Fujitsu Corporation

Keisuke Imai

Yasunori Nagakubo

Kazuhiro Suzuki

Motoyoshi Sekiya

Hiroshi Yamada

Kazuo Yamane

Tsukasa Takahashi

Takashi Tsuda

Yumiko Kawasaki

Yuji Tamura

Hiroyuki Itou

Setsuo Misaizu

Michikazu Shima

Yuji Miyaki

Yoshinori Ohkuma

Akihiko Hayashi

Mitsuharu Noda

Yoshitaka Shimura

The present invention relates to an optical sender applicable to WDM (wavelength division multiplexing), and a primary object of the present invention is to prevent interchannel crosstalk in WDM. The optical sender includes a light source for outputting a light beam, an optical modulator for modulating the light beam in accordance with a main signal to output an optical signal, and a unit for shutting down the optical signal when receiving at least one of a power alarm relating to on/off of power supply and a wavelength alarm relating to the wavelength of the light beam.

Optical sender, terminal device, and optical communication system each having the optical sender

The present invention relates to A drive circuit can stabilize a bias voltage of an optical modulator to realize long distance transmission by preventing degradation of waveform, even if there is a dispersion on a characteristic of an electro-absorption modulator according to temperature and a secular change. The drive circuit supplies a driving voltage to an electro-absorption modulator which adsorbs a carrier light, depending on the driving voltage and outputting an intensity-modulated signal, and a peak value detector for detecting a peak value of a voltage at an anode of the electro-absorption modulator, and a bias current supplying circuit for supplying a bias current to control the driving voltage according to a difference between the peak value detected by the peak value detector and a predetermined value.

Drive circuit for electro-absorption modulator and optical transmitter

An optical transmitter and an optical communication system, each for providing a good transmission characteristic of a main signal and allowing suppression of SBS (stimulated Brillouin scattering). The optical transmitter comprises a light source for outputting a carrier beam, an optical modulator for modulating the carrier beam based on a main signal and sending out an optical signal into an optical fiber transmission line, an oscillator for outputting a low frequency signal, a first circuit for frequency or phase modulating the carrier beam based on the low frequency signal, and a second circuit for superposing an opposite phase signal having a phase opposite to that of the low frequency signal with the main signal and supplying a resulting signal to the optical modulator.

Optical transmitter and optical communication system

An optical transmitter including a light source for outputting a carrier light, an electro-absorption optical modulator for absorbing the carrier light according to an applied voltage to thereby output an intensity-modulated signal light, a device for applying an offset voltage to the optical modulator so that the applied voltage enters a region where the generation of the carrier light in the light source is stable, and a device for receiving an input signal to superimpose a modulation signal corresponding to the input signal on the offset voltage. This optical transmitter prevents wavelength chirping of the light source due to residual reflection in the optical modulator to thereby allow improvement in waveform.

Drive circuit for electro-absorption optical modulator and optical

The optical amplifier includes a doped fiber doped with a rare earth element, a pumping light source, means for introducing signal light and pumping light into the doped fiber, detection means for detecting whether or not amplified signal light is included in light outputted from the doped fiber, and means for decreasing the intensity of the pumping light when it is detected that amplified signal light is not included. It can be possible to eliminate an influence of an optical surge arising from a characteristic of the doped fiber.

Optical amplifier and optical transmission apparatus

Growing community of inventors

Kawasaki, Japan

Keisuke Imai