Abstract: A configuration of a DFB laser-based wavelength tunable laser is well known, but long resonators have difficulty in forming uniform resonators due to production variations, thereby inducing limitation in narrowing the spectral linewidth in the DFB laser-based wavelength tunable laser as well. In the semiconductor laser device of the present invention, a semiconductor laser that oscillates in a single mode and a low-loss lightwave circuit using SiO2 glass are arranged on the common substrate. The lightwave circuit is configured such that part of output light from the semiconductor laser propagates through a certain length of an optical path, and then is reflected by a reflector and is fed back to the semiconductor laser. Output light from the semiconductor laser and an input waveguide of the lightwave circuit can also be configured to be optically connected directly to each other. The present invention can provide a compact laser device with a narrowed spectral linewidth and stable wavelength controllability.

Abstract: A configuration of a DFB laser-based wavelength tunable laser is well known, but long resonators have difficulty in forming uniform resonators due to production variations, thereby inducing limitation in narrowing the spectral linewidth in the DFB laser-based wavelength tunable laser as well. In the semiconductor laser device of the present invention, a semiconductor laser that oscillates in a single mode and a low-loss lightwave circuit using SiO2 glass are arranged on the common substrate. The lightwave circuit is configured such that part of output light from the semiconductor laser propagates through a certain length of an optical path, and then is reflected by a reflector and is fed back to the semiconductor laser. Output light from the semiconductor laser and an input waveguide of the lightwave circuit can also be configured to be optically connected directly to each other. The present invention can provide a compact laser device with a narrowed spectral linewidth and stable wavelength controllability.

Abstract: Provided is a laser apparatus including: a DFB fiber laser 40 including, as an amplitude medium, a rare earth doped silica optical fiber codoped with a high concentration of aluminum; an optical feedback path 50 formed by a ring-shaped optical fiber; and an optical coupler 70 a) feeding back a part of an output of the DFB fiber laser 40 to the DFB fiber laser 40 via the optical feedback path 50, and b) outputting, to outside, another part of the output of the DFB fiber laser 40, where the optical fiber forming the optical feedback path 50 is longer than a length at which a relaxation oscillation noise in the output to the outside becomes ?110 dB/Hz.

Abstract: A laser oscillator includes a ring resonator. The ring resonator includes an optical circulator having first, second, third, and fourth ports and a first optical amplification fiber connected to the optical circulator. Light incident on the first port is exited from the second port, and light incident on the second port is exited from the third port. The fourth port provides an exciting light and injects the exciting light into the ring resonator through the first port. The first optical amplification fiber amplifies light exited from the third port with the exciting light provided by the fourth port. The laser oscillator also includes an optical member connected to the optical circulator. The optical member reflects at least a part of the light exited from the second port and injects the same into the second port again.

Abstract: To compensate a waveform distortion by using a nature that a spectral shape is perfectly retained even if all the linear distortions occur on a time-axis. An optical pulse transmitted from an optical pulse transmitter (1) via an optical fiber transmission line (2) is transmitted. An optical Fourier transformer (3) receives an optical pulse, and optically Fourier-transforms an optical pulse on a time-axis onto a frequency-axis to reproduce the frequency spectrum of an optical pulse on a time-axis be effecting switching between frequency and time, thereby compensating a waveform distortion by a linear effect on the optical fiber transmission line (2). A photodetector (4) receives an optical pulse from the optical Fourier transformer (3) and transforms this into an electrical signal to thereby obtain a pulse waveform before a transmission over the optical fiber transmission line (2).

Abstract: The phase modulation in which the frequency chirp becomes 0 at the timing which the user wants to synchronize, and the frequency chirp becomes larger as the time deviates in a positive or negative direction from this timing is applied to the signal light with each wavelength comprising pulse train of different timing. Thus, the optical pulses which deviate from the timing which the user wants to synchronize receive the frequency chirp in accordance with the amount of the timing deviation. The WDM signal light which has been chirped in this way is made to pass a linear dispersive medium, and the dispersion fit for the amount of frequency chirp is made to be given. By adjusting the amount of dispersion, it is possible to obtain the pulses which conform to the timing at which the user wants to synchronize the pulses of each wavelength.

Abstract: A laser oscillator includes a ring resonator. The ring resonator includes an optical circulator having first, second, third, and fourth ports and a first optical amplification fiber connected to the optical circulator. Light incident on the first port is exited from the second port, and light incident on the second port is exited from the third port. The fourth port provides an exciting light and injects the exciting light into the ring resonator through the first port. The first optical amplification fiber amplifies light exited from the third port with the exciting light provided by the fourth port. The laser oscillator also includes an optical member connected to the optical circulator. The optical member reflects at least a part of the light exited from the second port and injects the same into the second port again.

Abstract: Provided is a laser apparatus including: a DFB fiber laser 40 including, as an amplitude medium, a rare earth doped silica optical fiber codoped with a high concentration of aluminum; an optical feedback path 50 formed by a ring-shaped optical fiber; and an optical coupler 70 a) feeding back a part of an output of the DFB fiber laser 40 to the DFB fiber laser 40 via the optical feedback path 50, and b) outputting, to outside, another part of the output of the DFB fiber laser 40, where the optical fiber forming the optical feedback path 50 is longer than a length at which a relaxation oscillation noise in the output to the outside becomes ?110 dB/Hz.

Abstract: An OTDM transmitting method and transmitter realizing an OTDM distortion-free transmission substantially not relying upon dispersion. A time division multiplexed OTDM signal from an OTDM signal transmitter (1) enters an optical Fourier transform unit (2). Optical Fourier transform can be carried out most accurately so long as the optical pulse is a chirp-free Fourier transform limit pulse. The optical Fourier transform unit (2) converts the time waveform of the pulse into a signal on the frequency axis, and an optical inverse Fourier transform unit (2?) converts a spectral shape on the frequency axis into a time waveform (pulse). An optical fiber transmission line (3) is a transmission line having an arbitrary dispersion and a polarization mode dispersion. These dispersions may involve a time variation. An OTDM signal receiver (4) demultiplexes a transmission signal into low-speed optical signals, in a light region, receives optical pulses for respective channels and converts them into electric signals.

Abstract: To extend the temperature range for a stable operation without mode hopping and obtain a stable laser oscillation, a laser oscillator is provided. The laser oscillator includes: an optical circulator in which light incident on a first port is exited from the second port, light incident on the second port is exited from a third port, and light incident on a fourth port is exited from the first port; a first optical amplification fiber that amplifies the light exited from the third port because of being excited by an exciting light and injects the same into the first port; a reflective optical filter that reflects light with a predetermined wavelength among the light exited from the second port and injects the same into the second port again; and an pump light source that generates an exciting light to excite the first optical amplification fiber.

Abstract: A small-sized, high-functionality optical pulse compressor capable of generating a low-power, high-repetition-frequency ultrashort pulse train used for ultrafast optical communication and photometry, and a simple-structure optical function generator for realizing an arbitrary time waveform. The optical pulse compressor comprises and optical Fourier transform device (F) having an optical phase modulator (9) driven by the repetition-frequency of an input optical pulse train and a dispersive medium (8), for converting the shape of an input optical pulse frequency spectrum into its time waveform, and an optical filter (3) inserted ahead of the optical Fourier transform device (F), for reducing the spectrum width of an input optical pulse, wherein the optical Fourier transform device (F) converts a small-spectrum-width optical pulse output from the optical function generator generates an optical pulse.

Abstract: Optical Fourier transform is executed over a wide time range. A quadratic function type optical pulse generator (7) generates a control light pulse of a shape expressed by a quadratic function or a parabola according to a clock signal based on a signal light pulse from an optical coupler (1). The signal light pulse inputted is multiplexed by a multiplexer (9) with the control light pulse optically delayed by an optical delay element (8) so that the timing is matched with the signal light pulse, and introduced into an optical Kerr medium (10). In the optical Kerr medium (10), the signal light pulse inputted by the mutual phase modulation between the signal light pulse and the control light pulse is subjected to a linear phase modulation (frequency chirp) over the entire pulse or a wide time range.

Abstract: Optical Fourier transform is executed over a wide time range. A quadratic function type optical pulse generator (7) generates a control light pulse of a shape expressed by a quadratic function or a parabola according to a clock signal based on a signal light pulse from an optical coupler (1). The signal light pulse inputted is multiplexed by a multiplexer (9) with the control light pulse optically delayed by an optical delay element (8) so that the timing is matched with the signal light pulse, and introduced into an optical Kerr medium (10). In the optical Kerr medium (10), the signal light pulse inputted by the mutual phase modulation between the signal light pulse and the control light pulse is subjected to a linear phase modulation (frequency chirp) over the entire pulse or a wide time range.

Abstract: To extend the temperature range for a stable operation without mode hopping and obtain a stable laser oscillation, a laser oscillator is provided. The laser oscillator includes: an optical circulator in which light incident on a first port is exited from the second port, light incident on the second port is exited from a third port, and light incident on a fourth port is exited from the first port; a first optical amplification fiber that amplifies the light exited from the third port because of being excited by an exciting light and injects the same into the first port; a reflective optical filter that reflects light with a predetermined wavelength among the light exited from the second port and injects the same into the second port again; and an pump light source that generates an exciting light to excite the first optical amplification fiber.

Abstract: An OTDM transmitting method and transmitter realizing an OTDM distortion-free transmission substantially not relying upon dispersion. A time division multiplexed OTDM signal from an OTDM signal transmitter (1) enters an optical Fourier transform unit (2). Optical Fourier transform can be carried out most accurately so long as the optical pulse is a chirp-free Fourier transform limit pulse. The optical Fourier transform unit (2) converts the time waveform of the pulse into a signal on the frequency axis, and an optical inverse Fourier transform unit (2?) converts a spectral shape on the frequency axis into a time waveform (pulse). An optical fiber transmission line (3) is a transmission line having an arbitrary dispersion and a polarization mode dispersion. These dispersions may involve a time variation. An OTDM signal receiver (4) demultiplexes a transmission signal into low-speed optical signals, in a light region, receives optical pulses for respective channels and converts them into electric signals.

Abstract: A small-sized, high-functionality optical pulse compressor capable of generating a low-power, high-repetition-frequency ultrashort pulse train used for ultralast optical communication and photometry, and a simple-structure optical function generator for realizing an arbitrary time waveform. The optical pulse compressor comprises and optical Fourier transform device (F) having an optical phase modulator (9) driven by the repetition-frequency of an input optical pulse train and a dispersive medium (8), for converting the shape of an input optical pulse frequency spectrum into its time waveform, and an optical filter (3) inserted ahead of the optical Fourier transform device (F), for reducing the spectrum width of an input optical pulse, wherein the optical Fourier transform device (F) converts a small-spectrum-width optical pulse output from the optical function generator generates an optical pulse.

Abstract: In a measuring-instrument remote-calibration system and measuring-instrument remote-calibration method, a measuring standard quantity is converted into a parameter adapted for communication, or based on measuring standard quantity, a parameter adapted for communication is generated and sent to a remote place. Alternatively, when the measuring standard quantity is not suitable for communication, it is converted into a form adapted for transportation and the converted measuring standard quantity is sent to a remote place. After the converted measuring standard quantity reaches the place, it is restored to the original measuring standard quantity, thus enabling calibration. The result of the calibration is certified.

Abstract: To compensate a waveform distortion by using a nature that a spectral shape is perfectly retained even if all the linear distortions occur on a time-axis. An optical pulse transmitted from an optical pulse transmitter (1) via an optical fiber transmission line (2) is transmitted. An optical Fourier transformer (3) receives an optical pulse, and optically Fourier-transforms an optical pulse on a time-axis onto a frequency-axis to reproduce the frequency spectrum of an optical pulse on a time-axis be effecting switching between frequency and time, thereby compensating a waveform distortion by a linear effect on the optical fiber transmission line (2). A photodetector (4) receives an optical pulse from the optical Fourier transformer (3) and transforms this into an electrical signal to thereby obtain a pulse waveform before a transmission over the optical fiber transmission line (2).

Abstract: The phase modulation in which the frequency chirp becomes 0 at the timing which the user wants to synchronize, and the frequency chirp becomes larger as the time deviates in a positive or negative direction from this timing is applied to the signal light with each wavelength comprising pulse train of different timing. Thus, the optical pulses which deviate from the timing which the user wants to synchronize receive the frequency chirp in accordance with the amount of the timing deviation. The WDM signal light which has been chirped in this way is made to pass a linear dispersive medium, and the dispersion fit for the amount of frequency chirp is made to be given. By adjusting the amount of dispersion, it is possible to obtain the pulses which conform to the timing at which the user wants to synchronize the pulses of each wavelength.

Abstract: In a measuring-instrument remote-calibration system and measuring-instrument remote-calibration method, a measuring standard quantity is converted into a parameter adapted for communication, or based on measuring standard quantity, a parameter adapted for communication is generated and sent to a remote place. Alternatively, when the measuring standard quantity is not suitable for communication, it is converted into a form adapted for transportation and the converted measuring standard quantity is sent to a remote place. After the converted measuring standard quantity reaches the place, it is restored to the original measuring standard quantity, thus enabling calibration. The result of the calibration is certified.