Abstract: In the conventional technique, only an output having a bandwidth identical to the bandwidth of individual DACs has been obtained even by using a plurality of DACs. Also, even when the output of a bandwidth broader than the individual DAC is obtained, there has been a problem associated with asymmetricity of a circuit configuration. In a signal generating device of the present invention, a plurality of normal DACs are combined to realize an analog output of a broader bandwidth beyond the output bandwidth of the individual DACs, and the problem of the asymmetricity of the circuit configuration is also resolved. A desired signal is separated into a low-frequency signal and a high-frequency signal in a frequency domain, and a series of operation of constant (r)-folding the amplitude of the high-frequency signal and shifting it on the frequency axis to superimpose it on the low-frequency signal are made in a digital domain. The output of each DAC is switched by an analog multiplexer.

Abstract: In the conventional technique, only an output having a bandwidth identical to the bandwidth of individual DACs has been obtained even by using a plurality of DACs. Also, even when the output of a bandwidth broader than the individual DAC is obtained, there has been a problem associated with asymmetricity of a circuit configuration. In a signal generating device of the present invention, a plurality of normal DACs are combined to realize an analog output of a broader bandwidth beyond the output bandwidth of the individual DACs, and the problem of the asymmetricity of the circuit configuration is also resolved. A desired signal is separated into a low-frequency signal and a high-frequency signal in a frequency domain, and a series of operation of constant (r)-folding the amplitude of the high-frequency signal and shifting it on the frequency axis to superimpose it on the low-frequency signal are made in a digital domain. The output of each DAC is switched by an analog multiplexer.

Abstract: In the conventional technique, only an output having a bandwidth identical to the bandwidth of individual DACs has been obtained even by using a plurality of DACs. Also, even when the output of a bandwidth broader than the individual DAC is obtained, there has been a problem associated with asymmetricity of a circuit configuration. In a signal generating device of the present invention, a plurality of normal DACs are combined to realize an analog output of a broader bandwidth beyond the output bandwidth of the individual DACs, and the problem of the asymmetricity of the circuit configuration is also resolved. A desired signal is separated into a low-frequency signal and a high-frequency signal in a frequency domain, and a series of operation of constant (r)-folding the amplitude of the high-frequency signal and shifting it on the frequency axis to superimpose it on the low-frequency signal are made in a digital domain. The output of each DAC is switched by an analog multiplexer.

Abstract: To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus.

Abstract: To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus.

Abstract: A frequency domain multiplexed signal receiving method which decodes received signals that are multiplexed in a frequency domain, includes: a digital signal acquisition step of acquiring digital signals from the received signals that are multiplexed in the frequency domain; an offset discrete Fourier transform step of applying an offset discrete Fourier transform to odd discrete point numbers based on the acquired digital signals; and a decode step of decoding frequency domain digital signals in the frequency domain obtained by the offset discrete Fourier transform, and that are the frequency domain digital signals of one or more frequency channels.

Abstract: To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus.

Abstract: To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus.

Abstract: A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-signal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-signal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.

Abstract: To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus.

Abstract: 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.

Abstract: In order to compensate for chromatic dispersion caused by optical fiber transmission in a communication system with coherent detection using optical signals, specific frequency band signals are used to enable estimation of a chromatic dispersion value.

Abstract: Provided is a frequency offset estimation apparatus that appropriately estimates and compensates for a frequency offset of a received signal when estimating the frequency offset which is the difference between a carrier frequency of the received signal and the frequency of an output signal of a local oscillator.

Abstract: A receiver device receives a signal inputted to one or a plurality of ports as a plurality of received signals, and includes: a phase offset estimating unit that, on the basis of a unique word of each signal block contained in said received signal, estimates the phase offset, and a phase offset compensating unit that, on the basis of a phase offset estimated by said phase offset estimating unit, compensates the phase offset; the receiver device uses a known signal component (unique word) contained in a frequency-domain equalized signal to compensate the phase offset, whereby it compensates complex phase offset fluctuation, and estimates the phase offset of a signal obtained at each port.

Abstract: An optical modulator and an optical transmission system convert continuous light of a multiple wavelength light source, which generates the continuous light with a fixed and complete phase but different frequencies, to a modulator driving signal so as to generate a light subcarrier with each frequency at the center and modulate the continuous light to the light subcarrier by using the modulator driving signal. In the case where an optical modulation is carried out by an optical IQ-modulator, transmitting data, for example, is converted to two parallel data A(t) and B(t), an I phase signal, in which the data A(t)+B(t) are modulated with a clock signal with a frequency ?, and a Q phase signal, in which the data A(t)?B(t) are modulated with a clock signal with a ?/2 phase shifted, are generated, and the I phase signal and the Q phase signal are applied to electrodes of the optical IQ-modulator, respectively.

Abstract: Provided is a frequency offset estimation apparatus that appropriately estimates and compensates for a frequency offset of a received signal when estimating the frequency offset which is the difference between a carrier frequency of the received signal and the frequency of an output signal of a local oscillator.

Abstract: 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.

Abstract: A high-performance optical OFDM receiver is realized. A subcarrier separation circuit receives an optical OFDM signal consisting of two subcarriers A and B and separates a subcarrier component, signal light and first local oscillator light are input to the subcarrier separation circuit, the subcarrier separation circuit converts the signal light and the first local oscillator into a baseband electrical signal, the subcarrier separation circuit converts the baseband electrical signal into a digital signal, the subcarrier separation circuit shifts the frequency of the converted digital signal so that a center frequency of the subcarrier A becomes zero, and the subcarrier separation circuit adds a frequency shifted signal to a signal obtained by delaying the frequency shifted signal by ½ of a symbol time to separate a component of the subcarrier A.

Abstract: A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-signal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-signal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.

Abstract: An oven wall three-dimensional profile data (701) representing concave and convex amounts on all over oven walls (14R, 14L) at a right side and left side of a coking chamber (11) is generated by using image signals obtained by a wall surface observation apparatus (200). A resistance index “k” in which a resistance received by pushed coke (15) resulting from a rising gradient existing on the oven wall (14) is indexed is asked by using the oven wall three-dimensional profile data (701). It can be verified that there is a correlation between this resistance index “k” and a pushing load. Accordingly, it is possible to quantitatively evaluate a state of the oven wall (14) affecting on the pushing load.