device reflectance is insensitive to polarization in the linear regime for arbitrary birefringence in the loop. Under certain conditions, birefringence leads to polarization sensitivity in the nonlinear regime, which is likely to be contributing to instabilities that have been observed recently in mode-locked fiber lasers.