Feedback Patents (Class 398/209)
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Patent number: 7103276Abstract: A scanning optical monitoring system and method are appropriate for high speed scanning of a WDM signal band. The system and method are able to identify dropped channels or, more generally, discrepancies between the determined or detected channel inventory and a perpetual inventory for the WDM signal, which perpetual inventory specifies the channels that should be present in the WDM signal assuming proper operation of the network. The system includes a tunable optical filter that scans a pass band across a signal band of a WDM signal to generate a filtered signal. A photodetector then generates an electrical signal in response to this filtered signal. A decision circuit compares the electrical signal to a threshold and a controller, which is responsive to the decision circuit, inventories the channels in the WDM signal.Type: GrantFiled: December 20, 2000Date of Patent: September 5, 2006Assignee: Axsun Technologies, Inc.Inventors: Jeffrey A. Korn, Walid A. Atia
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Patent number: 7092630Abstract: The present invention implements open fiber control in an optical transceiver. During normal operation, the transceiver transmits signals through a connection to an optical network. When the connection is intact, the total power transmitted can be greater than the eye-safety limit. When the connection breaks, the transceiver detects the loss of signal and disables transmissions over all channels except for one. The transceiver continues transmission on the single enabled channel at an eye-safe level. When the connection is fixed and a signal reappears, the transceiver detects the signal reappearance and re-enables all channels that had previously been disabled. By allowing the transceiver to transmit with greater optical power when the connection is intact, an increased data rate and longer transmission distances can be achieved. At the same time, safety is preserved, because transmissions drop to acceptable power levels whenever a break is detected.Type: GrantFiled: November 16, 2001Date of Patent: August 15, 2006Assignee: Avago Technologies Fiber IP(Singapore) Ptd. Ltd.Inventors: David G Cunningham, Frederick Miller, Jing Wang, Janet Yun
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Patent number: 7092638Abstract: An optical multiplex communication system includes a transmission part and a receiving part, wherein the transmission part includes a transmission quality detecting part which measures and transmits a transmission quality information for the channels based on a request from the transmission part; the receiving part includes a variable optical attenuation part controls the optical signal level for the channels, an optical level setting part controls the variable optical attenuation part based on a setting value, a setting control part adding the setting value to the optical level setting part based on a request for setting.Type: GrantFiled: October 15, 2002Date of Patent: August 15, 2006Assignee: Fujitsu LimitedInventors: Yoshihisa Funami, Tetsuo Wada, Kazumaro Takaiwa, Toshihisa Kyouno, Yasushi Tateno, Yoshiaki Shibayama, Akinori Nishiie
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Method for splitting an optical signal into a number of electrical data signals with lower bit rates
Patent number: 7079766Abstract: A method of splitting an optical data signal starting with an optical data signal split into n equal data sub-signals, and an optical binary auxiliary signal with the same bit rate and phase is added to each optical data sub-signal. Each nth bit of the optical binary auxiliary has a higher level, with the phases of each of the n optical auxiliary signals showing a relative displacement of one bit. As a result, n aggregate signals are generated, each of which is fed to a decision-maker. A decision-maker threshold is set above the amplitude of the data sub-signal and below the amplitude of the aggregate signal. Each decision-maker, therefore, emits an electrical data signal with 1/n times the bit rate of the data signal.Type: GrantFiled: April 4, 2003Date of Patent: July 18, 2006Assignee: Siemens AktiengesellschaftInventor: Erich Gottwald -
Patent number: 7062165Abstract: A data regenerator for regenerating a data signal, including a convertor for converting a received data signal into a binary data signal in dependence on conversion parameters, an error corrector for correcting errors in the binary data signal based on error correction code contained in the binary data signal to produce a corrected binary data signal, and a performance monitor for comparing the corrected binary data signal with an uncorrected representation of the binary data signal to determine information about the relative number of logic“1”s and logic “0”s that have been corrected by the error corrector and output a feedback signal representative of the relative number, wherein the convertor adjusts at least some of the conversion parameters in dependance on the feedback signal.Type: GrantFiled: December 26, 2001Date of Patent: June 13, 2006Assignee: Nortel Networks LimitedInventors: Patrice Brissette, Sandy A. Thomson
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Patent number: 7050724Abstract: The invention relates to an optical receiver comprising a transimpedance amplifier having an input and an output, a photo detector (PD) for converting the optical power arriving at the receiver, an adjustable impedance element (D1) operationally connected to the input of the transimpedance amplifier, and control means (CU) for controlling the current passinh through the impedance element by adjusting the impedance of the impedance means. In order for the receiver to have a high dynamic range, the adjustable impedance element is a PIN diode and the control means comprise (a) separating means (LPU) for separating the direct voltage component from the output voltage of the transimpedance amplifier, and (b) means (VCU) for adjusting the voltage over the PIN diode directly on the basis of the separated direct voltage component.Type: GrantFiled: May 8, 2000Date of Patent: May 23, 2006Assignee: Nokia CorporationInventor: Erkki Rantakari
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Patent number: 7039330Abstract: Mitigating errors caused by the dispersion of optical or electrical signals. Errors caused by dispersion in high frequency system are mitigated by passing a received signal through an adjustable linear filter that counteracts a channel response of a channel on which the received signal has traveled to produce an electrical signal. The adjustable linear filter has a number of coefficients. A figure of merit is calculated for the electrical signal, where the figure of merit includes the second and fourth moments of the electrical signal. The coefficients of the linear filter are adjusted based on the value of the figure of merit so as to minimize the figure of merit.Type: GrantFiled: October 10, 2003Date of Patent: May 2, 2006Assignee: Finisar CorporationInventor: Thomas Lenosky
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Patent number: 7035548Abstract: A dispersion compensation controlling apparatus used in a very high-speed optical communication system adopting optical time division multiplexing system comprises a first specific frequency component detecting unit (2a) detecting a first specific frequency-component in a baseband spectrum in a transmission optical signal inputted to a receiving side over a transmission fiber as a transmission line (6a), a first intensity detecting unit (3a) detecting information on an intensity of the first specific frequency component detected by the first specific frequency component detecting unit (2a and a polarization-mode dispersion controlling unit (220a) con trolling a polarization-mode dispersion quantity of the transmission line (6a) such that the intensity of the first specific frequency component detected by the first intensity detecting unit. (3a) becomes the maximum, thereby easily detecting and compensating polarization-mode dispersion generated in a high-speed optical signal.Type: GrantFiled: February 18, 2004Date of Patent: April 25, 2006Assignee: Fujitsu LimitedInventors: Hiroki Ooi, George Ishikawa, Yuichi Akiyama
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Patent number: 7027741Abstract: According to a PLL circuit of the present invention, an output of a phase comparator is adjusted according to a space-to-mark transition-probability of an input signal so that an output of a voltage controlled oscillator has a predetermined frequency and phase. Therefore, even when a phase of a timing clock is set other than at 0, an output of the PLL circuit can be kept at the set phase, irrespective of the space-to-mark transition-probability. By using the PLL circuit as such in an optical communication apparatus and an optical communication system, a discrimination point can be kept almost fixed, and therefore, it is possible to lower an error rate.Type: GrantFiled: April 23, 2002Date of Patent: April 11, 2006Assignee: Fujitsu LimitedInventors: Masazumi Marutani, Takuji Yamamoto, Naoki Kuwata, Katsuya Yamashita
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Patent number: 7006770Abstract: The invention relates to an optical receiving station, an optical communication system, and a dispersion controlling method for precisely controlling chromatic dispersion in an optical transmission line or chromatic dispersion in an optical transmission line that varies with time. An optical receiving station is provided with a dispersion compensating section for receiving, via an optical transmission line, an optical signal modulated according to an optical duo-binary modulation method and for changing a dispersion value to be used for compensating for chromatic dispersion in an optical transmission line, an intensity detecting section for detecting the intensity of a specific frequency component of the optical signal output from the dispersion compensating section, and a controlling section for adjusting the dispersion value of the dispersion compensating section so that the output of the intensity detecting section has a predetermined extreme value.Type: GrantFiled: February 23, 2001Date of Patent: February 28, 2006Assignee: Fujitsu LimitedInventors: Yuichi Akiyama, Hiroki Ooi, George Ishikawa
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Patent number: 6999688Abstract: A receiver system processes a received optical signal that carries user information. The receiver system includes a splitter, a first converter, a second converter, and a detection system. The splitter splits the received optical signal based on polarization into a first optical signal and a second optical signal. The first converter converts the first optical signal into a corresponding first electrical signal. The second converter also converts the second optical signal into a corresponding second electrical signal. The detection system applies radio frequency detection to the first electrical signal to generate a third electrical signal. The detection system applies radio frequency detection to the second electrical signal to generate a fourth electrical signal. The detection system then combines the third electrical signal and the fourth electrical signal to form a fifth electrical signal that carries the user information.Type: GrantFiled: December 20, 2001Date of Patent: February 14, 2006Assignee: Sprint Communications Company L.P.Inventors: Rongqing Hui, Christopher T. Allen, Kenneth Robert Demarest
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Patent number: 6999687Abstract: An optical receiving device. The optical receiving device has a photodiode, transimpedance amplifier, and a feedback component. The photodiode has a first terminal coupled to a voltage source and a second terminal. When detecting an optical signal, the photodiode generates a current signal output from the second terminal. The transimpedance amplifier converts the current signal to a voltage signal and outputs the voltage. The feedback component is coupled between the first terminal and a input terminal of the transimpedance amplifier. The feedback component feeds a first voltage-changing signal, occurring in the input terminal of the transimdepance amplifier with the current signal, to the first terminal.Type: GrantFiled: December 29, 2003Date of Patent: February 14, 2006Assignee: Industrial Technology Research InstituteInventor: Chia-Ming Tsai
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Patent number: 6987804Abstract: A process is proposed for recovering disturbed digital signals, wherein the electrical signals pass through a feedback equalizer and an analogue control of the setting parameters of the equalizers is performed. A pseudo-error monitor, which facilitates a high-speed adjustment of decision element thresholds, is also provided.Type: GrantFiled: March 26, 2001Date of Patent: January 17, 2006Assignee: AlcatelInventors: Fred Buchali, Henning Bülow
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Patent number: 6980747Abstract: An integrated, optically amplified receiver includes an optically pumped optical preamplifier for receiving, generally, wavelength division multiplexed optical communication signal over an optical communications line. A PIN photodetector receives the optical communication signal as a filtered demultiplexed signal from the optical preamplifier and converts the optical communication signal into an electrical communication signal. An amplifier circuit amplifies the electrical communication signal for digital retiming or demodulation. A housing or printed circuit card assembly contains the optical preamplifier, filter or demultiplexer, PIN photo detector and amplifier circuit as an integrated receiver unit.Type: GrantFiled: November 28, 2000Date of Patent: December 27, 2005Assignee: Harris CorporationInventors: John DeSalvo, Michael Lange, Scott Bricker, Randall K. Morse, Jane Claire White
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Patent number: 6963697Abstract: A method of decoding a signal in an optical fiber. In one embodiment the method includes receiving the optical signal, wherein the optical signal is a pulse amplitude modulated signal. Converting the optical signal to an electrical signal. Comparing the electrical signal with a plurality of levels. Producing comparison output signals based on the comparison of the electrical signal with the plurality of levels. Processing the comparison output signals on a clock to produce processed output signals and latching the processed output signals on a clock signal to generate the plurality of serial, digital data streams.Type: GrantFiled: October 29, 2003Date of Patent: November 8, 2005Assignee: ADC Telecommunications, Inc.Inventors: Aravanan Gurusami, Joseph F. Chiappetta
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Patent number: 6959154Abstract: Link robustness, chromatic dispersion and polarization mode dispersion (PMD) immunity can be improved in fiber optical system by using a method for receiving an optical double sideband signal over an optical fiber system, comprising the steps of splitting the received optical double sideband signal into an upper sideband signal and a lower sideband signal, photodetecting the upper sideband and the lower sideband, equalizing the photodetected upper sideband signal and the lower sideband signal, and combining the equalized upper sideband signal with the equalized lower sideband signal. While PMD compensation is envisioned as a major application, one may also use the method and system for chromatic dispersion compesation or dispersion slope compensation in high bit rate systems, i.e. using dispersion compensation fiber (DCF) for coarse compensation and diversity receiver with electrical equalizer for fine tuning.Type: GrantFiled: November 28, 2000Date of Patent: October 25, 2005Assignee: AT&T Corp.Inventors: Alan H. Gnauck, Cedric F. Lam, Sheryl L. Woodward
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Patent number: 6941079Abstract: Systems and methods for controlling power of WDM channels in a WDM receiver. A preamplifier is provided prior to a demultiplexer in the WDM receiver chain. The gain of the preamplifier may be controlled based on power measurements made on individual WDM channels. A filter with controllable tilt may be employed to compensate for amplifier gain tilt and assure that all of the WDM channels remain within the dynamic range of the photodetector and receiver electronics. This provides improved bit error rate performance.Type: GrantFiled: May 24, 2001Date of Patent: September 6, 2005Assignee: Cisco Technology, Inc.Inventors: Gianpaolo Barozzi, Cinzia Ferrari, Stefano Piciaccia
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Patent number: 6934476Abstract: A cosite interference rejection system allows cancellation of large interfering signals with an optical cancellation subsystem. The rejection system includes an interference subsystem coupled to a transmit system, where the interference subsystem weights a sampled transmit signal based on a feedback signal such that the weighted signal is out of phase with the sampled transmit signal. The optical cancellation subsystem is coupled to the interference subsystem and a receive antenna. The optical cancellation subsystem converts an optical signal into a desired receive signal based on an interfering coupled signal and the weighted signal. The weighted signal is therefore used to drive the optical cancellation subsystem. The rejection system further includes a feedback loop for providing the feedback signal to the interference subsystem based on the desired receive signal.Type: GrantFiled: August 31, 2001Date of Patent: August 23, 2005Assignee: The Boeing CompanyInventor: Michael J. LaGasse
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Patent number: 6928246Abstract: A detector outputs a detection signal indicating amplitude variation of an input frequency-multiplexed signal. An amplitude controller adjusts the amplitude of the frequency-multiplexed signal by referring to the detection signal. A modulator modulates the amplitude-adjusted frequency-multiplexed signal to produce a predetermined modulated signal. A second multiplexer multiplexes the modulated signal and the detection signal to produce a multiplexed signal. An optical transmitter converts the multiplexed signal into an optical signal, and then sends it out to an optical transmission path. An optical receiver converts the received optical signal into an electrical signal. A separator separates the modulated and detection signals from the electrical signal. A demodulator demodulates the modulated signal to output the frequency-multiplexed signal. An amplitude adjuster adjusts the amplitude of the frequency-multiplexed signal by referring to the detection signal to reproduce the original amplitude variation.Type: GrantFiled: October 9, 2003Date of Patent: August 9, 2005Assignee: Matsushita Electric Industrial Co., Ltd.Inventor: Masaru Fuse
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Patent number: 6915083Abstract: An Improved Signal Receiver Having Wide Band Amplification Capability is disclosed. Also disclosed is a receiver that is able to receive and reliably amplify infrared and/or other wireless signals having frequency bandwidths in excess of 40 MHz. The receiver of the present invention reduces the signal-to-noise ratio of the received signal to ?th of the prior systems. The preferred receiver eliminates both the shunting resistor and the feedback resistor on the input end by amplifying the signal in current form. Furthermore, the receiver includes transconductance amplification means for amplifying the current signal without the need for Cascode stages. Finally, the receiver includes staged amplification to amplify the current signal in stages prior to converting the signal into a voltage output.Type: GrantFiled: December 15, 1998Date of Patent: July 5, 2005Assignee: ZiLOG, Inc.Inventors: T. Allan Hamilton, Alan Grace
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Patent number: 6885828Abstract: An optical receiver configuration and method of controlling an optical signal receiver adjusts a decision threshold to reduce the bit error rate (BER). The receiver includes a comparator having a data input and a digital data output. An error detection & correction circuit provides an error signal representative of the number of corrected “1”s and “0”s in the data output from the comparator. Based on the error signal, a control circuit modifies the comparator decision threshold in a direction to reduce the BER of the receiver. Dynamic modification of the decision threshold may also be accomplished. A total percentage error indicator is preferably used as the basis of changing the decision threshold value. The total percentage error indicator may be used to variably adjust the decision threshold by an amount that varies according to the magnitude of the total percentage error indicator to thereby more quickly arrive at an acceptable decision threshold and prevent overshoot.Type: GrantFiled: July 27, 2001Date of Patent: April 26, 2005Assignee: Ciena CorporationInventor: Steve W. Cornelius
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Publication number: 20040264982Abstract: Apparatus and methods for noise-feedback controlled optical systems are disclosed. In one aspect, an apparatus includes a receiver adapted to receive an optical signal and to convert the optical signal to a corresponding electrical signal, and a control circuit coupled to the receiver. The control circuit includes a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust a gain of the receiver based on the noise level. In an alternate aspect, an optical system includes a transmitter, a receiver, and a monitoring component adapted to monitor a noise level of at least a portion of the electrical signal and to adjust at least one of an amplification of the transmitter and a gain of the receiver based on the noise level.Type: ApplicationFiled: June 27, 2003Publication date: December 30, 2004Inventor: Daniel N. Harres
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Patent number: 6826372Abstract: An optical receiver circuit includes a differential limiter amplifier receiving a binary electrical waveform generated by an optical-to-electrical converter receiving an optical communications signal. Low-pass filter circuits are coupled to differential outputs of the limiter amplifier to obtain the average DC values of the mirror-image output signals. The outputs of the low-pass filter circuits are provided to a differential amplifier to obtain the difference between these average DC values. The output of the differential amplifier is provided to an integrator circuit whose slowly-varying output is provided to the limiter amplifier to establish a switching threshold for distinguishing logic “0”s from logic “1”s in the received data signal. The switching threshold is automatically adjusted in response to varying operation conditions such as changes in the received optical signal power.Type: GrantFiled: August 30, 2000Date of Patent: November 30, 2004Assignee: Sycamore Networks, Inc.Inventor: Mehrdad Givehchi
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Patent number: 6798994Abstract: An optical communication system suitable for a coherent optical satellite communication is configured to include an optical transmission device having a laser signal generator, a first reference laser signal generator having a first local oscillating laser signal generator and an automatic frequency controller, an optical receiving device, and a second reference optical signal generator having a second local oscillating laser signal generator. The first reference local oscillating laser signal generator and the automatic frequency controller are used to generate a fixed beat reference optical signal, and thus the optical receiving device is capable of locking the transmitted laser signal according to the fixed beat reference laser signal in a way of heterodyne receiving so as to demodulate the transmitted signal frequency accurately and resolve the problem of laser frequency drifting.Type: GrantFiled: August 30, 2000Date of Patent: September 28, 2004Assignee: National Science CouncilInventors: Shyh-Lin Tsao, Hao-Chih Yu
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Patent number: 6768876Abstract: A tracking system and method in an optical communications system utilizing an optical communications beam. In one embodiment, the disclosed optical communications system includes a communications receiver circuit and a tracking circuit. The optical communications system generates a communications signal. The tracking system includes a tracking detector having a plurality of regions coupled to a corresponding plurality of tracking channel circuits. Each of the tracking channel circuits includes an optical detector coupled to receive the optical communications beam. The peak-to-peak amplitude modulation in the optical communications beam is measured by substantially reducing or removing a direct current (DC) offset present in the optical communications beam. In one embodiment, after the DC offset is substantially reduced or removed, the signal is then amplified, mixed with the communications signal and then filtered.Type: GrantFiled: July 28, 2000Date of Patent: July 27, 2004Assignee: Terabeam CorporationInventors: Ronald D. Steiger, Mark R. Pratt
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Patent number: 6731881Abstract: A device for interactively transmitting optical signals in a first wavelength and receiving optical signals in a second wavelength both through a one-core optical fiber, includes a first photodiode that converts a received optical signal into a first electric signal, a second photodiode that converts an optical signal into a second electric signal, a first amplifier connected between the second light-electricity signal converter and the coherent light remover, a second amplifier connected to the second light-electricity signal converter, and a differential amplifier that subtracts the second electric signal from the first electric signal.Type: GrantFiled: November 30, 2000Date of Patent: May 4, 2004Assignee: NEC CorporationInventor: Rintaro Nomura
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Patent number: 6728491Abstract: A dispersion compensation controlling apparatus used in a very high-speed optical communication system adopting optical time division multiplexing system comprises a first specific frequency component detecting unit (2a) detecting a first specific frequency component in a baseband spectrum in a transmission optical signal inputted to a receiving side over a transmission fiber as a transmission line (6a), a first intensity detecting unit (3a) detecting information on an intensity of the first specific frequency component detected by the first specific frequency component detecting unit (2a), and a polarization-mode dispersion controlling unit (220a) controlling a polarization-mode dispersion quantity of the transmission line (6a) such that the intensity of the first specific frequency component detected by the first intensity detecting unit (3a) becomes the maximum, thereby easily detecting and compensating polarization-mode dispersion generated in a high-speed optical signal.Type: GrantFiled: July 23, 1999Date of Patent: April 27, 2004Assignee: Fujitsu LimitedInventors: Hiroki Ooi, George Ishikawa, Yuichi Akiyama
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Patent number: 6728493Abstract: An optical receiver arrangement comprises a phase locked loop incorporating a voltage controlled oscillator whereby the loop can be matched in frequency to a received signal frequency. A frequency detector associated with the loop produces an output comprising first or second pulses indicative of whether the loop frequency is above or below the received signal frequency. A control circuit determines a time averaged measure of difference between the loop frequency and the received signal frequency, and issues a loss of lock alarm if this averaged difference exceeds a predetermined value.Type: GrantFiled: March 29, 2000Date of Patent: April 27, 2004Assignee: Nortel Networks LimitedInventors: Edward Whittaker, Darrell Smith, Paul Wilson
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Publication number: 20040062557Abstract: A variable optical attenuator VOA and a gain-clamped semiconductor optical amplifier GC-SOA are combined as an optical preamplifier. The variable optical attenuator is controlled so that a desired optical power is sent to the gain-clamped semiconductor optical amplifier or so that a desired optical power is sent to a photoelectric conversion stage. A optical power monitor is provided to compare a monitored value with a target value, and a variable optical attenuator control circuit controls the variable optical attenuator so that the deviation from the target value approximates 0.Type: ApplicationFiled: March 7, 2003Publication date: April 1, 2004Applicant: OpNext Japan, Inc.Inventors: Shigehiro Takashima, Hirofumi Nakagawa, Masanobu Okayasu
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Publication number: 20040047640Abstract: An optical receiver system for processing signals output from a polarization diversity detector that includes a plurality of photodetector cells. Each cell provides an signal that includes a phase generated carrier signal having a modulation frequency &ohgr; and a sensor signal that has an in-phase component I and a quadrature phase component Q superimposed on the phase generated carrier signal. A plurality of variable gain amplifiers are arranged to produce a plurality of amplified signals. A feedback circuit is connected to the plurality of variable gain amplifiers for controlling the gains thereof. A plurality of demodulator circuits are arranged to receive the amplified signals. The demodulator circuits are arranged to provide for each photodetector cell an I signal output that indicates an amplitude of the in-phase component I and a Q signal output that indicates an amplitude of the quadrature phase component Q.Type: ApplicationFiled: January 23, 2003Publication date: March 11, 2004Inventors: William Christopher Knaack, John Thomson Douglass, Eugene Louis Ferraro
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Publication number: 20040042802Abstract: A method and apparatus for reducing nonlinear phase noise that is induced in an optical transmission system by the interaction of optical amplifier noise and Kerr effect. The apparatus includes an intensity-scaled nonlinear phase noise compensator. The phase noise compensator reduces the nonlinear phase noise by rotating a phase estimate by a scaled signal strength estimate for the optical signal or by comparing a complex estimate to curved regions having scaled nonlinear decision boundaries. The scale factor is derived from the number of spans in the transmission system. Another embodiment of the phase noise compensator uses the scaled signal strength for re-modulating an optical signal.Type: ApplicationFiled: September 3, 2002Publication date: March 4, 2004Inventors: Keangpo Ho, Joseph Mardell Kahn
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Patent number: 6690889Abstract: The present invention is a device to increase the bit rate and distance at which data can be transmitted by optical fiber. The device compensates the polarization dispersion of the line by processing a received optical signal with the use of a polarization controller, the generation of a differential group delay between two orthogonal polarization modes and a control unit for the polarization controller. The data that is sent is redundant to enable detection of errors affecting the data received and the control unit is adapted to minimize the error rate calculated in real time by using the redundant data. The application of the device is to long-haul optical transmission, in particular over stranded fibers.Type: GrantFiled: November 30, 2000Date of Patent: February 10, 2004Assignee: AlcatelInventors: Bertrand Desthieux, François-Xavier Ollivier, Denis Penninckx
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Publication number: 20040008984Abstract: A monitoring system useful for monitoring the state of a fiber communication channel in which a portion of the fiber signal is tapped and detected by a photodiode. The dark current of the photodiode and other DC offsets of the system may be compensated by passing a known signal through the photodiode and extracting the component due to the known signal. The known signal may be a locally generated optical signal having a predetermined harmonic signature. Optionally, the fiber signal may be selectively attenuated before being combined with the known signal so only the known signal is detected. The known signal may also be a dark signal induced by selectively attenuating the fiber signal. The system may include a temperature sensor which allows the compensation to be performed against stored temperature dependent compensation values while the fiber signal is not attenuated.Type: ApplicationFiled: February 15, 2001Publication date: January 15, 2004Inventors: Kevin S. Gerrish, Scott T. Hilbert
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Publication number: 20030210917Abstract: A controller for controlling the reverse-bias voltage of an avalanche photodiode in a transceiver or receiver. The controller includes memory for storing information related to the avalanche photodiode, and analog to digital conversion circuitry for receiving an analog signal corresponding to the temperature of the avalanche photodiode, converting the received analog signal into a digital value, and storing the digital value in a predefined location within the memory. Control circuitry in the controller controls the operation of the avalanche photodiode in accordance with the digital value corresponding to the temperature of the avalanche photodiode and a temperature lookup table stored in the memory. A serial interface is provided to enable a host device to read from and write to locations within the memory.Type: ApplicationFiled: March 18, 2002Publication date: November 13, 2003Inventors: James Stewart, Anthony Ho, Rudolf J. Hofmeister, Darin James Douma, Stephen G. Hosking, Andreas Weber, Jeffrey Bryant Price
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Publication number: 20030206744Abstract: A bottom level detection device is disclosed for a burst mode optical receiver. The receiver includes a converter for converting a burst mode signal into a voltage signal and an automatic gain controller for automatically controlling a gain of the converter. The bottom level detection device detects a bottom level of an output signal from the converter and controls the automatic gain controller on the basis of the detected bottom level. The bottom level detection device includes an amplification circuit for receiving the output signal from the converter at its first input terminal and a fed-back output signal from the device at its second input terminal, respectively, and amplifying a difference between the received signals, a detector for detecting a bottom level of an output signal from the amplification circuit, and an output buffer.Type: ApplicationFiled: March 19, 2003Publication date: November 6, 2003Inventors: Hee-Chan Doh, Hyeon-Cheol Ki, Yun-Je Oh, Gil-Yong Park, Tae-Sung Park, Shin-Hee Won
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Publication number: 20030185578Abstract: A receiving device for an optical signal that is impaired by disturbances, wherein the receiving device has an adaptive filter device that serves to compensate at least partly for disturbances in the optical signal and that is controlled by a feedback signal is characterized in that the feedback signal is generated by correlating the optical signal with a further signal that is formed with respect to the optical signal in such a way that, in the absence of disturbances in the optical signal, at most a slight correlation is present.Type: ApplicationFiled: March 27, 2003Publication date: October 2, 2003Applicant: ALCATELInventor: Fred Buchali
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Publication number: 20030123884Abstract: Techniques for monitoring frequency-dependent parameter and optical property such as optical dispersion in a modulated optical signal with sidebands based on optical vestigial sideband filtering. Monitoring implementations for both chromatic dispersion and polarization-mode dispersion are described as examples.Type: ApplicationFiled: July 8, 2002Publication date: July 3, 2003Inventors: Alan E. Willner, Qian Yu, Zhongqi Pan, Lianshan Yan
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Patent number: 4984084Abstract: A video camera including an under grip which can be removably mount to the bottom portion of a main body of the video camera. In the video camera, on the side of the video camera main body, there is arranged photographing button of a double action type which instructs alternately the start and stop of photographing each time the button is operated and, on the side of the under grip, there is arranged a photographing button of a single action for instructing the start of photographing only while the button is being operated. In accordance with the mounting of the under grip to the video camera main body or in accordance with the electrical connection between the under grip and video camera main body, the start of photographing by the photographing button of a double action type is prohibited and the photographing button of a single action type is used preferentially.Type: GrantFiled: August 29, 1990Date of Patent: January 8, 1991Assignee: Fuji Photo Film Co., Ltd.Inventors: Hidemi Sasaki, Yoshiaki Nakayama, Katsuya Inana, Kozo Kokubun, Kazuhiro Tokuda, Mikio Utsugi