Abstract: The wavelength multiplex transmission device of the present invention includes a block band unit (block dispersion compensating unit etc.) for subjecting a plurality of signal lights of different wavelengths to dispersion compensation on a band basis and outputting the compensated signal lights, a CW light output unit (CW light source unit etc.) for outputting a CW light which supplements power of the signal light, a band multiplexing unit for multiplexing all the signal lights output from the block band unit together with the CW light output from the CW light output unit, and a total band optical amplifier for amplifying all the signal lights multiplexed by the band multiplexing unit in the lump and transmitting the amplified signal lights to a transmission path.

Abstract: An optical transmitter comprises a laser source, and two light-intensity modulators connected in series with the laser source. The first modulator modulates an optical signal based on a data signal and a first modulation signal. The second modulator modulates an optical signal based on a clock signal and a second modulation signal. First and second bias control circuits deliver first and second modulation signals as output, respectively. The first and second bias control circuits detect the first and second modulation signals in optical signal output respectively, and control bias voltages based on the detection results. As a consequence, optimum bias voltages are always applied independently of each other to the two light-intensity modulators.

Abstract: The wavelength multiplex transmission device of the present invention includes a block band unit (block dispersion compensating unit etc.) for subjecting a plurality of signal lights of different wavelengths to dispersion compensation on a band basis and outputting the compensated signal lights, a CW light output unit (CW light source unit etc.) for outputting a CW light which supplements power of the signal light, a band multiplexing unit for multiplexing all the signal lights output from the block band unit together with the CW light output from the CW light output unit, and a total band optical amplifier for amplifying all the signal lights multiplexed by the band multiplexing unit in the lump and transmitting the amplified signal lights to a transmission path.

Abstract: The object of the present invention is to provide a light limiter which can control the generation of an optical surge, comprises few components, and has high reliability; in order to achieve the object, the light limiter of the present invention comprise a parametric amplification element parametrically amplifying an input signal light, and a wavelength selection element removing a wavelength component, excepting a specified wavelength, from among the signal light output from said parametric amplification element.

Abstract: A wavelength-multiplexed light signal and noise light (or amplified spontaneous emission light) generated from an optical amplifier in an optical transmission line, along which the light signal is propagated is inputted to an input part 2. A noise light detector 3 detects the power level of the noise light in a predetermined wavelength range. A monitoring light detector 4 is provided as a stage subsequent to the noise light detector and serves to detect the power level of the light signal. Trouble occurrence in the optical transmission line is detected by computing the optical SN from the light power levels of different wavelength components.

Abstract: An optical modulation apparatus is provided with an optical modulator 2, a variable gain amplifying circuit 1 connected to this optical modulator 2, a detecting circuit 3 and a gain control circuit 4. A modulated input signal is entered into the variable gain amplifying circuit 1, and the variable gain amplifying circuit 1 amplifies this signal and delivers it to the optical modulator 2 as modulation drive signal. The detecting circuit 3 controls the variable gain amplifying circuit 1 on the basis of the detected signal. This optical modulation apparatus manifests steady optical modulation characteristics even if the amplitude of modulated input signals or ambient temperature varies.

Abstract: An optical transmitter comprises a laser source, and two light-intensity modulators connected in series with the laser source. The first modulator modulates an optical signal based on a data signal and a first modulation signal. The second modulator modulates an optical signal based on a clock signal and a second modulation signal. First and second bias control circuits deliver first and second modulation signals as output, respectively. The first and second bias control circuits detect the first and second modulation signals in optical signal output respectively, and control bias voltages based on the detection results. As a consequence, optimum bias voltages are always applied independently of each other to the two light-intensity modulators.

Abstract: The object of the present invention is to provide a light limiter which can control the generation of an optical surge, comprises few components, and has high reliability; in order to achieve the object, the light limiter of the present invention comprise a parametric amplification element parametrically amplifying an input signal light, and a wavelength selection element removing a wavelength component, excepting a specified wavelength, from among the signal light output from said parametric amplification element.

Abstract: The object of the present invention is to provide a light limiter which can control the generation of an optical surge, comprises few components, and has high reliability; in order to achieve the object, the light limiter of the present invention comprise a parametric amplification element parametrically amplifying an input signal light, and a wavelength selection element removing a wavelength component, excepting a specified wavelength, from among the signal light output from said parametric amplification element.

Abstract: The optical fuse of the present invention comprises: at least one light heatable portion for receiving an incident beam, and at least one thermally sensitive degradable portion with transparency and reflectivity, positioned in contact with the light heatable portion. The light heatable portion contains a light heatable material which generates heat depending on a specified light intensity of the incident beam. The thermally sensitive degradable portion contains a thermally sensitive degradable material which loses or reduces its transparency and reflectivity, depending on the heat generated by the light heatable portion when the light intensity of the incident beam exceeds a threshold value.

Abstract: Light signals having different oscillation wavelengths issued from a plurality of light sources are optically modulated and combined into a combined light signal to be later transmitted. The combined light signal is partly passed through an optical band pass filter and then sent to an optical detector so that the optical detector detects input timing of the light signals of the respective wavelengths in the combined light signal. A driving voltage detection circuit detects a voltage value of a driving electric signal corresponding to an output detection pulse of the optical detector to associate the respective wavelengths of the light signals with the corresponding voltage values. When a comparator finds a difference between the voltage values of the adjacent wavelengths and judges that the difference is smaller than a set value, an alarm generator issues an alarm indicating that the wavelengths are close.

Abstract: A light intensity attenuator and attenuating method is provided, by which a pulse-shaped optical surge can be attenuated and an optical signal component using desired light intensity can be output by using a simpler structural arrangement, and without using many optical components and circuits. In this method, an optical signal including a pulse-shaped optical surge component is received, and the optical signal is again output after the light intensity of the surge component is attenuated by a desired amount.