Abstract: A multicore fiber includes: a first core having a first propagation loss of a first light beam in a mode one order higher than a mode of a second light beam that transmits information. The first propagation loss is 0.02 dB/m or more and 1 dB/m or less, in a wavelength band of light beams including the second light beam that transmit the information when a bend having a diameter of 280 mm is applied to the multicore fiber.

Abstract: A multicore fiber includes: a first core having a first propagation loss of a first light beam in a mode one order higher than a mode of a second light beam that transmits information. The first propagation loss is 0.02 dB/m or more and 1 dB/m or less, in a wavelength band of light beams including the second light beam that transmit the information when a bend having a diameter of 280 mm is applied to the multicore fiber.

Abstract: A fiber fuse detecting apparatus provides early detection of a fiber fuse generation in an optical fiber that propagates laser light, preventing the damage from expanding. It comprises light input means arranged on a laser light incidence side of the optical fiber that inputs at least a portion of reverse direction propagation light propagating in a reverse direction to light incidenting the optical fiber, light receiving means that photo-electrically converts light input by the light input means, electric filter means that extracts from an output signal of the light receiving means a prescribed frequency band component that contains a periodic signal due to fiber fuse, detecting means that detects change of or a prescribed value in output level of the electric filter means, and warning means that emits a warning signal in response to a detection output of the detecting means. The laser light to the optical fiber is stopped or reduced by means of the warning means.

Abstract: The multi-core fiber of the present invention uses a multi-core fiber configuration, compatible with the “coupled” operation mode in which coupling between cores is positively utilized, to carry out mode division multiplexing transmission via a multi-core fiber that contains multiple single-mode cores in one optical fiber. The multi-core fiber of the present invention uses a configuration in which mode multiplexing transmission is carried out using a multi-core fiber that contains multiple single-mode cores in one optical fiber, wherein multiple cores are strongly coupled intentionally to form a coupled multi-core fiber that makes the coupled modes correspond, one to one, to the transmission channels.

Abstract: A multi-core fiber of the present invention employs the multi-core fiber mode, which corresponds to the “uncoupled” operation aspect in which individual cores are used independently for single-mode transmission, to perform space division multiplexing transmission using a multi-core fiber in which multiple single-mode cores are stored in one optical fiber. More specifically, the multi-core fiber of the present invention forms an uncoupled multi-core fiber that makes individual cores correspond to single-mode, independent transmission channels.

Abstract: A multi-core fiber of the present invention employs the multi-core fiber mode, which corresponds to the “uncoupled” operation aspect in which individual cores are used independently for single-mode transmission, to perform space division multiplexing transmission using a multi-core fiber in which multiple single-mode cores are stored in one optical fiber. More specifically, the multi-core fiber of the present invention forms an uncoupled multi-core fiber that makes individual cores correspond to single-mode, independent transmission channels.

Abstract: A fiber fuse detecting apparatus provides early detection of a fiber fuse generation in an optical fiber that propagates laser light, preventing the damage from expanding. It comprises light input means arranged on a laser light incidence side of the optical fiber that inputs at least a portion of reverse direction propagation light propagating in a reverse direction to light incidenting the optical fiber, light receiving means that photo-electrically converts light input by the light input means, electric filter means that extracts from an output signal of the light receiving means a prescribed frequency band component that contains a periodic signal due to fiber fuse, detecting means that detects change of or a prescribed value in output level of the electric filter means, and warning means that emits a warning signal in response to a detection output of the detecting means. The laser light to the optical fiber is stopped or reduced by means of the warning means.

Abstract: The multi-core fiber of the present invention uses a multi-core fiber configuration, compatible with the “coupled” operation mode in which coupling between cores is positively utilized, to carry out mode division multiplexing transmission via a multi-core fiber that contains multiple single-mode cores in one optical fiber. The multi-core fiber of the present invention uses a configuration in which mode multiplexing transmission is carried out using a multi-core fiber that contains multiple single-mode cores in one optical fiber, wherein multiple cores are strongly coupled intentionally to form a coupled multi-core fiber that makes the coupled modes correspond, one to one, to the transmission channels.

Abstract: In an ultrahigh-speed clock extraction circuit wherein a local pulse generating light source 22 for generating a local optical pulse stream synchronized in bit phase with an input optical signal pulse stream is placed in a phase-locked loop, when repetition frequencies of the input optical signal pulse stream and the local optical pulse stream bear a particular relationship, a frequency demultiplier 32 and multipliers 43 and 52 are set so that the frequency of a modulation signal for an optical modulator 41 and a frequency which is a natural-number multiple of the modulation signal frequency, and the frequency of a down-converted version of an optical pulse stream output from a photodetector 42 differ from each other.

Abstract: In an ultrahigh-speed clock extraction circuit wherein a local pulse generating light source 22 for generating a local optical pulse stream synchronized in bit phase with an input optical signal pulse stream is placed in a phase-locked loop, when repetition frequencies of the input optical signal pulse stream and the local optical pulse stream bear a particular relationship, a frequency demultiplier 32 and multipliers 43 and 52 are set so that the frequency of a modulation signal for an optical modulator 41 and a frequency which is a natural-number multiple of the modulation signal frequency, and the frequency of a down-converted version of an optical pulse stream output from a photodetector 42 differ from each other.

Abstract: A multiple-channel all-optical TDM-WDM converter and multiple-channel all-optical TDM demultiplexer which is able to simultaneously and spatially separate optical signal pulse trains of each channel from a TDM optical signal pulse train is structured without using a multistage-structure constitution. A control optical source 10 generates a control optical pulse train containing N optical frequencies, which is synchronous with optical signal pulse trains of N channels which are to be divided from a TDM optical signal pulse train wherein optical signal pulse trains of N channels have been multiplexed in time series. An optical wavelength multiplexer 11 combines the time-division-multiplexed optical signal pulse train and the control optical pulse train.

Abstract: A coherent white light source generates a uniform and continuous coherent white light spectra over 200 nm at a low pump power. The source is based on a pump light source which produces pump optical pulses at a wavelength .lambda..sub.0 and an optical waveguide to receive a pump optical pulse at .lambda..sub.0 to generate a white pulse having a wavelength spread of .DELTA..lambda.. The optical waveguide is characterized by having dispersion properties such that four-wave mixing light having a wavelength spread of .lambda..sub.0 .+-..DELTA..lambda./2 is produced, and the power gain of the four-wave mixing light is greater than 1. These properties of the waveguide are defined by: the path length of the waveguide device ln G.sub.0 /(2.vertline..gamma..vertline.P) in units of ?km!, an absolute value of the dispersion slope to be not more than 16(.vertline..gamma..vertline.E)(.DELTA..lambda..sup. ln G.sub.0) in units of ?ps/nm.sup.2 /km! and an absolute value of the dispersion at the wavelength .lambda..sub.

Abstract: The present invention provides an optical parametric circuit for separating four-wave-mixing wave(s) (FWM wave(s)) from signal wave(s) and/or pump waves without using a wavelength filtering device, and optical circuits using the same. The optical parametric circuit of the present invention is made by connecting two output ports of a 2.times.2 optical directional coupler to a nonlinear optical medium via dispersive optical media, each of which has a specific length and a specific propagation constant. By inputting signal waves having carrier angular frequencies .omega..sub.Sj (j=1, 2, . . . N) and pump waves having carrier angular frequencies .omega..sub.P1, .omega..sub.P2 into the first input port of the optical directional coupler, the FWM waves, generated in the nonlinear optical medium, having carrier angular frequencies .omega..sub.fj (=.omega..sub.P1 +.omega..sub.P2 -.omega..sub.S) are output from the second input port of the optical directional coupler.

Abstract: An all-optical polarization independent optical time division multiplexer and demultiplexer which are stable as well as very fast, while being independent of the polarization state of the input optical signal pulses.