Abstract: A plurality of cores 51 is disposed around the center axis of a first cladding 52 in a state in which an inter-core distance ? of cores adjacent to each other is equal, a refractive index n1 of the core 51 is provided higher than a refractive index n2 of the first cladding 52, and the refractive index n2 of the first cladding 52 is provided higher than a refractive index n3 of a second cladding 53. Moreover, 5.8??/MFD(2?c/(?c+?op))?8 is satisfied, where the inter-core distance is defined as ?, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as ?c, and a wavelength of communication light incident on the core 51 is defined as ?op.

Abstract: An optical fiber for amplification includes a core having an inner core and an outer core surrounding the outer circumferential surface of the inner core. The relative refractive index difference of the inner core to a cladding is smaller than the relative refractive index difference of the outer core to the cladding. The outer core is entirely doped with erbium. The theoretical cutoff wavelength of an LP11 mode light beam is a wavelength of 1,565 nm or more. The theoretical cutoff wavelength of an LP21 mode light beam is a wavelength of 1,530 nm or less. The theoretical cutoff wavelength of the LP02 mode light beam is a wavelength of 980 nm or less.

Abstract: The first cladding 52 has a two-layer structure formed of a solid inner layer 62A passed through the center axis of the first cladding 52 and an outer layer 62B enclosing the inner layer 62A and the plurality of cores 51 with no gap. A refractive index n1 of the core 51 is provided higher than refractive indexes n2A and n2B of the inner layer 62A and the outer layer 62B, the refractive indexes n2A and n2B of the inner layer 62A and the outer layer 62B are provided higher than a refractive index n3 of the second cladding 53, and the refractive index n2A of the inner layer 62A is provided lower than the refractive index n2B of the outer layer 62B.

Abstract: A plurality of cores 51 is disposed around the center axis of a first cladding 52 in a state in which an inter-core distance ? of cores adjacent to each other is equal, a refractive index n1 of the core 51 is provided higher than a refractive index n2 of the first cladding 52, and the refractive index n2 of the first cladding 52 is provided higher than a refractive index n3 of a second cladding 53. Moreover, 5.8??/MFD(2?c/(?c+?op))?8 is satisfied, where the inter-core distance is defined as ?, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as ?c, and a wavelength of communication light incident on the core 51 is defined as ?op.

Abstract: The first cladding 52 has a two-layer structure formed of a solid inner layer 62A passed through the center axis of the first cladding 52 and an outer layer 62B enclosing the inner layer 62A and the plurality of cores 51 with no gap. A refractive index n1 of the core 51 is provided higher than refractive indexes n2A and n2B of the inner layer 62A and the outer layer 62B, the refractive indexes n2A and n2B of the inner layer 62A and the outer layer 62B are provided higher than a refractive index n3 of the second cladding 53, and the refractive index n2A of the inner layer 62A is provided lower than the refractive index n2B of the outer layer 62B.

Abstract: The present invention relates to a white light source. This white light source comprises a plurality of amplified spontaneous emission light generating sections each comprising at least an active fiber. At least two of the amplified spontaneous emission light generating sections are connected together in series. The plurality of amplified spontaneous emission light generating sections generate amplified spontaneous emission lights having at least partially overlapping wavelength ranges. Furthermore, a white light source of the present invention includes amplified spontaneous emission light generating sections each comprising at least an active fiber. At least one of the amplified spontaneous emission light generating sections comprises a mirror.

Abstract: The present invention relates to a white light source. This white light source comprises a plurality of amplified spontaneous emission light generating sections each comprising at least an active fiber. At least two of the amplified spontaneous emission light generating sections are connected together in series. The plurality of amplified spontaneous emission light generating sections generate amplified spontaneous emission lights having at least partially overlapping wavelength ranges. Furthermore, a white light source of the present invention includes amplified spontaneous emission light generating sections each comprising at least an active fiber. At least one of the amplified spontaneous emission light generating sections comprises a mirror.

Abstract: A tellurite glass as a glass material of optical fiber and optical waveguide has a composition of 0<Bi2O3≦20 (mole %), 0≦Na2O≦35 (mole %), 0≦ZnO≦35 (mole %), and 55≦TeO2≦90 (mole %). The tellurite glass allows an optical amplifier and a laser device that have broadband and low-noise characteristics. In a splicing structure of non silica-based optical fiber (as a first fiber) and a silica-based optical fiber (as a second fiber), optical axes of the first and second optical fibers are held at different angles &thgr;1 and &thgr;2 (&thgr;1≠&thgr;2) respectively from a vertical axis of a boundary surface between their spliced ends, and a relationship between the angles &thgr;1 and &thgr;2 satisfies Snell's law represented by an equation of sin &thgr;1/sin &thgr;2=n2/n1 (where n1 is a refractive index of the first optical fiber and n2 is a refractive index of the second optical fiber) at the time of splicing the first and second optical fibers.

Abstract: A tellurite glass as a glass material of optical fiber and optical waveguide has a composition of 0<Bi2O3 ≦20 (mole %), 0≦Na2O≦35 (mole %), 0≦ZnO≦35 (mole %), and 55≦TeO2≦90 (mole %). The tellurite glass allows an optical amplifier and a laser device that have broadband and low-noise characteristics. In a splicing structure of non silica-based optical fiber (as a first fiber) and a silica-based optical fiber (as a second fiber), optical axes of the first and second optical fibers are held at different angles &thgr;1 and &thgr;2 (&thgr;1≠&thgr;2) respectively from a vertical axis of a boundary surface between their spliced ends, and a relationship between the angles &thgr;1 and &thgr;2 satisfies Snell's law represented by an equation of sin &thgr;1/sin &thgr;2=n2 /n1 (where n1 is a refractive index of the first optical fiber and n2 is a refractive index of the second optical fiber) at the time of splicing the first and second optical fibers.

Abstract: A tellurite glass as a glass material of optical fiber and optical waveguide has a composition of 0<Bi2O3≦20 (mole %), 0≦Na2O≦35 (mole %), 0≦ZnO≦35 (mole %), and 55≦TeO2≦90 (mole %). The tellurite glass allows an optical amplifier and a laser device that have broadband and low-noise characteristics. In a splicing structure of non silica-based optical fiber (as a first fiber) and a silica-based optical fiber (as a second fiber), optical axes of the first and second optical fibers are held at different angles &thgr;1 and &thgr;2 (&thgr;1≠&thgr;2) respectively from a vertical axis of a boundary surface between their spliced ends, and a relationship between the angles &thgr;1 and &thgr;2 satisfies Snell's law represented by an equation of sin &thgr;1/sin &thgr;2=n2/n1 (where n1 is a refractive index of the first optical fiber and n2 is a refractive index of the second optical fiber) at the time of splicing the first and second optical fibers.

Abstract: A tellurite glass as a glass material of optical fiber and optical waveguide has a composition of 0<Bi2O3≦20 (mole %), 0≦Na2O≦35 (mole %), 0≦ZnO≦35 (mole %), and 55≦TeO2≦90 (mole %). The tellurite glass allows an optical amplifier and a laser device that have broadband and low-noise characteristics. In a splicing structure of non silica-based optical fiber (as a first fiber) and a silica-based optical fiber (as a second fiber), optical axes of the first and second optical fibers are held at different angles &thgr;1 and &thgr;2 (&thgr;1≠&thgr;2) respectively from a vertical axis of a boundary surface between their spliced ends, and a relationship between the angles &thgr;1 and &thgr;2 satisfies Snell's law represented by an equation of sin &thgr;1/sin &thgr;2=n2/n1 (where n1 is a refractive index of the first optical fiber and n2 is a refractive index of the second optical fiber) at the time of splicing the first and second optical fibers.

Abstract: An optical amplifier includes an erbium doped fiber of which at least one of a core part and a clad part is doped with erbium, excitation light sources or exciting the optical fiber, optical means for inputting excitation light from the excitation light source and signal light to the Er-doped fiber, and an optical isolator. The erbium doped fiber is a 1.58 &mgr;m band optical fiber having an equivalent fiber length as a product of a fiber length (m) and an erbium doping concentration (ppm by weight), which length provides a signal gain obtained at a wavelength of the excitation light source used for excitation of the erbium doped fiber of more than a predetermined practical reference value.

Abstract: A motor drive system comprises a motor driven by a variable frequency power supply and a machine driven by the motor, which are mechanically connected by the drive shaft of the motor and the shaft of the machine via bearings. A stationary portion of the motor and the frame of the machine are electrically connected by a low-impedance conductor, so that a current can be caused to flow at least partially between the stationary portion of the motor and the frame of the machine.

Abstract: The power system stabilizer is provided at an individual power system to be separated due to an accident cutting off a link line which interconnects a number of power systems to form a large-scale power system. The power systems include power stations such as power plants and transformer substations. A simplified arithmetic processing unit of the stabilizer performs an arithmetic processing by a simple linear equation using an output frequency of a representative power station belonging to the separated power system immediately after the accident has been cleared, so that a total load drop of the separated power system can be assumed. Based on the assumption amount, balance control of demand and supply in the separated system is made.

Abstract: In a woodwind instrument of the type which opens a tone hole by means of the combination of a key and an arm having a tone hole cover at one end both supported by a pair of posts via a hinge rod, a woodwind instrument comprises a pair of bases respectively projecting from the outer periphery of an instrument body and adapted to support a pair of posts. Each of said bases is formed with a hole of sufficient depth so that proper securement of the posts to the instrument body may be obtained upon fitting the lower portion of each of the posts to the corresponding respective hole therein.