Abstract: A measurement apparatus includes: a light source unit configured to generate optical signals of, from among n+1 frequencies (n is an integer of 3 or larger) at a predetermined frequency interval, n frequencies except for a target frequency, and output the generated optical signals to an optical transmission path that is a measurement target; an optical power measurement device configured to measure of an optical signal of the target frequency output from the optical transmission path and generated in the optical transmission path as a result of four-wave-mixing of the optical signals of the n frequencies; and a processor configured to determine a power spectrum density of non-linear interference noise that occurs in the optical transmission path, by multiplying the power of the optical signal of the target frequency by an adjustment value.

Abstract: A measurement apparatus includes: a light source unit configured to generate optical signals of, from among n+1 frequencies (n is an integer of 3 or larger) at a predetermined frequency interval, n frequencies except for a target frequency, and output the generated optical signals to an optical transmission path that is a measurement target; an optical power measurement device configured to measure of an optical signal of the target frequency output from the optical transmission path and generated in the optical transmission path as a result of four-wave-mixing of the optical signals of the n frequencies; and a processor configured to determine a power spectrum density of non-linear interference noise that occurs in the optical transmission path, by multiplying the power of the optical signal of the target frequency by an adjustment value.

Abstract: A transmission wavelength band in an optical transmission line is divided into a plurality of sub-bands and signal lights or an ASE dummy light is disposed per sub-band as a unit. The optical power of the ASE dummy light in each sub-band is controlled so as to realize the gain profile at a full implementation in the optical transmission line. While new signal lights are being added, the optical power of whole ASE dummy lights or the optical power of the ASE dummy lights in sub-bands adjacent to the sub-band in which the new signal lights are to be added is controlled while increasing the optical power of the new signal lights so that the transmission characteristics of the existing signal lights are not affected by the signal addition.

Abstract: An optical receiving apparatus includes a signal brancher for branching an optical input signal received from an optical transmission line into a first signal component and a second signal component, a clock extractor for extracting a clock having an amplitude from the second signal component, and a discriminator for discriminating the first signal component. The apparatus also includes a threshold controller for generating a discrimination threshold for the discriminator according to a relationship between the extracted clock amplitude and a bit error rate to which the extracted clock amplitude corresponds.

Abstract: An optical repeater is provided which is operable to amplify signals propagated by a pair of optical transmission fibers. The optical repeater includes a first rare earth element doped (REED) fiber coupled to a first transmission fiber of the pair of optical transmission fibers. A second rare earth element doped (REED) fiber is coupled to a second transmission fiber of the pair of optical transmission fibers. A plurality of optical pump sources are provided, there being either four or more pump sources, or at least two pump sources in which each pump source has a different center wavelength. One or more optical energy couplers are coupled to combine portions of the outputs of all the optical pump sources and to distribute the combined portions for insertion into each of the first and second REED fibers for amplification of signals and into each of the first and second transmission fibers for Raman amplification of signals.

Abstract: In an FEC frame structuring method, and an FEC multiplexer, the order of information is changed by a first interleaving circuit 32, a first error correction code is generated by an RS (239, 223) coding circuit 33, the order is returned to the original order by a first deinterleaving circuit 34, and a second error correction code is generated by an RS (255, 239) coding means 5. The second error correction code is decoded by an RS (255, 239) decoding circuit 11 to correct errors in the information, the order of information is changed by a second interleaving circuit 35, the first error correction code is decoded by an RS (239, 223) decoding circuit 36 to correct residual errors in the information, and the order is returned to the original order by a second deinterleaving circuit 37.

Abstract: An optical receiving apparatus according to the present invention comprises an optical signal branching circuit for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical signal branch circuit, an evaluator for evaluating characteristics of another output signal of the optical signal branching circuit. The evaluator includes a saturable absorber for determining the discrimination threshold of the discriminator.

Abstract: A transmission wavelength band in an optical transmission line is divided into a plurality of sub-bands and signal lights or an ASE dummy light is disposed per sub-band as a unit. The optical power of the ASE dummy light in each sub-band is controlled so as to realize the gain profile at a full implementation in the optical transmission line. While new signal lights are being added, the optical power of whole ASE dummy lights or the optical power of the ASE dummy lights in sub-bands adjacent to the sub-band in which the new signal lights are to be added is controlled while increasing the optical power of the new signal lights so that the transmission characteristics of the existing signal lights are not affected by the signal addition.

Abstract: A method to expand a transmission capacity in a WDM optical transmission system including a first optical transmission unit to output to an optical transmission line a plurality of existing signal lights having existing wavelengths different from each other. The method comprises steps of providing a second optical transmission unit to output a plurality of additional signal lights having additional wavelengths different from each other and the existing wavelengths at an error correction ability higher than that of the existing signal lights, and controlling at least one of optical powers of the additional signal light and existing signal light so that the optical power of the additional signal light becomes lower than that of the existing signal light on the optical transmission line.

Abstract: An optical receiving apparatus according to the present invention comprises an optical receiver for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical receiver, an evaluator for evaluating transmission characteristics of the optical transmission line according to the received signal of the optical receiver, and a threshold controller for controlling the discrimination threshold of the discriminator according to the evaluated result of the evaluator.

Abstract: An optical receiving apparatus according to the present invention comprises an optical receiver for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical receiver, an evaluator for evaluating transmission characteristics of the optical transmission line according to the received signal of the optical receiver, and a threshold controller for controlling the discrimination threshold of the discriminator according to the evaluated result of the evaluator.

Abstract: An object of the present invention is to realize almost the same transmission characteristic in all wavelengths at a transmission rate of 10 Gb/s or more. An optical transmitter 10 outputs WDM signal light multiplexed with signal light of a plurality of wavelengths toward an optical transmission line 12. The optical transmission line 12 comprises an optical transmission fiber 14, an optical repeating amplifier 16 and a dispersion compensating fiber 18. The gain characteristic of the optical repeating amplifier 16 is set so that the gain becomes the maximum at the effective zero dispersion wavelength of the optical transmission line 12 and that lowers inversely proportional to the distance from the effective zero dispersion wavelength. The whole optical transmission line 12 is set so that the peak power deviation between the effective zero dispersion wavelength &lgr;0 and the wavelength &lgr;1 or &lgr;n on both end becomes approximately 4 dB.

Abstract: An optical signal generator comprises a light source to generate an optical carrier, a data modulator to modulate the optical carrier output from the light source with a transmission data, an optical phase modulator to modulate an optical phase of an output light from the data modulator in synchronization with the output light from the data modulator so as to emphasize one of sidebands, and an optical filter to remove harmonic components located outside the emphasized sideband out of an output light from the optical phase modulator.

Abstract: An optical receiving apparatus according to the present invention comprises an optical receiver for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical receiver, an evaluator for evaluating transmission characteristics of the optical transmission line according to the received signal of the optical receiver, and a threshold controller for controlling the discrimination threshold of the discriminator according to the evaluated result of the evaluator.

Abstract: To extend a distance of polarization-multiplexing, an optical transmitter in an optical transmission system has a first signal light output unit (24A, 124A) to output a first signal light (S1) of linear polarization to carry a first data (D1) using VSB modulation having one of sideband on a short wavelength side and sideband on a long wavelength side, a second signal light output unit (24B, 124B) to output a second signal light (S2) of linear polarization to carry a second data (D2) using VSB modulation having the other of sideband on a long wavelength side and sideband on a long wavelength side, and an optical coupler (26, 126) to couple the first signal light (S1) and the second signal light (S2) under different polarizations and output the coupled signal lights onto the optical transmission line (12, 112).

Abstract: An object of this invention is to manufacture an optical fiber cable having optical fibers with small characteristic differences at a high yield. Optical fibers in a first span are manufactured (S1), and each fiber is coated with a different color (S2). Each optical fiber is numbered in order of its chromatic dispersion value (S3). Optical fibers in a next span are manufactured (S4), and each optical fiber is arranged in order of its chromatic dispersion value (S5). Each optical fiber of the next span is coated with a color in inverse order to that of the antecedently connected optical fibers (S6). The optical fibers in the next span are connected to the antecedently connected optical fibers so that each optical fiber having a same color couples up (S7). Each connected optical fiber is renumbered in order of its chromatic dispersion value (S8). The operations of S4-S8 are repeated until reaching to a predetermined span number S9).

Abstract: To increase the number of multiplexed wavelengths and to improve transmission characteristics in a wavelength-division-multiplexed transmission, a bandwidth compressor for bandwidth-compressing the wavelength-division-multiplexed signal light is disposed at a front part of respective optical amplifiers and a bandwidth expander for bandwidth-expanding the wavelength-division-multiplexed signal light output from said optical amplifiers is disposed at a rear part of said optical amplifiers.

Abstract: A feature of this invention is to realize a VSB modulation with a simple configuration.

Abstract: An object of this invention is to manufacture an optical fiber cable having optical fibers with small characteristic differences at a high yield.

Abstract: A laser diode continuously laser-oscillates and its output light is applied to an optical modulator. A pulse driver drives the optical modulator according to a data to be transmitted. A phase modulator is driven by a phase modulator driver and phase-modulates the output from the optical modulator. The polarization direction of the incident light of the phase modulator is set so that the modulation efficiency of the phase modulator becomes the maximum. The output light of the phase modulator inputs a birefringent medium and applies to an optical transmission line after transmitting the birefringent medium. The principal axis of the birefringent medium is disposed so as to be at an angle of 45° to the polarization direction of the output light from the phase modulator.