Abstract: An optical transceiver that includes an optical modulator of a Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified spontaneous emission in regions out of the wavelength band of the light.

Abstract: A coherent optical transceiver is disclosed. The coherent optical transceiver installs an integrated coherent receiver (ICR), an optical modulator, an intelligent wavelength tunable laser diode (i-TLD), a digital signal processor (DSP), a driver to drive the optical modulator, and so on within a compact housing. The ICR is connected to the printed circuit board (PCB) through flexible printed circuit (FPC) boards and mounted thereon through a holder. The holder forms a gap against the PCB, where the FPC boards pass through the gap and connected on the pads formed on the surface of the PCB beneath the holder.

Abstract: An optical transceiver that installs an optical modulator with the Mach-Zehnder type and made of primarily semiconductor materials, and an Erbium Doped Fiber Amplifier (fiber amplifier) is disclosed. The fiber amplifier and the MZ modulator, in addition to a wavelength tunable laser diode, an intelligent coherent receiver, and a polarization maintaining splitter, are installed within a compact case following the standard of CFP2. The fiber amplifier provides a wavelength tunable filter that passes light amplified by the fiber amplifier but eliminates amplified stimulated emission in regions out of the wavelength band of the light.

Abstract: A bias control circuit for an optical modulator including a pair of optical waveguides and a power monitor is disclosed. The bias control circuit includes a bias generator, a differential amplifier, and a controller. The bias generator provides a bias signal to one of the optical waveguides. The bias signal includes a dither signal having a predetermined frequency. The differential amplifier receives a monitor signal from the power monitor and a reference signal, and generates an amplified signal corresponding to a difference between the monitor signal and the reference signal. The controller detects frequency components contained in the amplified signal. The frequency components originates from the dither signal. The controller generates a control signal according to intensity of the frequency components. The bias signal is adjusted according to the control signal provided from the controller.

Abstract: A method for testing a tunable wavelength laser device, which can suppress any error of light transmission characteristics of an etalon, and a tunable wavelength laser device are provided. The method for testing a tunable wavelength laser device is a method for testing a tunable wavelength laser device including a tunable wavelength laser and a wavelength sensing unit having an etalon. The testing method includes a first step of measuring a free spectral range interval of the etalon, a second step of acquiring a driving condition by tuning a wavelength to a target value provided between a top and a bottom of the free spectral range interval, and a third step of storing the driving condition in a memory.

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: A bias control circuit for an optical modulator including a pair of optical waveguides and a power monitor is disclosed. The bias control circuit includes a bias generator, a differential amplifier, and a controller. The bias generator provides a bias signal to one of the optical waveguides. The bias signal includes a dither signal having a predetermined frequency. The differential amplifier receives a monitor signal from the power monitor and a reference signal, and generates an amplified signal corresponding to a difference between the monitor signal and the reference signal. The controller detects frequency components contained in the amplified signal. The frequency components originates from the dither signal. The controller generates a control signal according to intensity of the frequency components. The bias signal is adjusted according to the control signal provided from the controller.

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 coherent optical transceiver is disclosed. The coherent optical transceiver installs an integrated coherent receiver (ICR), an optical modulator; an intelligent wavelength tunable laser diode (i-TLD), a digital signal processor (DSP), a driver to drive the optical modulator, and so on within a compact housing. The ICR is connected to the printed circuit board (PCB) through flexible printed circuit (FPC) boards and mounted thereon through a holder. The holder forms a gap against the PCB, where the FPC boards pass through the gap and connected on the pads formed on the surface of the PCB beneath the holder.

Abstract: A method to tune an emission wavelength of a laser diode (LD) finely is disclosed. The method first controls a temperature of the etalon filter in T1 or T2, where the transmittance of the etalon filter becomes 40 to 50%, assuming a height between the peak and the bottom of the periodic transmittance to be 100%, at the grid wavelength ?1 or ?2, respectively. Then, the temperature of the LD is adjusted such that the intensity of light emitted from the LD and transmitted through the etalon filter becomes 40 to 50%.

Abstract: A method for testing a tunable wavelength laser device, which can suppress any error of light transmission characteristics of an etalon, and a tunable wavelength laser device are provided. The method for testing a tunable wavelength laser device is a method for testing a tunable wavelength laser device including a tunable wavelength laser and a wavelength sensing unit having an etalon. The testing method includes a fast step of measuring a free spectral range interval of the etalon, a second step of acquiring a driving condition by tuning a wavelength to a target value provided between a top and a bottom of the free spectral range interval, and a third step of storing the driving condition in a memory.

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: A method to tune an emission wavelength of a laser diode (LD) finely is disclosed. The method first controls a temperature of the etalon filter in T1 or T2, where the transmittance of the etalon filter becomes 40 to 50%, assuming a height between the peak and the bottom of the periodic transmittance to be 100%, at the grid wavelength ?1 or ?2, respectively. Then, the temperature of the LD is adjusted such that the intensity of light emitted from the LD and transmitted through the etalon filter becomes 40 to 50%.

Abstract: A semiconductor laser device includes: a semiconductor laser having a reflector region, a gain region for laser oscillation and a plurality of refraction index controllers, the reflector region having a plurality of segments in which a diffraction region and a space region are coupled to each other, the plurality of segments being separated into a plurality of segment groups having a same optical length, the plurality of refractive index controllers being provided according to each segment group and controlling an equivalent refraction index of each segment group; a wavelength controller controlling an oscillation wavelength of the semiconductor laser by controlling the plurality of the refraction index controllers as at least one of control parameters; and a dither controller inputting a dither signal into only one of the segment groups having the most segments from one of the refractive index controllers according to the segment group.

Abstract: A semiconductor laser device includes: a semiconductor laser having a reflector region, a gain region for laser oscillation and a plurality of refraction index controllers, the reflector region having a plurality of segments in which a diffraction region and a space region are coupled to each other, the plurality of segments being separated into a plurality of segment groups having a same optical length, the plurality of refractive index controllers being provided according to each segment group and controlling an equivalent refraction index of each segment group; a wavelength controller controlling an oscillation wavelength of the semiconductor laser by controlling the plurality of the refraction index controllers as at least one of control parameters; and a dither controller inputting a dither signal into only one of the segment groups having the most segments from one of the refractive index controllers according to the segment group.