Abstract: An optical fiber and an optical transmission system are provided which enable a large-volume and long-haul transmission, using light signals having a plurality of wavelengths in a wide range of wavelength bands including 1.31 ?m band, 1.45 ?m band, 1.55 ?m band and 1.58 ?m band. The chromatic dispersion of the optical fiber according to the present invention is ?20 ps•nm?1•km?3 or more but ?3 ps•nm?1•km?1 or less in the whole wavelength range of 1300 nm to 1600 nm. The optical transmission system according to the present invention is also equipped with (1) a plurality of transmitters to transmit light signals having wavelengths in the range of 1300 nm to 1600 nm, (2) an optical fiber of the present invention, and (3) receivers which receive the light signals.

Abstract: The present invention relates to a wavelength converter of structure enabling generation of converted light with high power even with a large difference between the wavelength of pumping light and the zero-dispersion wavelength. The wavelength converter includes an optical fiber having a dispersion slope whose absolute value at the wavelength of 1550 nm is 0.01 ps/nm2/km or less, for example.

Abstract: A high-frequency oscillation apparatus wherein an oscillation signal output from a voltage controlled oscillator (VCO) is transferred through a transfer line to a resonator and the resonator is excited. The resonator is coupled with a second transfer line and an RF signal having a level corresponding to the frequency of the oscillation signal is transferred through the second transfer line. When the resonant frequency of the resonator is set to a frequency higher than the oscillation-frequency modulation range of the VCO, the oscillation frequency and the RF-signal level have one-to-one correspondence. A detector detects the RF signal and outputs to a control section. The control section compensates a control voltage signal applied to the VCO according to the detected-signal level, and outputs the control voltage signal to the VCO to compensate the oscillation signal of the VCO.

Abstract: In order to generate a sampling clock having a higher accuracy, a synchronous signal generating circuit is provided with a phase error detector, detecting a phase error of a read out signal digitized on the basis of FDTS algorithm, and a VCO, controlling an oscillation frequency on the basis of a phase error detected by the phase error detector, to generate a synchronous signal by the VCO. On the basis of the synchronous signal generated by the synchronous signal generating circuit, an ADC digitizes the read out signal. The digitized read out signal is then converted to binary data by a detection circuit.

Abstract: Proposed are a dispersion compensating fiber and an optical transmission system that can, using a short length of the fiber, compensate the chromatic dispersion and the dispersion slope of a non-zero dispersion shifted fiber whose chromatic dispersion is +2 ps·nm−1·km−1 to +10 ps·nm−1·km−1 and whose dispersion slope is +0.04 ps·nm−2·km−1 to +0.12 ps·nm−2·km−1 at 1550 nm. In the optical transmission system 1, an optical transmission line 30 that consists of a dispersion-shifted fiber 31 and a dispersion compensation fiber 32 is installed between stations 10 and 20. The dispersion compensating fiber 32 has the chromatic dispersion of −250 ps·nm−1·km−1˜−40 ps·nm−1·km−1 and the dispersion slope of 0.015 ps·nm−2·km−1˜0.030 ps·nm−2·km−1 at 1550 nm.

Abstract: A high-frequency circuit device includes a substrate and a high-frequency circuit. The high-frequency circuit is provided on the substrate and has a signal line. The signal line is configured with a slot line provided by electrodes that are arranged side-by-side with a space therebetween on the substrate. The slot line can facilitates circuit design compared to a microstrip line and has significantly low conduction loss compared to a coplanar line, and can improve the Q-value of the high frequency circuit. This can provide an improved high-frequency circuit device having small phase noise. The high-frequency circuit device, which also serves as an oscillator, employs a slot output and thus can provide an advantage of better continuity for a class-B push-pull amplifier that operates more efficiently than a class-A one.

Abstract: An optical fiber comprising a core region 100 doped with Cl which raises the refractive index; and a cladding region 200, provided at the outer periphery of the core region 100, having a cladding layer 201 doped with F which lowers the refractive index is formed. The cladding region 201 to become the outermost cladding layer is configured such that the doping amount of F successively decreases within an outer peripheral part 205 including the outer periphery thereof to a predetermined doping amount which is the minimum doping amount of F within the cladding layer 201. Therefore, the stress within the optical fiber is dispersed into the outer peripheral part 205 having an enhanced viscosity, whereby the stress concentration into the core is suppressed. Since the favorable tension range at the time of drawing the optical fiber becomes wider at this time, tension control is facilitated.

Abstract: The present invention relates to an optical fiber or the like which allows more precise compensation for the chromatic dispersion of a transmission optical fiber over a broad wavelength band. The optical fiber has a chromatic dispersion of −100 ps/nm/km or less in a wavelength band of 1535 to 1565 nm, 1565 to 1610 nm, 1554 to 1608 nm or 1535 to 1610 nm. In particular, the chromatic dispersion profile of the fundamental mode of this optical fiber defined by the orthogonal coordinate system of the wavelength and chromatic dispersion value has a shape such that, over the entire wavelength band except for the shortest and longest wavelengths thereof, the chromatic dispersion values on the chromatic dispersion profile are respectively located on the minus side of the associated chromatic dispersion values on a straight line connecting the chromatic dispersion values at the shortest and longest wavelength.

Abstract: The optical transmission system in accordance with the present invention is an optical transmission system in which an optical fiber transmission line is laid between a transmitting station and a receiving station, first and second optical couplers are provided on the optical fiber transmission line, a first Raman amplification pumping light source is connected to the first optical coupler, a second Raman amplification pumping light source is connected to the second optical coupler, the optical fiber transmission line Raman-amplifies signal light in S band when Raman amplification pumping light is supplied thereto while transmitting the signal light, and the optical fiber transmission line has a zero-dispersion wavelength of 1350 nm to 1440 nm and a cable cutoff wavelength of less than 1368 nm.

Abstract: A waveguide, a high-frequency circuit, and a high-frequency circuit device having the waveguide are provided. The waveguide includes two conductor plates each of which has a surface having a groove. At least one of the conductor plates has protrusions extending from the surface at both sides of the groove. The two conductor plates are in contact with each other such that the grooves face each other. Screws disposed between the protrusions and bumps, which are formed outside the protrusions on the conductor plate, fasten the conductor plates with a predetermined pressure.

Abstract: A method of splicing optical fibers is provided to reduce the splicing loss of the first and second optical fibers having different MFDs from each other. In a pre-fusion heating step, the MFD at the adjacent end face of the optical fiber having larger MFD is enlarged by heating a portion including the adjacent end face thereof so as to diffuse a dopant. After the pre-fusion heating step, fusion-splicing of the first and the second optical fibers is performed. Thereafter, during the post-fusion heating step, the dopant is diffused by heating a portion including the fusion-spliced part between the first and the second optical fibers.

Abstract: The present invention relates to an optical fiber having a large positive dispersion in a wavelength band of 1.55 &mgr;m in order to compensate for a negative dispersion inherent in an NZ-DSF in the wavelength band of 1.55 &mgr;m. This optical fiber comprises a depressed cladding structure constituted by a core region; an inner cladding, provided on the outer periphery of the core region, having a lower refractive index; and an outer cladding having a higher refractive index. In this optical fiber, the relative refractive index difference of the core region with respect to the outer cladding is 0.30% or more but 0.50% or less, and the relative refractive index difference of the inner cladding with respect to the outer cladding is −0.50% or more but −0.02% or less. Also, the optical fiber has a dispersion greater than 18 ps/nm/km at a wavelength of 1.55 &mgr;m, and an effective area of 70 &mgr;m2 or more at the wavelength of 1.55 &mgr;m.

Abstract: A high-frequency circuit device includes a substrate and a high-frequency circuit. The high-frequency circuit is provided on the substrate and has a signal line. The signal line is configured with a slot line provided by electrodes that are arranged side-by-side with a space therebetween on the substrate. The slot line can facilitates circuit design compared to a microstrip line and has significantly low conduction loss compared to a coplanar line, and can improve the Q-value of the high frequency circuit. This can provide an improved high-frequency circuit device having small phase noise. The high-frequency circuit device, which also serves as an oscillator, employs a slot output and thus can provide an advantage of better continuity for a class-B push-pull amplifier that operates more efficiently than a class-A one.

Abstract: An optical fiber capable of compensating in the L-band both the chromatic dispersion and dispersion slope of a positive-dispersion optical fiber, an optical transmission line incorporating the optical fiber, and an optical communications system incorporating the optical transmission line. An optical communications system 1 comprises an optical transmission line 10, an optical transmitter 20, and an optical receiver 30. The optical transmission line 10 comprises an optical fiber 11 and an optical fiber 12 that are mutually fusion-spliced. The optical fiber 12 has at a wavelength of 1,590 nm a chromatic dispersion, D2, and a dispersion slope, S2, that satisfy the formulae −200 ps/nm/km≦D2≦−50 ps/nm/km, and 0.009/nm≦S2/D2.

Abstract: An optical fiber comprising a core region 100 doped with Cl which raises the refractive index; and a cladding region 200, provided at the outer periphery of the core region 100, having a cladding layer 201 doped with F which lowers the refractive index is formed. The cladding region 201 to become the outermost cladding layer is configured such that the doping amount of F successively decreases within an outer peripheral part 205 including the outer periphery thereof to a predetermined doping amount which is the minimum doping amount of F within the cladding layer 201. Therefore, the stress within the optical fiber is dispersed into the outer peripheral part 205 having an enhanced viscosity, whereby the stress concentration into the core is suppressed. Since the favorable tension range at the time of drawing the optical fiber becomes wider at this time, tension control is facilitated.

Abstract: The present invention relates to a compact dispersion compensator and the like. The dispersion compensator comprises a housing and an optical fiber coil. The optical fiber coil has a coiled part constituted by a dispersion-compensating optical fiber wound like a coil while being in a bundle state with its winding distortion substantially eliminated. The housing is filled with a resin surrounding the coiled part of the optical fiber coil, whereas the coiled part is held by the resin. By this structure, the dispersion compensator can realize a further compactness.

Abstract: The present invention relates to a compact dispersion compensator and the like. The dispersion compensator comprises a housing and an optical fiber coil. The optical fiber coil has a coiled part constituted by a dispersion-compensating optical fiber wound like a coil while being in a bundle state with its winding distortion substantially eliminated. The housing is filled with a resin surrounding the coiled part of the optical fiber coil,whereas the coiled part is held by the resin. The dispersion-compensating optical fiber constituting the optical fiber coil has a chromatic dispersion of −140 ps/nm/km or less at a wavelength of 1.55 &mgr;m, whereas the housing has a volume of 500 cm3 or less. This configuration allows the dispersion compensator to attain an accumulated chromatic dispersion of −1200 ps/nm/km or more but less than −600 ps/nm at a wavelength of 1.55 &mgr;m.

Abstract: The present invention relates to an optical fiber having a structure suitable for long-distance optical communications, and an optical transmission line including the same. The optical fiber in accordance with the present invention comprises a core region extending along a predetermined axis, and a cladding region disposed so as to surround the outer periphery of the core region; and, as characteristics at a wavelength of 1.55 &mgr;m, an effective area of at least 110 &mgr;m2, a dispersion of 18 to 23 ps/nm/km, and a dispersion slope of 0.058 to 0.066 ps/nm2/km.

Abstract: The present invention relates to an optical fiber transmission line having a structure offering superior connection loss characteristics at the fusion-spliced position between optical fibers. This optical fiber transmission line has at least first and second optical fibers that are fusion-spliced. Each of these first and second optical fibers has a core region doped with 10 mol % or more of Ge and has a mode field diameter with a minimum value of 7 &mgr;m or less at the wavelength of 1550 nm. The difference between the minimum mode diameter of the first optical fiber and that of the second optical fiber is 1 &mgr;m or less.

Abstract: A radio frequency module includes a multi-chip substrate divided into separate substrates. An antenna block, a duplexer block, a transmitter block, a receiver block, and an oscillator block are formed on the separate substrates. Connection resonators, which are connected to transmission lines, are formed at edges of the separate substrates. The connection resonators on adjacent ones of the separate substrates are arranged close to each other such that the two adjacent resonators are electromagnetically coupled to each other. Thus, the transmission lines on the separate substrates are interconnected, and a signal can be propagated among the blocks.