Class / Patent application number | Description | Number of patent applications / Date published |
398194000 | For noise or distortion | 19 |
20080292323 | SYSTEMS AND METHODS FOR REDUCING CLIPPING IN MULTICHANNEL MODULATED OPTICAL SYSTEMS - A system for reducing clipping may be used between a multichannel RF source and a laser to reduce or correct clipping that might occur in the laser as a result of negative spikes or peaks in a multichannel RF signal. The system generally includes a clipping correction circuit that receives the multichannel RF signal and responsive to the RF signal, prevents one or more of the negative peaks in the RF signal from causing clipping. The clipping correction circuit may either detect an envelope of the RF signal and/or may detect one or more peaks in the RF signal. One or more negative peaks may be prevented from causing clipping by adjusting a bias current provided by a bias control circuit and/or by modifying the RF signal with one or more clipping correction pulses coinciding with one or more negative peaks. | 11-27-2008 |
20080292324 | SYSTEMS AND METHODS FOR REDUCING CLIPPING IN MULTICHANNEL MODULATED OPTICAL SYSTEMS - A system for reducing clipping may be used between a multichannel RF source and a laser to reduce or correct clipping that might occur in the laser as a result of negative spikes or peaks in a multichannel RF signal. The system generally includes a clipping correction circuit that receives the multichannel RF signal and responsive to the RF signal, prevents one or more of the negative peaks in the RF signal from causing clipping. The clipping correction circuit may either detect an envelope of the RF signal and/or may detect one or more peaks in the RF signal. One or more negative peaks may be prevented from causing clipping by adjusting a bias current provided by a bias control circuit and/or by modifying the RF signal with one or more clipping correction pulses coinciding with one or more negative peaks. | 11-27-2008 |
20090324254 | Optical transmission apparatus and method - In an optical transmission apparatus, a light-emitting laser varies its output wavelength when applied with a wavelength control signal for switching wavelengths. A wavelength controller outputs the wavelength control signal, and a filter unit subjects the wavelength control signal to a filtering process to remove high-frequency noise superimposed on the wavelength control signal. The filter unit stops the filtering process during the wavelength control and executes the filtering process during the operation. | 12-31-2009 |
20100111543 | OPTICAL COMMUNICATION SYSTEM - An optical transmitter is of the reflective modulation type and has a means of generating reflection, a mixer for mixing a data stream and a sub-carrier, and an optical modulator for modulating an optical carrier with the output from the mixer in order to avoid optical beat-interference noise arising from, for example, Rayleigh backscattering. The modulator is in one embodiment of the interferometric type such as a Mach-Zehnder Modulator (MZM) operated to suppress the optical carrier at the transmitter output in order to reduce optical beat interference noise. The modulator preferably implements CSS-AMPSK modulation, which suppresses optical beat noise and achieves strong dispersion tolerance, enabling, for example, 10 Gb/s data transmission over 100 km distance without dispersion compensation. The transmitter may have a duobinary encoder, which encodes the data prior to mixing with the sub-carrier. | 05-06-2010 |
20100226661 | WAVELENGTH DIVISION MULTIPLEXING TRANSMISSION SYSTEM AND APPARATUS AND OPTICAL SIGNAL NOISE RATIO CALCULATION METHOD - A wavelength division multiplexing (WDM) transmission system for transmitting a wavelength division multiplexed signal light from a sender transmission apparatus to a receiver transmission apparatus is provided. The system comprises a computing unit that subtracts from a first optical signal noise ratio (OSNR) of the signal light measured by the receiver transmission apparatus a second OSNR ascribed to a sideband of the signal light measured by the sender transmission apparatus so as to compute a corrected OSNR of an amplified spontaneous emission (ASE) noise light with a reduction of an effect of the sideband. | 09-09-2010 |
20110052211 | Optical wavelength division multiplexing (WDM) system including adaptive cross-talk cancellation - An optical communication system comprising a transmitter including a data register having a plurality of outputs, each output comprising a separate data channel, a plurality of signal processors, each signal processor corresponding to a data, a plurality of laser modules, each laser module coupled to an output of a corresponding signal processor, wherein each laser module modulates the modified signal from its corresponding data channel onto an optical carrier having a selected wavelength, and an optical multiplexer coupled to an output of all the laser modules. Each signal processor comprises a first input to receive a signal from the corresponding data channel and one or more additional inputs to receive a signal from one or more adjacent data channels, a control input to receive a control signal generated at a receiver based upon a monitored characteristic of the received signal from the corresponding data channel, and logic to modify a characteristic of the signal from the corresponding channel based upon the control signal and the signals from the one or more adjacent data channels. | 03-03-2011 |
20110211846 | Transmitter Frequency Peaking for Optical Fiber Channels - Frequency peaking is used in the transmitter to improve link performance. In one example, frequency peaking improves the PIE | 09-01-2011 |
20120027421 | Four Wave Mixing Suppression - Methods, systems and computer program products for countering the effects of four wave mixing are described. In one implementation, a controller can be used to shift an operating wavelength of an optical transmitter away from a zero-dispersion wavelength through which signals of the optical transmitter are transmitted. The controller can perform the shifting process while allowing sufficient margin for division multiplexing and minimal dispersion. The controller may determine an appropriate offset to be used for shifting the operating wavelength without subjecting the signals to a significant increase in undesirable effects such as dispersion, crosstalk and signal distortion which can impact the overall bit-error rate. | 02-02-2012 |
20120045222 | Method of Operating an Optical Transmission System and Optical Transmission System - The invention relates to a method of operating an optical transmission system ( | 02-23-2012 |
20120163833 | SYSTEM AND METHOD FOR REDUCING MUTUAL LEAKAGE BETWEEN DISTRIBUTED FEEDBACK LASER AND ELECTRO-ABSORPTION MODULATOR IN INTEGRATED ELECTRO-ABSORPTION MODULATED LASER - A device is provided for use with a dither tone signal and an information signal. The device includes a laser diode, an electro-optic modulator, a first filter and a second filter. The laser diode can output a first light signal, whereas the electro-optic modulator can transmit a second light signal. The first filter can generate a first filtered signal based on the information signal. The second filter can generate a second filtered signal based on the dither tone signal. The first light signal is based on the dither tone signal, the information signal and the first filtered signal. The second light signal is based on the first light signal, the information signal, the dither tone signal and the second filtered signal. The filtered signals reduce or cancel the undesired leaked/interfering signals. | 06-28-2012 |
20120213530 | SIGNAL PROCESSING APPARATUS, TRANSMITTER, RECEIVER AND METHOD - A signal processing apparatus configured to correct a distortion introduced by a signal processing path into a processed signal comprising a transformer that transforms the processed signal into a transformed signal in frequency domain, a processor that determines a first correction function and a second correction function upon the basis of a transfer function of the signal processing path, a first multiplier that multiplies values of the transformed signal with coefficients of the first correction function to obtain a first corrected signal, a signal reverser that reverses an order of values in a copy of the transformed signal to obtain a reversed transformed signal, a second multiplier that multiplies values of the reversed transformed signal with coefficients of the second correction function to obtain a second corrected signal, and an adder that adds the first corrected signal and the second corrected signal to obtain a corrected output signal. | 08-23-2012 |
20130163996 | Printed Circuit Board and Optical Transmission Device - A printed circuit board includes a substrate, a signal output circuit formed on the substrate for outputting a clock signal, a shield for covering the signal output circuit, a power supply wiring for connecting the signal output circuit and a power source, and a trap filter provided to the power supply wiring and provided inside the shield, for attenuating a frequency component corresponding to a frequency of clock signal. The trap filter includes a resonance circuit having one portion of the power supply wiring, an inner-layer wiring of the substrate located below the one portion of the power supply wiring, an inner-layer ground wiring of the substrate located below the inner-layer wiring, and a via hole for connecting the one portion of the power supply wiring and the inner-layer wiring. | 06-27-2013 |
20140270808 | METHOD AND SYSTEM FOR A POLARIZATION MODE DISPERSION TOLERANT OPTICAL HOMODYNE DETECTION SYSTEM WITH OPTIMIZED TRANSMISSION MODULATION - An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion. | 09-18-2014 |
20140314427 | OPTICAL TRANSMISSION APPARATUS AND OPTICAL TRANSMISSION METHOD - An optical transmission apparatus receives an optical signal of an optical wavelength. The optical transmission apparatus has a variable wavelength filter, a neighboring frequency detection unit, and an ADC/DSP. The variable wavelength filter detects a neighboring of another optical transmission apparatus that receives an optical signal of a wavelength different from the wavelength. The neighboring frequency detection unit determines whether or not a second frequency supported by the another optical transmission apparatus where a neighboring has been detected by the variable wavelength filter is different from a first frequency supported by the optical transmission apparatus. The ADC/DSP changes a parameter for removing a phase noise from the optical signal of the wavelength according to a difference between the first frequency and the second frequency when it is determined that the second frequency is different from the first frequency. | 10-23-2014 |
20150071656 | NON-LINEAR DISTORTION COMPENSATOR, METHOD OF COMPENSATING NON-LINEAR DISTORTION, AND COMMUNICATION APPARATUS - A non-linear distortion compensator includes: a first signal generator configured to generate a signal with a second multivalued level lower than a first multivalued level from an input signal; a non-linear distortion calculator configured to calculate non-linear distortion of the signal with the first multivalued level based on the signal with the second multivalued level generated by the first signal generator; and a non-linear compensator configured to compensate the non-linear distortion of the signal with the first multivalued level based on the non-linear distortion calculated by the non-linear distortion calculator. | 03-12-2015 |
20150104197 | Optimal Signal Constellation Design for Ultra-High-Speed Optical Transport in the Presence of Phase Noise - A method to process applicable to coherent optical channels with either linear or nonlinear phase noise includes: splitting a received sequence of data into clusters of points according to a cumulative log-likelihood function from constellation obtained in a previous iteration; generating new constellation points by calculating a center of mass of the clusters of points; repeating until convergence or until a predetermined number of iterations has been reached to determine a signal constellation; and transmitting signals over the coherent optical channels with nonlinear phase noise using the disclosed signal constellation and LDPC-coded modulation concepts. | 04-16-2015 |
20160065312 | OPTICAL TRANSMISSION DEVICE, NONLINEAR DISTORTION COMPENSATION METHOD, AND NONLINEAR DISTORTION PRE-EQUALIZATION METHOD - An optical receiver includes a dividing unit, a control unit, and a compensating unit. The dividing unit divides an optical transmission signal into a plurality of frequency components by a set number of divisions and a set division bandwidth. The control unit controls the number of divisions and the division bandwidth on the basis of transmission path information about an optical transmission line through which the optical transmission signal is transmitted and signal information about the optical transmission signal. The compensating unit compensates optical nonlinear distortion of each of the frequency components divided by the dividing unit. | 03-03-2016 |
20160191161 | ELECTROMAGNETIC INTERFERENCE REDUCTION - A method of reducing electromagnetic interference in a multi-channel transmitter is described. The method may include receiving multiple signals configured to be transmitted through multiple channels. The method may additionally include adjusting delays of the multiple signals to generate multiple delayed signals. Each two adjacent delayed signals may be configured to have a corresponding phase difference that satisfies a phase delay requirement. The method may additionally include generating multiple load signals from the multiple delayed signals. | 06-30-2016 |
20160197680 | NONLINEAR COMPENSATION METHOD AND APPARATUS AND SYSTEM IN MULTICARRIER OPTICAL COMMUNICATION SYSTEM | 07-07-2016 |