Abstract: An optical fiber has a section of the first kind having a chromatic dispersion not less than a given positive value x and a negative chromatic dispersion slope at a given wavelength and a section of the second kind has a chromatic dispersion not more than −x and a positive chromatic dispersion slope at the same wavelength. Another optical fiber has a chromatic dispersion higher than a positive value x and a negative chromatic dispersion slope at a given wavelength band.

Abstract: A Raman amplifier having a great Raman amplification gain is disclosed. An optical transmission system 1 is provided with an optical fiber 31 for Raman amplification and an optical multiplexer 41 between a transmitter 10 and a receiver 20 in the order of enumeration, and further provided with a pump light source 51 for Raman amplification that is connected with the optical multiplexer 41. The wavelength of signal light to be transmitted from the transmitter 10 to the receiver 20 is at 1.65 &mgr;m band, and the wavelength of the pump light that is output from the light source 51 is C-band or L-band. Since the pump light for Raman amplification propagates at a low loss through the optical fiber for Raman amplification, a great Raman amplification gain can be attained by the Raman amplifier.

Abstract: An optical variable attenuator has a planar waveguide, which is provided with optical waveguides forming an input optical line A and an output optical line B. A cantilever is disposed at the upper face of the planar waveguide, whereas a movable mirror for reflecting light passing through the input optical line A toward the output optical line B is secured to the leading end part of the cantilever. An electrode is disposed at the upper face of the planar waveguide. The cantilever and the electrode are connected to each other by way of a voltage source. The voltage source applies a voltage between the cantilever and the electrode, so as to generate an electrostatic force therebetween, which flexes the leading end side of the cantilever toward the electrode. As a consequence, the movable mirror moves toward the electrode.

Abstract: An optical switch that can restrain the occurrence of cross talk is provided. A first waveguide path 11 and a second waveguide path 12 are provided on a waveguide substrate PCL so as to intersect each other at a given angle. A trench T is formed in a straight line in the surface of the waveguide substrate PCL so as to cross the central axes of the first waveguide path and the second waveguide path. The trench T is as deep as to expose the whole end face of the first waveguide path and the second waveguide path. The first waveguide path 11 and the second waveguide path 12 are arranged such that their central axes are arranged asymmetrically with respect to the straight line.

Abstract: The invention provides an apparatus for and method of monitoring wavelength multiplexed signal light, which can obtain monitored data for multi-channel optical signals contained in the wavelength multiplexed signal light, which can avoid a large size and complicated structure and high cost of monitoring apparatus, and which can easily monitor the wavelength multiplexed signal light. The invention also provides an optical transmission system employing the monitoring apparatus and method. An optical filter being able to control a loss pattern is disposed on a monitoring waveguide for the wavelength multiplexed signal light, which is branched for monitoring from an input waveguide and an output waveguide constituting a main optical transmission path in a wavelength multiplexed signal light monitoring apparatus.

Abstract: An optical fiber composite that can easily have a desired mean transmission property as a whole even after a length of optical fiber is cut off from one end or both ends, a cable comprising the composites, and methods for producing the composite and cable. An optical fiber composite 10 is produced by splicing a first optical fiber 11, a second optical fiber 12, and a third optical fiber 13 in this order. The first optical fiber 11 and the third optical fiber 13 each have a first chromatic dispersion, D1, at the wavelength of a signal-carrying lightwave. The second optical fiber 12 has a second chromatic dispersion, D2, at the wavelength of the signal-carrying lightwave. The third optical fiber has a length, L3, shorter than the length, L1, of the first optical fiber. It is desirable that the ratio L3/L1 be at most 0.1.

Abstract: An optical fiber has a section of the first kind having a chromatic dispersion not less than a given positive value x and a negative chromatic dispersion slope at a given wavelength and a section of the second kind has a chromatic dispersion not more than −x and a positive chromatic dispersion slope at the same wavelength. Another optical fiber has a chromatic dispersion higher than a positive value x and a negative chromatic dispersion slope at a given wavelength band.

Abstract: The present invention relates to an optical transmission system and a channel assigning method with structure to reduce dispersion of power levels among signals dropped at respective signal branchpoints on an optical transmission line out of signals of multiple channels amplified in an optical amplifier. The optical transmission system has an optical transmission line in which signals of multiple channels propagate, an optical amplifier provided on the transmission line, and a plurality of signal branchpoints disposed on the downstream transmission line in which the signals of the channels outputted from the optical amplifier propagate. Each of the signal branchpoints drops a signal of a channel with a lowest power level out of arriving signals in the channels. This reduces the dispersion of power levels among signals dropped at the respective branchpoints, as a whole of the optical transmission system.

Abstract: An optical cable has a reduced slicing loss and superior characteristics in the efficiency of the installation work thereof, and is therefore suitable for installation on land. First and second optical fibers have been connected together by fusion splicing to form joints thereby providing an optical fiber line. Each first optical fiber has a positive chromatic dispersion at a signal light wavelength while each second optical fiber has a negative chromatic dispersion at the same wavelength. The first and the second optical fibers, including the joints, are accommodated in the optical cable.

Abstract: Disclosed are an optical transmission system and a Raman amplifying control unit that can stabilize the effective loss of a transmission line even if the optical transmission system has a relay station between a transmitting station and a receiving station. The optical transmission system and the Raman amplifying control unit have an introducing means for outputting inspection light and introducing it to the transmission line, a receiving means for receiving the back-scatter from the inspection light, and a control means for inspecting the transmission line and controlling an exciting light supplying means according to the received backscattering light. The introducing means, the receiving means, and the control means are provided together with the exciting light supplying means in a station at the transmitting side or receiving side of a relay section in the optical transmission system.

Abstract: In an optical fiber including a core region and a cladding region surrounding said core region in a cross section and having a cross-sectional structure in which a plurality of regions constituted by sub mediums are arranged in main mediums, at least one of refractive indices of the main mediums and the sub mediums are changed in a radial direction.

Abstract: The present invention relates to an operation mode switching apparatus comprising a structure for making it possible to minimize the waste of energy caused by troubles occurring in optical fiber lines and the like in order to efficiently utilize the energy consumed in an optical transmission system aimed for a long-term operation; a Raman amplifier including the operation mode switching apparatus; and an optical transmission system including the Raman amplifier. If an optical fiber line acting as an optical transmission medium breaks in the optical transmission system, the signal power detected from the optical fiber decreases, whereby it changes to a set value or less or the amount of decrease in signal power per unit time changes by a set value or more.

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: An optical module has a planar waveguide which is provided with an optical circuit for an optical switch formed by 2×2 cross optical waveguides A1 to D1 and an optical circuit for an optical variable attenuator formed by 2×2 cross optical waveguides A2 to D2. Joined onto the planar waveguide is an actuator structure and the actuator structure is constituted by an actuator section for an optical switch and an actuator section for an optical variable attenuator. The optical circuit of the planar waveguide and the actuator section constitute an optical switch, whereas the optical circuit of the planar waveguide 2 and the actuator section constitute an optical variable attenuator.

Abstract: An optical variable attenuator has a planar waveguide, which is provided with optical waveguides forming an input optical line A and an output optical line B. A cantilever is disposed at the upper face of the planar waveguide, whereas a movable mirror for reflecting light passing through the input optical line A toward the output optical line B is secured to the leading end part of the cantilever. An electrode is disposed at the upper face of the planar waveguide. The cantilever and the electrode are connected to each other by way of a voltage source. The voltage source applies a voltage between the cantilever and the electrode, so as to generate an electrostatic force therebetween, which flexes the leading end side of the cantilever toward the electrode. As a consequence, the movable mirror moves toward the electrode.

Abstract: An optical signal, which is to become the subject of dispersion compensation, is split by optical combining/splitting unit 2, and each frequency component of the optical signal that is split is reflected by each reflective surface of reflective mirror 40 of reflective means 4 to apply a predetermined phase shift to the respective frequency components. Each reflected frequency component is then combined using optical combining/splitting unit 2, to give dispersion compensated optical signal. Furthermore, in regards to reflective means 4, which is used to apply phase shift to each frequency component of an optical signal, reflective mirror 40 is made a variable movable mirror by reflection position at each reflective surface, which reflects the frequency components, deforming the entire reflective surface. This allows dispersion that is created in an optical signal to be compensated with favorable controllability and high accuracy.

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: A main optical path and an auxiliary optical path which are formed in a substrate are optically coupled to each other with a plurality of optical couplers, so as to constitute a Mach-Zehnder interferometer. By controlling the temperature regulation of main and auxiliary optical paths effected by heaters, a control unit regulates the transmissivity of light across an optical input end and an optical output end. Respective optical path lengths of the main and auxiliary optical paths are set so as to lower birefringence when optical loss becomes greater.

Abstract: In an optical fiber composed of a core region and a cladding region surrounding the core region and having a plurality of regions made of sub mediums having refractive indices different from a refractive index of a main medium disposed in a main medium constituting this cladding region, these regions made of the sub mediums are arranged in one given or a plurality of a given circular annular regions and the centers of the regions made of the sub mediums in respective circular annular regions are arranged on the same circumference centered at the center of the core.

Abstract: A main optical path disposed between light input and output ends and an auxiliary optical path disposed so as to correspond to the main optical path are optically coupled to each other with first, second, and third optical couplers. The respective optical path lengths of main and auxiliary optical paths differ from each other between the first and second optical couplers and between the second and third optical couplers. Between the first and second optical couplers and between the second and third optical couplers, at least one of the main and auxiliary optical paths is provided with temperature adjusting means for adjusting the temperature of the corresponding optical path.