Optical Switch

The peer-to-peer technology offers many advantages, but at the same time, it poses many novel challenges for the research community. Modern peer-to-peer systems are characterized by large scale, poor reliability, and extreme dynamism of the participating nodes, with a continuous flow of nodes joining and leaving the systems. Selection of an optimal network requires estimation of its rank using attributes such as storage, average load, cost, reliability etc. There are multiple networks, each vying for users business by providing them novel services. The user in turn has to decide which network best meets its service requirements and accordingly join a network.

A free-space contra-propagation configuration is implemented and pump-probe studies are undertaken in order to study polarization-dependent gain dynamics in bulk semiconductor optical amplifiers (SOAs) and their application to gain and polarization switching. The polarization dependence of the gain compression shows that the co-polarized case, in which the pump and probe are TE-polarized, is the optimum for gain switching. When injecting

Optical switch is widely used in the optical ®bre communication networks. This paper described an advanced microelectromechanical systems (MEMS) optical switch that consists of actuator, suspension beam, micromirror, and ®ber grooves using deep RIE (DRIE) etching fabrication process. Based on the speci®cation and design requirements of optical switch, the DRIE etching fabrication process is combined with the anisotropic and isotropic, the two different types of etching methods that improve the surface roughness of the micro mirror. Net structure with arcs is introduced to obtain a good release and microloading effect is used and prevented trickily. As a result, promising performances of the optical switch such as low driving voltage of 30 V, low insertion loss, fast switching speed of less than 100 ms and high reliable operation of more than 20 million cycles are achieved. The actuator of the optical switch enables to the delivery of a moving displacement which is as large as 45 mm. This MEMS optical switch has a broad applications for ®bre optical communication systems such as n  n optical crossconnects (OXCs), variable optical attenuator (VOA), etc. #

We present simulation results for 192 Gb/s (16 ×12) OTDM transmission with different time delays over standard fiber G.652. The optical 192 Gb/s to 12 Gb/s demultiplexing (OTDM) is used and the results compared with 160 Gb/s to 10 Gb/s OTDM demultiplexing. The observations show the feasibility of an error free 192 Gb/s OTDM transmission with a minimum time delay of 1 ps which yields BER as low as 3.38E-89 while the minimum BER obtained at 1 ps time delay for 160 Gb/s OTDM is 1.21E-244, which is practically error free.

The switching or isomerization speed of photochromic dyes in a rigid polymeric matrix (i.e. an ophthalmic lens) is generally significantly slower than that observed in the mobile environment of a solution. Here we describe that the attachment of flexible, low Tg oligomers such as poly(dimethylsiloxane) to photochromic dyes greatly increases their switching speeds in a rigid polymer matrix. Greatest impact was observed in the thermal fade parameters T 1/2 and T 3/4 which were reduced by 40-95% and 60-99% respectively for spirooxazines, chromenes and an azo dye in a host polymer with a glass transition temperature of 120 ºC. The method does not alter the electronic nature of the dyes but simply protects them from the host matrix and provides greater molecular mobility for the switching process The generic nature of the method may find further utility in the anticipated applications of data recording or optical switching.

Antimony glasses based on the composition Sb 2 O 3-SbPO 4 were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n 2 , of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response ͑Ͻ100 fs͒ for all compositions. Enhancement of n 2 was observed by adding lead oxide to the Sb 2 O 3-SbPO 4 composition. Large values of n 2 Ϸ 10 −14 cm 2 / W and negligible two-photon absorption coefficients (smaller than 0.01 cm/ GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.

This paper characterizes the gain and the carrier density responses of a semiconductor optical amplifier (SOA). In order to achieve the switching functions in SOA-based optical switches, such as Symmetric Mach-Zehnder (SMZ), the effect of the input signal on the total gain response of the SOA is investigated. The theoretical operation principle is demonstrated using a segmentation model that employs the complete rate equation with third order gain coefficients. Results obtained show the input boundaries and requirements in which the SOA can be efficiently used as an amplifier and as a switch.

This paper studies the overall energy consumption of a pan-European optical transport network for three different time periods: today and in five and ten years from now. In each time period the pan-European network was dimensioned using traffic predictions based on realistic data generated by the optical networking roadmap developed in the framework of the European project Building the Future Optical Network in Europe-BONE. A wavelength routed wavelength division multiplexed optical network based on either ...

Optical burst switching (OBS) is the most promising optical switching technology for the future Internet, but it suffers from security vulnerabilities. In this paper, we propose to embed a security framework which incorporates the strengths of classical and the emerging quantum cryptography techniques in the native OBS network architecture, providing a means to make the future Internet secure from the ground up. The proposed embedded security architecture allows the best suited classical and quantum cryptography techniques to be deployed, making it possible to offer robust security. The security of quantum cryptography is based on the inherent randomness in quantum phenomena. The application of quantum techniques to optical networks is ideally suited to the problem because photons, which carry information in optical modality, are quantum objects. Since the well-known BB84 quantum cryptography protocol is susceptible to siphoning attacks on the multiple photons emitted by practical sources, we propose to use a new 3-stage quantum cryptography protocol which is immune to siphoning attacks, as it is based on random rotations of the polarization vector. This would allow multiple photons to be used in the quantum key exchange, and make it feasible to extend quantum cryptography services beyond trusted routers.

A smart-pixel array is a two-dimensional array of optoelectronic devices that combine optical inputs and outputs with electronic processing circuitry. A field-programmable smart-pixel array ͑FP-SPA͒ is a smart-pixel array capable of having its electronic functionality dynamically programmed in the field. Such devices could be used in a diverse range of applications, including optical switching, optical digital signal processing, and optical image processing. We describe the design, VLSI implementation, and applications of a first-generation FP-SPA implemented with the 0.8-m complementary metal-oxide semiconductor-self-electro-optic effect device technology made available through the Lucent Technologies-Advanced Research Projects Agency Cooperative ͑Lucent͞ARPA͞ COOP͒ program. We report SPICE simulations and experimental results of two sample applications: In the first application, we configure this FP-SPA as an array of free-space optical binary switches that can be used in optical multistage networks. In the second, we configure the device as an optoelectronic transceiver for a dynamically reconfigurable free-space intelligent optical backplane called the hyperplane. We also describe the testing setup and the electrical and the optical tests that demonstrate the correct functionality of the fabricated device. Such devices have the potential to reduce significantly the need for custom design and fabrication of application-specific optoelectronic devices in the same manner that field-programmable gate arrays have largely eliminated the need for custom design and fabrication of application-specific gate arrays, except in the most demanding applications.

Power trends in communication networks are analyzed using a transaction-based model. Traffic models are developed for North America and used to evaluate the relative power trends of wireline networks and mobile networks through 2020. An ideal case for aggressive network-efficiency improvement measures is evaluated within this framework and shown to lead to roughly unchanged consumption over the next decade. Implications for future technology requirements are discussed.

S. Benton published a definitive taxonomy of the first one hundred and seventy years of 3D displays covering the field up to the year 2000. In this article we review how display technologies have advanced in the last ten years and update Benton's taxonomy to include the latest additions. Our aim is to produce a display taxonomy suitable for content producers highlighting which displays have common requirements for image delivery. We also analyze key technical characteristics of 3D displays and use these characteristics to suggest the future applications for each category of display.

Absrract-The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks. This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design. The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required.

A highly efficient monolithically integrated Mach-Zehnder interferometer (MZI) optical switch based on a 1.5m InGaAs-AlGaInAs multiple-quantum-well structure is reported. The device was fabricated by integrating phase shifter sections with bandgap-shifted low-loss waveguides obtained by a single step sputtered SiO 2 -annealing quantum-well intermixing technique. Evaluation of the refractive index change induced by current injection (plasma, band-filling, band-shrinkage effects) and applied electric field (quantum confined Stark effect) based on the MZI was investigated. A device with an active length of 400 m in one of the MZI arms had an extinction ratio 20 dB with a half-wavelength current ( ) and half-wavelength voltage as low as 3.2 mA and 3.5 V (1.9 V in push-pull configuration), respectively.

| Reconfigurable antennas, with the ability to radiate more than one pattern at different frequencies and polarizations, are necessary in modern telecommunication systems. The requirements for increased functionality (e.g., direction finding, beam steering, radar, control, and command) within a confined volume place a greater burden on today's transmitting and receiving systems. Reconfigurable antennas are a solution to this problem. This paper discusses the different reconfigurable components that can be used in an antenna to modify its structure and function. These reconfiguration techniques are either based on the integration of radio-frequency microelectromechanical systems (RF-MEMS), PIN diodes, varactors, photoconductive elements, or on the physical alteration of the antenna radiating structure, or on the use of smart materials such as ferrites and liquid crystals. Various activation mechanisms that can be used in each different reconfigurable implementation to achieve optimum performance are presented and discussed. Several examples of reconfigurable antennas for both terrestrial and space applications are highlighted, such as cognitive radio, multiple-input-multipleoutput (MIMO) systems, and satellite communication.

The strong coupling of light and excitons in a two-dimensional semiconductor microcavity results in a new eigenstate of quasiparticles called polaritons. Microcavity polaritons have generated much interest due to the wealth of interesting optical phenomena recently observed in these systems such as nonlinear emission, macroscopic coherence, and bosonic stimulated scattering. The efficiency of amplification, parametric oscillation, and coherent emission of

Abstract. We show that Friedel oscillations of the electron density exist in junctions between quasi-one-dimensional and two-dimensional systems. The backscattering of electrons by the Friedel oscillations can qualitatively explain a number of transport features observed in recent experiments.

After resuming the basic facts about Bose–Einstein condensation of weakly interacting systems, we review the main experimental and theoretical works aimed at the realization of this intriguing phenomenon in the system of microcavity polaritons. All the experimental results until present suggest that Bose–Einstein condensation is still eluding the experimentalists' efforts. On the theoretical side, only recently polaritons have been described within a quantum field theory of an interacting Bose gas, suggesting that polariton condensation might occur at least as a consequence of polariton parametric scattering under resonant excitation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

95 List of publications 99 Curriculum Vitae 101 IX X Switching in optical communication 1 Chapter 1 Switching in optical communication " Light brings us the news of the Universe" Sir William Bragg 1.1 Introduction Glass fibers are known from the time of Roman civilization. The history of modern fiber optics communication, however, starts with two Nature papers [1], one by the Dutch scientist Abraham van Heel and the other by Harold Hopkins and Narinder Kapani. In these two papers, optical fiber contains a transparent layer of low refractive index that confines the light and protects the surface of the fiber from contamination. These two properties make the fiber capable for transmitting optical signals with low loss. After the invention of semiconductor lasers, the optical communication field progressed rapidly. In 1961, Bernard et.al [2] predicted laser emission from direct inter-band transitions in InAs like semiconductors. In 1962, Hall et.al observed coherent light emission from a GaAs p-n junction. In 1963 Alferov patented his historic invention of semiconductor heterojunction lasers. He first observed lasing in an AlGaAs-GaAs double heterostructure [3]. In 1970 Kapron [4] demonstrated the first glass optical fiber for the low-loss (20 dB/km) transmission of signals in the 1.5 µm wavelength region. In 1986 Kanamori

This is to certify that I have examined this copy of a doctoral thesis by Alex A. Volinsky and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examination committee have been made.

All-optical networking can be the sole approach to provide the huge bandwidth required for future networks. The essential elements in such an optical network are optical switches. A number of options have been proposed in order to implement them efficiently. We focus on thermooptical switches. First, the physical principles of the thermo-optic effect are briefly introduced. A description of the most common technologies used for the fabrication of thermo-optic switches is provided along with the values of thermo-optic coefficient for a number of materials. The main steps useful in order to design thermo-optical switches are also briefly introduced. Finally, a bird's-eye view of the main and recent proposals of switches based on the thermo-optic effect is reported and their performances compared. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

The interconnect plays a key role in both the cost and performance of large-scale HPC systems. The cost of future high-bandwidth electronic interconnects is expected to increase due to expensive optical transceivers needed between switches. We describe a potentially cheaper and more power-efficient approach to building high-performance interconnects.

Leveraging MEMS's inherent advantages such as batch fabrication technique, small size, integratability, and scalability, MEMS is positioned to become the dominant technology in optical crossconnect switches. MEMS optical switches with complex movable 3D mechanical structures, micro-actuators, and micro-optics can be monolithically integrated on the same substrate by using the matured fabrication process of the integrated circuit industry. In this article we report various popular actuating mechanisms and switch architectures of MEMS optical switches. The basics of surface and bulk micromachining techniques used to fabricate MEMS devices will be reviewed. Examples of 2D and 3D approaches to MEMS optical switches will be described. The pros and cons of the two approaches will be analyzed. In the short term, MEMS-based optical switches seem to have captivated t h e a t t e n t i o n of b o t h t h e industry a n d academia. However, there are challenges that threaten the long-term survival of this technology. The problems that remain to be fully addressed will be discussed. 158 0163-6804/01/$10.00 0 2001 IEEE

Conventional digital circuits lose energy because the bits of information are destroyed during the operation. Reversible circuits are currently on the top approaches to power minimization with its application in all-optical-based systems. Fredkin gate is a very common reversible logic gate. In this paper, a modification of the Fredkin gate is proposed. All-optical circuit of this modified Fredkin gate (MFG) is also designed using semiconductor optical amplifier on the Mach-Zehnder interferometer switch. A 16-Boolean logical operational circuit is also shown using this MFG. The main advantage of this scheme is that we can design a 15-Boolean logical function using a single MFG unit. Only one operation (nand) required two MFG units. Hence, complexity of the circuit can be reduced. Also, multivalued T-gate circuit using MFG is proposed.

A theoretical investigation based on DFT predictions on 1,2-dithienylperfluorocyclopentene derivatives is presented. Molecules of this class have been demonstrated to show efficient thermally irreversible photochromism for developing optical switches. In particular, by doping a glassy polymer matrix with 1,2-dithienylperfluorocyclopentene derivatives, an optical element with a light induced modulation of the refractive index can be obtained.

We have theoretically analyzed all-optical switching in Pt:ethynyl complex based on nonlinear excited-state absorption. A detailed analysis for Pt:ethynyl complex has been presented based on rate equation approach. It is shown that a pulsed pump laser beam at 355 nm switches the transmission of a cw probe laser beam at 633 nm through a Pt:ethynyl sample. The effect of various parameters, such as pump pulse width, peak pumping intensity, normalized parameter bðs T 1 P NLÞ, transition times of S 1 -S 0 and S 1 -T 1 states and lifetime of triplet state, on switching characteristics has been analyzed in detail. It has been shown that the probe beam can be completely switched off (i.e. 100% modulation) by a pulsed pump laser beam at 50 kW/cm 2 . These results have been used to design all-optical NOT and the universal NOR and NAND logic gates with multiple pump laser pulses.

The extinction ratio (defined as the difference in the optical power between 0-dB fiber-to-fiber loss and the off state level) is enhanced with the introduction of an S-bend waveguide structure using asymmetric twin waveguide techniques for a spot-size converter integrated semiconductor optical amplifier (SSC-SOA) with a polarization-insensitive offset superlattice. Angled waveguides are introduced in order to obtain low facet reflectivity without the need for antireflection coating. A curved waveguide is introduced to connect the angled and straight waveguide, minimizing their coupling loss while achieving a lateral spatial mode filter. The SSC-SOA, operating at 1.62-m wavelength, achieves an extinction ratio up to 70 dB and a fiber-to-fiber gain of 10 dB using cleaved, flat end single-mode optical fibers.

We demonstrate an electrically-controlled liquid crystal
(LC) core waveguide, using 4-cyano-4
-pentylbiphenyl (5CB)
nematic liquid crystal, fabricated on a glass substrate. A negative
photoresist, AZ15nXT layer was coated on the glass substrate to
realize a channel waveguide of core thickness 4.8 μm. The LC
core waveguide exhibits strong differential attenuation for propagation
of the TE- (horizontal) and TM-like (vertical) polarizations
of light. The experimental results show that the output power suddenly
drops down by several dB at an applied voltage of 1 V, for
a waveguide of length 10 mm, due to the re-orientation of the LC
molecules. The waveguide can be used as an optical switch, as well
as an optical attenuator.


This paper reviews the basic of multimode interference (MMI) coupler and its application in optics, especially for optical switching. We have demonstrated the design & performance of 2 x 2 MMI coupler based all optical switch of lesser dimensions than conventional structures. This structure is based on special multimode region shape, which leads switch to have less coupling loss & lesser cross talk. The variations of the refractive indices of various sections to achieve switching actions are kept in the range of 1-2%.

We present the observation of an all-optical switching effect that takes place when a light beam of suitable wavelength irradiates a "layered" structure made of polymer slices alternated to films of well aligned liquid crystal ͑LC͒ which contain also a small percentage of azo-LC molecules. The simple and reliable fabrication procedure exploits a holographic UV curing technique. The observed switching effect takes place in samples that exhibit diffraction efficiency as high as 85% and is induced in less than 0.5 s by an unfocused pump beam of 245 mW/ cm 2 power density.

Absrract-The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks. This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design. The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required.

Optical switching behavior of low-molecular-weight and polymer azobenzene liquid crystals (LCs) was explored by means of reflection-mode analysis. Reflectivity changed on pulse irradiation under various conditions of orientations of LC molecules with respect to incident probe light, either s-polarization or p-polarization. For the low-molecular-weight LCs, we obtained a response time of 100 µs, which was very similar to that observed in the transmission-mode analysis, while we observed a decay time of 1 ms, which was significantly shorter than that observed in the transmission-mode analysis. The fast decay may be due to diffusion and reorientation processes which are characteristic of the reflection-mode analysis. For the polymer LCs, we observed a much slower decay than those for the low-molecular-weight LCs.

This paper has outlined a method (called OBGP) of extending BGP to support lightpath setup and management across an optical network. The development of OBGP has been discussed by reviewing current BGP behavior and design requirements for OBGP. An implementation of OBGP using simulation tools has been presented, along with initial test results, which have shown that a seamless migration from BGP to OBGP is possible.

There is a potential for significant cost, footprint and power savings by eliminating unnecessary Opto-Electronic (OE) conversions on a signal path in a core optical mesh network. This paper addresses and clarifies some fundamental issues surrounding all-optical networking and all-optical switching and analyzes the tradeoffs between transparent (no OE conversions) and opaque networking (with OE conversions). It investigates a number of networking and interface compatibility issues that arise for an opaque network with transparent switches and presents a number of ways on how this issues can be addressed.

We experimentally demonstrate optical switching in a Fabry-Perot saturable absorber using a pump-probe technique. The saturable absorbers are multiple quantum wells, 35 and 42 pairs of alternating layers of 7 nm thick compressively strained Ga 0.42 In 0.58 AsP. These quantum wells are separated by 8 nm thick InP barriers. The reflectivity of these samples as a function of the input optical power is theoretically and experimentally investigated. A switching rate of better than 20 MHz is observed. This optical switching is based on the mechanism of controlling the reflectivity of the Fabry-Perot saturable absorber, while operating at its resonant wavelength, by the pump power. Optical switching speed of 10 ns is possible.

The study and development of Structural Health Monitoring (SHM) systems for aerospace applications is one of the best challenges for the research in the field of fiber optic (FO) sensors. The harsh environments in which these aerospace structures have to work are the major limit for the employment of standard fiber optic sensors for the thermo-mechanical monitoring processes. Thermal loads which act on these structures do not allow using standard fiber optic sensors used for classic avionics application. In fact, many aerospace structures can be exposed to temperatures up to 1000°C, higher than the operation temperature of the standard fiber optic sensors. In this paper a new fiber optic system for structural analysis of ultra high temperature ceramic (UHTC) materials is proposed. A tunable laser source is used to easily measure the spectral response of different fiber optic sensors. Moreover the employment of an in-fiber optical circulator and TLC 1x4 optical switch, allows to perform a multi-sensor interrogation, to analyse many physical parameters, such as: temperature, strain, pressure, etc.. In particular the monitoring system has been used to test high temperature resistant Fiber Bragg Grating sensors. The first tests at high temperature, up to 600°C, have shown a good response in terms of: sensitivity, resolution, repeatability and dynamic range of the measurement. At last, the flexibility of the electro-optical system developed for the interrogation of the fiber optic sensors, allows the extension of the instruments to mechanical stress analysis, using custom fiber optic strain sensors currently under development.

We demonstrate highly efficient evanescent coupling between a highly nonlinear chalcogenide glass two dimensional photonic crystal waveguide and a silica fiber nanowire. We achieve 98% insertion efficiency to the fundamental photonic crystal waveguide mode with a 3dB coupling bandwidth of 12nm, in good agreement with theory. This scheme provides a promising platform to realize low power nanocavity based all-optical switching and logic functions.

This paper describes recent research activities and results in the area of photonic switching carried out within the Virtual Department on Switching (VDS) of the European e-Photon/ ONe Network of Excellence. Contributions from outstanding European research groups in this field are collected to offer a platform for future research in optical switching. The paper contains the main topics related to network scenarios, switch architectures and experiments, with an effort to investigate synergies and challenging opportunities for collaboration and integration of research expertise in the field.

Integrated optical cross connects and add-drop multiplexers require low loss polarization independent phase shifting elements. In a composite quantum well, a 0.46 mm phase shifter provides a π/4 phase shift by combining the quantum confined Stark effect (QCSE) and carrier depletion effect. All-optical switching due to state filling effect is also experimentally investigated recently. We investigate whether the discrete energy levels and the high peak absorption in quantum dots (QDs) provide an opportunity for increasing the electrorefraction. The electrorefraction in strained InAs/GaAs and InAs/InP quantum dots (QDs) is explored using a numerical model based on the 4×4 Luttinger-Kohn Hamiltonian. The excitonic states are calculated by matrix diagonalization with plane-wave basis states. We observe that the QCSE sharply increases with the height of the QD and is also optimized for small radius QDs. The QCSE in pyramidal QDs is considerably larger than in squares or cylinders. We finally present large electrorefraction in cone shaped pyramidal QDs. State filling effect in QDs further resulted to an electrorefraction higher than an order of magnitude compared to that by QCSE for an acceptable waveguide absorption loss.