Abstract: Methods and apparatus for dither control of a micromirror using a servo control loop in an optical switching apparatus, an optical switching apparatus and optical network are disclosed. A servo control loop may use dither tone having two or more frequency components to dither an output driver that controls the position of a micromirror in an optical switch. The two components may be demodulated from an optical signal deflected by the micromirror. The optical signal may be fed into two band-pass filters. Each band-pass filter may have a pass band centered on a different one of the two frequency components. The envelope detector may compare the envelopes of the band-pass filter outputs. If the envelopes differ by more than a set threshold the output of the envelope detector may be forced to zero. Otherwise, the output of the envelope detector may be the sum of the two band-pass filter outputs.

Abstract: Methods for adjusting dither amplitude for MEMS mirrors in optical switches and optical switches employing such a method are disclosed. A dither amplitude of one or more MEMS mirrors may be adjusted in an optical switch having an input port, and an array of one or more MEMS mirrors that can be selectively optically coupled to one or more of N?3 optical input/output (I/O) ports. The MEMS mirrors are aligned mirrors to achieve nominal peak coupling at each of the N collimators. Digital-to-analog (DAC) settings for positioning mirrors in an open control loop as a function of the selected collimator are stored to a non-volatile memory. The DAC settings are used to determine a dither amplitude DITHER(x) for one of the MEMS mirrors positioned to couple optical signals to an output port at a position x.

Abstract: Effects of diffraction of a spectral beam from an edge of the micromirrors are reduced in order to optimize the passband in a wavelength selective switch. The effects of diffraction on the pass band may be reduced by using rotation of the micromirror about both the attenuation axis and the switching axis to achieve the desired level of attenuation. Peak coupling can be attained by dithering the micromirror about a dither axis that is tangent to a contour of constant attenuation using simultaneous rotation about the switching and attenuation axes. A power level of a spectral channel may be attenuated by rotating the channel micromirror with respect to an effective attenuation axis that is non-orthogonal to the dither axis through a combination of rotations about the switching axis and the attenuation axis.

Abstract: Effects of diffraction of a spectral beam from an edge of the micromirrors are reduced in order to optimize the passband in a wavelength selective switch. The effects of diffraction on the pass band may be reduced by using rotation of the micromirror about both the attenuation axis and the switching axis to achieve the desired level of attenuation. Peak coupling can be attained by dithering the micromirror about an axis tangent to a contour of constant attenuation using simultaneous rotation about the switching and attenuation axes.

Abstract: One aspect is a method for controllably attenuating the beam of light (108) coupled between incoming and outgoing optical fibers (106) by misaligning minor surfaces (116a, 116b) included of an optical switching module (100). Misalignment of the mirror surfaces (116a and 116b) causes only a portion of the beam of light (108) propagating along the incoming optical fiber (106), which is less than when the light beam deflectors' mirror surfaces (116) are precisely aligned, to propagate along the outgoing optical fiber (108). Thus, the optical switching module (100) controllably attenuates the beam of light (108) coupled between the incoming and the outgoing optical fibers (106). Another aspect is a variable-optical-attenuator (“VOA”) (212) that includes an optically reflective membrane (222) upon which the beam of light (108) impinges. Application of an electrostatic field between an adjacent electrode (228) and the membrane (222) deforms the membrane (222) thereby attenuating an impinging beam of light (108).

Abstract: A system and method for canceling disturbance in a MEMS device. The system 200 includes a MEMS device 203, which may include a substrate 205 and a plurality of individually movable MEMS elements 203-1 through 203-N, and a control assembly 207. The optical system 200 may be utilized in and/or form a portion of any optical apparatus employing an array of MEMS devices. The control assembly 207 uses feed-forward control signals to cancel disturbance in the MEMS device 203, and more particularly, to cancel disturbance in the non-switched or static mirrors of the MEMS device 203 caused by switched or moving mirrors.

Abstract: Structures of storage media for optical storage systems, especially for systems in the near-field configuration to couple radiation between the optical head and the media at least in part by evanescent fields.

Abstract: One aspect is a method for controllably attenuating the beam of light (108) coupled between incoming and outgoing optical fibers (106) by misaligning minor surfaces (116a, 116b) included of an optical switching module (100). Misalignment of the mirror surfaces (116a and 116b) causes only a portion of the beam of light (108) propagating along the incoming optical fiber (106), which is less than when the light beam deflectors' mirror surfaces (116) are precisely aligned, to propagate along the outgoing optical fiber (108). Thus, the optical switching module (100) controllably attenuates the beam of light (108) coupled between the incoming and the outgoing optical fibers (106). Another aspect is a variable-optical-attenuator (“VOA”) (212) that includes an optically reflective membrane (222) upon which the beam of light (108) impinges.

Abstract: Structures of storage media for optical storage systems, especially for systems in the near-field configuration to couple radiation between the optical head and the media at least in part by evanescent fields. Manufacturing methods are also disclosed.

Abstract: An optical position detector which has adjacent detector cells connected to each other in a zig-zag pattern offers a wider dynamic range than a detector with a vertical separation line during transition between a read laser power and a write laser power. This allows use of a fast response bi-cell in place of a slower position sensing device (PSD). The optical position detector has detector cells coupled to each other in a zig-zag pattern. Each detector cell produces a signal when a light beam is focused onto the cell to indicate a location of the light beam relative to the cell.

Abstract: In a disc drive, a position error signal (PES) can be generated that is insensitive to the read element's magnetic and physical geometry and micro-track profile, and that has a spatial domain periodic frequency that corresponds to a frequency region of the micro-track profile that facilitates a high magnitude response. The servo pattern for generating this PES includes a first servo burst pair (A,B) and a second servo burst pair (C,D) of servo burst members, each pair written as normal and quadrature channels.

Abstract: A method for optimizing the demand velocities in a disc drive velocity profile using both time and vibro-acoustic constraints. An accurate, high-order dynamic model of the disc drive is formulated which describes the vibro-acoustic output of the drive in response to actuator coil current input, taking into account the disc drive actuator structure and the electrical response of the disc drive servo circuit. From this dynamic model, the shortest possible seek time is determined for a selected seek length which can achieve a vibro-acoustic output below a selected, maximum limit, as well as settling within a specified tolerance of the target track. Once the shortest possible seek time is determined, the demand velocity values in the velocity profile are selected so as to minimize the maximum position error during the seek settle. The demand velocity values are subsequently provided in a look up table for use during a seek by the disc drive servo circuit.

Abstract: The present invention utilizes the output of a voltage regulator to control the drive voltage to the stepper motor driven transducer positioning system. This technique will significantly reduce the access time. More specifically, in this invention, the output of a digital-to-analog converter (DAC) is used to control the output voltage level of a voltage regulator circuit which supplies the voltage of the stepper motor drive transistors. In order to optimize the drive voltage output from the voltage regulator to the stepper motor for each disc drive, circuitry is provided to determine the minimum settling time for a specific actuator movement resulting from the application of a given drive voltage. A detector circuit monitors the settling time of the head over the center of the target track. The data identifying the voltage regulator output which results in minimum settling time is stored and used from then on for that stepper motor disc drive system as the optimum access tuned voltage.

Abstract: The output of the ring detector is used to change or control the timing of specially generated torque damping pulses which are fed to the stepper motor at the end of a SEEK step sequence. These torque damping pulses are step pulses, the timing, amplitude and/or duration of which applies either a positive or negative torque to the stepper motor relative to the target track based on the "energy" that has to be dissipated to settle the read/write head over the desired track. The energy is measured indirectly by monitoring the back emf voltage of an open winding or unenergized phase of the motor, and developing an indication of how fast the read/write head is going through the desired track center or target track point. By bringing an additional signal out of the ring detector, the direction in which the read/write head has crossed the track can also be defined.

Abstract: A disc drive system is disclosed including a data storage disc having a plurality of data storage tracks. Each track has a centerline, the centerlines of adjacent tracks being spaced by a fixed track space distance. The disc surface also includes wedge servo sectors; servo data in each sector includes first servo information stored at a position on one side of said data track centerline and one-half said track space distance from said centerline, and second servo information stored at the other side of said data track centerline and one-half of said track space distance from said centerline. Positionable accessing is provided for reading the servo data and for generating servo signals representing the first and second servo burst information, to positioning said transducer accurately.

Abstract: A servo system incorporating an attenuator for reducing the error signal an amount proportional to the magnitude of the error signal so as to minimize overshoot without affecting the stability in the system.