Abstract: In Raman gain slope measurement for measuring Raman gain slope which is a value obtained by normalizing a gain generated by Raman amplification caused by pump light incident on an optical fiber by optical power of the pump light in question, based on a relationship between optical power of pump light incident on an optical fiber and optical power of noise light generated by the application of the pump light, Raman gain slope of the optical fiber in question is calculated.

Abstract: A patch cord into which a collimator pair has been intercalated is attached to the output end of a high-level light amplifier for transmitting high-level light through optical fibers from outside in a replaceable manner. Even if burnout occurs at an end face of an optical fiber and the heat is conducted to the patch cord with collimators that is connected with an optical connector, meltdown by the fiber-fuse phenomenon can be prevented before it reaches the high-power optical amplifier without being propagated to the high-power optical amplifier because heat energy is dissipated at the collimator pair. By this, the high-power optical amplifier can be protected from the fiber-fuse phenomenon.

Abstract: A Raman amplifier of the present invention includes a loss measuring unit (110) for measuring loss distribution of an object of measurement by means of OTDR based on reflected light with respect to outputted test light; an optical coupler (114) in which the test light is supplied to a first input terminal thereof and one of output terminals thereof is connected to an optical fiber transmission line; a wavelength filter (116) inserted between the loss measuring unit (110) and the optical coupler (114); a control circuit (200) for generating a control signal for reducing an error signal obtained by comparing a Raman gain obtained with a reference value; and an excitation light source (140) for changing an excitation light power based on the control signal.

Abstract: An optical data transmitting apparatus and method allows data transmission over a distance that surpasses a limit, which has been imposed due to group velocity dispersion (GVD) and self phase modulation (SPM) effect within optical fiber. This has been accomplished by allocating trinal duobinary symbols to optical 1, P, −1 symbols. These optical symbols have the same intensity, +1 and −1 symbols have inverted optical phases each other, and orthogonally polarized each other between ±1 and P symbols. At the receiver, conventional polarization shift keying receiver can be used to restore original binary data stream.

Abstract: An optical data transmitting apparatus and method allows data transmission over a distance that surpasses a limit previously experienced in the prior art and which has been imposed due to group velocity dispersion (GVD) and self phase modulation (SPM) effects within an optical fiber. This has been accomplished by allocating trinal duobinary symbols to optical 1, P, −1 symbols. These optical symbols have the same intensity, but the +1 and −1 symbols have inverted optical phases from each other, and are orthogonally polarized from each other between the +1 and P symbols. At the receiver, a conventional polarization shift keying receiver can be used to restore the original binary data stream.

Abstract: Two semiconductor laser light sources for outputting light of two properly selected wavelengths are employed as excitation light sources. That is, as excitation light sources, there are used a first semiconductor laser excitation light source for exciting ion from a base level to a laser low level or an energy level higher than the laser low level and a second semiconductor laser excitation light source having a wavelength different from that of the first excitation light source for exciting ion from a laser low level to a laser high level. For example, an amplification fiber uses a fluoro zirconate glass as a base material. Two multiple wavelength couplers are disposed at the input side of the amplification fiber. The multiple wavelength couplers are connected to the first excitation light source and the second excitation light source, respectively.

Abstract: Disclosed is a method for generating a duobinary signal which has the step of: modulating individually an intensity and a phase of a carrier wave. Also disclosed is a duobinary-manner optical transmitter which has: a laser device which outpus signal light; an optical intensity modulator which intensity-modulates the signal light according to a first data signal generated by dividing a data signal into two signals; a precoder which inputs a second data signal generated by dividing the data signal into two signals; and an optical phase modulator which phase-modulates the intensity-modulated signal light according to a signal which is obtained delaying 0.5 bit an output signal of the precoder.

Abstract: An input optical data pulse 120 encoded by pulse amplitude modulation is branched into two parts by an optical coupler 111, and one part is input to an optical clock generation device, such as mode-locked laser diode (MLLD) 113 and the other part is input to an optical/optical intensity modulator, such as semiconductor optical amplifier 110 or electro-absorption light intensity modulator 216. A regenerated optical clock pulse drives the optical/optical intensity modulator and thereby, an input optical data pulse 120 is intensity-modulated to serve as an optical data pulses 121 which are output. An input optical data pulse can drive the light intensity modulator. Therefore, a high-speed inexpensive regenerative repeater for regenerating a signal in the form of light is attained.

Abstract: Disclosed is a method for generating a duobinary signal which has the step of: modulating individually an intensity and a phase of a carrier wave. Also disclosed is a duobinary-manner optical transmitter which has: a laser device which outputs signal light; an optical intensity modulator which intensity-modulates the signal light according to a first data signal generated by dividing a data signal into two signals; a precoder which inputs a second data signal generated by dividing the data signal into two signals; and an optical phase modulator which phase-modulates the intensity-modulated signal light according to a signal which is obtained delaying 0.5 bit an output signal of the precoder.

Abstract: An input optical data pulse 120 encoded by pulse amplitude modulation is branched into two parts by an optical coupler 111, and one part is input to an optical clock generation device, such as mode-locked laser diode (MLLD) 113 and the other part is input to an optical/optical intensity modulator, such as semiconductor optical amplifier 110 or electro-absorption light intensity modulator 210. A regenerated optical clock pulse drives the optical/optical intensity modulator and input optical data pulses 120 are intensity-modulated to serve as optical data pulses 121 which are output. An input optical data pulse can drive the light intensity modulator.

Abstract: An automatic decision-point control type decision circuit has a main decision unit, a sub-decision unit, an exclusive-OR circuit, and a controller. The main decision unit receives a data signal and one of two branched signals while the sub-decision unit receives the data signal and the other of the two branched signals. The two branched signals is obtained by branching a clock signal extracted from the data signal. The exclusive-OR circuit detects the difference between the output signal from the main decision unit and the output from the sub-decision unit. The controller calculates a bit error rate. In order to set the initial value of the decision point of the main decision unit, the controller detects a bit error rate by scanning the difference between the decision point of the main decision unit and the decision point of the sub-decision unit only at the beginning of its operation, and calculates an optimum decision point based on the relationship between the decision points and the bit error rate.

Abstract: An optical clock regenerator using a laser includes an optical modulator for mode locking in a laser resonator. The optical modulator is driven by an intensity-modulated optical signal. When an intensity-modulated optical data pulse train including a clock frequency component close to a frequency n (n is an integer) times or one-nth times a resonance frequency of the laser resonator is input to the optical modulator, the laser outputs clock pulse light locked by the frequency n times or one-nth times a clock frequency of the optical data pulse train. The optical data pulse train and the laser resonator are spatially separated from each other.

Abstract: A method for manufacturing a low carbon ferrochrome with a high chromium content of at least 70 weight % Cr comprising the steps of at least once nitriding and crushing a low carbon ferrochrome to form a crushed ferrochrome nitride and subjecting the crushed ferrochrome nitride to an acid treatment comprising introducing the crushed ferrochrome nitride into an acid solution and stirring the resultant mixture of the ferrochrome nitride and the acid solution, to remove iron. The acid treated ferrochrome nitride is denitrided by heating in a vacuum.

Abstract: Ores including oxides of Cr and Fe and melted by means of a furnace, thereby forming molten metal. The molten metal is poured from the furnace into a ladle. A reducing agent, such as SiCr, is added to the molten metal in the ladle. Then, an oxidizing gas or an inert gas is introduced into the molten metal at a rate of more than 7.0 l/min. but not exceeding 29.0 l/min., for each ton of the molten metal, thereby bubbling and stirring the molten metal. Alternatively, an oxidizing gas or an inert gas is introduced into the molten metal, thus bubbling the molten metal and, thus, lowering the temperature of the molten metal to a desired value, and then the molten metal is reladled, thereby to decrease the nitrogen content of the molten metal to a desired value.

Abstract: To quickly change rocket flight direction immediately after a rocket has been launched without increasing the wing area, the rocket flight direction control system comprises four steering wings for controlling rocket flight directions; four deflectable nozzles for jetting combustion gas backward to generate rocket thrust; a controller for generating steering control signals; and at least one actuator for actuating the deflectable nozzles in response to the steering control signals in synchronism with steering motion of the steering wings. Further, when the deflectable nozzle is divided into two, fixed and movable, nozzles, the diameter of the outlet end of the fixed divergent nozzle of the overexpansion type nozzle in matched with that of the movable nozzle for prevention of gas leakage through a gap between the two nozzles.

Abstract: A strobe adapter for adapting an electrically operated strobe for use with a camera having a percussive striker comprising a lever, and a spring connected to said lever whereby said lever has a dead center position. On one side of the dead center position, one end of the lever is urged to contact the striker, and on the other side of the dead center position the other end of the lever is urged to make electrical contact with a stationary contact for energizing the strobe. A leaf spring interposed between the other end of the lever and the stationary contact breaks the electrical contact with relationship, in order to inhibit continuous short circuiting of the strobe.