Flavio Pardo

Wavelength-selective 1/spl times/K switches using free-space optics and MEMS micromirrors: theory, design, and implementation

The design and performance of several generations of wavelength-selective 1/spl times/K switches are reviewed. These optical subsystems combine the functionality of a demultiplexer, per-wavelength switch, and multiplexer in a single, low-loss unit. Free-space optics is utilized for spatially separating the constituent wavelength division multiplexing (WDM) channels as well as for space-division switching from an input optical fiber to one of K output fibers (1/spl times/K functionality) on a channel-by-channel basis using a microelectromechanical system (MEMS) micromirror array. The switches are designed to provide wide and flat passbands for minimal signal distortion. They can also provide spectral equalization and channel blocking functionality, making them well suited for use in transparent WDM optical mesh networks.

1100 x 1100 port MEMS-based optical crossconnect with 4-dB maximum loss

We present a microelectromechanical systems-based beam steering optical crossconnect switch core with port count exceeding 1100, featuring mean fiber-to-fiber insertion loss of 2.1 dB and maximum insertion loss of 4.0 dB across all possible connections. The challenge of efficient measurement and optimization of all possible connections was met by an automated testing facility. The resulting connections feature optical loss stability of better than 0.2 dB over days, without any feedback control under normal laboratory conditions.

Beam-steering micromirrors for large optical cross-connects

This paper describes Si-micromachined two-axis beam-steering micromirrors and their performance in 256 /spl times/ 256- and 1024 /spl times/ 1024-port large optical cross-connects (OXCs). The high-reflectivity wavelength-independent mirrors are electrostatically actuated; capable of large, continuous, controlled, dc tilt in any direction at moderate actuation voltages; and allow setting times of a few milliseconds. Packaged two-dimensional (2-D) arrays containing independently addressable identical 256 and 1296 mirrors are used to build fully functional bitrate and wavelength-independent single-stage, low-insertion-loss, single-mode fiber OXC fabrics.

1296-port MEMS transparent optical crossconnect with 2.07 petabit/s switch capacity

A 1296-port MEMS transparent optical crossconnect with 5.1dB/spl plusmn/1.1dB insertion loss at 1550 nm is reported. Measured worst-case optical crosstalk in a fabric was n38 dB and nominal switching rise/fall times were 5 ms. A 2.07 petabit/s switch capacity was verified upon cross-connecting a forty-channel by 40 Gb/s DWDM data stream through a prototype fabric.

Wavelength-selective 1/spl times/4 switch for 128 WDM channels at 50 GHz spacing

We present a reconfigurable wavelength-selective switch that independently distributes 128 input WDM channels to four output ports. The switch is based on bulk optics and MEMS micro-mirrors, exhibits <5 dB insertion loss and flat-top pass-bands, and is well suited for transparent switching of 10 Gb/s signals.

Crystalline silicon tilting mirrors for optical cross-connect switches

This paper discusses a two-piece approach for fabricating two-dimensional (2-D) arrays of tilting MEMS mirrors with application in very-large optical cross-connect switches. In the new process, a two-sided etching of silicon-on-insulator (SOI) wafers is used to create crystalline mirrors on a first wafer that is later aligned and bonded to a separate wafer containing the activation electrodes, traces, and bond pads. The approach allows a very close spacing of mirror elements and a very simple design for the mechanical structures, and also greatly simplifies wire routing.

238 x 238 micromechanical optical cross connect

This letter describes a 238/spl times/238 beam-steering optical cross connect constructed using surface micromachined mirrors. Its innovative optical configuration resulted in superior optical performance, achieving a mean fiber-to-fiber insertion loss of 1.33 dB and a maximum insertion loss for all 56 644 connections of 2 dB.

Lucent Microstar micromirror array technology for large optical crossconnects

Electrostatically actuated, 500micrometers diameter, Si surface micromachined 2-axis tilting micromirrors were designed and fabricated in a 2 structural + 1 interconnect layer polysilicon process. The mirrors are capable of large, continuous, controlled, DC tilt in any direction at moderate actuation voltages. The lowest-mode resonance frequency is sufficiently high to decouple from the ambient vibration noise and allow setting times of less than a few milliseconds. The Au- coated reflectors, suspended in gimbal mounts via torsional springs and bearings, are tilted by applying voltage to four electrically independent sets of fixed electrodes on the substrate. The electrodes and the springs are designed to optimize actuation voltages, resonance frequencies and the deflection range. To achieve the range, the mounts are lifted and fixed fifty microns above the substrate surface during the release process by a self-assembly mechanism powered by tailored residual stress in a separate metalization layer. Square arrays with 1 mm pitch containing independently addressable identical 16, 64 and 256 mirrors were fabricated and hermetically packaged. Based on these devices, fully functional, bitrate and wavelength independent, single stage, low insertion loss, single mode fiber optical crossconnect system are built.

Observation of smectic and moving-Bragg-glass phases in flowing vortex lattices

The defining characteristic of the superconducting state is its ability to carry electrical currents without loss. The process by which it does this has been extensively studied for decades but there are still many unresolved issues. In particular, the critical current, which is the maximum electrical current that a superconductor can carry without loss, remains a poorly understood concept at the microscopic level. In a type II superconductor, a flux-line lattice (FLL) forms if a magnetic field between Hc1 and Hc2, the lower and upper critical fields, is applied: flowing electrical currents will exert a force on this FLL. If the FLL remains pinned, the current flows without loss of energy and the effective resistance remains zero. However, if the lattice moves in response to the current, energy is dissipated and the zero-resistance state is lost. Because of its relevance to the critical current, the types of structures that these moving lattices can form have attracted much recent theoretical attention. Here we report magnetic decoration studies of flowing vortex lattices which show evidence for a transition, as a function of increasing flux density, from a layered (or smectic) FLL to a more well-ordered moving Bragg glass.

MEMS-based channelized dispersion compensator with flat passbands

This paper describes a continuously variable and independently addressable channelized dispersion compensator. The optical system is a free-space grating-based system used in a four-pass configuration to ensure flat passbands. The variable dispersion is produced by an array of thermally adaptable curvature micromechanical mirrors. A per-channel variable dispersion greater than +/-400 ps/nm has been demonstrated, with 58 GHz +/-0.4 dB flat passband on 85 GHz spacing. The group delay ripple is less than 7 ps and the penalty with 40 Gb/s CSRZ is 0.7 dB.