Abstract: The reception (102) reception unit includes; a first processing unit processing a first signal received from a source channel, and including a filtering unit to filter said first signal in digital domain, and extract unit to extract a information from said first signal; a second processing unit processing a second signal received from a destination channel, and said source channel and said destination channel are distinct each other; a third processing unit providing said information extracted from said first signal to said second signal said third processing unit executes; providing said information from said first processing unit to said second processing unit using information lanes of a clock rate strictly lower than a symbol rate of said second signal, a monitoring unit to generate a monitor signal according to the quality of said second signal; and a control unit controlling a skew between said first signal and said second signal in a bandwidth of said filtering units in said first processing unit.

Abstract: It is necessary to improve the signal quality of the optical signal emitted by a reconfigurable transmitter after a reconfiguration event, therefore, an optical transmitter according to an exemplary aspect of the invention includes a modulation means for modulating light by a driving signal with a reconfigurable format; a digital signal processing means for processing digital data to be transmitted by using parameters in order to generate the driving signal; and a control means for controlling the digital signal processing means by means of changing the parameters so as to keep the driving signal stable before and after changing the reconfigurable format.

Abstract: A method for transmitting optical signals over multiple channels is provided, the method including: coding tributaries of data to be transmitted; firstly rearranging the coded tributaries, thereby scrambling the data among the coded tributaries and outputting rearranged coded tributaries; modulating optical carriers with data from one of the coded tributaries, creating modulated optical signals; transmitting the modulated optical signals; spatially multiplexing the modulated optical signals into spatially multiplexed channels; converting the spatially multiplexed optical signals into individual optical signals; receiving the individual optical signals through the multiple channels; demodulating the individual optical signals into electrical signals; decoding the electrical signals into decoded tributaries; and secondly rearranging the decoded of tributaries to recover the tributaries of data before step, wherein, a number of tributaries of data is equal to or more than two and is less than or equal to a numbe

Abstract: Since it is difficult to control correctly and optimally the DC biases of an IQ modulator driven with pre-equalized data, a method for controlling an optical transmitter according to an exemplary aspect of the invention includes the steps of (a) making direct current biases for driving children Mach-Zehnder modulators of an IQ modulator in the optical transmitter converge to values close to null driving points of the children Mach-Zehnder modulators, (b) driving the children Mach-Zehnder modulators with special driving data including a pair of training patterns between which there is a significant correlation, (c) scanning direct current biases for setting quadrature angle of the IQ modulator, (d) monitoring output of the IQ modulator during step (c), and (e) setting the direct current bias for setting quadrature angle on the basis of the driving data and monitored results in step (d).

Abstract: To provide signal generating apparatus that is capable of controlling the DC bias of the optical modulator applicable to various kinds of modulation format, a signal processing apparatus includes a digital processing unit for deserializing an input digital data into parallel data lanes, for comparing the value of the digital data of symbol rate F to at least one predetermined threshold value, for selecting an offset value based on the result of the comparison; and for adding the selected offset value to the digital data, a converting unit for converting the digital data added the offset value to analog signals in each lane; an optical modulating unit for modulating a lightwave according to the analog signals with predetermined modulation format at the symbol rate F, where the modulated signal contains a frequency component at F/N.

Abstract: An optical transmitting/receiving system using a timing extracting method that allows a feed forward type of optimized structure exhibits increased cost and increased power consumption, therefore, an optical transmitting/receiving system according to the present invention includes an optical transmitter apparatus including a light source, an optical modulator, and a pseudo RZ carver; and an optical receiver apparatus including a coherent receiver, an AD converter, a main signal processing unit, and a timing extracting unit; wherein the pseudo RZ carver forms a dip in an optical signal phase-modulated with a frequency f by the optical modulator by dropping the optical intensity at a symbol transition point to approximate zero per n-symbol interval; the AD converter outputs a sample obtained by AD converting an electrical signal which is detected and outputted by the coherent receiver; the timing extracting unit extracts a clock component of a frequency f/n from the sample and derives from the clock component a

Abstract: Since it is difficult to emit a control a IQ modulator emitting modulated lightwave according to QAM format without signal degradation of said emitted signal due to low frequency dither used for the control of said modulator, a method for controlling an optical transmitter according to an exemplary aspect of the invention includes: generating a multilevel electrical signal by means of combining two or more binary electrical signals, where said multilevel signal is used to drive the modulator of adding a low frequency dither signal on several of the binary electrical signals, wherein the phase of the added dither signal depends on the value of the binary signal to which it is added; tapping a portion of light after the modulator and generating a monitor signal from the tapped light; controlling the modulator according to the monitor signal.

Abstract: The reception (102) reception unit includes; a first processing unit processing a first signal received from a source channel, and including a filtering unit to filter said first signal in digital domain, and extract unit to extract a information from said first signal; a second processing unit processing a second signal received from a destination channel, and said source channel and said destination channel are distinct each other; a third processing unit providing said information extracted from said first signal to said second signal said third processing unit executes; providing said information from said first processing unit to said second processing unit using information lanes of a clock rate strictly lower than a symbol rate of said second signal, a monitoring unit to generate a monitor signal according to the quality of said second signal; and a control unit controlling a skew between said first signal and said second signal in a bandwidth of said filtering units in said first processing unit.

Abstract: An optical transmitter (10) outputs basic transmission light of an optical signal for transmission to an optical receiver (20). A first optical signal generation means (210) of the optical receiver (20) receives the optical signal for transmission, and generates a first optical signal by causing the received optical signal for transmission and locally generated light to interfere with each other. A second optical signal generation means (220) of the optical receiver (20) receives the transmission light, and generates an optical signal for denoising by causing the received transmission light and the locally generated light to interfere with each other. A first photoelectric conversion means (230) of the optical receiver (20) photoelectrically converts the first optical signal to generate a received signal. A second photoelectric conversion means (240) photoelectrically converts the optical signal for denoising to generate a noise signal.

Abstract: Since it is difficult to emit a stable and reliable modulated lightwave signal by means of IQ modulators used for QAM format, a method for controlling an optical transmitter according to an exemplary aspect of the invention includes the steps of (a) keeping an optical amplitude of a continuous wave light output from the optical transmitter constant, (b) making operating point values in optical modulation converge to predetermined values during step (a), and (c) modulating the continuous wave light with multiple amplitudes and phase levels around the operating point values converged in step (b).

Abstract: It becomes difficult to perform the optimum equalization signal processing in coherent receiving systems if a channel response in an optical fiber transmission line includes a factor without temporal centrosymmetry, therefore, an equalization signal processor according to an exemplary aspect of the invention includes an equalization filter means configured to receive digital signals by coherent receiving systems; a coefficient control means configured to control coefficients defining characteristics of the equalization filter means; a significant coefficient holding means configured to hold significant coefficients of significant values among initial values of the coefficients; a significant coefficient positioning means configured to determine a significant coefficient position, a position of the significant coefficients in the initial values, so that equalization characteristics of the equalization filter means may be optimized; and a significant coefficient setting means configured to allocate the signific

Abstract: Since it is difficult to transmit optical signal over multiple channels with an improved received signal quality, better system margins, and reduced system outages, a method for transmitting optical signal over multiple channels according to an exemplary aspect of the invention includes: (a) firstly rearranging a plurality of tributaries of data to be transmitted in order to scramble the data among the plurality of tributaries; (b) transmitting optical signals modulated with rearranged data generated in step (a) over the multiple channels; (c) receiving the optical signals through the multiple channels; (d) demodulating the optical signals into a plurality of tributaries of the rearranged data; (e) secondly rearranging the plurality of tributaries of the rearranged data in order to recover the plurality of tributaries of data before step (a); and wherein, the number of tributaries of the rearranged data is equal to or more than two and is less than or equal to the number of the multiple channels.

Abstract: In order to appropriately demultiplex the polarization multiplexed BPSK signal without using a training sequence and decreasing the resistance to a frequency offset, an optical receiver includes a coherent optical detection unit receiving an optical signal in which BPSK modulated carrier waves are polarization-multiplexed, performing coherent detection by mixing the received optical signal with local light, and outputting first electrical signals corresponding to the carrier waves; a butterfly FIR filter receiving the first electrical signals and extracting second electrical signals corresponding to each of the carrier waves from the first electrical signals; and a coefficient control unit for calculating a sum of respective phases of the second electrical signals output from the butterfly FIR filter, adaptively controlling tap coefficients of the butterfly FIR filter so that the calculated phase sum may become equal to 0 or ?, and outputting tap coefficients after being controlled to the butterfly FIR filter

Abstract: Since it is difficult to fast, simply monitor impairments of received signals with higher receiver sensitivity, a monitoring method for an optical communication system according to an exemplary aspect of the invention includes the steps of emitting lightwave signals to be modulated according to a data, forming dips at transitions between temporally consecutive groups of n symbols of the lightwave signals, wherein the dips are formed at each of (n?1) first transitions of the group, no dip is formed at the n-th transition on the lightwave signals, receiving the lightwave signals, extracting frequency components characterized by the numerical value n from received lightwave signals, and monitoring the received lightwave signals by using the frequency components.

Abstract: It is difficult in an optical transmission system using a multicore optical fiber to provide high-capacity transmission in which good signal quality is obtained, therefore, a multiplexed optical transmission line according to an exemplary aspect of the present invention includes at least one first optical transmission line propagating first signal light in a first direction; and at least one second optical transmission line propagating second signal light in a second direction opposite to the first direction, wherein the second optical transmission line is disposed in at least one of positions adjacent to the first optical transmission line wherever the first optical transmission line may be disposed.

Abstract: A method of monitoring chromatic dispersion when transmitting an optical signal includes: applying, to an optical signal in which the symbol rate is f, a dip in optical intensity for every n symbols by means of pseudo-RZ modulation where n is an integer equal to or greater than 2, and transmitting the optical signal to which dips have been applied to a transmission path; receiving the optical signal that is transmitted in by the transmission path and detecting the intensity of a frequency component of k*f/n from the received signal where k is an integer equal to or greater than 1; and based on the detected intensity, generating a monitor signal that represents the chromatic dispersion amount.

Abstract: A method is provided for detecting the skew between parallel light signals generated from a serial data stream. The method can be used with polarization multiplexed signal, as well as with wavelength division multiplexed signals, spatial division multiplexed signals, phase modulated signals, or intensity modulated signals. The method can be used with direct detection schemes as well as with coherent detection schemes. The method is provided with: imprinting dips between a fixed number of transmitted symbols of the parallel signals; detecting an electrical signal related to the dips for each parallel signal; and comparing the electrical signals in delay.

Abstract: Since it is difficult to control correctly and optimally the DC biases of an IQ modulator driven with pre-equalized data, a method for controlling an optical transmitter according to an exemplary aspect of the invention includes the steps of (a) making direct current biases for driving children Mach-Zehnder modulators of an IQ modulator in the optical transmitter converge to values close to null driving points of the children Mach-Zehnder modulators, (b) driving the children Mach-Zehnder modulators with special driving data including a pair of training patterns between which there is a significant correlation, (c) scanning direct current biases for setting quadrature angle of the IQ modulator, (d) monitoring output of the IQ modulator during step (c), and (e) setting the direct current bias for setting quadrature angle on the basis of the driving data and monitored results in step (d).

Abstract: It becomes difficult to perform the optimum equalization signal processing in coherent receiving systems if a channel response in an optical fiber transmission line includes a factor without temporal centrosymmetry, therefore, an equalization signal processor according to an exemplary aspect of the invention includes an equalization filter means configured to receive digital signals by coherent receiving systems; a coefficient control means configured to control coefficients defining characteristics of the equalization filter means; a significant coefficient holding means configured to hold significant coefficients of significant values among initial values of the coefficients; a significant coefficient positioning means configured to determine a significant coefficient position, a position of the significant coefficients in the initial values, so that equalization characteristics of the equalization filter means may be optimized; and a significant coefficient setting means configured to allocate the signific

Abstract: A Pseudo-Return-to-Zero modulator is provided with a narrow pulse clock generator, a modulator driver, and an optical modulator. The narrow pulse clock generator generates a narrow pulse clock of order n, where one of levels occupies half a symbol period and the other level occupies (n?1) plus half a symbol period, n being equal to or more than two. The modulator driver generates an electrical signal in response to binary data and the narrow pulse clock. The optical modulator modulates an optical carrier in response to the electrical signal so that the modulated optical carrier is in a PRZ(n) format.