Showing papers on "Optical switch published in 1999"

Active and passive chalcogenide glass optical fibers for IR applications: a review

Abstract: Chalcogenide glass fibers based on sulfide, selenide, telluride and their rare earth doped compositions are being actively investigated worldwide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite these problems, current single mode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy/spectroscopy, fiber IR sources/lasers, amplifiers and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements in the optical quality of the fibers and the performance of the fibers in existing and future applications.

Wavelength add-drop switching using tilting micromirrors

Abstract: This paper describes a single-mode optical fiber switch which routes individual signals into and out of a wavelength multiplexed data stream without interrupting the remaining channels. The switch uses free-space optical wavelength multiplexing and a column of micromechanical tilt-mirrors to switch 16 channels at 200 GHz spacing from 1531 to 1556 nm. The electrostatically actuated tilt mirrors use an 80 V peak-to-peak 300 KHz sinusoidal drive signal to switch between /spl plusmn/10/spl deg/ with a 20 /spl mu/s response. The total fiber-to-fiber insertion loss for the packaged switch is 5 dB for the passed signals and 8 dB for added and dropped signals, with 0.2 dB polarization dependence. Switching contrast was 30 dB or more for all 16 channels and all input and output states. We demonstrate operation by switching 622 Mb/s data on eight wavelength channels between the two input and output ports with negligible eye closure.

Free-space micromachined optical switches for optical networking

Abstract: Fiber-optic switches with high port count have emerged as leading candidates for deployment in future optical transport networks, where restoration and provisioning in the optical layer will become increasingly important. This paper reviews the principle and performance of free-space micromachined optical switches (FS-MOS) featuring free-rotating hinged micromirrors. A single-chip FS-MOS that implements the critical function of bridging-essential for restoration in core optical networks is also proposed and demonstrated. The scalability of FS-MOS devices, and the dependence of their insertion losses on mirror-angle, are estimated theoretically. Simulation results suggest that the FS-MOS approach holds considerable promise for being expandable to the port-count values that will be needed in future core-transport lightwave networks.

Enhanced all-optical switching by use of a nonlinear fiber ring resonator.

Abstract: We predict dramatically reduced switching thresholds for nonlinear optical devices incorporating fiber ring resonators. The circulating power in such a resonator is much larger than the incident power; also, the phase of the transmitted light varies rapidly with the single-pass phase shift. The combined action of these effects leads to a finesse-squared reduction in the switching threshold, allowing for photonic switching devices that operate at milliwatt power levels in ordinary optical fibers.

A silicon MEMS optical switch attenuator and its use in lightwave subsystems

Abstract: A single-mode fiber connectorized microelectromechanical systems (MEMS) reflective optical switch attenuator operating in the 1550-nm wavelength region is described The device consists of an electrostatically actuated gold-coated silicon vane interposed in a fiber gap yielding 081-dB minimum insertion loss in the transmit state and high transmission isolation in the reflection state with 215-dB minimum return loss The switch attenuators also work as continuously variable optical attenuators capable of greater than 50-dB dynamic range and can be accurately regulated with a simple feedback control circuit Switching voltages were in the range of 5-40 V and a switching time of 64 /spl mu/s was achieved The MEMS switch can be used in optical subsystems within a wavelength-division-multiplexed (WDM) optical network such as optical power regulators, crossconnects, and add/drop multiplexers We used a discrete array of 16 switch attenuators to implement a reconfigurable 16-channel 100-GHz spacing WDM drop module of an add/drop multiplexer Thru-channel extinction was greater than 40 dB and average insertion loss was 21 dB Both drop-and-transmit of multiple channels (11-18-dB contrast, 14-19-dB insertion loss) and drop-and-detect of single channels (>20-dB adjacent channel rejection, 10-14-dB insertion loss) were demonstrated

Free-space fiber-optic switches based on MEMS vertical torsion mirrors

Abstract: This paper reports on the design, fabrication, and performance of a novel MEMS (micro-electro-mechanical-system) fiber-optic switch based on surface-micromachined vertical torsion mirrors. The vertical torsion mirror itself can be used as a 1/spl times/2 or an ON-OFF switch. A 2/spl times/2 MEMS fiber-optic switch with four vertical torsion mirrors has also been fabricated. The switching voltage is measured to be 80 V for switching angles of 45/spl deg/. We have achieved a switching time of less than 400 /spl mu/s (fall time) and an optical insertion loss of 1.25 dB for single-mode fibers. In addition, a bulk-micromachined silicon submount has been developed to package the switch with microball lenses and multimode fibers with passive alignment. With the micromachined switch chip and the hybrid-packaging scheme, the size, weight, and potentially the cost of the fiber-optic switches can be dramatically reduced.

Multichannel time-resolved optical tomographic imaging system

Abstract: A time-resolved optical imaging system using near-infrared light has been developed. The system had three pulsed light sources and total 64 channels of detection, working simultaneously for acquisition of the time-resolved data of the pulsed light transmitted through scattering media like biological tissues. The light sources were provided by high power picosecond pulsed diode lasers, and optical switches directed one of the light sources to the object through an optical fiber. The light signals reemitted from the surface of the object were collected by optical fibers, and transmitted to a time-resolved detecting system. Each of the detecting channels consisted of an optical attenuator, a fast photomultiplier, and a time-correlated single photon counting circuit which contained a miniaturized constant fraction discriminator/time-to-amplitude converter module, and a signal acquisition unit with an A/D converter. The performance and potentiality of the imaging system have been examined by the image reconstruction from the measured data using solid phantoms.

Micro-opto-mechanical 2/spl times/2 switch for single-mode fibers based on plasma-etched silicon mirror and electrostatic actuation

Abstract: This paper reports on a new optical 2/spl times/2 switch for single-mode fibers. The switching principle is based on a vertical micro-mirror which can be moved into the optical path to switch light between two pairs of fibers. The micromirror switch is designed for by-pass applications. When power is turned off the mirror spring back into its rest position and brings the switch into its bar state. This operation is very reliable, since the moving parts do not get into contact. Fabrication is based on the silicon micromachining technology, which allows to integrate the switching mirror, its electrostatic actuator and the alignment grooves for the fibers on the same chip. The mechanical switching principle brings with it a number of optical advantages such as a high crosstalk attenuation above 50 dB and wavelength and polarization insensitivity. At a wavelength of 1310 nm a minimum insertion loss of 0.6 dB was measured in the bar state, i.e. when the mirror is out of the optical path. In the cross state the light is reflected on the gold coated micro-mirror which has a reflectivity of about 80%. The insertion loss of the bar state was thus higher and a minimum value of 1.6 dB could be obtained. The switching time was well below 1 ms.

Integrated Optical Circuits and Components: Design and Applications

Abstract: Commercialization of lithium niobate modulators requirements for integrated optics devices in communication systems silica waveguide devices erbium doped gas waveguide devices erbium doped lithium niobate waveguide devices inP-based photonic circuits and components polymeric thermo-optic digital optical switches hybrid integration of optical devices on silicon integrated optics in sensors - advances toward miniaturization nonlinear integrated optical devices design and simulation tools for integrated optics.

Input switch configuration suitable for rail-to-rail operation of switched-opamp circuits

Abstract: A switch configuration to be used at the input of switched op amp circuits is introduced. The circuit is an extension of the gate-source bootstrapping technique such that rail-to-rail operation of the input switch becomes possible. Simulations show the usefulness of the proposed circuit down to 0.9 V.

Intermediate-state-assisted optical coupler

Abstract: An optical coupler, for coupling two optical waveguides (50, 60), and an optical switch based on the optical coupler. The indices of refraction of parallel sections of the two waveguides (50, 60) are reversibly perturbed periodically in space by imposing a mechanism (58, 68, 59, 69) to couple low order modes in the two waveguides via a high order mode common to the two waveguides. The waveguides are thus coupled with a beat length that may be five or more orders of magnitude shorter than it would be without the periodic perturbations.

A high-speed low-voltage stress-induced micromachined 2 x 2 optical switch

Abstract: A low-voltage electrostatically actuated 2/spl times/2 fiber optic switch is achieved using a stress-induced curved polysilicon actuator. The curved polysilicon beam substantially lowers the electrostatic operating voltage of the switch. Large mirror displacement (300 /spl mu/m) and low operating voltage (20 V) are obtained simultaneously. Sub-millisecond switching time (<600 /spl mu/s), low optical insertion loss (0.7 dB), and small polarization-dependent loss (0.09 dB) have been achieved.

Micromachined free-space integrated micro-optics

Abstract: The surface-micromachining technique has been employed to fabricate novel three-dimensional micro-optical elements for free-space integrated optics. The optical axes of these optical elements are parallel to the substrate, which enables the entire free-space optical system to be integrated on a single substrate. Microscale Fresnel lenses, mirrors, beam splitters, gratings, and precision optical mounts have been successfully fabricated and characterized. In addition, micropositioners such as rotary stages and linear translational stages are monolithically integrated with the optical components using the same surface-micromachining process to provide on-chip optical alignment or optomechanical switching. Self-aligned hybrid integration with semiconductor edge-emitting lasers and vertical cavity surface-emitting lasers are also demonstrated for the first time. This new free-space micro-optical bench (FSMOB) technology could significantly reduce the size, weight, and cost of most optical systems, and could have a significant impact on optical switching, optical sensing and optical data-storage systems as well as on the packaging of optoelectronic components.

Tunable add/drop optical filter

Abstract: In all-optical networks, optical switching and routing become the most important issues for interconnecting the transport network layers. This invention describes a novel tunable optical add/drop filter for the all-optical wavelength-division-multiplexing (WDM) network applications. This filter can add or drop part of the high transmission capacity signals of a WDM link. It can be used to decentralized access point in the access network or as small core network node to realizing branching points in the network topology. It works in both wavelength and space domains. It has the advantages of: 1) High throughput and low voltage operation; 2) Wide tuning range and therefore, high channel capacity; 3) High isolation and high directivity between input and output ports; 4) Compact device packaging is possible as compares to the conventional grating and mechanical switching type of add/drop filter; 5) Multiple ports add/drop tunable filters can be realized with this invention to interconnect multiple WDM networks. This novel add/drop filter can be used in various WDM topologies. It enhances the performance of the conventional tunable filter by re-routing the rejected wavelengths back to network, which not only save the precious optical energy, but also cut down the return loss of the device.

Multichannel photon counting instrument for spatially resolved near infrared spectroscopy

Abstract: We have developed a multichannel photon counting instrument for near infrared spatially resolved spectroscopy. The instrument uses two laser diodes at 780 and 830 nm. The two wavelengths are time multiplexed at a rate of 5 MHz for virtually simultaneous measurements at the two wavelengths. The photon pulses are then multiplexed with an optical switch so that the incident optical signals are directed to different source positions. Eight time-correlated channels have been employed for simultaneous acquisition of spectroscopic data at multiple locations. Photon detection is performed by multichannel plate photomultiplier tubes. Robust and accurate data analysis tools to perform deconvolution, data fitting, and absorption change quantification are presented. The instrument has been tested with phantoms simulating tissue optical properties. Absolute optical properties, namely absorption and reduced scattering coefficient, have been determined with an accuracy of ±5%. Quantification of absorption changes can be...

Fluid-encapsulated MEMS optical switch

Abstract: A fluid encapsulated MEMS optical switch includes an optical waveguide matrix with MEMS mirrors (22) situated in trenches located at waveguide cross-points (29). The trenches are filled with collimation-maintaining fluid (30) and the mirrors (22) are immersed therein. The collimation maintaining fluid (30) prevents the light beam from spreading when it enters the switch cross-points. This feature enables the use of much smaller MEMS mirrors (22) and prevents some of the typical MEMS mirror (22) problems found in the related art. In particular, the MEMS mirrors (22) disclosed in the present invention is reduced to approximately 15 wide and 2 thick, resulting in shorter actuation distances to approximately 15. This feature results in an optical switch having faster switching times.

Refractive index changes of Pd-coated magnesium lanthanide switchable mirrors upon hydrogen insertion

Abstract: The optical effect upon insertion of hydrogen into Pd-coated magnesium lanthanide switchable mirrors is investigated in terms of the changes of their complex refractive indices. A significant change in the optical constants of LnMg layers is seen between the as-deposited state and the dehydrided state after one cycle. Furthermore, the optical effect of switching the Pd cap layer to a PdH cap layer was determined. It is shown that the Pd layer mainly limits the visible transmittance of the hydrided stack to about 35%–40%. Whereas the extinction coefficient of dehydrided LnMg layers at 550 nm is between 2.2 and 3.1, it is as low as 10−4 in the transparent state. This is of great promise to applications requiring large optical contrast (e.g., optical switches).

Micro-electro system (MEMS) switch

Abstract: An RF switch formed as a micro electro-mechanical switch (MEMS) which can be configured in an array forming a micro electro-mechanical switch array (MEMSA). The MEMS is formed on a substrate. A pin, pivotally carried by the substrate defines a pivot point. A rigid beam or transmission line is generally centrally disposed on the pin forming a teeter-totter configuration. The use of a rigid beam and the configuration eliminates the torsional and bending forces of the beam which can reduce reliability. The switch is adapted to be monolithically integrated with other monolithic microwave integrated circuits (MMIC) for example from HBTs and HEMTs, by separating such MMICs from the switch by way of a suitable polymer layer, such as polyimide, enabling the switch to be monolithically integrated with other circuitry. In order to reduce insertion losses, the beam is formed from all metal, which improves the sensitivity of the switch and also allows the switch to be used in RF switching applications. By forming the beam from all metal, the switch will have lower insertion loss than other switches which use SiO2 or mix metal contacts.

Method for fabricating a hybrid optical integrated circuit employing SOI optical waveguide

Abstract: The present invention relates to an optical integrated circuit; and, more particularly, to a method for preparing an improved hybrid optical integrated circuit which is capable of accommodating optical waveguides, optical devices, such as light emitting devices and light receiving devices, and optical fibers in an effective manner. The present invention has the advantages of minimizing horizontal misalignment error between the SOI waveguide rib area, the V-groove etch window and the alignment marks, decreasing the manufacturing cost by passively aligning the waveguides, the optical devices and the optical fibers on a single substrate. Also, the present invention has an effect of reducing fresnel reflection loss by providing the LPCVD silicon nitride layer capable of being used as an anti-reflection coating layer at both ends of the waveguide.

Multiwavelength mode-locked dense wavelength division multiplexed optical communication systems

Abstract: A multiwavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmission method and system including a MWML-DWDM optical transmitter having a multiwavelength mode-locked (MWML) laser (21) which generates a wavelength-ordered repetitive periodic (WORP) sequence of discrete optical pulses for modulation with data carried by at least one electronic carrier. Signals from multiple telecommunications transmission interfaces are multiplexed together by a high speed digital transmission stream that is encoded onto the optical pulse stream output by the MWML-DWDM optical transmitter by an optical modulator so as to provide multiple channels of information carried on a DWDM data stream over an optical fiber to a receiver where the data is received and decoded. A single MWML-DWDM optical transmitter and a single modulator may replace the numerous laser sources and associated modulators used in conventional WDM optical transmission systems.

Planar lightwave circuit-based optical switches using micromirrors in trenches

Abstract: A planar lightwave circuit (PLC) is formed to include switching elements in which optical coupling among waveguides is determined by positions of displaceable members, such as micromirrors. Each switching element includes at least two light-transmitting waveguides extending along a waveguide substrate to a trench. The optical coupling between the waveguides of a switching element is dependent upon the optical characteristics exhibited at the trench. The displaceable device of a switching element has a transmitting position and a reflecting position. The displaceable device may be manipulated using microelectromechanical system (MEMS) techniques or techniques similar to those used in a dot matrix printer engine. The trench at the crosspoint of waveguides may include a liquid having a refractive index that closely matches the refractive index of the core material of the waveguides. If no index-matching liquid is included at the trench, the walls of the trench are preferably coated with an anti-reflection coating.

High-speed electro-optic modulator

Abstract: An optical modulator is provided to control the intensity of a transmitted or reflected light. In a transmission mode, a separator splits arbitrarily polarized light into two polarization rays and one is made to travel a separate path from the other. A recombiner causes the two rays to recombine at an output unless an electro-optic phase retarder changes the polarization of the two rays, in which case, both of them miss the output by an amount which is a function of the voltage on the retarder. A normally-off version with low polarization mode dispersion is obtained by changing the orientation of the recombiner. A normally-on version with low polarization mode dispersion is obtained with a passive polarization direction rotation. Similar results can be obtained in a reflection mode where the input and output are on the same side of the modulator. Versions using a GRIN lens are particularly suited to modulation of light out of and back into fiber-optic cables. The device can be operated as a variable optical attenuator, an optical switch, or a high speed modulator and is insensitive to polarization of the input light. A preferred material for the phase retarder is a hot-pressed ceramic lead lanthanum zirconate titanate composition.

Micromechanical light steering optical switch

Abstract: An optical switch uses a micromachined adjustable phase hologram device to route optical signals from an input fiber to selected output fibers is described. The adjustable phase hologram includes a large number of micromachined reflective ribbons which can be individually controlled and adjusted to produce a wide range of phase profiles to route the light beams from the input fiber. This optical switch is capable of dealing directly with optical signals, has fast switching speeds, is capable of routing WDM input signals, is polarization independent, is scalable to large switches, and avoids the complexity of other switches.

Optical multistage interconnection networks: new challenges and approaches

Abstract: Optical interconnections for communication networks and multiprocessor systems have been studied extensively. A basic element of optical switching networks is a directional coupler with two inputs and two outputs or switching elements (SEs). Depending on the control voltage applied to it, an input optical signal is coupled to either of the two outputs, setting the SE to either the straight or cross state. A class of topologies that can be used to construct optical networks is multistage interconnection networks, which interconnect their inputs and outputs via several stages of SEs. Although optical MINs hold great promise and have demonstrated advantages over their electronic counterparts, they also introduce new challenges such as how to deal with the unique problem of avoiding crosstalk in the SEs. In this article we survey the research carried out, including major challenges encountered and approaches taken, on optical MINs.

Embedded fiber optic circuit boards and integrated circuits

Abstract: A circuit board has optical fibers embedded in at least one layer for optical transmission of data at high speed, digital signal rates and electrically conductive strips in other layers to provide for conventional data signals and power for optoelectronic and electronic integrated circuits (IC). Optical fibers connect to optoelectronic IC's, off board IC's, circuit boards and conductors to reduce high speed digital signal latency and increase signal bandwidth/throughput. Optical fibers are used within printed circuit boards, integrated circuits, circuit board connectors, and backplane connectors to interface printed circuit boards and backplane.

Bistable micromechanical fiber-optic switches on silicon with thermal actuators

Abstract: A new bistable moving-fiber switch for applications in optical communication systems is developed by employing advanced bulk silicon micromachining. The bistable switch utilizes actuators based on thermal expansion and the bimetal effect. Switches and switch arrays are successfully fabricated and tested. Due to the low number of process steps and the high yield and reliability, the process technology is suitable for low-cost single- and multi-mode fiber optic switches. A typical fiber-to-fiber insertion loss of 2±0.5 dB (single-mode fibers at 1300 nm wavelength, including MT-connector losses of typically 0.5–1.5 dB) is achieved in an array of 12 switches. The cross talk is below the detection limit (

High-extinction ratio and low-loss silica-based 8/spl times/8 strictly nonblocking thermooptic matrix switch

Abstract: This paper describes a silica-based 8/spl times/8 strictly nonblocking thermooptic matrix switch with a high-extinction ratio and low loss. We realized this matrix switch by using a configuration which combines a double Mach-Zehnder interferometer (MZI) switching unit and an N/spl times/N matrix arrangement thus reducing the total waveguide length. The 8/spl times/8 matrix switch was fabricated on a 4-in wafer using planar lightwave circuit technology. We obtained an average extinction ratio of 60.3 dB and an average insertion loss of 5.1 dB. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs).

Design issues of optical IP routers for Internet backbone applications

Abstract: The rapid increase of Internet traffic is pushing the deployment of WDM technology in the next-generation high-speed Internet backbone. Routers in the backbone could still be the potential bottleneck. In this article we consider some design issues of high-throughput optical routers which combine the advantages of WDM with the new optical switching technology. We first introduce a proposed Internet architecture based on the optical burst switching mechanism. Some important design issues in optical buffering and control function are addressed which are expected to have significant effects on router performance. Numerical results of a simulation study are also presented along with discussions.

A three-dimensional optical photonic crystal

Abstract: We report on the successful fabrication of a working three-dimensional (3D) crystal operating at optical wavelength /spl lambda/. The minimum feature size of the 3D structure is 180 nm. The 3D crystal is free from defects over the entire 6-inch silicon wafer and has an absolute photonic bandgap (PBG) centered at /spl lambda//spl sim/1.6 /spl mu/m. Our data provides the first conclusive evidence for the existence of a complete 3D PBG in optical /spl lambda/. This development will pave the way to tinier, cheaper, more effective waveguides, optical switches and lasers.

Scalable WDM access network architecture based on photonic slot routing

Abstract: This paper introduces an approach to solving the fundamental scalability problem of all-optical packet switching wavelength-division multiplexing (WDM) access networks. Current optical networks cannot be scaled by simply adding nodes to existing systems due to the accumulation of insertion losses and/or the limited number of wavelengths. Scalability through bridging requires, on the other hand, the capability to switch packets among adjacent subnetworks on a wavelength basis. Such a solution is, however, not possible due to the unavailability of fast-switching wavelength sensitive devices. In this paper, we propose a scalable WDM access network architecture based on a recently proposed optical switching approach, termed photonic slot routing. According to this approach, entire slots, each carrying multiple packets (one on each wavelength) are "transparently" routed through the network as single units so that wavelength sensitive data flows can be handled using fast-switching wavelength nonsensitive devices based on proven technologies. The paper shows that the photonic slot routing technique can be successfully used to achieve statistical multiplexing of the optical bandwidth in the access network, thus providing a cost-effective solution to today's increasing bandwidth demand for data transmissions.