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: Disclosed are a gain module and an optical communication system which have gain in a broad wavelength range and are of low cost. The gain module 10 has two optical fibers 111 and 112 which differ from each other with respect to the composition of their respective optical waveguide region and which are connected in series. Because they differ from each other with respect to the quantity of their respective Stokes shift, they have gain in a different wavelength, respectively. The signal lights are introduced into the input end 10a, amplified with the gain module 10 in a wide wavelength range where an optical fiber has a Raman amplification gain, and are emitted from the output end 10b.

Abstract: The present invention provides a Raman amplification pumping module and others with a structure for effectively suppressing degradation of quality of signal light even with a breakdown in either one of a plurality of light sources. The Raman amplification pumping module is provided with light sources for emitting respective lightwaves with center wavelengths different from each other, and each of the center wavelengths of the lightwaves from these light sources is adjusted so that a difference between two center wavelengths selected therefrom is less than 6 nm.

Abstract: This invention relates to an optical amplification fiber having a structure capable of exhibiting an excellent amplification characteristics, and the like. In the optical amplification fiber, the ratio (&agr;P/&agr;S) of an unsaturated absorption peak value &agr;P in a pumping light wavelength band of 0.98 &mgr;m to an unsaturated absorption peak value &agr;S in a signal wavelength band of 1.55 &mgr;m is 0.8 or more and, more preferably, 0.9 or more.

Abstract: The present invention relates to a Raman amplification optical fiber and the like comprising a structure which can Raman-amplify signal light including a plurality of wavelength components at a high efficiency and effectively restrain signal waveforms from deteriorating due to influences of nonlinear optical phenomena, while improving the degree of freedom in the design of optical fiber transmission lines and Raman amplifiers. As characteristics at each wavelength of signal light, the Raman amplification optical fiber has a chromatic dispersion with an absolute value of 6 ps/nm/km or more but 20 ps/nm/km or less, and an effective area Aeff of 20 &mgr;m2 or less, preferably less than 15 &mgr;m2. More preferably, as a characteristic at each wavelength of signal light, the Raman amplification optical fiber has a Raman gain coefficient GR/Aeff of 0.005 (W·m)−1 or more.

Abstract: A Raman amplifier is structured for resistance to signal waveform deterioration and excellent transmission quality. A wavelength spacing is arranged so that non-degenerate type four-wave mixing is effectively suppressed. When the Raman amplification optical waveguide has a positive dispersion slope with respect to the signal light, the zero-dispersion wavelength &lgr;0 of the Raman amplification optical waveguide is shorter than the center wavelength &lgr;center. When the Raman amplification optical waveguide has a negative dispersion slope with respect to the signal light, the zero-dispersion wavelength &lgr;0 of the Raman amplification optical waveguide is longer than the center wavelength &lgr;center.

Abstract: An optical fiber for optical amplification used for 1.58 &mgr;m band signal light amplification, at least a core region thereof being doped with Er has a core region at least a part thereof made of silica glass co-doped with Ge and Al together with Er, and Er average atomic concentration in the core region is from 1000 wt-ppm to 3000 wt-ppm inclusive, and cutoff wavelength is from 1.3 &mgr;m to 1.5 &mgr;m inclusive.

Abstract: The present invention relates to a practical optical amplification module and the like realizing a wide-band gain spectrum with a small relative gain non-uniformity in L band. Pumping light from a pumping light source is supplied to a Bi type EDF by way of an optical coupler. Multiplexed signal light of L band inputted by way of an input end reaches the Bi type EDF by way of an optical coupler, an optical isolator, and an optical coupler, and is collectively amplified in the Bi type EDF. The multiplexed signal light amplified in the Bi type EDF is outputted from an output end by way of an optical coupler, an optical isolator, and an optical coupler.

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: Provided are a broadband light source suitable for a pump light module for Raman amplification and a Raman amplifier which uses such light source. The broadband light source comprises a light source system for emitting light having two or more different output peak wavelengths and a nonlinear medium having an input port and an output port, and the nonlinear medium affords nonlinear effect on light emitted from the light source system and input from the input port, and outputs the resultant light as pump light from the output port. The Raman amplifier, which comprises an optical fiber for Raman amplification, a multiplexing module, and the broadband light source of the present invention, amplifies signal light propagating through the optical fiber for Raman amplification.

Abstract: Disclosed are an optical amplifier and an optical transmission system using the same in which not only can the dispersion of optical waveguide paths for optical amplification be easily and sufficiently compensated, but also the waveform degradation of signal light can be restrained. An optical amplifier according to one embodiment of the present invention comprises at least two erbium-doped fibers 10 and 20, having erbium doped to optically amplify signal light with the pump light, and having dispersion different from each other in sign, and being connected together in series, and two pump light sources 11 and 12 for supplying pump light to them.

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: The present invention relates to a light-amplifying optical fiber comprising a structure for realizing a flat gain characteristic or oscillation characteristic in a wider wavelength band, and a method of making the same. The light-amplifying optical fiber according to the present invention comprises a second doped area containing a first doped area including an optical axis center and having a larger outer diameter than the first doped area. The second doped area is doped with at least one of Al2O3, P2O5, Y2O3, and B2O3 as an oxide of an element having a valence different from that of a cation constituting a main material of the light-amplifying optical fiber; whereas the first doped area is doped with at least one of Er, Nd, Tm, Yb, and Pr as a rare-earth element together with the oxide.

Abstract: The present invention relates to a WDM optical communication system comprising a structure which effectively suppresses the waveform deterioration resulting from nonlinear optical phenomena of each signal in a 1.58-&mgr;m wavelength band in an optical transmission line including a dispersion-shifted optical fiber having a zero-dispersion wavelength in a 1.55-&mgr;m wavelength band. The WDM optical communication system includes a hybrid transmission unit in which a single-mode optical fiber and a dispersion-shifted optical fiber are arranged such that signals successively pass therethrough. The single-mode optical fiber has a zero-dispersion wavelength in a 1.3-&mgr;m wavelength band and an effective area ASMF at a wavelength of 1.58 &mgr;m. The dispersion-shifted optical fiber has a zero-dispersion wavelength in the 1.55-&mgr;m wavelength band and, at a wavelength of 1.58 &mgr;m, a dispersion with an absolute value of 0.

Abstract: In an optical amplifier according to the present invention, a change signal from a change signal source is fed into a light source or a drive circuit. The wavelength of light outputted from the light source is changed based on the change signal. The wavelength-changed output light from the light source is outputted as pumping light from a pumping light generator to be supplied backwardly via an optical multiplexer/demultiplexer into an optical fiber. Signal light is Raman-amplified in the optical fiber with the supply of the pumping light.

Abstract: The present invention relates to an optical amplifier and the like having a flatter gain spectrum in the wavelength band of 1490 nm to 1520 nm than before. The optical amplifier according to the present invention comprises an Er-doped optical waveguide and a Tm-doped optical waveguide having gain spectra difference from each other in the wavelength band. The signal light entered through the input end is first amplified by the Er-doped optical waveguide, and thereafter is amplified by the Tm-doped optical waveguide. The gain deviation of the amplified signal light, which has been amplified in the Er- and Tm-doped optical waveguides and outputted through the output end, can be reduced over the wavelength band.

Abstract: An optical fiber for optical amplification used for 1.58 &mgr;m band signal light amplification, at least a core region thereof being doped with Er has a core region at least a part thereof made of silica glass co-doped with Ge and Al together with Er, and Er average atomic concentration in the core region is from 1000 wt-ppm to 3000 wt-ppm inclusive, and cutoff wavelength is from 1.3 &mgr;m to 1.5 &mgr;m inclusive.

Abstract: The present invention relates to an optical amplifier (TDFA) or the like comprising a structure for constantly keeping the power of outputted signal light and gain flatness even when the power or number of channels of input signal light fluctuates.

Abstract: The present invention provides a Raman amplification pumping module and others with a structure for effectively suppressing degradation of quality of signal light even with a breakdown in either one of a plurality of light sources. The Raman amplification pumping module is provided with light sources for emitting respective lightwaves with center wavelengths different from each other, and each of the center wavelengths of the lightwaves from these light sources is adjusted so that a difference between two center wavelengths selected therefrom is less than 6 nm.