| Patent application number | Description | Published |
|---|
| 20080253761 | DETECTING ABNORMALITY IN AN OPTICAL RECEIVER - An optical apparatus comprising: a branching unit branching an input light modulated by DQSPK format and thereby outputting a first branched light and a second branched light; a first branch and a second branch inputting the first branched light and the second branched light, respectively, the first branch and the second branch having an interferometer, a photo detector, and discriminator and demodulating I-signal and Q-signal, respectively; and an abnormality detection unit detecting an abnormality of the input light based on a synchronized detection of a first demodulated signal output from the photo detector in the first branch and a first recovered signal output from the discriminator in the first branch, and a synchronized detection of a second demodulated signal output from the photo detector in the second branch and a second recovered signal output from the discriminator in the second branch. | 10-16-2008 |
| 20090116849 | DQPSK modulation apparatus and DQPSK modulation method - An optical transmitting apparatus includes a branching unit that branches light output from a light source into light beams, a phase control unit and an ABC circuit that control the phase of one of the light beams to π/2, a data processing unit that performs phase modulation on each of the light beams, phase modulating units, an interfering unit that makes the light beams on which the phase modulation has been performed interfere with each other, and a signal-generation control unit that changes the phase amount from π/2 by an amount corresponding to a desirable penalty amount. | 05-07-2009 |
| 20090214226 | OPTICAL DQPSK RECEIVER AND OPTICAL PHASE MONITOR APPARATUS FOR USE IN OPTICAL DQPSK RECEIVER - First and second delay interferometers respectively have a phase-shift element. First and second photo detectors respectively detect optical signals output from the first and second delay interferometers. First and second data recovery circuits recover data from signals detected by the first and second photo detectors, respectively. A common adjustment unit adjusts the phase-shift elements of both first and second delay interferometers in accordance with an output signal from the first photo detector and an output signal from the second data recovery circuit. An individual adjustment unit adjusts the phase-shift element of the second delay interferometer in accordance with the output signal from the first photo detector and an output signal from the second photo detector. | 08-27-2009 |
| 20090220249 | DEMODULATION CIRCUIT - A demodulation circuit for reproducing transmitted data from a signal received by a receiver, the demodulation circuit includes a selector, converters and data recovery circuits. The selector demultiplexes the transmitted data into a plurality of divided signals. The converters receives the divided signal from the selector, respectively, the plurality of converters including a delay device and an adding circuit, the delay device for delaying the divided signal from the selector and for outputting a delayed signal, the adding circuit for adding the divided signal from the selector to the delayed signal from the delay device. The plurality of data recovery circuits receives an output signal from the adding circuits, respectively, each of the data recovery circuits discriminating the output signal from the adding circuit. | 09-03-2009 |
| 20100322622 | OSNR MONITOR DEVICE AND OSNR MEASUREMENT DEVICE - An OSNR monitor device includes an optical receiver including a delay interferometer which inputs an optical signal in accordance with a given bandwidth and outputs two optical signals and causes the optical signals to interfere with each other and optical detectors which outputs currents in accordance with optical powers of the optical signals output from the interferometer, an optical power monitor configured to obtain the optical powers of the optical signals received by the optical detectors included in the optical receiver, and an OSNR calculator configured to calculate an optical signal-to-noise ratio in accordance with the optical powers obtained from the optical power monitor and the reception bandwidth. | 12-23-2010 |
| 20110026935 | OPTICAL SIGNAL TRANSMITTER AND METHOD FOR CONTROLLING POLARIZATION MULTIPLEXED OPTICAL SIGNAL - An optical signal transmitter includes: first outer modulator to generate first modulated optical signal, the first outer modulator including a pair of optical paths and a first phase shifter to give phase difference to the pair of optical paths; second outer modulator to generate second modulated optical signal, the second outer modulator including a pair of optical paths and a second phase shifter to give phase difference to the pair of optical paths; combiner to generate polarization multiplexed optical signal by combining the first and second modulated optical signals; phase controller to control the phase difference by the first phase shifter to A−Δφ and control the phase difference by the second phase shifter to A+Δφ; and power controller to control at least one of the first and second outer modulators based on AC component of the polarization multiplexed optical signal. | 02-03-2011 |
| 20110044702 | POLARIZATION MULTIPLEXED OPTICAL TRANSMITTER AND METHOD FOR CONTROLLING POLARIZATION MULTIPLEXED OPTICAL SIGNAL - A polarization multiplexed optical transmitter includes first and second modulation units, combiner, phase controller, and signal controller. The first and second modulation units generate first and second modulated optical signals, respectively. The first and second modulation units include first and second phase shifter to give phase difference between optical paths of corresponding Mach-Zehnder interferometer, respectively. The combiner generates polarization multiplexed optical signal from the first and second modulated optical signals. The phase controller controls the phase difference by the first phase shifter to a target value and the phase difference by the second phase shifter to a value shifted by π from the target value. The signal controller controls operation state of at least one of the first and second modulation units based on optical intensity waveform of the polarization multiplexed optical signal. | 02-24-2011 |
