Abstract: An optical amplification system connected via a connector to an optical transmission path through which Raman excitation lights are sent out prevents the Raman excitation lights from entering and keeps the Laser Safety function caused by the detection of reflection light when the optical connector is disconnected. The optical amplification system includes an optical amplifier to amplify optical main signals; an optical receiver element to detect reflection lights from an end face of the connector, when the connector is disconnected; a circuit to reduction control the output power of the optical amplifier, based on the detection of the reflection light by the optical receiver element; and a blocking filter inserted between the optical amplifier and the connector, for blocking the Raman excitation lights.

Abstract: A diagnosing method and apparatus non-destructively performing damage evaluation of a piled up structure of conductive materials by using acoustic waves. The diagnosing method according to the present invention includes the steps of placing an electro-magnetic acoustic transducer 20 out of contact with a piled up structure 34 of conductive materials 32 and 34 piled up with a non-conductive interface 33 (35) interposed therebetween, transmitting ultrasonic waves from one side 31 of the piled up structure by the electro-magnetic acoustic transducer 20, receiving ultrasonic waves reflected from the other side of the piled up structure, and diagnosing a damaged condition of the piled up structure on the basis of the ultrasonic velocity and attenuation of the received ultrasonic waves.

Abstract: The invention is aimed at providing a simple noise light elimination technique capable of eliminating noise light components contained in a signal light, together with wavelength components same as for the signal wavelength, with the condition of the light remaining as is, and an optical transmission system. To this end, an optical transmission system applied with a noise light elimination method according to the present invention comprises a high output type optical repeater and a noise light elimination unit for each required repeating span. This noise light elimination unit includes a dummy transmission path that, when a light of a power exceeding a threshold value is input, generates a return light due to stimulated Brillouin scattering (SBS). The signal light amplified in the optical repeater up to the power exceeding the threshold value is input to the dummy transmission path via an optical input/output section of the noise light elimination unit.

Abstract: An optical amplifier and an optical multiplexing transmission system using the same are disclosed. Automatic restoration of the operation becomes possible and malfunctioning of an APSD function is prevented. The optical amplifier using Raman amplification includes; a Raman excitation light source for generating Raman light; and a detection circuit for detecting a signal error in an OSC (optical supervisory channel) signal transmitted in addition to optical transmission signal. When the detection circuit detects a bit error in the OSC signal, an output power from Raman excitation light source is controlled so as not to injure the human body.

Abstract: Disclosed herein is a method including the steps of wavelength division multiplexing a plurality of optical signals having different wavelengths to obtain resultant WDM signal light; transmitting the WDM signal light by an optical fiber transmission line; supplying reference light having a predetermined wavelength to the optical fiber transmission line; generating four-wave mixing in the optical fiber transmission line by the interaction of the WDM signal light and the reference light; detecting the power of light generated as the result of the four-wave mixing; and controlling the power of the WDM signal light to be supplied to the optical fiber transmission line according to the power detected. According to this method, the effect of four-wave mixing can be suppressed.

Abstract: A Raman excitation control method enabling to reduce the number of couplers and photodetectors (PD) for providing an optical transmission unit with reduced cost. The method is provided for use in optical amplification to amplify an optical signal using Raman excitation light fed into an optical transmission line. A backward light of a laser diode producing the Raman excitation light is monitored by an optical back power monitor. The monitored power value is compared with an initial set value stored in a memory for the laser diode. Based on this comparison result, a feedback control is performed against the light emission power of the laser diode.

Abstract: An optical amplifier and an optical multiplexing transmission system using the same are disclosed. Automatic restoration of the operation becomes possible and malfunctioning of an APSD function is prevented. The optical amplifier using Raman amplification includes; a Raman excitation light source for generating Raman light; and a detection circuit for detecting a signal error in an OSC (optical supervisory channel) signal transmitted in addition to optical transmission signal. When the detection circuit detects a bit error in the OSC signal, an output power from Raman excitation light source is controlled so as not to injure the human body.

Abstract: A multiaxial optical coupler for use in a device using an LiNbO3 substrate, which is reliable over a wide temperature range and capable of reducing coupling loss. A capillary has a plurality of linear through holes formed therethrough in a manner each inclined with respect to the central axis of the capillary such that the extension line of the central axis of the linear through hole extends through the center of a lens. A plurality of optical fibers are inserted into the linear through holes, respectively. This construction enables the optical axis of an optical beam emitted from each of the optical fibers within the capillary to pass through the center of the lens and reach the end face of a corresponding one of the optical waveguides. Similarly, the construction enables the optical axis of an optical beam emitted from the end face of each of the optical waveguides on the substrate to pass through the center of the lens and reach a corresponding one of the optical fibers within the capillary.

Abstract: An electromagnetic acoustic transducer is provided which includes magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can accomplish evaluating the absolute value of ultrasonic attenuation.

Abstract: An object of the invention is to provide a polarization scrambler wherein the polarization of linearly polarized signal light can be rotated to facilitate obtaining a minimum degree of polarization, and wherein scrambling operation is possible even if signal light of optional polarization states is input. Accordingly with the polarization scrambler, a polarization rotation section is provided on an input side on a chip on which is formed an optical waveguide, and a polarization scrambling section is provided on an output side. With the polarization rotation section, the polarization of linearly polarized signal light which is transmitted by the optical waveguide is rotated by means of an acousto-optic effect due to an elastic surface wave generated by an electrode, so as to become 45.degree. with respect to a vertical direction of the optical waveguide.

Abstract: A focusing electromagnetic acoustic transducer is provided which comprises a pair of meander coils, three insulation sheets and a magnet. The meander coils are formed on both surfaces of one of the insulation sheets to be positioned such that the meander coils are coincident with each other, and they are covered with the other insulation sheets. Each of the meander coils comprises a plurality of coil segments wherein intervals between adjacent coil segments sequentially are varied from one end to the other end. The magnet is positioned above the layers consisting the meander coils and insulation sheets. The coil segments of each meander coil are straight lines in parallel with each others, sector shapes on respective circulars having the same center point, or generally circular shapes having the same center point.

Abstract: An optical waveguide module including a metal package having a bottom surface formed with a chip insertion groove, and a waveguide chip inserted and fixed in the chip insertion groove. The waveguide chip has an optical waveguide formed on a substrate having an electro-optic effect. A signal electrode is formed on the optical waveguide, and a ground electrode is formed on the substrate. The ground electrode is connected to the metal package through first and second ribbons respectively located in the vicinity of first and second bent portions of the signal electrode.

Abstract: An electromagnetic acoustic transducer for magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can evaluates the absolute value of ultrasonic attenuation.

Abstract: A spindle motor comprising a stator including a support shaft positioned on a base, a cap-shaped rotor rotatably and concentrically disposed around the support shaft, thrust and radial bearings disposed between the stator and the rotor, a stator coil secured to the stator, and a rotor magnet member secured to the rotor opposing the stator coil. The thrust and radial bearings are hydrodynamic bearings. A movable piece that constitutes a part of the thrust bearing is secured to the lower end of a cylindrical portion of the rotor and extended outwardly or inwardly from the cylindrical portion, or is disposed above the rotor. The stator coil is secured to the outer peripheral portion of the support shaft above or below the radial bearing. The rotor magnet member is securd to the inner peripheral surface or inner top surface of the rotor. Either a radial or axial gap is provided between the stator coil and the rotor magnet member.

Abstract: A rotation supporting device of a polygon mirror comprising a stationary shaft provided with a shaft sleeve around its circumference, a rotary assembly rotatably mounted around the circumference of the shaft sleeve and having a radial circumferential surface of a polygon made to serve as mirror surfaces and having a magnet member, thrust plates for suppressing the motion of a rotary assembly in the axial direction. The rotary assembly comprises a first rotor rotatably mounted at the outer circumference of the shaft sleeve, a second rotor having a circumferential surface of a polygon made to serve as mirror surfaces and being disposed at the outer circumference of the first rotor, and a yoke secured on the outer circumference of the first rotor. The first rotor is made of a ceramic material, the second rotor is made of aluminum and the yoke is made of steel. Radial dynamic pressure bearing is included between the outer circumference of the shaft sleeve and the rotary assembly.