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: The present invention relates to a method of producing an optical fiber-processing phase mask having minimized connection errors that may degrade the spectral line shape and group delay characteristics of an optical fiber diffraction grating fabricated by using the phase mask. The present invention provides a method of producing an optical fiber-processing phase mask having a repeating pattern of grating-shaped grooves and strips provided on one surface of a transparent substrate, so that diffracted light produced by the repeating pattern is applied to an optical fiber to fabricate a diffraction grating in the optical fiber by interference fringes of diffracted light of different orders.

Abstract: An arrayed-waveguide grating (AWG) is provided in a tunable mode-locked laser resonator where when a clock signal corresponding to a predetermined wavelength is input, the arrayed-waveguide grating (AWG) generates an output signal having an oscillation wavelength which has an arbitrary wavelength interval independent of the wavelength of said clock signal and a different propagation delay for each wavelength. Furthermore, a transmitter and a wavelength converter is provided that uses a tunable mode-locked laser where the frequency of the clock signal determines the wavelength and where a transmitted data signal at a fixed data rate is generated by setting the clock signal frequency sufficiently higher than the data rate. Furthermore, a wavelength converter and wavelength router is provided that uses said tunable mode-locked laser and in which the output wavelength is determined by extracting said clock signal from the input data signal.

Abstract: The present invention provides a method for manufacturing a photonic crystal fiber that has a core portion in which a fiber core extends in a lengthwise direction and is formed as a solid or a void, and a porous clad portion provided around the core portion and having numerous pores extending along the core portion. A preform is fabricated by packing numerous capillaries into a cylindrical support pipe such that they are parallel to the central axis of the support pipe and disposing a core rod to serve as the solid core portion at the central axis portion of the support pipe. The preform is drawn to make it small in diameter.

Abstract: The present invention relates to a method of producing an optical fiber-processing phase mask having minimized connection errors that may degrade the spectral line shape and group delay characteristics of an optical fiber diffraction grating fabricated by using the phase mask. The present invention provides a method of producing an optical fiber-processing phase mask having a repeating pattern of grating-shaped grooves and strips provided on one surface of a transparent substrate, so that diffracted light produced by the repeating pattern is applied to an optical fiber to fabricate a diffraction grating in the optical fiber by interference fringes of diffracted light of different orders.

Abstract: The invention relates to a method of fabricating an optical fiber-processing phase mask in which a stitching error ascribable to a deterioration in the wavelength selectivity of the optical fiber diffraction grating to be fabricated is reduced. At an exposure step, a writing stage 5 with a phase mask blank 10 placed thereon is continuously fed in one direction while portions of the phase mask blank corresponding to grooves 26 or strips 27 in a direction perpendicular to the direction of feeding are sequentially scanned with writing beams 14, whereby the entire area of the phase mask blank 10 to be written is continuously written.

Abstract: An ultra-stable microwave output with less jitter than a prior art atomic oscillator is obtained and an ultra-short optical pulse train is generated with a repetition frequency stabilized at the same level as a time standard. The repetition frequency of a regeneratively mode-locked laser pulse oscillator with a superior low-jitter characteristic is locked directly to a resonance frequency of various atoms. The oscillator provides the means for detecting the frequency difference between the clock signal frequency and a predetermined atomic resonance frequency and outputting it as an error signal, a cavity length tuning device for varying the length of a laser cavity so that the clock signal frequency and the predetermined resonance frequency coincide, and a device for negatively feeding back the error signal output from the frequency difference detection device to the cavity length tuning device.

Abstract: The object of the present invention is to provide an optical pulse generator which very stably generates for a long period of time a high cycling frequency optical pulse chain. In order to obtain this object, in a ring type resonator R, the present invention provides an optical path length regulator 14 which performs high precision optical path length adjustment and an optical path length regulator 60 which performs wide range optical path length adjustment, and extracts a clock signal by converting an optical pulse emitted from the ring type resonator R to an electrical signal by a clock extractor 42, detects the frequency difference between a base frequency signal output form a synthesizer 52 by a frequency difference detector 50, and controls said optical path length regulator 14 and said optical path length regulator 60.

Abstract: According to the present invention, damage to a photo-detector disposed in clock signal extractor by means of an optical pulse having an optical power exceeding a rated value is prevented. A ring resonator generates a repetitive, high-frequency optical pulse. Optical branching circuit branches a portion of the optical pulse circulating through ring resonator, while optical branching circuit further branches a portion thereof to protective device. Pumping source generates an excitation light for exciting a rare-earth doped optical fiber. Optical multiplexer couples the optical pulse branched by optical branching circuit, and the excitation light. Upon excitation by means of the excitation light, rare-earth doped optical fiber amplifies and emits the incoming optical pulse. The optical power of the excitation light is adjusted such that the output of rare-earth doped optical fiber reaches a saturation power.

Abstract: A harmonically and regeneratively mode-locked laser pulse oscillator having a clock extraction circuit for picking up from a fragment of a laser output a clock signal corresponding to a high-order integer multiple of the fundamental frequency determined by the cavity length of the laser, a phase shifter and an electric amplifier for driving an optical modulator disposed in the laser cavity at the frequency of the clock signal. The laser pulse oscillator has a phase-locked loop including a phase comparator for detecting the phase difference between the clock signal and an external signal fed from a synthesizer with its frequency fixed, a fiber stretcher for controlling the cavity length such that the repetition rate frequency of the laser pulse oscillator is locked to the external signal, and an electric filter and electric amplifier for expanding and contracting the fiber length by feeding back the phase difference detected by the phase comparator to the fiber stretcher.

Abstract: Lead-containing fluoride glass comprises 50-70 mol % of ZrF.sub.4, 3-5 mol % of LaF.sub.3, 0.1-3 mol % of YF.sub.3, and 2-15 mol % of NaF and/or LiF and/or CsF, where LaF.sub.3 +YF.sub.3 =4.5-6 mol %, and further comprises lead. An optical fiber comprises a core made of the lead-containing fluoride glass and a cladding surrounding the core. A process for producing an optical fiber comprises forming a base material for a core of the lead-containing fluoride glass, forming a base material for a cladding of fluoride glass containing 30-60 mol % of HfF.sub.4, and drawing the base materials into an optical fiber at a drawing temperature of 315-340 .degree. C.

Abstract: A pulse compression device is disclosed for generating ultra short pulses in the femtosecond range In the device an input soliton is subjected to pulse width compression by propagation in a rare-earth doped optical fiber having a gradually diminishing group velocity dispersion from an input end to an output end. The pulse compression is produced by the diminishing dispersion value of the optical fiber as well as by adiabatic narrowing generated by a pumping light coupled, through an optical coupler, to the optical fiber by increasing the energy of the input soliton propagating in the optical fiber. By adjusting the light power of the pumping light, the pulse width of the soliton can be freely controlled.

Abstract: Lead-containing fluoride glass comprises 50-70 mol % of ZrF.sub.4, 3-5 mol % of LaF.sub.3, 0.1-3 mol % of YF.sub.3, and 2-15 mol % of NaF and/or LiF and/or CsF, where LaF.sub.3 +YF.sub.3 =4.5-6 mol %, and further comprises lead. An optical fiber comprises a core made of the lead-containing fluoride glass and a cladding surrounding the core. A process for producing an optical fiber comprises forming a base material for a core of the lead-containing fluoride glass, forming a base material for a cladding of fluoride glass containing 30-60 mol % of HfF.sub.4, and drawing the base materials into an optical fiber at a drawing temperature of 315.degree.-340.degree. C.

Abstract: A core waveguide having a substantially rectangular cross section, with the width thereof greater than the thickness thereof, is provided in a cladding formed on a substrate, and a rare earth element-doped layer is provided in the core waveguide along the waveguiding direction of the waveguide. With the width of the core waveguide set greater than the thickness of the core waveguide, good optical confinement in the width direction of the waveguide is obtained, which enables light to be absorbed by the rare earth element-doped layer efficiently and concentratedly. It is thereby possible to achieve a marked improvement in the excitation efficiency of excitation power. Thus, an enhanced excitation efficiency is achieved with less addition of a rare earth element, and a high-gain optical amplification waveguide free of concentration extinction is provided.

Abstract: An optical waveguide star coupler includes a light propagating core provided on a substrate. An exciting light and a signal light are supplied to the light propagating core. The light propagating core includes a plurality of Y-branching waveguides connected one after another to provide a multi-stage waveguide structure. A signal light inputted in the core is combined during the propagation through the core with the exciting light so that the signal light is amplified.