Abstract: In the dispersion-compensating system of the present invention, a demultiplexer demultiplexes optical signals in a signal wavelength band of 1520 nm to 1620 nm propagating through a first common transmission line into C band (1520 nm to 1565 nm) and L band (1565 nm to 1620 nm). Then, the demultiplexer outputs the optical signals of C band into a first branched transmission line and the optical signals of L band into a second branched transmission line. A first dispersion-compensating device is provided on the first common transmission line and compensates for the dispersion in C and L bands. A second dispersion-compensating device is provided on the second branched transmission line and compensates for the dispersion in L band, which has not fully been compensated for by the first dispersion-compensating device. Hence, the dispersion of optical transmission line can fully be reduced in a wide signal light wavelength band.

Abstract: A dispersion compensating optical fiber comprises a minimum wavelength at which an increase amount of an actual loss value with respect to a theoretical loss value is not less than 10 mdB/km in a use wavelength band and on a long wavelength side of the use wavelength band. The actual loss value is measured in a state that the fiber is looped around a bobbin. The minimum wavelength falls within a range of 1,565 to 1,700 nm. This dispersion compensating optical fiber is suitably used for an optical transmission line of a large-capacity high-speed WDM optical transmission system.

Abstract: An optical fiber is formed for use in optical communications systems capable of transmitting and receiving a large volume of information. The optical fiber has a chromatic dispersion of at least 4 ps/nm/km and at most 15 ps/nm/km at a wavelength of 1,550 nm, a transmission loss of at most 0.190 dB/km at a wavelength of 1,530 to 1,570 nm, and an effective cutoff wavelength measured by the 2-meter method of 1610 nm or more. An optical transmission line and an optical communications system are structured by using the foregoing optical fiber.

Abstract: In the dispersion-compensating system of the present invention, a demultiplexer demultiplexes optical signals in a signal wavelength band of 1520 nm to 1620 nm propagating through a first common transmission line into C band (1520 nm to 1565 nm) and L band (1565 nm to 1620 nm). Then, the demultiplexer outputs the optical signals of C band into a first branched transmission line and the optical signals of L band into a second branched transmission line. A first dispersion-compensating device is provided on the first common transmission line and compensates for the dispersion in C and L bands. A second dispersion-compensating device is provided on the second branched transmission line and compensates for the dispersion in L band, which has not fully been compensated for by the first dispersion-compensating device. Hence, the dispersion of optical transmission line can fully be reduced in a wide signal light wavelength band.

Abstract: The present invention relates to a dispersion-compensating module having a structure which compensates for the dispersion of an optical transmission line in a wavelength band of 1.55 ?m and adjusts loss fluctuations among wavelengths in the wavelength band of 1.55 ?m into an appropriate range. The module comprises a structure adapted to be installed in an already installed optical fiber transmission line, and has a loss slope with a polarity opposite to that of the optical fiber transmission line in the wavelength band of 1.55 ?m. An example of the module comprises a dispersion-compensating optical fiber as a dispersion-compensating device, and an optical fiber doped with a transition metal element as a loss-equalizing device. Consequently, the loss fluctuations among individual wavelengths in the whole transmission line including the dispersion-compensating module are adjusted by the loss-equalizing device in the dispersion-compensating module so as to fall within an appropriate range.

Abstract: An optical transmission line including a portion formed by fusion-splicing optical fibers having structures different from each other; wherein, in the optical fibers having structures different from each other, a first optical fiber 1 has a mode field diameter smaller than that of a second optical fiber 2 fusion-spliced thereto; and wherein the first optical fiber 1 has an average viscosity from a center to an outermost layer greater than that of the second optical fiber from a center to an outermost layer.

Abstract: The present invention relates to an optical transmission line comprising a structure for effectively lowering both of nonlinearity and dispersion slope, and an optical transmission system including the same. The optical transmission line comprises, as a repeatered transmission line disposed between stations, a single-mode optical fiber having a zero-dispersion wavelength in a 1.3-&mgr;m wavelength band and a dispersion-compensating optical fiber for compensating for the chromatic dispersion of the single-mode optical fiber. The optical transmission line has an average dispersion slope Save of −0.0113 ps/nm2/km or more but 0.0256 ps/nm2/km or less at a wavelength of 1550 nm, and an equivalent effective area EAeff of 50 &mgr;m2 or more at the wavelength of 1550 nm, whereas the average dispersion slope Save and the equivalent effective area EAeff are designed so as to satisfy a predetermined condition such that the bending loss falls within a permissible range of 2 dB/m or more but 10 dB/m or less.

Abstract: A dispersion compensating optical fiber comprises a minimum wavelength at which an increase amount of an actual loss value with respect to a theoretical loss value is not less than 10 mdB/km in a use wavelength band and on a long wavelength side of the use wavelength band. The actual loss value is measured in a state that the fiber is looped around a bobbin. The minimum wavelength falls within a range of 1,565 to 1,700 nm. This dispersion compensating optical fiber is suitably used for an optical transmission line of a large-capacity high-speed WDM optical transmission system.

Abstract: An optical fiber suitable for use in optical communications systems capable of transmitting and receiving a large volume of information. The optical fiber has a chromatic dispersion of at least 4 ps/nm/km and at most 15 ps/nm/km at a wavelength of 1,550 nm and a transmission loss of at most 0.190 dB/km at a wavelength of 1,530 to 1,570 nm. The optical fiber comprises an inner core (refractive index: n1) including the optical central axis, an outer core (refractive index: n2) encircling the inner core, and a cladding (refractive index: n3) encircling the outer core. The relationship between the refractive indexes is expressed as n1>n2>n3. The inner core is made of practically pure silica glass undoped with GeO2. The outer core and the cladding are doped with a refractive-index-reducing dopant such as fluorine. An optical transmission line and an optical communications system are structured by using the foregoing optical fiber.

Abstract: The present invention is related to a chromatic dispersion compensating module which realizes signal transmission at a high bit rate by its simple constitution, and an optical transmission system comprising the same. The chromatic dispersion compensating module according to the present invention comprises a chromatic dispersion compensator which compensates for the chromatic dispersion of an optical fiber transmission line at a predetermined wavelength, and a temperature controller which controls the temperature of the chromatic dispersion compensator in such a manner to set the chromatic dispersion of the chromatic dispersion compensator at a desired value. By this constitution, the dispersion compensation control in correspondence with the chromatic dispersion fluctuation in the optical fiber transmission line caused by the temperature fluctuation and the like is made possible.

Abstract: The present invention relates to an optical transmission line suitably used for a large-capacity high-speed WDM optical transmission system, and an optical fiber suitably used for such an optical transmission line. The dispersion compensating optical fiber has a minimum wavelength at which an increase amount of an actual loss value with respect to a theoretical loss value is not less than 10 mdB/km in a use wavelength band and on a long wavelength side of the use wavelength band. The actual loss value is measured in a state that the fiber is looped around a bobbin, and the minimum wavelength falls within a range of 1,565 to 1,700 nm.

Abstract: The present invention relates to an optical transmission line enabling WDM communications in a wide signal light wavelength band centered at a wavelength of 1.55&mgr;m, in which nonlinear optical phenomena are less likely to occur; and an optical fiber constituting a part of the optical transmission line. The optical fiber has a dispersion D (unit:ps/nm/km) and a dispersion slope S (unit:ps/nm2/km) satisfying the conditions of −69≦D≦−35 and 0.0050×D≦5≦0.0025×D; and, as characteristics with respect to light having a wavelength of 1.55 &mgr;m an effective area of 15 &mgr;m2 or more and a bending loss of 50 dB/m or less when wound at a diameter of 20 mm.

Abstract: An optical transmission line and an optical communication system for high-quality transmission of signal light using distributed Raman amplification are disclosed. In an optical communication system 1, an optical transmission line 10 including a first optical fiber 11 and a second optical fiber 12, which are connected to each other by means of fusion, is disposed between an optical repeater 30 and an optical repeater 40. The effective core area of the optical fiber 11 is smaller than the effective core area of the optical fiber 12. The absolute value of the chromatic dispersion of the optical fiber 12 is smaller than that of the optical fiber 11. When the lengths of the optical fibers 11 and 12 are represented by L1 and L2, respectively, the ratio L2/(L1+L2) is not less than 0.5.

Abstract: The present invention relates to a dispersion-compensating module having a structure which compensates for the dispersion of an optical transmission line in a wavelength band of 1.55 &mgr;m and adjusts loss fluctuations among wavelengths in the wavelength band of 1.55 &mgr;m into an appropriate range. The dispersion-compensating module comprises a structure adapted to be installed in an already installed optical fiber transmission line, and has a loss slope with a polarity opposite to that of the optical fiber transmission line in the wavelength band of 1.55 &mgr;m. A configurational example of the dispersion-compensating module comprises a dispersion-compensating optical fiber as a dispersion-compensating device, and an optical fiber doped with a transition metal element as a loss-equalizing device.

Abstract: The present invention relates to an optical transmission line comprising a structure for effectively lowering both of nonlinearity and dispersion slope, and an optical transmission system including the same. The optical transmission line comprises, as a repeating transmission line disposed between stations, a single-mode optical fiber having a zero-dispersion wavelength in a 1.3-&mgr;m wavelength band and a dispersion-compensating optical fiber for compensating for the chromatic dispersion of the single-mode optical fiber. The optical transmission line has an average dispersion slope Save of −0.0113 ps/nm2/km or more but 0.0256 ps/nm2/km or less at a wavelength of 1550 nm, and an equivalent effective area EAeff of 50 &mgr;m2 or more at the wavelength of 1550 nm, whereas the average dispersion slope Save and the equivalent effective area EAeff are designed so as to satisfy a predetermined condition such that the bending loss falls within a permissible range of 2 dB/m or more but 10 dB/m or less.

Abstract: The present invention relates to an optical transmission line suitably used for a large-capacity high-speed WDM optical transmission system, and an optical fiber suitably used for such an optical transmission line. The optical transmission line is formed by connecting a single-mode optical fiber (SMF) and a dispersion compensating optical fiber (DCF). The dispersion compensating optical fiber has a dispersion value DDCF (unit: ps/nm/km) and dispersion slope SDCF (unit: ps/nm2/km) falling within the ranges of −82 ≦DDCF≦−29 and 0.0023×DDCF≦SDCF≦0.033+0.0015×DDCF at a wavelength of 1,550 nm, respectively. At the wavelength of 1,550 nm, the transmission loss is 0.5 dB/km or less. Letting LDCF be the length of the dispersion compensating optical fiber, and LSMF be the length of the single-mode optical fiber, the value LDCF/(LDCF+LSMF) in the optical transmission line is 0.2 to 0.4.

Abstract: The present invention relates to a dispersion-compensating module having a structure which compensates for the dispersion of an optical transmission line in a 1.55-&mgr;m wavelength band and adjusts loss fluctuations among signal wavelengths in the 1.55-&mgr;m wavelength band into an appropriate range. The dispersion-compensating module comprises a structure adapted to be installed in an already installed optical fiber transmission line, and has a loss slope with a polarity opposite to that of the optical fiber transmission line in the 1.55-&mgr;m wavelength band. One application of the dispersion-compensating module comprises a dispersion-compensating optical fiber as a dispersion-compensating device, and an optical fiber doped with a transition metal element as a loss-equalizing device.

Abstract: The present invention relates to a dispersion-compensating module having a structure which compensates for the dispersion of an optical transmission line in a 1.55-&mgr;m wavelength band and adjusts loss fluctuations among signal wavelengths in the 1.55-&mgr;m wavelength band into an appropriate range. The dispersion-compensating module comprises a structure adapted to be installed in an already installed optical fiber transmission line, and has a loss slope with a polarity opposite to that of the optical fiber transmission line in the 1.55-&mgr;m wavelength band. One application of the dispersion-compensating module comprises a dispersion-compensating optical fiber as a dispersion-compensating device, and an optical fiber doped with a transition metal element as a loss-equalizing device.

Abstract: The present invention relates to an optical transmission line comprising a structure for effectively lowering both of nonlinearity and dispersion slope, and an optical transmission system including the same. The optical transmission line comprises, as a repeating transmission line disposed between stations, a single-mode optical fiber having a zero-dispersion wavelength in a 1.3-&mgr;m wavelength band and a dispersion-compensating optical fiber for compensating for the chromatic dispersion of the single-mode optical fiber. The optical transmission line has an average dispersion slope Save of −0.0113 ps/nm2/km or more but 0.0256 ps/nm2/km or less at a wavelength of 1550 nm, and an equivalent effective area EAeff of 50 &mgr;m2 or more at the wavelength of 1550 nm, whereas the average dispersion slope Save and the equivalent effective area EAeff are designed so as to satisfy a predetermined condition such that the bending loss falls within a permissible range of 2 dB/m or more but 10 dB/m or less.

Abstract: The present invention relates to an optical transmission line enabling WDM communications in a wide signal light wavelength band centered at a wavelength of 1.55 &mgr;m, in which nonlinear optical phenomena are less likely to occur; and an optical fiber constituting a part of the optical transmission line. The optical fiber has a dispersion D (unit: ps/nm/km) and a dispersion slope S (unit: ps/nm2/km) satisfying the conditions of −83≦D≦−18 and 0.0050×D≦S≦0.0025×D; and, as characteristics with respect to light having a wavelength of 1.55 &mgr;m, an effective area of 15 &mgr;m2 or more and a bending loss of 50 dB/m or less when wound at a diameter of 20 mm.