Abstract: A learning schedule of a user is generated on the basis of information indicating a learning history of the user. A question answer data acquisition section (111) acquires the information.

Abstract: Statistical analysis taking into account potential features that affect an occurrence of a predetermined event is enabled. A data processing method according to an embodiment acquires data including a plurality of records, divides the data based on external condition identification information such as a user ID to generate data sets Di for respective external conditions, divides each of the data sets Di based on label information indicating whether the record corresponds to a positive label indicating that a predetermined event has occurred or a negative label indicating that the predetermined event has not occurred to generate two data sets Di+ and Di? for the respective label information, generates difference data for a combination of a record included in one data set of the two data sets and a record included in the other data set, combines the generated difference data to generate integrated data Dnew, performs statistical analysis using Dnew, and outputs a result of performing the statistical analysis.

Abstract: A packet transfer method in a network apparatus that transfers packets is disclosed. In the packet transfer method, a sending side apparatus generates two copies of a send packet, provides a sequence number identifying the same sending sequence to each of the copied packets, provides an identifier corresponding to a send/receive pair to each of the copied packets to send the packets, and a receiving side apparatus receives each of the packets with two receiving units; recognizes the identifiers each corresponding to a send/receive pair; identifies packets having the same information and the sequence based on the sequence number when the identifiers are the same; selects one of the packets of the same sequence so as to send the packet downstream, and discards another packet, wherein, when only one of the packets of the same sequence arrives, the arriving packet is sent downstream.

Abstract: A packet transfer method in a network apparatus that transfers packets is disclosed. In the packet transfer method, a sending side apparatus generates two copies of a send packet, provides a sequence number identifying the same sending sequence to each of the copied packets, provides an identifier corresponding to a send/receive pair to each of the copied packets to send the packets, and a receiving side apparatus receives each of the packets with two receiving units; recognizes the identifiers each corresponding to a send/receive pair; identifies packets having the same information and the sequence based on the sequence number when the identifiers are the same; selects one of the packets of the same sequence so as to send the packet downstream, and discards another packet, wherein, when only one of the packets of the same sequence arrives, the arriving packet is sent downstream.

Abstract: A packet transfer method in a network apparatus that transfers packets is disclosed. In the packet transfer method, a sending side apparatus generates two copies of a send packet, provides a sequence number identifying the same sending sequence to each of the copied packets, provides an identifier corresponding to a send/receive pair to each of the copied packets to send the packets, and a receiving side apparatus receives each of the packets with two receiving units; recognizes the identifiers each corresponding to a send/receive pair; identifies packets having the same information and the sequence based on the sequence number when the identifiers are the same; selects one of the packets of the same sequence so as to send the packet downstream, and discards another packet, wherein, when only one of the packets of the same sequence arrives, the arriving packet is sent downstream.

Abstract: The present invention provides an optical signal quality monitoring circuit and an optical signal quality monitoring method for measuring correct optical signal quality parameters when a signal bit rate is changed. The optical signal quality monitoring circuit which samples and converts an electrical signal converted from an optical signal with a given repeated frequency f1 to digital sampling data through an analog to digital conversion, thereafter, evaluates an optical signal quality parameter of the optical signal by subjecting sampling data to electrical signal processing in an integrated circuit in which a signal processing function is programmed, receives a control signal notifying that the bit rate of the optical signal is changed, or detects that the bit rate of the optical signal is changed to correct optical the signal quality parameter of the optical signal corresponding to the signal bit rate of the optical signal which is changed.

Abstract: The present invention provides an optical signal quality monitoring circuit and an optical signal quality monitoring method for measuring correct optical signal quality parameters when a signal bit rate is changed. The optical signal quality monitoring circuit which samples and converts an electrical signal converted from an optical signal with a given repeated frequency f1 to digital sampling data through an analog to digital conversion, thereafter, evaluates an optical signal quality parameter of the optical signal by subjecting sampling data to electrical signal processing in an integrated circuit in which a signal processing function is programmed, receives a control signal notifying that the bit rate of the optical signal is changed, or detects that the bit rate of the optical signal is changed to correct optical the signal quality parameter of the optical signal corresponding to the signal bit rate of the optical signal which is changed.

Abstract: A packet transfer method in a network apparatus that transfers packets is disclosed. In the packet transfer method, a sending side apparatus generates two copies of a send packet, provides a sequence number identifying the same sending sequence to each of the copied packets, provides an identifier corresponding to a send/receive pair to each of the copied packets to send the packets, and a receiving side apparatus receives each of the packets with two receiving units; recognizes the identifiers each corresponding to a send/receive pair; identifies packets having the same information and the sequence based on the sequence number when the identifiers are the same; selects one of the packets of the same sequence so as to send the packet downstream, and discards another packet, wherein, when only one of the packets of the same sequence arrives, the arriving packet is sent downstream.

Abstract: A monitoring system includes first and second evaluation sections for obtaining an averaged Q-factor parameter and a waveform distortion parameter from an optical signal amplitude histogram collected from optical signals under measurement. The monitoring system further includes a third evaluation section for determining both averaged Q-factor parameter and waveform distortion parameter, and for making a decision as to whether the main factor of the optical signal quality degradation is waveform distortion or not by comparing the averaged Q-factor parameter and waveform distortion parameter with their initial values or initial characteristics which are obtained when no optical signal quality degradation is present.

Abstract: The scale and complexity of an apparatus is reduced by omitting a clock extraction section. The apparatus includes: a sampling pulse train generation device which generates an optical or electrical sampling pulse train, independently of an input optical or electrical data signal with a bit rate f0(bit/s), and which has a repetition frequency f1(Hz); a data signal sampling device which samples the data signal in accordance with the sampling pulse train to obtain a sampled signal; a voltage retaining device which converts the sampled signal, and stores pieces of electrical digital data; an electrical signal processing device which reads the digital data at once or sequentially to obtain a signal eye-diagram and evaluates optical data signal quality parameters; and a trigger signal generation device which applies triggers indicating the start/finish of data acquisition and data read to the voltage retaining device and the electrical signal processing device, respectively.

Abstract: An optical signal quality degradation monitoring apparatus for monitoring an optical wavelength division multiplex signal is implemented in a small size. To monitor the optical signal quality degradation in the optical wavelength division multiplex signal by a configuration as simple as possible, the following configurations are used: A configuration using an optical wavelength division demultiplexer and a sampling clock generator to make one an electric signal processor; A configuration using an optical sampling pulse train generator, an optical multiplexer, a nonlinear optical medium, and an optical wavelength division demultiplexer to make one an electric signal processor; or a configuration using a selection wavelength control section, an optical wavelength selecting section, and a sampling clock generator to make one electric signal.

Abstract: An optical modulation/multiplexing circuit can fabricate a plurality of nonlinear optical waveguide devices and silica optical waveguides through a small number of processes, and achieve the simplification of the fabrication process and stabilization of the operation by hybrid integration with reduced connection loss. It employs lithium niobate domain inversion optical waveguides as nonlinear optical switches, and implements functions necessary for modulation and multiplexing such as input, splitting, multiplexing and timing adjustment of optical modulation signals and an optical clock signal by connecting glass waveguides to the input and output terminals of the domain inversion optical waveguides. Nonlinear optical media generate a second harmonic light beam of the optical clock signal, and at the same time produces a light beam with a frequency corresponding to the difference frequency of the two high frequency signals, the second harmonic light beam and the signal pulses.

Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.

Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.

Abstract: Signal channels are identified easily by uniquely correlating the port numbers of the optical time-division-demultiplexing unit with channel numbers. The extraction apparatus includes an optical time-division-demultiplexing unit that separates multiplexed signals into N channels and provides them to N separate ports, a channel extraction unit that is connected to N separate ports and extracts one channel number of the N channels, a channel switch that switches the N channels to the output ports of which port numbers uniquely match with the numbers of the N channels based on the relationship between the number of the one channel extracted and the output port number corresponding to the one channel number, and a data output unit that has N output ports and provides the signals of the switched N channels to the output ports of which port numbers match with the channel numbers.

Abstract: The scale and complexity of an apparatus is reduced by omitting a clock extraction section. The apparatus includes: a sampling pulse train generation device which generates an optical or electrical sampling pulse train, independently of an input optical or electrical data signal with a bit rate f0 (bit/s), and which has a repetition frequency f1 (Hz); a data signal sampling device which samples the data signal in accordance with the sampling pulse train to obtain a sampled signal; a voltage retaining device which converts the sampled signal, and stores pieces of electrical digital data; an electrical signal processing device which reads the digital data at once or sequentially to obtain a signal eye-diagram and evaluates optical data signal quality parameters; and a trigger signal generation device which applies triggers indicating the start/finish of data acquisition and data read to the voltage retaining device and the electrical signal processing device. respectively.

Abstract: An optical modulation/multiplexing circuit can fabricate a plurality of nonlinear optical waveguide devices and silica optical waveguides through a small number of processes, and achieve the simplification of the fabrication process and stabilization of the operation by hybrid integration with reduced connection loss. It employs lithium niobate domain inversion optical waveguides as nonlinear optical switches, and implements functions necessary for modulation and multiplexing such as input, splitting, multiplexing and timing adjustment of optical modulation signals and an optical clock signal by connecting glass waveguides to the input and output terminals of the domain inversion optical waveguides. Nonlinear optical media generate a second harmonic light beam of the optical clock signal, and at the same time produces a light beam with a frequency corresponding to the difference frequency of the two high frequency signals, the second harmonic light beam and the signal pulses.

Abstract: It is the object of the present invention to provide a transmission system that transmits a control signal corresponding to the overhead accommodating time division multiplexing information at a frequency that is the same (or nearly the same) as that of the main signal. In order to attain this object, an optical transmitter broadens in a time range the optical waveform of the OTDM signal having a wavelength &lgr;0 and the control light having a wavelength &lgr;1(≈&lgr;0), and multiplexes the signal light having an optical peak intensity set low compared to the OTDM signal peak intensity and sending this to an optical transmission fiber.

Abstract: A monitoring system includes first and second evaluation sections for obtaining an averaged Q-factor parameter and a waveform distortion parameter from an optical signal amplitude histogram collected from optical signals under measurement. The monitoring system further includes a third evaluation section for determining both averaged Q-factor parameter and waveform distortion parameter, and for making a decision as to whether the main factor of the optical signal quality degradation is waveform distortion or not by comparing the averaged Q-factor parameter and waveform distortion parameter with their initial values or initial characteristics which are obtained when no optical signal quality degradation is present.

Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.