Fujitsu Corporation

Kenichi Torii

Takao Naito

Toshiki Tanaka

Hiroshi Nakamoto

Toru Katagiri

Masahiro Yuki

The present invention has an object to provide a technology for monitoring the quality of a WDM signal light, capable of quickly and accurately judging an occurrence of quality deterioration of signal light and a deterioration factor thereof. To this end, according to a quality monitoring apparatus of WDM signal light of the present invention, a part of the WDM signal light being propagated through an optical transmission path is branched as a monitor light, a signal light of one wavelength contained in the monitor light is selected as a channel to be measured. Then, the frequency of occurrences of bit error for the channel to be measured is repeatedly measured for a plurality of times, and whether or not the signal quality is deteriorated is judged, together with the deterioration factor based on the measurement results, and a control signal light for adjusting the signal light power according to the judgment result is transmitted to the optical transmission path, to achieve the improvement of a characteristic of the WDM signal light.

Quality monitoring method and apparatus for wavelength division multiplexed optical signal and optical transmission system using the same

A plurality of pump light sources generate plural variations of pump light having different frequencies. A modulation circuit intensity-modulates the plural variations of pump light in the predetermined periods, respectively. A pump light pair whose frequency difference equals a Raman shift frequency are modulated such that they cannot simultaneously enters an emission state. A wavelength-multiplexer wavelength-multiplexes the plural variations of pump light modulated by the modulation circuit. A optical guide device guides the plural variations of pump light wavelength-multiplexed by the wavelength-multiplexer to an optical fiber.

Raman amplifier utilizing pump modulation for expanding gain band width

It is an object of the present invention to provide a Raman amplifier capable of easily reducing the wavelength deviation of a Raman gain while suppressing system performance degradation, and an optical transmission system using such a Raman amplifier. To this end, the Raman amplifier of the present invention supplies, to an amplification medium, first pumping lights arranged at equal wavelength spacing in a signal light wavelength band, which is shifted to a shorter wavelength side in accordance with a Raman shift frequency, and second pumping lights arranged in a wavelength band on a shorter wavelength side and a longer wavelength side than a wavelength band of the first pumping lights, the wavelength and power of which are set so that peak wavelength spacing of the Raman gain in the signal light wavelength band is substantially equal to each other, to Raman amplifies a WDM signal light, and reduces the wavelength deviation of power of the WDM signal light by using a gain equalizer having the periodicity corresponding to the peak wavelength spacing of the Raman gain.

Raman amplifier and optical transmission system using the same

The present invention aims at providing a Raman amplifier and an optical transmission system, capable of reducing characteristic deterioration to be caused by excitation lights mixedly existing within a wavelength band of signal lights. To this end, the Raman amplifier of the present invention comprises an excitation light source that generates excitation lights having a wavelength band overlapped with a wavelength band of the signal lights, a multiplexing unit that supplies the excitation lights to an optical transmission path, and an optical filter that suppresses optical components which are included in lights propagated through an optical transmission path and are of the same wavelengths as those of the excitation lights.

Growing community of inventors

Arakawa, Japan

Kenichi Torii