CrossWave$TM) multiplexed domain switches enable low cost, simple, reliable and scalable architectures for a wide variety of wavelength selective cross connects, dynamically reconfigurable add/drop multiplexers and hybrid optical core switches. As DWDM becomes ubiquitous in long haul and metro core networks, carriers are looking to optical switching to manage the ever-growing number of wavelengths and to automate wavelength routing, restoration and grooming. To meet these requirements, optical core switches (OCSs) need to scale to accommodate high wavelength counts, high TDM bit rates and various types of transport protocols such as SONET and GbE.

In this document, we study the complexity of routing and wavelength assignment problem in WDM rings with limited wavelength conversion capability. We address a specific wavelength conversion capability, represented by a cluster model. In the cluster model, we first define a set of disjoint clusters of wavelengths among the available wavelength set. We allow wavelength conversion only between wavelengths belonging to the same cluster. Because the cluster model is able to describe a large number of conversion limited WDM systems, we expect that our results be valuable for the design and performance study of RWA algorithms for a large number of WDM ring systems.

This paper discusses functional requirements of optical path cross-connect (OPXC) node. Generic optical path cross-connect (OPXC) node architectures are introduced, and a new OPXC node architecture is proposed. OPXC node architectures are assessed. A transport system with two new OPXC nodes and a 100km dispersion-shifted fiber are simulated. It shows that the new OPXC architecture is superior to generic OPXC architectures.

This paper reports the design, fabrication, and testing of drawbridge micromirrors that is used to form a monolithic 4 X 4 optical crossconnect (OXC) having dimensions about 4 mm X 4 mm. The OXC is composed of 16 individual drawbridge micromirrors that are fabricated by the surface micromachining technology and then manually assembled. In each drawbridge micromirror the mirror is driven by electrostatic force to cut off the laser beam or let it pass through, enabling the switching. The measured switching times range from 94 microsecond(s) to 181.1 microsecond(s) for the switches with different bending bean sizes. The configuration of this OXC is scalable and capable to build up a large array of OXC system.

In this paper a new kind optical switch, which is called spectral switch, is presented. When a particular class of broad-band partially coherent light is diffracted by a circular aperture, the spectrum of the light in the far zone of the diffractive field is different from the spectrum at the aperture, i.e., there exists spectral shift (Delta) (omega) equals (omega) _m - (omega) ((omega) _m is the frequency at which the spectrum of the diffractive field takes its maximum, and (omega) is the frequency at which the spectrum at the aperture takes its maximum). It is demonstrated that when the spectral coherence of the light at the aperture changes, there will be gradual change in the spectral shift. However when the coherence is equal to a critical value, the spectral shift will exhibit a rapid transition. We call this phenomenon as spectral switch. The scheme for generating 1 X N spectral switch is also discussed.

This paper describes recent progress on large-scale integrated thermo-optic switches including N X N switches (up to 16 X 16), 1 X N switches (up to 1 X 128), N-arrayed 2 X 2 switches (up to 16-arrayed for optical add/drop multiplexers, which all employ silica-on-silicon planar lightwave circuit technology. These switches exhibit low insertion loss, low polarization loss and high switch extinction ratio. I also describe a trial with the goal of reducing drive power consumption, and report the reliability of the thermo-optic switch modules.

Integrated multimode interference coupler based on silicon-on- insulator has been become a kind of more and more attractive device in optical systems. Thin cladding layers (< 1.0 micrometers ) can be used in SOI waveguide due to the large index step between Si and SiO₂, making them compatible with the VLSI technology. Here we demonstrate the design and fabrication of multimode interference (MMI) optical couplers and optical switches in SOI technology.

In this work, we presented several different types of liquid-crystal WDM (wavelength-division-multiplexing) signal processors including broadband optical switches, voltage-controlled variable attenuators and optical harmonic equalizers.

In this paper, a kind of free-space optical switch based on polarization was proposed. Its operation principle was described in detail. Based on this method, some basic types of optical switches were presented, such as 1 X 2, 2 X 1 and 2 X 2 optical switches. Then, taken as an example, the 1 X 2 type was tested to give the experiment performance of this kind of free-space optical switch based on polarization. Its insertion loss was less than 3 dB, crosstalk between different channels were as low as -32 dB, and its switching time was about 2 ms. It showed that this kind of optical switches could be well used in OADM for optical networks protection and reconfigurration. Also its disadvantages were discussed at the end of this paper.

In this paper, we demonstrate a weak photon switch by Fano interference in a double quantum well structure. GaAs/AlGaAs and InGaAs/AlAs heterostructures are taken as switch media to show that the weak switch can work at different wavelength by choosing materials and structures. We also estimate the order of the switch power and show that this photon switch by Fano interference in coupled double quantum well structures is a weak optical switch that can be used to realize one optical beam control another beam.

High speed, low insertion loss optical add/drop multiplexer (ADM) is designed and fabricated. The optical vertical micromirror is fabricated by deep dry etching, the aspect ratio reaches as high as 20. A thin aluminum film is deposited on the sidewall of the micromirror to increase the reflectivity. The anchors and pads are fabricated firstly, followed by the comb drive, micromirror and fiber grooves. Refilling technique is introduced to electrically insulate the anchors and pads from the substrate while still maintaining the mechanical support. The anchors and pads are strong enough to sustain the floating structures (micromirror and moving comb) and also assure good electrical connection to the electrostatic comb drive so that the external voltage can be applied. By improving dry etching, the finger width is only 2micrometers and the gap is only 2.5micrometers . A typical electrostatic comb drive is fabricated by the deep reactive ion etching (RIE) and underneath releasing. Folded suspension beams of 800micrometers long, 2.0 micrometers wide and 35micrometers deep are employed to support the movable micromirror. The stiffness along the desired lateral direction is 0.21N/m. Comb drive using three electrodes is employed. Its applied voltage is decreased by a ratio of 0.707 compared with that of the two electrodes system, and the switching speed is also increased. To simply the optical fiber assembly, fiber grooves are fabricated along with the other structures. This device has a typical of optical ADM that can be widely used in all optical networks. All of the processes are compatible with IC technology and can be integrated with control circuits in a single chip.

This paper presents finite element (FE) simulation and theoretical analysis of novel MEMS fiber-optical switches actuated by electrostatic attraction. FE simulation for the switches under static and dynamic loading are first carried out to reveal the mechanical characteristics of the minimum or critical switching voltages, the natural frequencies, mode shapes and response under different levels of electrostatic attraction load. To validate the FE simulation results, a theoretical (or analytical) model is then developed for one specific switch, i.e., Plate_40_104. Good agreement is found between the FE simulation and the analytical results. From both FE simulation and theoretical analysis, the critical switching voltage for Plate_40_104 is derived to be 238 V for the switching angel of 12 degree(s). The critical switching on and off times are 431 microsecond(s) and 67 microsecond(s) , respectively. The present study not only develops good FE and analytical models, but also demonstrates step by step a method to simplify a real optical switch structure with reference to the FE simulation results for analytical purpose. With the FE and analytical models, it is easy to obtain any information about the mechanical behaviors of the optical switches, which are helpful in yielding optimized design.

An integrated MEMS tunable laser of approximately 2 mm X 1.5 mm size is demonstrated in this paper. The tunable laser is formed by the integration of a surface-micromachined 3D micromirror with a Fabry-Perot laser diode and an optical fiber. The micromirror can be driven to translate by a comb drive to change the external cavity length of laser diode, enabling the wavelength tuning. A tunable range of 16 nm is obtained, which covers 20 channels of WDM systems spaced by 100GHz. The three-mirror Fabry-Perot cavity model is modified to explain the continuous wavelength change as well as the mode hopping. An array of the tunable laser is potential to supply light sources for multiple channels of WDM systems.

Variable optical attenuator (VOA) is undergoing to be a mainstream component of wavelength division multiplex (WDM) networks to monitor and control the optical power of wavelength channels. In this paper, a free-space VOA fabricated by micro electromechanical systems (MEMS) technology to operate in the 1.55 micrometers wavelength region is described. It employs a micromirror driven by an electrostatic comb drive to cut partially into the light beam between two single mode fibers (SMFs), enabling the attenuation. The micromirror has a size of 30 micrometers X 30 micrometers and is coated with aluminum to increase the reflectance. The moving fingers of comb drive and the micromirror are supported by folded suspension beams over the substrate. By applying different voltage to the comb drive, the micromirror translates to different position to achieve an attenuation ranging from 0.4dB to 50dB, and even higher. The nonlinear relationship between the position of the micromirror and attenuation is analyzed. The distributions of the light beams at the micromirror and the output fiber end are investigated respectively. And the influence of the separations between the micromirror, the input and output fiber ends is also discussed to obtain different attenuation resolutions. At low attenuation stages, fine tuning of attenuation is obtainable. The largest attenuation is driven by 21voltage. Deep reactive ion etching (DRIE) process is employed to fabricate the VOA and the micro loading effect is remedied by mask design.

This paper discusses optical-label switching and an experimental demonstration of high-speed all-optical packet switching with all-optical label-swapping capabilities. The subcarrier optical-label content was optically extracted and compared against the forwarding table, which induced packet forwarding as well as label-swapping decisions. The all- optical label processing technique was immune from dispersion induced fading and polarization induced degradation effects. The packet switching was accomplished by a combination of rapidly tunable wavelength conversion and a uniform-loss cyclic frequency (ULCF) 8 X 8 arrayed waveguide grating router (AWGR). The packet routing system achieved 600 psec switching time with a forwarding decision time of 250 nsec. All optical label swapping incorporated optical subcarrier filtering using fiber Bragg gratings. Accumulated packet-by- packet Bit-Error-Rate measurements confirm the successful and low-penalty packet routing with label swapping technique, while maintaining optical transparency for the data payload.

A kind of multi-wavelength labeled optical packet switching technology is presented, in which optical header is consisted of several optical pulses in different wavelength that are in the same WDM optical channel band as optical signal payload. A probable scheme to realize such optical switching as well as an optical switching node structure is proposed. A simplify principle experiment has proved the possibility of such switching method.

In this paper, we propose an optical switch that combines both shared tunable wavelength converter and partially shared buffering together. The packet contention can be resolved both in the time domain (output buffering and partially shared buffering) and frequency domain (wavelength conversion) simultaneously and switching performance can be greatly improved. Various simulations are carried out to show the performance of different buffering and wavelength conversion structures. The results confirm that the switching architecture we proposed has excellent performance.

A novel optical switch structure is proposed to implement the function of cross-connection, optical power control and crosstalk reduction for optical cross-connect (OXC) in wavelength division multiplexing (WDM) optical transport networks. Based on the conventional AS/AC network structure, the proposed one deploys a set of 1x2 digital optical switches (DOS) between the AS and AC modules. Thus the optical signal power can be controlled and the crosstalk can be reduced by adjusting the driving voltage of the 1x2 DOSs. Experiments with a 4x4 polymeric thermo-optical DOS demonstrate that the power control range is more than 35 dB, and the delay for 3 dB power control is within 7.5 ms in the worst case. Analytical result also shows that the crosstalk can be suppressed at least 35 dB.

Growing demands for bandwidth have stimulated the development of high-speed optical shared media networks. At present, most research on optical networking has concentrated on wavelength- division multiplexing (WDM). Optical time-division multiplexing (OTDM) is considered as an alternative to WDM offering data rates greater than 100 Gb/s using just a single wavelength. In such systems all optical routers, which overcomes the bottleneck of optoelectronic conversion, play an important role. This paper investigates TOAD based 1 X 4 optical router by developing a mathematical model. The proposed model is simulated and results for crosstalk are presented and compared with 1 X 2 router.

A giga-bit per second optical ring has been designed. The data link layer bandwidth of the network is 1.5 Gbit/s. Hardware routing has been achieved by field programmable gate array (FPGA) to minimize the communication latency. As a result, the point-to-point communication latency between adjacent node computers is less than 300 ns. To reduce the data communication latency and have a more efficient usage of the data link layer bandwidth, virtual multi-channel transmission mechanism has been achieved with hardware. The network supports a maximum of four virtual channels for each physical data link. Time slots can be dynamically assigned to each virtual channel. The length of each time slot can also be dynamically selected based on the length of each data packets. Zero wait time has been achieved for the switching between different virtual channels. The relationship between the network performance and the number of virtual channels has also been analyzed in this paper.

Active fiber bundles (FBs) are aimed to model photonic switching and processing in 3-D without the restrictions of the photonic technology. The 2-D photonic architectures are assumed to be implemented by networks of directional couplers (DCs) and Mach-Zehnder interferometers (MZIs), respectively. For the implementation several crucial problems are expected: (1) proper operation of the spatial couplers/switches (nonblocking interconnections) and (2) coupling in the interstage interconnection section mainly caused by parallel and crossing fibers/waveguides (WGs). For the design of proper operating switches (refinement of couplers) the application of decoupling concepts of modern control theory is proposed. The final goal is to translate the refined couplers into integrated photonic architectures rather than into additional lightwave circuits (LWCs) which simply would increase the coupling. The decoupling concepts are reviewed. The paper is an attempt to prepare for applying well-known system engineering concepts to the upcoming technology of photonics.

We propose that without rapid advances, optical testing of optical components will continue to be a major obstacle in the economical deployment of optical communications. We explore the communications-system drivers of these changes, the implications of these changes on the test process and apparatus, and identify certain obstacles which must be overcome. In some cases, solution paths are being identified, and we outline a number of these.

The problem of electromagnetic wave propagation in the nearly plane heterogeneous weakly absorbing dielectric layer in case of the wave streaming on the layer nearly perpendicularly is solved. Phenomenon of qualitative dependence of the near zero permittivity (critical point) solution of the problem on small variations of its parameters is discovered. The author's mathematical methods in the case of plane and spherical coordinate systems is applied. Surface wave propagation in plane layer is described and criterium of this wave appearance is given. Discovery may be applying in optical switching, which near zero permittivity depends on small physical parameters: absorption, angle of wave incidence, inverse radius of curvature and temperature at first.

This paper presents a novel multibuffer-shared ATM switching architecture based on optical interconnects and optoelectronic hybrid crossbar modules. The core of this switching architecture is the 16 X 16 CMOS-SEED crossbar switching module, and the optical interconnects between the input interface and switching core provide high-speed data paths. Many buffers placed in an output module of the interface are partial shared, which take advantages of output buffer and shared buffer, so these buffers are used more effectively than the output buffer. And these shared buffers bring an advantage that the speed of the accessing each of these buffers is not need very high due to these buffers can write/read many cells in a parallel way. The performance of this ATM switching system is analyzed under the uniform traffic and bursty traffic. The simulation results show that the cell loss probability of this ATM switching system is less than 10e-9 under the uniform traffic with 12-cell length of each shared- buffer, and the cell loss probability is less than 10e-9 under the bursty traffic with 160-cell length of each shared-buffer.

Dense Wavelength Division Multiplexed Optical networks using all-optical devices represent the promising solution for future high-capacity wide-area network applications. In this paper, numerous Optical Cross-connect Architectures are briefly concluded firstly, and then the analysis of WP and VWP mode, ILP formulations for physical topology and restoration strategies is presented to explain the relationship of various factors of different optical interconnecting architectures.

A novel optical implementation method of 4 X 4 polarization-independent bi-directional fiber optical switch in free-space optical architecture is presented in this paper. This 4 X 4 fiber optical switch is based on elementary 2 X 2 optical switch module. The 4 X 4 optical switch constituted by polarization beam splitters (PBS), 1/4 waveplates (QWP), polarization light modulator (PLM), right angle prism (RAP), and total reflection mirror (TR). Operation is independent by input signals of polarization of the optical beams. This new kind of configuration of the optical switch grants the features of less optical components, high compactness, low optical interchannel crosstalk, fast switching speed, polari insensitivity, and easiness to optical assembly. A matrix description is deduced with respect to this 4 X 4 fiber optical switch architecture.

This paper proposes a novel optical crossbar switching architecture. The proposed IP switch is based on an optical crossbar switching system, which take full use of advantages of electronics and photonics to face the challenge of the terabits per second IP switching. Group interconnect network is regarded as an ideal switching structure for its low blocking and excellent scalability. We add feedback loops to the group interconnect network, and got the better performance at the cost of slight extra hardware. In the paper, we simulated the cell loss rate of our optical crossbar switching network with feedback loops and several other switching network in the condition of uniform traffic and the burst traffic. The result shows that, in uniform traffic, the cell loss ratio (CLR) of our novel structure is less than 10e-9 , which is much lower than others; while in burst traffic, the CLR of ours is also lower than any of others. The hardware implementation of the switching network is also discussed. We proposed a high density optical waveguide interconnect board based on VCSEL/MSM detector arrays and free-space optical interface modules, which grants the features of high density signal channel, low cell loss rate, low optical interchannel crosstalk, small volume and simple structure.

Imperfect isolation of switching elements inside optical space switches gives rise to leakage signals that results in homodyne crosstalk. An analysis of the impact of this phenomenon is developed considering an architecture based on a strictly non-blocking Horizontal Expanded and Vertical Replicated Banyan network and implemented using directional couplers. The analysis uses a rigorous approach based on the Gaussian Quadrature Rules method. The obtained results show that there is a compromise between the power penalty due to homodyne crosstalk and the network cost. In particular, a 1024 X 1024 optical switch, obtained by expanding the basic Banyan network with seven more stages, and with a switching element crosstalk of - 35 dB, gives a power penalty of 2.8 dB and requires a minimum of 117760 switching elements. However, if a network with no horizontal expansion is used, the power penalty can be reduced to approximately 1.2 dB, but the number of switching elements must increase to 369664.

The electromagnetic optical switch combines with Ni/Fe permalloy magnetic circuit design, high aspect ratio microstructure electroplating, bulk micromachining, excimer laser ablation and low temperature wafer bonding. The result shows it can output force 68 mN, deflection angle can reach 82 degree(s) only with 4820A/m, frequency can reach 2 kHz, and bonding strength can be larger than 216 kg/cm².

Silicon micromechanics including bulk micromachining and surface micromachining are an emerging field, which are beginning to impact almost every area of science and technology. Since the early days of fiber optics, it has been recognized that micro-optics was a fertile ground for the applications of microelectromechanical systems (MEMS). Mechanical movable structures and micromotors can be integrated on silicon using MEMS technology, which is finding its way into both large-scale and small-scale optical switches, variable optical attenuators, tunable lasers and filters, active equalizers, add/drop multiplexers, optical crossconnects, gain tilt equalizers, data transmitters and many others are beginning to find ubiquitous application in advanced lightwave systems. We are investigating the use of MEMS fabrication technology for applications in optical communications. Also we will describe what they are, how they are built and show how they have the potential to revolutionize lightwave systems. Using silicon microfabrication to produce optical components provides some compelling advantages. First, the silicon surface when treated properly can provide an optical surface of extremely high quality. Second, single-crystal silicon allow fabrication of fatigue-free devices since it has no dislocation. Third, the electrical properties of silicon allow for the integration of sensors and detectors with extraordinarily high precision. In addition, the require forces provided by microactuators have very limited force capabilities, and often the required displacements in many applications are also quite small, on the order of a wavelength (a few microns), which again provides a good match for the capabilities of MEMS. Finally, the lithographic batch fabrication of these devices, driven and made possible by the infrastructure of the IC industry, provides a relatively inexpensive fabrication method.

One of the key issues of high performance IP Gigabit Switching Router (GSR) design is about switching fabrics. In the traditional bus-based router architectures, the data transfer rate of copper backplanes will soon reach the speed limit because of connector reflections and crosstalk. An alternative optical switching fabric technology is necessary in order to satisfy the demand for high switching bandwidth. In this paper we firstly present a novel all-optical broadcasting switch fabric design scheme based on broadcasting bus architecture. In this section we also illustrate the advantages and disadvantages of this kind of architecture and demonstrate that this kind of switching fabric architecture have no interior block as well as none I/O block. Second, we discuss such implementation scheme of all-optical broadcasting switch fabric architecture as queuing, scheduling and multicasting. Finally, we get a conclusion that all-optical broadcasting switch fabric is one of the cost-effective solutions to design high-speed, scalable and simple switch fabrics compared with those complicated electric crossbar switch fabrics in GSR design.

With advent of escalating internet data traffic demand, the optical networks are migrating to more data-centric, dynamic and intelligent networks. Optical core switch (OCS) that effectively provides DWDM wavelength level switching emerges as the key enabler for the next generation optical internet. We proposed and developed a novel ultra-scalable optical core switching system incorporating wide range tunable laser for wavelength switching and simple 1xM photonic switch for fiber switching. The system provides flexible wavelength switching and DWDM transport in a single network element, and offer ultra-scalability to transport and switching from single to over 1000 wavelengths with total capacity over 10 Tbps.