Abstract: A wavelength tunable laser device includes: a first mirror; a second mirror; an optical amplifier provided between the first mirror and the second mirror; a wavelength tunable filter provided between the first mirror and the second mirror; and an optical waveguide coupling the optical amplifier and the wavelength tunable filter. The optical waveguide includes a first waveguide formed with a first width and a second waveguide formed with a second width wider than the first width.

Abstract: A wavelength filter includes a first filter circuit and a second filter circuit. The first filter circuit that has a passband that is obtained from a vernier effect by connecting, in series, a plurality of ring resonators each having a different transmission wavelength interval and that is within a gain band of an optical amplifier, and that passes, from the gain band, light at a selected wavelength and light that has a wavelength in a recursive mode and that is produced on a short wavelength side or a long wavelength side of the selected wavelength. The second filter circuit is connected to the first filter circuit in series and suppresses the light at the wavelength in the recursive mode from the light passing through the first filter circuit.

Abstract: A receiving device, includes a memory; and a processor coupled to the memory and configured to: when amplifying a multi-valued signal of a multi-valued modulation technique according to a control signal, acquire a first multi-valued signal before amplifying the multi-valued signal and a second multi-valued signal after amplifying the multi-valued signal, detect a first peak voltage of the first multi-valued signal, detect a second peak voltage of the second multi-valued signal, and control the control signal based on the first peak voltage and the second peak voltage such that a maximum amplitude of the second multi-valued signal and linearity of the second multi-valued signal are maintained.

Abstract: A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.

Abstract: An optical modulator includes a first optical waveguide dividing light input thereto, first and second diodes shifting phases of light beams as a result of the division of the light by the optical waveguide, a second optical waveguide causing the light beams passing through the first and second diodes to interfere, a control circuit adjusting at least one of a current flowing in the first diode and a current flowing in the second diode to control a phase difference of the light beams interfering in the second optical waveguide, and an electrical resistance element having one end coupled to the first and second diodes and the other end grounded.

Abstract: A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.

Abstract: An optical modulator includes an optical wave guide that passes light, a first phase shifter that adjusts a phase of the light passing through the optical waveguide by passing an electric current through a diode formed in the optical waveguide, a second phase shifter that adjusts a phase of the light passing through the optical waveguide by adjusting a temperature of the optical waveguide, and a controller that corrects a phase shift of the light passing through the optical waveguide based on a result of detection of power of the light that passed through the optical waveguide, the controller controls the first phase shifter to correct the phase shift when the magnitude of the phase shift of the light passing through the optical waveguide is less than a predetermined magnitude, and the controller controls the second shifter to correct the phase shift.

Abstract: A laser diode control circuit includes, a control signal supply circuit that supplies a control signal including a direct current component and an alternating current component to a laser diode, an optical output signal acquisition circuit that acquires an optical output signal indicating an optical output of the laser diode according to the control signal, a phase determination circuit that determines whether a phase of the alternating current component included in the optical output signal is the same as the phase of the alternating current component included in the control signal, and a control signal determination circuit that determines to decrease the direct current component of the control signal when it is determined that the phase of the alternating current component included in the optical output signal is not the same as the phase of the alternating current component included in the control signal.

Abstract: An apparatus includes a first coupler configured to input input light through an input waveguide and branch the input light into first and second branch waveguides; a second coupler configured to combine the first and second branch waveguides and to output the output light through an output waveguide; a phase adjuster having a birefringent property, provided to the second branch waveguide; and a polarization converter having a birefringent property, provided to the output waveguide and configured to, when reflected light corresponding to the output light is input to the output waveguide, convert a polarization state of the reflected light such that a first part of the reflected light for traveling through the first path and a second part of the reflected light for traveling through the second path are in antiphase at the input waveguide.

Abstract: A computing method includes: detecting, in a circuit board, a coordinate of an area where a current greater than or equal to a threshold flows; extracting signal layer currents and GND layer currents within a given range based on the coordinate, the signal layer currents flowing in a signal layer and the GND layer currents flowing in a GND layer; computing, by a computer, a first current as a sum of the signal layer currents and a second current as a sum of the GND layer currents; and computing a third current as a sum of the first current and the second current in a section direction of the circuit board.

Abstract: An electromagnetic field simulation method includes: obtaining, when a reference signal including a plurality of frequencies is input to a first point of design data of an object, a variation of a reference signal at a second point by a computer through an electromagnetic field simulation; calculating variable data at each of the plurality of frequencies based on the variation of the reference signal; frequency-decomposing a signal applied to the first point; and calculating a frequency distribution of the signal at the second point which propagates from the first point based on the frequency-decomposed signal and the variable data at each of the plurality of frequencies.

Abstract: A chirp measuring device includes a chirp measuring unit that measures chirps indicating a time variation of an optical frequency of input light signal; a signal averaging unit that computes, based on a predetermined number of additions for signal averaging, an average of the chirps measured by the chirp measuring unit; a chirp threshold value determining unit that determines whether the average computed by the signal averaging unit is not less than a predetermined chirp threshold value; and a determination result output unit that outputs a determination result obtained by the chirp threshold value determining unit.

Abstract: In an optical module, a lens collects input light to generate a collected beam. A VIPA plate includes a reflective surface for highly reflecting light and a transmissive surface on which a reflection film having a lower reflectivity than the reflective surface is deposited. The VIPA plate causes multiple reflection of the collected beam within an internal area between the reflective surface and the transmissive surface, and emits diffracted light via the transmissive surface. A reflection mirror reflects outgoing light emitted from the transmissive surface to generate return light which returns to the transmissive surface. The reflection film includes a high-reflection film deposited on a portion from which the outgoing light of a high light intensity is emitted and a low-reflection film deposited on a portion from which the outgoing light having a lower light intensity is emitted.

Abstract: A chromatic dispersion compensator whereby the amount of dispersion and the group delay time can be easily adjusted. A dispersion unit, a transmitting lens and a group delay generation unit are arranged along the optical axis of incident light. The dispersion unit separates the incident light into beams of respective different wavelengths. The transmitting lens is arranged across the optical paths of the beams of different wavelengths separated by the dispersion unit, and refracts the beams at different angles according to their respective incidence positions. The group delay generation unit is arranged across the optical paths of the beams of different wavelengths refracted by the transmitting lens, causes the beams to undergo propagation delay for periods corresponding to their respective incidence positions, and converges and emits the beams of different wavelengths. Consequently, the beams of different wavelengths are imparted group delay corresponding to the refracting angles of the transmitting lens.

Abstract: Efficient absorption of radio wave emission can be ensured from a high frequency signal processing circuit in an optical transmitter/receiver module. The optical transmitter/receiver module pluggable to a communication device includes a housing having openings on an anterior and a posterior ends; an optical connector disposed at the anterior opening; a photoelectric converting unit that converts a wavelength-division multiplexed optical signal, that is input from an optical transmission line connected to the optical connector, into an electric signal; and a high frequency circuit board that performs high frequency signal processing of an electric signal converted by the photoelectric converting unit, whereinat the posterior opening, a connecting terminal of the high frequency circuit board is formed so that it is pluggable to a mother board of a communication device, and wherein radio wave absorbers are arranged in spaces between the top/bottom surfaces of the high frequency circuit board and the housing.

Abstract: A chromatic dispersion compensator whereby the amount of dispersion and the group delay time can be easily adjusted. A dispersion unit, a transmitting lens and a group delay generation unit are arranged along the optical axis of incident light. The dispersion unit separates the incident light into beams of respective different wavelengths. The transmitting lens is arranged across the optical paths of the beams of different wavelengths separated by the dispersion unit, and refracts the beams at different angles according to their respective incidence positions. The group delay generation unit is arranged across the optical paths of the beams of different wavelengths refracted by the transmitting lens, causes the beams to undergo propagation delay for periods corresponding to their respective incidence positions, and converges and emits the beams of different wavelengths. Consequently, the beams of different wavelengths are imparted group delay corresponding to the refracting angles of the transmitting lens.

Abstract: The invention provides a spectral apparatus capable of making the passing wavelength of VIPA board variable easily and at high speed. For this purpose, the apparatus of the invention includes an optical component having two opposing parallel reflection surfaces, for receiving the light focused in one-dimensional direction between the reflection surfaces, multiple-reflecting the incident light on each reflection surface and emitting a part of the incident light through one reflection surface, and allowing the emitted light to interfere mutually to form luminous fluxes different in propagation direction depending on the wavelength, and a rotary mechanism for rotating and displacing the position of the optical component, on an axis substantially vertical to the optical axis of the incident light, and which axis substantially vertical to the one-dimensional direction for focusing the incident light.

Abstract: A spectroscopic apparatus which is compact in size and performs high-precision light-splitting with a large angular dispersion. An optical input-processing section outputs a filtered transmitted light, using a bandpass filter that transmits only wavelength bands at one period of an input light, and collects the filtered transmitted light to generate a collected beam. An optic includes a first reflection surface and a second reflection surface which are high but asymmetric in reflectivity, and causes the collected beam incident thereon to undergo multiple reflections within an inner region between the first reflection surface and the second reflection surface, to thereby cause split beams to be emitted via the second reflection surface. A received light-processing section performs received light processing of the beams emitted from the optic. A control section variably controls at least one of a filter characteristic of the bandpass filter and an optical length through the optic.

Abstract: An electromagnetic wave analyzer that accurately calculates electromagnetic waves emanating from a given wave source, without the need for assessing accuracy in other than the wave source domain. An analysis condition receiver receives analysis conditions including position parameters specifying observation points, as well as frequency parameters specifying frequencies to be analyzed. Upon receipt of analysis conditions, a Fourier transform processor transforms time-series electromagnetic current data to produce frequency-specific electromagnetic current data for each frequency specified by the frequency parameters. Based on the frequency-specific electromagnetic current data, an electromagnetic field calculator calculates the electric field at each observation point specified by the position parameters, by integrating electric fields produced by electric and magnetic currents in each small volume of the electromagnetic wave source.

Abstract: The present invention has an object to provide an optical apparatus of VIPA-type for achieving the reduction of the inter-channel loss deviation to realize a high accurate demultiplexing function. To this end, the optical apparatus according to the present invention comprises: a collimator lens converting an input light into a parallel light; a phase mask changing a phase of the parallel light from the collimator lens to change the intensity distribution into a shape different from the Gaussian distribution; a line focal lens condensing the light output from the phase mask onto a one-dimensional direction; and a VIPA plate multi-reflecting the light condensed by the line focal lens to emit the multi-reflected light.