Abstract: The present invention relates to a multi-core optical fiber applicable to an optical transmission line of bi-directional optical communication and a bi-directional optical communication method. The multi-core optical fiber has plural cores in a common cladding. Signal light is transmitted in a first direction through an arbitrary core among the cores, whereas the signal light is transmitted in a second direction opposite to a first direction, through all the nearest-neighbor cores to the arbitrary core.

Abstract: This invention provides an optical transmission system which allows to perform high-quality transmission of each of a plurality of signal channels multiplexed. In the optical transmission system, signal light in which a plurality of signal channels with an optical frequency spacing of 400 GHz or more but 12.5 THz or less is transmitted from an optical transmitter to a Raman amplifier through an optical fiber transmission line. In the Raman amplifier, pumping light from a pumping light source unit is supplied to an optical fiber through an optical coupler. The multiplexed signal light inputted to the Raman amplifier arrives at the optical fiber through an optical isolator and optical coupler, and Raman-amplified by the optical fiber. The Raman-amplified multiplexed signal light is outputted from the Raman amplifier through an optical coupler and optical isolator.

Abstract: The present invention provides fluorescent glass containing at least 50 mol % of at least one kind of oxide selected from the group consisting of SiO2, GeO2, and P2O5 as a glass constituent of a region containing a Bi ion as a dopant.

Abstract: An optical communication system is formed by connecting a base station to user stations. Each user station has a transmitting section for upstream communication. The base station has a light source which supplies transmission light used for upstream communication.

Abstract: The present invention relates to an optical component and others in structure capable of implementing improved compensation for a gain slope. The optical component is equipped with first and second Mach-Zehnder interferometers. The first Mach-Zehnder interferometer is provided with a first temperature controller for controlling a temperature of at least one of a part of an optical main path and a first optical side path, while the second Mach-Zehnder interferometer 42 is also provided with a second temperature controller for controlling a temperature of at least one of a part of the optical main path and a second optical side path.

Abstract: A optical filter has a loss spectrum whose gradient dL/d? of a loss L (dB) with respect to the wavelength ? (nm) is variable in the wavelength band of multiplexed signal light. A control circuit detects each power of signal light components demultiplexed by an optical coupler and controls the power of optical pumping light to be supplied to an optical amplification section from an optical pumping light sources such that the power of output signal light has a predetermined target value. The control circuit also controls the gradient dL/d? of the optical filter on the basis of powers of the signal light components.

Abstract: The present invention relates to an optical device and the like which can facilitate a fine adjustment for an optical waveguide type diffraction grating device. The optical device includes a flexible member in which the optical waveguide type diffraction grating device is secured to a predetermined position, and bending means for applying a stress to said optical waveguide type diffraction grating device by bending said flexible member. The optical device changes the optical characteristics of the optical waveguide type diffraction grating device by adjusting the stress applied thereto by the bending means, to thereby perform easily various functions such as optical multiplexing, optical demultiplexing, path changing, and adjustment of dispersion characteristics.

Abstract: The present invention relates to an optical transmission system having a structure to enable signal transmission while maintaining superior transmission characteristics over a broader wavelength band. Signal light outputted from a signal light source has a positive chirp, and propagates through a transmission line fiber to an optical receiver, after being Raman-amplified by a lumped Raman amplifier. The lumped Raman amplifier includes, as a Raman amplification fiber, a high-nonlinearity fiber having a negative chromatic dispersion at a wavelength of the signal light and intentionally generating a self-phase modulation therein. The positive chirp of the signal light propagating through the high-nonlinearity fiber is effectively compensated by both of the negative chromatic dispersion and the self-phase modulation generated in the high-nonlinearity fiber.

Abstract: The present invention relates to a fluorescent glass capable of being doped with a high concentration of rare earth ions and suitable for optical communication application, and an optical component incorporating it. The fluorescent glass comprises Al2O3 of 15 to 50 mol %; SiO2 of 0 to 80 mol %; an oxide of 5 to 85 mol % in total comprising at least one of B2O3, Ga2O3, Y2O3, Ta2O5, Sb2O3, Nd2O5, La2O3, and Yb2O3; and a rare earth ion. Concentration quenching is more suppressed in this fluorescent glass than in conventional fluorescent glasses, and it is thus feasible for the fluorescent glass to be doped with a high concentration of rare earth ions and to highly efficiently generate fluorescence of wavelengths in the signal wavelength bands generally used in optical communication.

Abstract: The present invention provides fluorescent glass containing at least 50 mol % of at least one kind of oxide selected from the group consisting of SiO2, GeO2, and P2O5 as a glass constituent of a region containing a Bi ion as a dopant.

Abstract: An optical filter with improved ability to control a loss spectrum and an optical amplifier using the same are provided. The optical filter includes a first optical element with a first loss spectrum and a second optical element with a second loss spectrum which are connected together in series between an input port and an output port. The optical filter provides a predetermined loss to input light. A loss control unit controls the overall loss spectrum by shifting the first and second loss spectra in the same direction with respect to wavelength or by shifting only one of the loss spectra.

Abstract: An optical communication system is formed by connecting a base station to user stations. Each user station has a transmitting section for upstream communication. The base station has a light source which supplies transmission light used for upstream communication.

Abstract: The present invention relates to an optical component and others in structure capable of implementing improved compensation for a gain slope. The optical component is equipped with first and second Mach-Zehnder interferometers. The first Mach-Zehnder interferometer is provided with a first temperature controller for controlling a temperature of at least one of a part of an optical main path and a first optical side path, while the second Mach-Zehnder interferometer 42 is also provided with a second temperature controller for controlling a temperature of at least one of a part of the optical main path and a second optical side path.

Abstract: The present invention relates to an optical transmission system and others with excellent noise characteristics. The optical transmission system is provided with an optical fiber transmission line through which signal light propagates, an optical device, and a Raman amplifier placed upstream of the optical device. The optical device functions as an element that degrades a noise characteristic in a signal wavelength band from the long wavelength side toward the short wavelength side when a desired gain is given to the signal light propagating in the optical fiber transmission line. On the other hand, the Raman amplifier is configured so as to adjust optical powers of respective pumping channels in pumping light and thereby Raman-amplify the signal light so that optical powers of the signal channels increase from the long wavelength side toward the short wavelength side in the signal wavelength band, in order to improve the noise characteristic of the whole optical fiber transmission line.

Abstract: This invention provides an optical transmission system which allows to perform high-quality transmission of each of a plurality of signal channels multiplexed. In the optical transmission system, signal light in which a plurality of signal channels with an optical frequency spacing of 400 GHz or more but 12.5 THz or less is transmitted from an optical transmitter to a Raman amplifier through an optical fiber transmission line. In the Raman amplifier, pumping light from a pumping light source unit is supplied to an optical fiber through an optical coupler. The multiplexed signal light inputted to the Raman amplifier arrives at the optical fiber through an optical isolator and optical coupler, and Raman-amplified by the optical fiber. The Raman-amplified multiplexed signal light is outputted from the Raman amplifier through an optical coupler and optical isolator.

Abstract: The semiconductor optical device is provided with an optical waveguide part and an optical amplification part respectively provided on the GaAs semiconductor substrate. The optical amplification part includes at least one semiconductor optical amplifier. The optical waveguide part includes optical elements including optical waveguides. The optical waveguides are optically connected to the semiconductor optical amplifier. The semiconductor optical amplifier is provided with an active layer including a GaxIn1−xNyAs1−y semiconductor, a first conductive type clad layer and a second conductive type clad layer respectively with the active layer between them. The optical waveguides are respectively provided with a core semiconductor layer including at least either of a GaInNAs semiconductor or a GaAs semiconductor, a first clad semiconductor layer and a second clad semiconductor layer respectively with the core semiconductor layer between them.

Abstract: The present invention relates to a grating device and the like which can lower the degree of polarization of light, while having a structure which can be obtained inexpensively in a small size. The grating device comprises a polarization-maintaining optical fiber, and a long-period grating formed in at least a core region of the polarization-maintaining optical fiber. The grating period of the long-period grating, its effective refractive index with respect to a first mode light component, its effective refractive index with respect to a second mode light component, and respective wavelengths of the first and second mode light components satisfy a phase matching conditional expression.

Abstract: The present invention relates to an optical device and the like which can facilitate a fine adjustment for an optical waveguide type diffraction grating device. The optical device includes a flexible member in which the optical waveguide type diffraction grating device is secured to a predetermined position, and bending means for applying a stress to said optical waveguide type diffraction grating device by bending said flexible member. The optical device changes the optical characteristics of the optical waveguide type diffraction grating device by adjusting the stress applied thereto by the bending means, to thereby perform easily various functions such as optical multiplexing, optical demultiplexing, path changing, and adjustment of dispersion characteristics.

Abstract: The present invention relates to a WDM transmission system and the like suitable for optical communications between local stations having a relatively short repeater interval. In particular, the WDM transmission repeater employed in the WDM transmission system demultiplexes a plurality of signal lights propagating through a transmission line into first and second groups, takes out the second group, comprises a multiplexer for sending into the transmission line a new WDM signal group in which the first group thus demultiplexed and a third group of signal lights different from those of the first group are multiplexed, and has a special structure for reducing the influence of the not-demultiplexed crosstalk components within the second group upon the optical communications.

Abstract: An optical fiber amplifier has an optical amplification portion, pumping light source, and optical circulator portion. The optical amplification portion has a signal input port, signal output port, and two erbium-doped optical fibers. These optical fibers are connected in series between the signal input port and the signal output port. The pumping light source is optically coupled to the optical fibers through an optical coupler to supply pumping light to the optical fibers. The optical circulator portion supplies backward ASE light obtained from the signal input port of the optical amplification portion to the signal output port thereof. With this arrangement, not only forward ASE light but also backward ASE light can be supplied to the optical amplification portion. There is no additional optical fiber, which is not pumped by light for the light source, to use both ASE light components for optical amplification.