Abstract: Signal processing means includes carrier compensation means for compensating for a phase difference and a frequency difference between signal light and local light in relation to two polarization signals, so as to generate two carrier compensated signals, symbol determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement of multi-value modulation, symbol rough-determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement in which the number of multi-values of the multi-value modulation is reduced, selection means for selecting either of an output of the symbol determination means and an output of the symbol rough-determination means, and coefficient setting means for updating filter coefficients of polarized wave separation means by using an output selected by the selection means.

Abstract: An optical signal generation unit (110) generates an optical signal for transmission by adding modulation based on a driving signal to a carrier wave. A filtering unit (120) performs a filtering process on the driving signal. The filtering unit (120) may perform time domain equalization, and may perform frequency domain equalization. Specifically, the filtering unit (120) performs a filtering process on the driving signal, and thus sets a peak value of a power spectral density of the optical signal for transmission to be equal to or less than a second reference value while an integrated value obtained by integrating the power spectral density of the optical signal for transmission in a frequency direction is maintained at equal to or greater than a first reference value.

Abstract: In the case where a terminal under an RPR node (240) which does not belong to an interlink connection node group in an RPR network (20) transmits an Ethernet frame to a terminal under an RPR node of other RPR network (10), the RPR node (240) transmits an RPR frame in which the Ethernet frame is contained to any of interlink connection nodes (200, 230, and 270) in the same network. The interlink connection node which receives the RPR frame extracts the Ethernet frame from the RPR frame and transfers the extracted Ethernet frame to the other RPR network (10).

Abstract: When a frequency deviation compensation amount is compensated for by use of frequency shift, a phase offset occurs between adjacent input blocks included in a plurality of input blocks as divided, with the result that an error occurs in a reconstructed bit sequence. A frequency deviation compensation system of the invention is characterized by comprising: a frequency deviation compensation means for compensating for a frequency deviation occurring in a signal by use of frequency shift; and a phase offset compensation means for compensating for a phase offset occurring, in the signal, due to the frequency shift.

Abstract: Because a phase offset occurs between adjoining input blocks of multiple divided blocks when the amount of frequency deviation compensation is dynamically changed, there is the possibility that a restored bit string contains an error. This frequency deviation compensation scheme is equipped with: a frequency deviation compensation means for compensating for a frequency deviation in a frequency-domain signal; and a phase offset compensation means for compensating for a phase offset caused to the signal due to change in an amount of compensation during the frequency compensation.

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 receiver (20) includes an electrical signal generation unit (200), a first phase compensation unit (101), a distortion compensation unit (102), and a first dispersion compensation unit (400). The electrical signal generation unit (200) generates an electrical signal on the basis of received signal light. The first phase compensation unit (101) performs a phase rotation compensation process on the electrical signal generated by the electrical signal generation unit (200). The distortion compensation unit (102) performs a dispersion compensation process and a phase rotation compensation process in this order, at least once, on the electrical signal after having compensation performed thereon by the first phase compensation unit. The electrical signal generation unit (200), the first phase compensation unit (101), and the distortion compensation unit (102) are incorporated into one semiconductor device.

Abstract: In order to reduce influence of noise due to a phase deviation, and to estimate an amount of phase compensation with superior accuracy in a polarization multiplexing/demultiplexing optical communication system, a signal processing circuit includes: optical frequency deviation estimating unit for estimating a frequency deviation which is a difference between a frequency of local light and a frequency of the optical carrier wave which is included in a signal data which corresponds to the polarizations and are generated by mixing a plurality of the optical carrier waves with the local light, which optical carrier wave is phase-modulated and have polarizations able to be demultiplexed and for outputting the estimated frequency deviation as an estimated value; for outputting the estimated frequency deviation as an estimated value; optical frequency deviation compensation amount analyzing unit for calculating an amount of frequency compensation which is an amount of compensation to make a phase of the signal data r

Abstract: A polarization demultiplexing optical communication receiver is provided with a signal quality change imparting means which imparts a signal quality change to multiplexed two optical signals; and a signal quality monitoring means which compares signal qualities of the two optical signals with each other after the multiplexed two optical signals imparted with the signal quality change are subjected to polarization separation so as to specify the two optical signals based on a result of the comparison. This makes it possible to reduce transmission characteristics degradation of a polarization-multiplexed optical signal, and to implement transmission having high reliability.

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: Provided is a polarization separation device which converges filter coefficients used in polarization separating process more quickly.

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: An optical signal generation unit (110) generates an optical signal for transmission by adding modulation based on a driving signal to a carrier wave. A filtering unit (120) performs a filtering process on the driving signal. The filtering unit (120) may perform time domain equalization, and may perform frequency domain equalization. Specifically, the filtering unit (120) performs a filtering process on the driving signal, and thus sets a peak value of a power spectral density of the optical signal for transmission to be equal to or less than a second reference value while an integrated value obtained by integrating the power spectral density of the optical signal for transmission in a frequency direction is maintained at equal to or greater than a first reference value.

Abstract: It becomes difficult to regenerate transmitting signals depending on modulation systems for the optical phase modulation in a polarization multiplexed optical communication system employing the optical digital coherent communication system, therefore, an optical transmitter according to an exemplary aspect of the invention includes first optical quadrature modulation means for performing a phase modulation on a first continuous light beam and outputting a first transmitting light beam; second optical quadrature modulation means for performing a phase modulation on a second continuous light beam belonging in the same frequency band as that of the first continuous light beam and outputting a second transmitting light beam; optical phase difference adding means for adding an optical phase difference varying temporally between the first transmitting light beam and the second transmitting light beam; and polarization multiplexing means for polarization-multiplexing the first transmitting light beam and the second

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: Signal processing means includes carrier compensation means for compensating for a phase difference and a frequency difference between signal light and local light in relation to two polarization signals, so as to generate two carrier compensated signals, symbol determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement of multi-value modulation, symbol rough-determination means for demodulating the two carrier compensated signals on the basis of a signal arrangement in which the number of multi-values of the multi-value modulation is reduced, selection means for selecting either of an output of the symbol determination means and an output of the symbol rough-determination means, and coefficient setting means for updating filter coefficients of polarized wave separation means by using an output selected by the selection means.

Abstract: In order to reduce influence of noise due to a phase deviation, and to estimate an amount of phase compensation with superior accuracy in a polarization multiplexing/demultiplexing optical communication system, a signal processing circuit includes: optical frequency deviation estimating unit for estimating a frequency deviation which is a difference between a frequency of local light and a frequency of the optical carrier wave which is included in a signal data which corresponds to the polarizations and are generated by mixing a plurality of the optical carrier waves with the local light, which optical carrier wave is phase-modulated and have polarizations able to be demultiplexed and for outputting the estimated frequency deviation as an estimated value; for outputting the estimated frequency deviation as an estimated value; optical frequency deviation compensation amount analyzing unit for calculating an amount of frequency compensation which is an amount of compensation to make a phase of the signal data r

Abstract: In a communication system formed of two or more networks in which a part or all of nodes belonging to each said network form a plurality of combinations of nodes so as not to overlap with other node on the network to which each node belongs, the nodes belonging to the same combination are connected with each other and terminals are connected under the control of a part or all of the nodes belonging to the same combination, a node belonging to the combination transmits a frame received from a terminal under the control of the node itself to any of adjacent nodes on the network to which the node itself belongs and a node belonging to the same combination to which the node itself belongs and connected to the node itself. This obtains a highly reliable communication system whose desired transmission capacity can be realized at low costs and which can be restored from an abnormal state in a short time period.

Abstract: In order to reduce influence of noise due to a phase deviation, and to estimate an amount of phase compensation with superior accuracy in a polarization multiplexing/demultiplexing optical communication system, a signal processing circuit includes: optical frequency deviation estimating unit for estimating a frequency deviation which is a difference between a frequency of local light and a frequency of the optical carrier wave which is included in a signal data which corresponds to the polarizations and are generated by mixing a plurality of the optical carrier waves with the local light, which optical carrier wave is phase-modulated and have polarizations able to be demultiplexed and for outputting the estimated frequency deviation as an estimated value; for outputting the estimated frequency deviation as an estimated value; optical frequency deviation compensation amount analyzing unit for calculating an amount of frequency compensation which is an amount of compensation to make a phase of the signal data r