Lossless optical packet multicast using active vertical coupler based optical crosspoint switch matrix

Construction of large scale switch matrix by interconnecting integrated optical switch chips with EDFAs

Large-scale optical switching matrix is the core technology of automatically switched optical network. With the significant increase of the matrix size, the study showed that the nonlinear factors, such as the correlation of the wavelength, phase and polarization between the optical switches have major impacts for the system performance. Because the full-size optical simulation is not available now, the research will be a great significance that we establish an overall model with not only considering the performance of optical switch unit, but also reflecting the structural characteristics of the network.In this paper, we calculated the transmission field of 2×2 Mach –Zehnder(MZI) silica on silicon thermo optic(TO) switch with different structure by using the finite difference beam propagation method(BPM). On the basis of optimization design, we constructed and simulated the large-scale 16×16 MZI silicon-based SiO2 Silica on silicon thermo switching matrix. The results are: In TE Mode, for Crossbar and banyan structures, insertion losses are 13.35 dB and 4.3638 dB; crosstalk losses are 27.125~29.0173 dB and 42.2318-43.7159 dB; extinction ratios are 29.57 dB and 26.79 dB respectively.

A novel optical serial multicast mode scheme using an active vertical coupler optical crosspoint switch matrix has been successfully demonstrated. A fibre delay line has been employed to recirculate optical packets, providing one serial output packet for each recirculation. A minimum Q-factor of 5.68 dB and an optical signal-to-noise-ratio penalty of <2.3 dB are found after nine recirculations.

Packet-switching characteristics are optimized across an integrated 4 x 4 optical cross-point switch matrix based on active vertical coupler switch cells. Optical gain is demonstrated across the entire matrix with a <3-dB difference between the shortest and longest switching paths.

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 /spl times/ 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 /spl times/ 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths.

A folding rearrangeable nonblocking 4×4 optical matrix switch was designed and fabricated on silicon-on-insulator wafer. To compress chip size, switch elements (SEs) were interconnected by total internal reflection (TIR) mirrors instead of conventional S-bends. For obtaining smooth interfaces, potassium hydroxide anisotropic chemical etching of silicon was utilized to make the matrix switch for the first time. The device has a compact size of 20×1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a fast response of 7.5 μs. The power consumption of each 2×2 SE and the average excess loss per mirror were 145 mW and -1.1 dB, respectively. Low path dependence of /spl plusmn/0.7 dB in total excess loss was obtained because of the symmetry of propagation paths in this novel matrix switch.

The optical switch matrix is the one of the key elements in constructing optical switching systems. Many types of optical switch matrix architectures have been proposed1 to improve their characteristics and to construct devices with larger switch dimensions. However, since the substrate for fabricating the optical switch matrix is limited in size, the switching voltage of these structures was still relatively high. In addition, crosstalk characteristics degraded with increasing the number of output and input ports. The architecture wich can be obtained3 by simplifying the structure of tree-structure,2 wich we propose is one of the candidates for solving these problems. We report on the basic characteristics of this structure and some measured results from devices fabricated on LiNbO3 by indiffusion of Ti.

We successfully reduced the chip size of a 16/spl times/16 optical matrix switch with silica-based planar lightwave circuit technology to 36 %, and the power consumption to 37 % by employing 1.5 % /spl Delta/ waveguides, heat insulating grooves, and a new circuit layout.

High-speed low-drive power guided-wave optical matrix switches should perform various functions in future wideband multichannel integrated and fiber optic systems. An integrated optical switching matrix (network) was first described by Taylor(1) and a 4x4 switching network was later realized in a LiNbO3 substrate using five stepped Δβ reversal directional-coupler switches(2) by Schmidt.(3) In this paper we will report on an electrooptical channel waveguide matrix switch which utilizes total internal reflection (TIR) in a Y-cut LiNbO3 substrate. We will first present the performance characteristics of a basic channel waveguide TIR switch which is an improved version of the one we reported earlier.(4) We will then describe the design, fabrication, measurement technique, and the performance characteristics of a 3x3 and a 4x4 integrated switching matrices consisting of such basic TIR switches.

Integrated optics switch matrices are expected to play an important role in optical space switching systems due to their ability to route information practically irrespective of its bandwidth and coding format (” code and frequency transparency”), in marked contrast to electronic switching networks. The integrated optics switches also offer the advantage of integration, as opposed to mechanical optical switches. Accordingly a number of integrated optics matrices have been reported1,2,3. However , all of these have been polarization sensitive, requiring interfacing to non-standard polarization holding fibers, and this can be considered a major factor in complicating systems applications. Ref4describes a polarization independent 1×16 switch in the tree structure employed below, however with strict fabrication tolerance on the switches. One reason for staying with polarization sensitive matrices has been the difficulty to combine integratability (reasonably low voltage -length product) with high yield for low crosstalk switch points. Here we report a matrix based on a switch point which combines these features by electronic tuning of its switching characteristics, relaxing fabrication tolerances5. The switch points are further arranged in a tree structure6,7which combines the capability for communicative as well as distributive switching with relaxed requirements on the crosstalk of each switching point. This is achieved at the expense of the number of switches: The 4×4 matrix reported in this paper (Fig 1) comprises 24 switches as opposed to the 16 switches of a crossbar structure, but the number of cascaded levels is only 4, as opposed to 7 in the crossbar case.

The effect of amplified spontaneous emission (ASE) noise on the optical signal quality of coherent optical communications, characterized by optical signal to noise ratio (OSNR) and error vector magnitude (EVM), is investigated numerically. The influences of ASE noise only and the interaction of ASE noise, dispersion and nonlinear optical effect on the signal OSNR and EVM are investigated. Moreover, the relationship between OSNR and EVM is derived theoretically, for systems with ASE noise only and with ASE noise and nonlinearity.

SOI (Silicon on Insulator) based photonic devices has attracted more and more attention in the recent years. Integration of SOI optical switch matrix with isolating grooves, total internal reflection (TIR) mirrors and spot size converter (SSC) was studied. A folding re-arrangeable non-blocking 4times4 optical switch matrix and a blocking 16times16 matrix with TIR mirrors and SSC were fabricated on SOI wafer. The performances, including extinction ratio and the crosstalk, are better than before. The insertion loss and the polarization dependent loss (PDL) at 1.55mum increase slightly with longer device length, more bend and intersecting waveguides. The insertion losses decrease 2-3 dB when anti-reflection films are added in the ends of the devices. The rise and fall times of the devices are 2.1mus and 2.3mus, respectively

We demonstrate a simple passive method to generate broadband chirped super-Gaussian pulses from high-gain ytterbium-doped fiber amplification system without obvious bandwidth degradation. By use of the inherent gain shaping effect of fiber amplifiers, pulses can recover the initial Super-Gaussian profile and bandwidth with large gain and optical signal-to-noise ratio (OSNR). In this method, fiber amplifier itself works as a spectral filter with flexible transmission profiles and gain, which can be optimized by pump power and fiber length. A spectrally resolved numerical model with amplified spontaneous emission (ASE) is developed for broadband ytterbium-doped double-clad fiber pulse amplifiers. In a proof-of-principle two-stage amplification system, with a shorter fiber preamplifier working in the gain-narrowing region as a pre-shaper, broadband Super-Gaussian pulses resemble themselves after the second amplification stage with the largest total gain and OSNR. Experimental results quantitatively confirm the numerical predictions. The proposed gain shaping method also provides a new way to compensate the pulse deformation and bandwidth narrowing in high-gain fiber chirped pulse amplification systems.

A scalable pulsewidth control approach with 7-bit resolution for thermal control of optical ring resonator switch matrices in 0.16- $\mu\text{m}$ Bipolar-CMOS-DMOS (BCD) with a cell size of $79\ast 105 \mu\text{m}^2$ is introduced. One Gray counter at up to 1.2-GHz clock and pulsewidth modulation generation in each matrix cell leads to an electrical power consumption of 330 mW for all electronic control circuits of an optical 1000-switch-node matrix, resulting in a reduction of 11.1% of the power needed by a constant-voltage control approach.

A broadband and fast optical space switch is a crucial part of optical networks. A broadband, compact, and fast monolithically integrated InP/InGaAsP strictly nonblocking optical space switch based on semiconductor optical amplifiers (SOA) gates has been designed, fabricated via the generic InP technology and characterized. The component losses, gain, and switching properties of the optical switch are analysed. The gain of three SOAs on a path was measured to be 31 dB on average and is enough to balance component losses whenever a reasonable number of waveguide crossings is encountered (< 25). An optical signal to noise ratio (OSNR) and extinction ratio (ER) as large as 42.4 dB and 37.6 dB, respectively, are obtained in the best path. The performance can be further improved with optimized optical routing and design of lower loss crossings. These results pave the way to scale the switch to higher port counts by using this switch as a building block on a modular basis. Additionally, the use of ultra-compact bends and the number of components integrated on this single chip also shows to be promising for achieving compact optical switches in generic technology.