Abstract: Provided is a driving device for PWM control of voltage pulses for controlling the temperature of a heater in a phase controller, the driving device being capable of increasing the response speed of an optical element such as an optical switch. Phase controllers include first and second heaters for changing the temperatures of first and second optical waveguides extending in parallel. Driving devices include pulse generation circuits that generate voltage pulses to apply to the first and second heaters. To start raising the temperature of the second heater, the pulse generation circuit generates a first voltage pulse and consecutive second voltage pulses to apply to the second heater with zero voltage pulse being applied to the first heater, the first voltage pulse having a long pulse width and the second voltage pulses following the first voltage pulse and having a shorter pulse width than the first voltage pulse.

Abstract: Provided is a driving device for PWM control of voltage pulses for controlling the temperature of a heater in a phase controller, the driving device being capable of increasing the response speed of an optical element such as an optical switch. Phase controllers include first and second heaters for changing the temperatures of first and second optical waveguides extending in parallel. Driving devices include pulse generation circuits that generate voltage pulses to apply to the first and second heaters. To start raising the temperature of the second heater, the pulse generation circuit generates a first voltage pulse and consecutive second voltage pulses to apply to the second heater with zero voltage pulse being applied to the first heater, the first voltage pulse having a long pulse width and the second voltage pulses following the first voltage pulse and having a shorter pulse width than the first voltage pulse.

Abstract: An optical transmitter that includes a wavelength tunable laser diode (LD) with a narrowed emission linewidth is disclosed. The optical transmitter further includes a feedback unit and an optical attenuator. The feedback unit, receiving a portion of laser light of the wavelength tunable LD, generates feedback light by rotating the polarization of the laser light by 90±5°, and returns thus generated feedback light in the wavelength tunable LD. The optical attenuator adjusts power of the feedback light to reduce a line wide of the laser light, or frequency noises thereof.

Abstract: An optical transmitter that includes a wavelength tunable laser diode (LD) with a narrowed emission linewidth is disclosed. The optical transmitter further includes a feedback unit and an optical attenuator. The feedback unit, receiving a portion of laser light of the wavelength tunable LD, generates feedback light by rotating the polarization of the laser light by 90±5°, and returns thus generated feedback light in the wavelength tunable LD. The optical attenuator adjusts power of the feedback light to reduce a line wide of the laser light, or frequency noises thereof.

Abstract: A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.

Abstract: A system includes: a splitter to branch an optical signal output by a wavelength-tunable light source into first to third optical signals; a first photodiode to perform an optical electrical conversion of the first optical signal transmitting a first etalon; a second photodiode to perform an optical electrical conversion of the second optical signal transmitting a second etalon, an FSR of the second etalon being identical to that of the first etalon, peak wavelengths of intensity of a transmitted light of the second etalon being different from those of the first etalon; a third photodiode to perform an optical electrical conversion of the third optical signal; and a controller to control the wavelength-tunable light source with use of a coefficient calculated by following formulas (1) or (2), Coefficient=(PD1?A·PD3)/(PD2?B·PD3) (1) and Coefficient=(PD2?B·PD3)/(PD1?A·PD3) (2).

Abstract: In order to improve reliability by preventing an edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector comprises a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.

Abstract: A system includes: a splitter to branch an optical signal output by a wavelength-tunable light source into first to third optical signals; a first photodiode to perform an optical electrical conversion of the first optical signal transmitting a first etalon; a second photodiode to perform an optical electrical conversion of the second optical signal transmitting a second etalon, an FSR of the second etalon being identical to that of the first etalon, peak wavelengths of intensity of a transmitted light of the second etalon being different from those of the first etalon; a third photodiode to perform an optical electrical conversion of the third optical signal; and a controller to control the wavelength-tunable light source with use of a coefficient calculated by following formulas (1) or (2), Coefficient=(PD1?A·PD3)/(PD2?B·PD3) (1) and Coefficient=(PD2?B·PD3)/(PD1?A·PD3) (2).

Abstract: In order to improve reliability by preventing an edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector comprises a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: In order to improve reliability by preventing an edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector includes a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: A wavelength conversion system includes a Mach-Zehnder interferometer including two optical waveguides, a non-linear medium provided on one of the two optical waveguides, and a branching ratio adjuster for adjusting the branching ratio of multiplexed light produced by multiplexing signal light and pumping light so that the powers of the signal light and the pumping light which are to be emitted from the two optical waveguides are equal to each other. The multiplexed light whose branching ratio is adjusted by the branching ratio adjuster is introduced into the two optical waveguides such that the non-linear medium generates phase conjugation light of the signal light and the light guided through the one optical waveguide and the light guided through the other one of the two optical waveguides interfere with each other so that the phase conjugation light is extracted as wavelength conversion light.

Abstract: In order to improve reliability by preventing an edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector comprises a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: In order to improve reliability by preventing edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector includes a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: A wavelength conversion system includes a Mach-Zehnder interferometer including two optical waveguides, a non-linear medium provided on one of the two optical waveguides, and a branching ratio adjuster for adjusting the branching ratio of multiplexed light produced by multiplexing signal light and pumping light so that the powers of the signal light and the pumping light which are to be emitted from the two optical waveguides are equal to each other. The multiplexed light whose branching ratio is adjusted by the branching ratio adjuster is introduced into the two optical waveguides such that the non-linear medium generates phase conjugation light of the signal light and the light guided through the one optical waveguide and the light guided through the other one of the two optical waveguides interfere with each other so that the phase conjugation light is extracted as wavelength conversion light.

Abstract: A semiconductor photodetecting device including a PIN photodiode formed on an SI-InP substrate; a buried optical waveguide portion formed on the SI-InP substrate and including the film thickness continuously increased toward the PIN photodiode and an InP clad layer covering the upper surface and the side surface of the InGaAsP core layer; and a ridge-shaped connection optical waveguide portion formed on the SI-InP substrate between the PIN photodiode and the buried optical waveguide portion and including the InGaAsP core layer and the InP clad layer selectively covering only the upper surface of the InGaAsP core layer.

Abstract: A wavelength conversion system includes a Mach-Zehnder interferometer including two optical waveguides, a non-linear medium provided on one of the two optical waveguides, and a branching ratio adjuster for adjusting the branching ratio of multiplexed light produced by multiplexing signal light and pumping light so that the powers of the signal light and the pumping light which are to be emitted from the two optical waveguides are equal to each other. The multiplexed light whose branching ratio is adjusted by the branching ratio adjuster is introduced into the two optical waveguides such that the non-linear medium generates phase conjugation light of the signal light and the light guided through the one optical waveguide and the light guided through the other one of the two optical waveguides interfere with each other so that the phase conjugation light is extracted as wavelength conversion light.

Abstract: An optical integrated device includes a plurality of input optical waveguides connected respectively to a plurality of input ports provided on one end face of the optical integrated device, a single output optical waveguide connected to an output port, an optical coupler for optically coupling signal lights propagated along the plural input optical waveguides to the single output optical waveguide, and a semiconductor optical amplifier gate array formed from a plurality of semiconductor optical amplifiers provided on the input optical waveguides, respectively, and each having an electrode on the surface thereof. The optical integrated device further includes a plurality of signal lines formed on the surface of the optical integrated device in such a manner as to extend from the electrodes to an end face of the optical integrated device on which none of the input ports and the output port is provided.

Abstract: An optical integrated device includes a plurality of input optical waveguides connected respectively to a plurality of input ports provided on one end face of the optical integrated device, a single output optical waveguide connected to an output port, an optical coupler for optically coupling signal lights propagated along the plural input optical waveguides to the single output optical waveguide, and a semiconductor optical amplifier gate array formed from a plurality of semiconductor optical amplifiers provided on the input optical waveguides, respectively, and each having an electrode on the surface thereof. The optical integrated device further includes a plurality of signal lines formed on the surface of the optical integrated device in such a manner as to extend from the electrodes to an end face of the optical integrated device on which none of the input ports and the output port is provided.

Abstract: A wavelength conversion system includes a Mach-Zehnder interferometer including two optical waveguides, a non-linear medium provided on one of the two optical waveguides, and a branching ratio adjuster for adjusting the branching ratio of multiplexed light produced by multiplexing signal light and pumping light so that the powers of the signal light and the pumping light which are to be emitted from the two optical waveguides are equal to each other. The multiplexed light whose branching ratio is adjusted by the branching ratio adjuster is introduced into the two optical waveguides such that the non-linear medium generates phase conjugation light of the signal light and the light guided through the one optical waveguide and the light guided through the other one of the two optical waveguides interfere with each other so that the phase conjugation light is extracted as wavelength conversion light.