Optical Space Switch Research Articles

Scalable SOA-based Banyan optical space switch on InP membrane on silicon (IMOS)

Optical switches (OS) are vital for meeting modern data centers’ capacity and latency needs, overcoming the bandwidth and speed limitations that electronic switches encounter. To this end, this work proposes a semiconductor optical amplifier (SOA)-based OS on the IMOS, a unique platform with a combination of high refractive index contrast for compactness and monolithic active-passive integration for active functionalities, thereby enabling the creation of compact SOA-based OSes. An 8 × 8 Banyan SOA-based OS is integrated on a 4 × 4 mm2 area on the standard 4 × 6 mm2 IMOS cell. This marks the first application of the IMOS technology platform for SOA-based OSes and sets the stage for compact and large-scale monolithic photonic integrated OS circuits. The basic 2 × 2 switch module delivers a high optical signal-to-noise ratio (OSNR) and an extinction ratio (ER) above 45 dB. Employing NRZ-OOK routing on the 2 × 2 basic OS module, a 15 dB input power dynamic range (IPDR) is achieved within a 1 dB power penalty at 12.5 Gb/s. Data routing at higher data rates of 25 Gb/s and 40 Gb/s incurs power penalties of 0.8 and 1.4 dB, respectively. Furthermore, data routing for a 3-stage 8 × 8 switch operating at 25 Gb/s results in a power penalty of 1.2 dB. Compared to the 1-stage 2 × 2 switch, only a 0.4 dB additional penalty is observed despite incorporating 2 additional SOAs in the cascade. This indicates that the switch can scale to higher radix to accommodate multi-stage switches with numerous ports, large bandwidth, and fast speed, which is essential in modern large-scale data centers.

Switching in microseconds: design of a 5 × 5 non-blocking free space optical switch at 1550nm with a piezo-actuator and beam-steering lens system

Modern data center networks (DCNs) require optical switches with ultra-low loss, ultra-fast reconfiguration speed, high throughput, and high extinction ratio performances. In this work, we propose the design of a 5 × 5 optical switch at 1550 nm based on a piezo-actuator serving as a translating input optical source, and a beam-steering system built of spherical lenses to complete the switching behaviour. An ultra-fast actuator switching speed is estimated as 1.55 μs latency for a single connection with a demo circuit. We further simulate the beam-steering system end-to-end in a commercial optical design software CODE V and demonstrate a theoretical 2.16 dB insertion loss for a single connection in the switch at optimum alignment.

Multi-functional photonic processors using coherent network of micro-ring resonators

Silicon photonics have widespread applications in optical communications, photonic sensors, and quantum information processing systems. Different photonic integrated circuits often require similar basic functional elements such as tunable filters, optical switches, wavelength de-multiplexers, optical delay lines, and polarization crosstalk unscrambling. Other optical signal processing functional elements may be needed in specific applications, for example, the differentiation with respect to time of time-varying optical signals and the implementation of very high extinction interferometers in some integrated quantum photonic circuits. Just as reconfigurable electronic processors in microelectronics have advantages in terms of ready availability and low cost from large-volume generic manufacturing and are useful for configuration into different functionalities in the form of field-programmable gate arrays, here, we show how an integrated coherent network of micro-ring resonators can be used in reconfigurable photonic processors. We demonstrate the implementation of optical filters, optical delay lines, optical space switching fabric, high extinction ratio Mach–Zehnder interferometer, and photonic differentiation in a reconfigurable network where the control of the phase in the different arms of the coherent network can determine the implemented functionality.

Lossless Photonic Integrated Add-Drop Switch Node for Metro-Access Networks

We assess the performance of a modular photonic integrated circuit (PIC) for space and time optical switching as an optical add-drop node for metro-access network applications. The PIC based on semiconductor optical amplifier (SOA) technology enables the implementation of compact, low cost and lossless add-dropping through fast optical switching. Data integrity measurements demonstrate error-free switching operation with less than 1 dB and 2.5 dB power penalty for 10 Gb/s and 40 Gb/s NRZ OOK optical signal, respectively. The dynamic control of the SOA based optical gates by the switch controller permits the power equalization of the switched channels. The experimental results also demonstrate dynamic forwarding, dropping and multicasting operation for a packetized 10 Gb/s NRZ OOK optical signal. The transparency of the SOA technology towards the optical signal’s data rate allows to avoid costly and power consuming dedicated interfaces at the add-drop node and open a path towards efficient statistical multiplexing.

Hybrid QKD Protocol Outperforming Both DV- and CV-QKD Protocols

To overcome the limitations of both discrete variable (DV) and continuous variable (CV) QKD protocols, in this paper, a hybrid QKD protocol is proposed. In the proposed hybrid QKD protocol, Alice simultaneously performs discrete modulation (DM)-based encoding for CV-QKD subsystem and time-phase encoding for DV-QKD on a transmitter side and transmits such hybrid encoded pulse with optimized average number of photons per pulse. On receiver side, Bob employs a 1:2 optical space switch to select either DV-QKD receiver or CV-QKD receiver with the optimized probability of selection. Other compatible CV-QKD and DV-QKD protocols can also be used in hybrid QKD. Bob further performs the classical postprocessing applied to both subsystems so that resulting joint secure key is derived from both subsystems. The proposed hybrid QKD protocol significantly outperforms previously introduced both Gaussian modulation (GM)- and DM-based CV-QKD protocols as well as DV-QKD protocols in terms of both secret-key rate and achievable transmission distance.

Modular Optical Cross-Connects (OXCs) for Large-Scale Optical Networks

Due to the explosive growth of traffic demands, large-scale optical cross-connects (OXCs) are highly desired in next-generation optical networks. However, the scalability of classical OXCs is not good in terms of the size of optical switching modules and cabling complexity to meet application requirement. To address this issue, this letter proposes a two-phase approach to construct modular large-scale OXCs, using a set of small-size OXC modules. We first decompose each optical space switch (OS) in a classical OXC to a Clos network and then merge the corresponding links and decomposed optical switching modules of different Clos networks to form small-size OXC modules, which finally yields a modular OXC. We show that the proposed modular OXC has good scalability and acceptable physical-layer performance.

Semiconductor optical amplifier space switch BER improvement and guard-time reduction through feed-forward filtering

Analysis of the guard-time interval impact on bit error rate (BER) of a linear SOA-based space switch aiming the guard-time reduction is presented, including effects of fiber propagation. The characterization employed feed-forward filtering and optical switching techniques, through several types and lengths of fibers (with and without dispersion compensation). The Wiener filter (with 2 taps) consistently showed a switching performance improvement, with a guard-time (GT) reduction enough to achieve the BER pre-FEC limit. In most configurations the average GT was of 429ps (3 bits GT at 7Gbps). The overall best GT result achieved was using 100mA of SOA bias current and applying the Wiener Filter, resulting in a GT of 286ps (2 bits GT at 7Gbps). The space-switch operating parameters with focus on the bias current and switching technique configuration were also analyzed, aiming at reducing the SOA-based electro-optical space switch guard-time, allowing the achievement of high commutation rates.

On-chip broadband silicon thermo-optic 2☓2 four-mode optical switch for optical space and local mode switching.

We present a silicon thermo-optic 2☓2 four-mode optical switch optimized for optical space switching plus local optical mode switching. Four asymmetric directional couplers are utilized for mode multiplexing and de-multiplexing. Sixteen 2☓2 single-mode optical switches based on balanced thermally tunable Mach-Zehnder interferometers are exploited for switching function. The measured insertion losses are 8.0~12.2 dB and the optical signal-to-noise ratios are larger than 11.2 dB in the wavelength range of 1525~1565 nm. The optical links in "all-bar" and "all-cross" states exhibit less than 2.0 dB and 1.4 dB power penalties respectively below 10-9 bit error rates for 40 Gbps data transmission.

General architectures for on-chip optical space and mode switching

The optical switches for single-mode operation cannot be directly utilized in optical communication and interconnect systems adopting mode-division multiplexing. In this paper, three general architectures for on-chip optical space and mode switching are proposed, which are optimized for optical space switching, optical space switching plus local optical mode switching, and global optical mode switching, respectively. A silicon thermo-optic 2×2 four-mode optical switch is demonstrated. The minimum and maximum optical link insertion losses are 16.0 and 20.9 dB (including ∼6 dB coupling loss), respectively, in the wavelength range of 1525–1565 nm, while the optical signal-to-noise ratios of the optical links are larger than 15.3 dB. The optical power penalty at a bit error rate of 10−9 varies from 1.0 to 5.6 dB for 40 Gbps data transmission through different optical links. This work provides a systematic solution to on-chip information switching for different physical and mode channels.

Optical trends in data centers architectures for smart cities

This paper aims to present a new data center topology using new components such as top of rack (ToR), switches for the aggregation of each rack, optical space switches (OSS) used for intra/inter connectivity, and software defined network (SDN) as control plane for the configuration of the associated network resources. The effect of flows streams is examined further on the performance of the data centers developed into smart cities. Moreover, a comparison between the traditional non-blocking hierarchical network and the proposed new topology all-optical in terms of completion time for multicast and unicast flows are presented.

Proposal of optical mode switch

Here, we propose a novel optical mode switch, which is a new concept of the optical switch. It can overcome the matrix size limitation issue, which has been a general issue for the waveguide optical space switch, because of its simple fiber coupling configuration. In addition, it contributes to the lossless mux/demux function such as wavelength multiplexing with powerless mode conversion unlike wavelength conversion. In this paper, we propose the principle of the optical mode switch. The simulation results showed less than −30 dB mode crosstalk, with less than only 0.1 dB excess loss for a two-mode optical switch. Moreover, the scalable configuration up to four modes is also proposed in this paper.

All Optical Packet Switches Based On Space Switch Array for the Transmission of Higher Data Rate Using NRZand RZ Modulation

The explosive growth of the Internet traffic requires the design of next generation switching systems accommodating huge data-centric traffic at the packet level. All-optical packet switching (OPS) with greater flexibility, granularity and switching capacity is able to meet the complexity of traffic. An all-optical fiber-optic switching device maintains the signal as light, from input to output. Semiconductor optical amplifiers (SOAs) are widely studied as nonlinear elements for high bit rate all-optical switching applications, such as wavelength conversion and regeneration. All optical switches incorporating SOAs have peculiarities like small size, low switching energy requirement and high non linearity. Here simulation of a 4 x 4 optical packet space switch array based on Optically Amplified Suppressed Interference Switches (OASIS) with different data rate has been performed. The OptiSystem version-12 simulator is used to model the structure, it is also used to assess the behavior and performance of this switch array. The simulation of 4x4 space switch array with different bit rate and for different modulation format is done which gives the BER within the acceptable range. Implications of cascadability of this switch array will be analysed which improves the quality and capacity of the existing networks

Heterogeneous Optical Space Switches for Scalable and Energy-Efficient Data Centers

Optical space switches are key elements for the next generation of switching fabrics in backbone routers, high performance computing systems, and large data processing and storage systems. A number of architectures and alternative options for gating elements have been proposed, assessed, and implemented for a limited port count. The challenge is to further enhance the scalability and energy efficiency of space switches to support future traffic loads. This paper proposes a heterogeneous implementation of the space switches based on two different types of gating elements, namely semiconductor optical amplifiers (SOA) and Mach-Zehnder Interferometers (MZI). With respect to the existing homogeneous implementations, a higher energy efficiency can be achieved by minimizing the number of SOAs, but crosstalk is introduced by MZI. To reduce the power consumption while still guaranteeing adequate physical layer performance, the design of both Spanke and multi-stage architectures is optimized by strategically placing the different gating and amplification elements, and a physical layer analysis is carried out to validate the performance. The proposed heterogeneous implementation is able to achieve power savings up to 10% and 50% in the Spanke and multi-stage Benes architectures, respectively, with respect to SOA-based space-switch implementations. Moreover, an improvement of the physical layer performance is achievable in the Spanke architecture thanks to the different placement of the SOAs.

Hypernetwork Model and Architecture for Deep Space Information Networks

The increasing world-wide demands in deep space scientific missions, such as Lunar, Mars and other Planetary Exploration, along with the rapidly growing advances in space communication technologies have triggered the vision of so called future Deep Space Information Networks (DSINs). The coined DSIN paradigm is envisioned to be an integrated high speed self-organizing hypernetwork consisting of the terrestrial ground-based information networks and the outer space- based entities to provide maximum network capacity. In this document, the problem of network infrastructure and architecture for DSINs is investigated. Taking into account the major challenges or characteristics affecting link, networking, transport, and security design of DSINs, this document employs hypergraph theory to construct network infrastructure and node architecture of space optical switching, and further presents a five-layered hypernetwork model of DSINs to enhance network connectivity. Combining with the benefits in interconnection and interoperability of heterogeneous challenged networks, brought by the well-known Delay-and Disruption-Tolerant Networking (DTN) architecture, this document proposes a novel architecture of DSINs from two levels including Layered Protocol Stack and Management Plane. The proposed architecture preliminarily achieves the basic concepts and the relevant mechanisms of wisdom network, and the performance and quality of service (QoS) of DSINs are thereby improved.

Integrated Fabry-Perot Comb Filters for Optical Space Switching

The first implementation of an integrated filter for optical space switching based on coupled Fabry-Perot cavities built in a planar waveguide and working at oblique incidence is presented in this paper. Parabolic mirrors are used to collimate and direct light into a filter defined by deep etching in a GaAs waveguide and formed of four high-order cavities that provide a 200 GHz comb response. The filter has a theoretical passband bandwidth of more than 50 GHz and allows the switch to work over an entire wavelength band. It was possible to contain 50 channels of the International Telecommunication Union 100 GHz grid within the filter response. Bit error rate tests at 10 Gb/s were performed to evaluate the switch power penalty. To assess the scalability of this switch design, crossbar and shuffle Benes¿ layout for devices with 2-16 ports were optimized. The dominating factor that limits the minimization of a switch fabric area is the beam waist required to avoid distortion by the filters.

新颖的微流控电调谐空间光开关

A novel space optical switch device of optofluidic is proposed to solve the problems of electrical controlling without mechanical device.The basic structure of the switch includes a core exchange space sandwiched between two optical arrays.The basic unit of array is made from liquid prism as a beam control unit including three kinds of immiscible liquids(water / oil / water).Through the electro-wetting effect,the beam deflection angle of the liquid prism can be adjusted about -15 °~15 °continuously in a specific voltage range(30 ~ 110 V).Thus one can construct a variety of two-dimensional or even three-dimensional optical switch array.

Design of Fabry-Perot filters in planar waveguides with deep-etched features for spatial switching

Scalable optical space switches compatible with high bit rates which can be reconfigured on-the-fly are needed to increase the flexibility of optical networks. We present the design of integrated Fabry-Perot filters working at oblique incidence, which can be used to build optical space switches. A comprehensive planar waveguide optimization was conducted to minimize radiation losses in the deep-etch features forming the filter mirrors. Four high order cavities were coupled to create a 200 GHz comb wavelength response with passbands larger than 50 GHz and extinction ratio greater than 20 dB over the entire C-band. Gaussian beam propagation analysis showed that the minimum beam waist required to avoid distortion increases rapidly with incident angle.

Loss Analysis of Multiple Service Classes in Shared-per-Wavelength Optical Packet Switches

Management of quality of service in optical packet switches equipped with fixed input, tunable output wavelength converters is described. This kind of switch is considered with the aim to keep switch cost low by employing simple shared optical components and low-complexity space switching matrices. In particular, differentiation among classes of service in terms of loss performance for bufferless switches is addressed. The functionalities described refer to the high-speed multiservice networking context foreseeable for the future Internet. A switch control algorithm to manage service classes in a slotted multiplexing context is described. An analytical model to evaluate the loss probability of each class is developed and validated against a simulation and is used to prove the effectiveness of the quality-of-service approach. Numerical results show that the proposed scheme achieves basic class isolation as needed in core network optical packet switches.

16×16 Mirror type optical switch with integrated fiber alignment and steady switching state

AbstractThis paper reports a micro electro mechanical system (MEMS) 16×16 free space optical switch based on high‐reflectivity mirrors. The mirror monolithically integrated with the fiber grooves can enlarge its rotation angles up to 90°, and keep this as a steady state to steer the optical signal. The reflectivity of the mirror is measured to be 93.1 ∼ 96.3%. The smallest fiber‐mirror‐fiber insertion loss is 2.1 dB by utilizing optiFocusTM collimating lensed fibers. Moreover, only about ±0.01 dB oscillating amplitude of insertion loss is provoked after the device is tested for 15 min for 5 ∼ 90 Hz in the vertical vibration amplitude of 3 mm. In addition, excellent antifatigue performance of the mirror, which can endure more than 109 cycles of actuation, has been proven. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3012–3016, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23879

Multifiber Shared-Per-Wavelength All-Optical Switching: Architectures, Control, and Performance

A new wavelength converter sharing strategy for multifiber optical switches, namely shared-per-wavelength (SPW), which employs wavelength converters with fixed input wavelengths is presented. The aim is to reduce switch costs by using simpler optical components and low complexity space switching matrices. Practical implementations of both the well-known shared-per-node (SPN) and the new SPW schemes are presented, as well as the related scheduling algorithms to manage optical packet forwarding in synchronous scenario. An analytical model to evaluate blocking performance of the SPN architecture is also provided. Results show the accuracy of the model in the range of interest for switch design. The proposed architectures are compared in terms of performance and number of optical components employed. The SPW approach is shown to save a large number of semiconductor optical amplifier gates with respect to the SPN one when the number of fibers per interface is suitably not too high. In these cases, the SPW architecture requires a number of wavelength converters higher than the SPN, but simpler, being their inputs tuned on a single wavelength.