摘要:
An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by π/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage Vπ of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonal bias electrode portion which supplies an orthogonal bias voltage to the phase shifter; a data bias power supply portion that adjusts delay times in the two phase modulating portions by applying the data bias voltages to the data bias electrode portion; an orthogonal bias power supply portion that adjusts a delay amount relative to a light output from at least one of the two phase modulating portions by applying the orthogonal bias voltage to the orthogonal bias electrode portion; a dither signal adding portion that adds a dither signal to at most three of the four data bias voltages; a dither detecting portion which detects a wave that is n-times a dither component from an output of the multiplexing portion (where n is an integer equal to or greater than one); and an orthogonal bias control portion which feeds back a detection result of the dither detecting portion to the orthogonal bias power supply portion. The orthogonal bias power supply portion adjusts the delay amount relative to the light output from at least one of the two phase modulating portions by controlling the orthogonal bias voltage to be applied to the orthogonal bias electrode portion based on feedback from the orthogonal bias control portion.
摘要:
An optical signal transmitter of the present invention includes: two phase modulating portions; a phase shifter which displaces carrier phases of two output lights from the phase modulating portions by π/2; a multiplexing portion which multiplexes two signal lights, carrier phases of the two signal lights being made orthogonal to each other by the phase shifter; a drive signal electrode portion which supplies a differential data signal to each of four paths of interference optical waveguides, each of the two phase modulating portions having the interference optical waveguides, the differential data signal having an amplitude which is equal to a half-wave voltage Vπ of the two phase modulating portions; a drive amplifier which amplifies the differential data signal to be supplied to each of the four paths of the interference optical waveguides; a data bias electrode portion which supplies a total of four data bias voltages to two arms, each of the two phase modulating portions having the two arms; an orthogonal bias electrode portion which supplies an orthogonal bias voltage to the phase shifter; a data bias power supply portion that adjusts delay times in the two phase modulating portions by applying the data bias voltages to the data bias electrode portion; an orthogonal bias power supply portion that adjusts a delay amount relative to a light output from at least one of the two phase modulating portions by applying the orthogonal bias voltage to the orthogonal bias electrode portion; a dither signal adding portion that adds a dither signal to at most three of the four data bias voltages; a dither detecting portion which detects a wave that is n-times a dither component from an output of the multiplexing portion (where n is an integer equal to or greater than one); and an orthogonal bias control portion which feeds back a detection result of the dither detecting portion to the orthogonal bias power supply portion. The orthogonal bias power supply portion adjusts the delay amount relative to the light output from at least one of the two phase modulating portions by controlling the orthogonal bias voltage to be applied to the orthogonal bias electrode portion based on feedback from the orthogonal bias control portion.
摘要:
An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.
摘要:
The present invention relates to an optical receiver, in which the transmittance of a Mach-Zehnder interferometer can be locked at a normal operation point in a simple structure and control.A transmittance detecting circuit and a minute modulation signal detecting circuit are provided in parallel after a balanced optical receiver, and a switch is selectively connectable either a minute modulation signal detecting circuit and a transmittance detecting circuit. In the initial stage of frequency pull-in, the switch is set to connect the transmittance detecting circuit to the synchronous detection circuit. If the transmittance detecting circuit detects that the transmittance of the Mach-Zehnder interferometer at the carrier frequency becomes a desired transmittance, the connection of the switch is switched from the transmittance detecting circuit to the minute modulation signal detecting circuit.
摘要:
An optical modulation device including: bias power supplies that output a signal having a bias voltage corresponding to the null point of an optical modulation unit to the optical modulation unit; and synchronous detection circuits that determine whether an intensity of a QAM signal at a drift non-occurrence time where no drift occurs in the bias voltage becomes larger or smaller than the intensity of the QAM signal at a drift occurrence time where a drift occurs in the bias voltage, adjust the bias voltage to maximize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes larger than the intensity of the QAM signal at the drift occurrence time, and adjust the bias voltage to minimize the intensity of the QAM signal when determining that the intensity of the QAM signal at the drift non-occurrence time becomes smaller than the intensity of the QAM signal at the drift occurrence time.
摘要:
The present invention relates to an optical receiver, in which the transmittance of a Mach-Zehnder interferometer can be locked at a normal operation point in a simple structure and control. A transmittance detecting circuit and a minute modulation signal detecting circuit are provided in parallel after a balanced optical receiver, and a switch is selectively connectable either a minute modulation signal detecting circuit and a transmittance detecting circuit. In the initial stage of frequency pull-in, the switch is set to connect the transmittance detecting circuit to the synchronous detection circuit. If the transmittance detecting circuit detects that the transmittance of the Mach-Zehnder interferometer at the carrier frequency becomes a desired transmittance, the connection of the switch is switched from the transmittance detecting circuit to the minute modulation signal detecting circuit.
摘要:
A light receiver for detecting incident time is installed on the side of a radiation source of a scintillator (including a Cherenkov radiation emitter), and information (energy, incident time, an incident position, etc.) on radiation made incident into the scintillator is obtained by the output of the light receiver. It is, thereby, possible to identify an incident position and others of radiation into the scintillator at high accuracy.
摘要:
A method includes: etching a silicon substrate except for a silicon substrate portion on which a channel region is to be formed to form first and second trenches respectively at a first side and a second side of the silicon substrate portion; filling the first and second trenches by epitaxially growing a semiconductor layer having etching selectivity against silicon and further a silicon layer; removing the semiconductor layer selectivity by a selective etching process to form voids underneath the silicon layer respectively at the first side and the second side of the substrate portion; burying the voids at least partially with a buried insulation film; forming a gate insulation film and a gate electrode on the silicon substrate portion; and forming a source region in the silicon layer at the first side of the silicon substrate portion and a drain region at the second side of the silicon substrate portion.
摘要:
When a circuit that calculates a frequency offset using a shape of a frequency spectrum is implemented by hardware, the circuit size can be reduced. A frequency offset estimating method for estimating the difference between a carrier frequency of a reception signal and the frequency of an output signal of a local oscillator includes performing a discrete Fourier transform on a reception signal previously sampled at a predetermined sampling frequency and outputting a frequency spectrum with a plurality of frequency components, calculating an average power of the frequency spectrum, calculating a threshold by adding a predetermined value to the average power or power obtained by multiplying the average power by a constant, performing 1-bit quantization on powers of the frequency components of the frequency spectrum based on the threshold, and calculating a centroid frequency by multiplying frequencies of the frequency components by powers of 1-bit quantized frequency components, calculating the sum of multiplied products, and dividing the sum of the products by the sum of the powers of the 1-bit quantized frequency components of the frequency spectrum.
摘要:
In a coincidence determination processing of a PET device for regarding and counting a pair of annihilation radiations detected within a predetermined time as occurring from the same nuclide, a priority of a line of response to acquire is set and a true coincidence is extracted from multiple coincidences by using information on a detection time difference if a plurality of coincidences are detected with the predetermined time. Consequently, a true coincidence is extracted from multiple coincidences which have heretofore been discarded. This improves detection sensitivity at high radioactive concentration and contributes to an improved dynamic range.