Abstract: An electro-optic waveguide device may include a slot waveguide including a lower high-refractive-index layer with a first refractive index and an upper high-refractive-index layer with a second refractive index, wherein the lower high-refractive-index layer and the upper high-refractive-index layer have conductivity and are disposed to face each other with a gap; and a slot part formed as a low-refractive-index layer, wherein the low-refractive-index layer is formed of a material producing an electro-optic effect and has a third refractive index lower than the first refractive index and the second refractive index, wherein the low-refractive-index layer is formed in the gap to come into contact with the lower high-refractive-index layer and the upper high-refractive-index layer, and wherein one of the lower high-refractive-index layer or the upper high-refractive-index layer includes a stretch stretching on both sides of a contact portion with the slot part in a width direction intersecting a transmission dir

Abstract: Provided is an optical transmission module which can generate PAM4 optical modulation signals without converting a plurality of binary electric signals to a multi-level electric signal. An optical transmission module (200) comprising: a light source (60) for emitting continuous waveform (CW) light; optical modulators (51,52,53) arranged in series with a path of the CW light configured to modulate the CW light by switching relatively large absorption and relatively small absorption of the optical modulators in response to a modulation signal applied to the respective optical modulators; and an arithmetic logic circuit (100) configured to receive a plurality of binary electrical signals, and then to perform logic operation on the plurality of binary electrical signals for generating a new plurality of binary electrical signals, wherein each of the new plurality of binary electrical signals is applied to the respective optical modulators as the modulation signal.

Abstract: An electro-optic waveguide device may include a slot waveguide including a lower high-refractive-index layer with a first refractive index and an upper high-refractive-index layer with a second refractive index, wherein the lower high-refractive-index layer and the upper high-refractive-index layer have conductivity and are disposed to face each other with a gap; and a slot part formed as a low-refractive-index layer, wherein the low-refractive-index layer is formed of a material producing an electro-optic effect and has a third refractive index lower than the first refractive index and the second refractive index, wherein the low-refractive-index layer is formed in the gap to come into contact with the lower high-refractive-index layer and the upper high-refractive-index layer, and wherein one of the lower high-refractive-index layer or the upper high-refractive-index layer includes a stretch stretching on both sides of a contact portion with the slot part in a width direction intersecting a transmission dir

Abstract: Provided is an optical transmission module which can generate PAM4 optical modulation signals without converting a plurality of binary electric signals to a multi-level electric signal. An optical transmission module (200) comprising: a light source (60) for emitting continuous waveform (CW) light; optical modulators (51,52,53) arranged in series with a path of the CW light configured to modulate the CW light by switching relatively large absorption and relatively small absorption of the optical modulators in response to a modulation signal applied to the respective optical modulators; and an arithmetic logic circuit (100) configured to receive a plurality of binary electrical signals, and then to perform logic operation on the plurality of binary electrical signals for generating a new plurality of binary electrical signals, wherein each of the new plurality of binary electrical signals is applied to the respective optical modulators as the modulation signal.

Abstract: Multilevel optical intensity modulation high in accuracy is performed using electro-absorption optical modulators. There is provided a plurality of EA modulators connected in series in a path of an optical signal from a light source, and a multilevel-coded modulated optical signal is generated by modulating an intensity of an input optical signal from the light source based on a modulation signal using the EA modulators. Each of the EA modulators is switched between an ON state and an OFF state of optical absorption in accordance with the modulation signal. Regarding an extinction ratio of the ON state to the OFF state in each of the EA modulators, the EA modulators have respective values difference from each other, and are arranged in ascending order of the extinction ratio from the light source side.

Abstract: Preferable simultaneous achievement of the target characteristics with respect to both of the modulation bandwidth and the extinction ratio in the optical intensity modulation using the electro-absorption optical modulator is realized with a simple circuit configuration. The modulator integrated semiconductor laser element includes a plurality of EA modulators disposed in series in an optical signal path, and each adapted to absorb light in accordance with an applied voltage. The modulator driver for supplying the EA modulator with the applied voltage is provided for each of the EA modulators. The plurality of modulator drivers generates the applied voltage common to the plurality of EA modulators in accordance with a control signal. The modulator lengths of the plurality of EA modulators are set so that the closer to the light source the EA modulator is, the shorter the modulator length is.

Abstract: Preferable simultaneous achievement of the target characteristics with respect to both of the modulation bandwidth and the extinction ratio in the optical intensity modulation using the electro-absorption optical modulator is realized with a simple circuit configuration. The modulator integrated semiconductor laser element includes a plurality of EA modulators disposed in series in an optical signal path, and each adapted to absorb light in accordance with an applied voltage. The modulator driver for supplying the EA modulator with the applied voltage is provided for each of the EA modulators. The plurality of modulator drivers generates the applied voltage common to the plurality of EA modulators in accordance with a control signal. The modulator lengths of the plurality of EA modulators are set so that the closer to the light source the EA modulator is, the shorter the modulator length is.

Abstract: Multilevel optical intensity modulation high in accuracy is performed using electro-absorption optical modulators. There is provided a plurality of EA modulators connected in series in a path of an optical signal from a light source, and a multilevel-coded modulated optical signal is generated by modulating an intensity of an input optical signal from the light source based on a modulation signal using the EA modulators. Each of the EA modulators is switched between an ON state and an OFF state of optical absorption in accordance with the modulation signal. Regarding an extinction ratio of the ON state to the OFF state in each of the EA modulators, the EA modulators have respective values difference from each other, and are arranged in ascending order of the extinction ratio from the light source side.

Abstract: A communication system includes a termination-side optical transmitter comprising a reflective semiconductor optical amplifier, a reflective unit configured to reflect output light from the termination-side optical transmitter, and a terminal station-side optical receiver connected to the termination-side optical transmitter via a transmission line and configured to receive the output light from the termination-side optical transmitter by limiting a frequency band of the output light. The reflective semiconductor optical amplifier amplifies the output light reflected by the reflective unit, modulates the amplified output light based on an electric signal, and outputs the modulated output light.

Abstract: A technology to automatically control the biasing of an optical duobinary transmitter using a single-drive LN-MZ modulator is provided. A low-frequency signal is amplitude modulated onto a voltage signal input into a Mach-Zehnder optical modulator 22. The optical output from the optical modulator 22 is detected by an optical detection subsystem 30. In a bias control subsystem 40, the low-frequency signal component amplitude modulated onto the electrical signal is detected from the optical output, and a DC bias voltage applied to the optical modulator is controlled such that the low-frequency signal component is either minimized or maximized.

Abstract: A technology to automatically control the biasing of an optical duobinary transmitter using a single-drive LN-MZ modulator is provided. A low-frequency signal is amplitude modulated onto a voltage signal input into a Mach-Zehnder optical modulator 22. The optical output from the optical modulator 22 is detected by an optical detection subsystem 30. In a bias control subsystem 40, the low-frequency signal component amplitude modulated onto the electrical signal is detected from the optical output, and a DC bias voltage applied to the optical modulator is controlled such that the low-frequency signal component is either minimized or maximized.

Abstract: There are provided an optical transmitter and a method for transmitting an optical signal, which realizes an optimum desired temperature arrival time without changing a Peltier element size, a drive current and a drive voltage, and which is stabilized by control having a sufficient phase margin. Different loop filters for heating and cooling are provided for a control loop of the Peltier element on which a laser diode is mounted, and the respective appropriate loop filters are selected and used on the basis of heating or cooling information.

Abstract: A spectrum analyzer having an improved local oscillator for use in a digital step sweep is capable of minimizing a dynamic spurious response which is inverse proportional to a unit step time in the step sweep. The local oscillator includes a random clock delay which provides a random clock to a direct digital synthesizer to incorporate random timings in a time length of the unit step time for sweeping the local oscillator. In another aspect, the local oscillator includes a sweep step number control which maximizes the number of steps in the step sweep to ultimately decrease the dynamic spurious response.

Abstract: A spectrum analyzer in which automatic setting of parameters such as band width is done by the analyzer without manual operator input and noise measurements are determined and displayed to the operator. This is accomplished by an input signal being supplied to a frequency mixer via an input variable attenuator. The frequency of the input signal is mixed with the frequency of a local signal from a frequency sweep generator. The mixed signal is then supplied to a band pass filter and the output of the filter is amplified by an amplifier. The frequency of the amplified output is mixed with the frequency of a local signal from a local oscillator by a frequency mixer. The intermediate frequency signal is taken out by a band pass filter and the output is detected by a detector. The detected output is converted into a digital signal by an A/D converter after passing through a low pass filter and the digital signal is stored in a buffer memory. A CPU sets an attenuation amount.

Abstract: A measuring device and method use a spectrum analyzer. The spectrum analyzer comprises a display screen controlled by a processor on which a spectrum of an input signal is displayed in a frequency region on a half portion of the display screen and a noise level at a frequency associated with the input signal is displayed in a time region on another half portion of the display screen.

Abstract: An information terminal transmits small amount data such as a command to a Web server on the internet to an asymmetric router via an interactive radio network. The asymmetric router transmits the command to the Web server via the internet. The asymmetric router transmits large amount data (for example, HTML formatted browser data) from the Web server to a data superimposing broadcast apparatus. The data superimposing broadcast apparatus determines a scheduled time of broadcasting according to a data amount. The scheduled time is transmitted to the information terminal via the asymmetric router and the interactive radio network. When the scheduled time comes, the large amount data is superimposed on an empty portion of a television signal, and is broadcasted. The information terminal carries out a predetermined processing operation whereby a broadcast receiving circuit is turned on, and the television signal on which the large amount data has been superimposed is received.

Abstract: An improved local oscillator for use in a digital step sweep is capable of minimizing dynamic spurious which is an inverse of the unit step time T.sub.step. The local oscillator includes a random clock delay 12 which provides a random clock 12.sub.rndclk to the DDS 40 to modify a time length of the unit step time T.sub.step for sweeping the local oscillator to be random.