Fujitsu Corporation

Michikazu Shima

Kazuo Yamane

Yumiko Kawasaki

Hiroyuki Itou

Yuji Tamura

Tsukasa Takahashi

Norifumi Shukunami

Shinya Inagaki

Kenji Tagawa

Yuji Miyaki

Kazuhiro Suzuki

Hiroshi Nishimoto

Takashi Tsuda

Yasunori Nagakubo

Yoshihito Onoda

Yoshinori Ohkuma

Keisuke Imai

An optical amplifier amplifies a wavelength-division-multiplexed optical input signal composed of optical signals having different wavelengths such that the output level of each of the optical signal is always optimized and such that the difference between the gains of the amplifier on the optical signals is minimized when the number of optical signals is two. The output level of the amplifier is controlled according to the number of the optical signals, to optimize the output level of each of the optical signals.

Wavelength-division-multiplexing optical amplifier

The object of the present invention is to provide an optical amplifying apparatus for collectively amplifying wavelength-division multiplexed signal lights, which can perform amplification in response to input signal light, whose power level is within a wide input dynamic range, without saturating, and which suppresses the influence of the wavelength dependency of gain thereof. Thus, this optical amplifying apparatus is composed of: three optical amplifying portions connected in cascade; an optical attenuating portion for controlling the level of signal light output from the optical amplifying portion provided in the post-stage by regulating the power level of signal light input to the optical amplifying portion provided in the middle stage; and a dispersion compensation fiber provided between the middle stage and post stage optical amplifying. A gain of each of the optical amplifying portions is controlled to be constant by an AGC circuit. As a result of providing the optical amplifying portions in a three-stage constitution, the gain of optical amplifying portion provided in the first stage can be set at a low value. Thus, even when a signal light having a high power level is input, the first stage optical amplifying portion does not saturate. Consequently, the gain is controlled to be constant.

Optical amplifying apparatus

The invention provides a multi-wavelength optical batch amplification apparatus wherein, upon batch amplification of a multi-wavelength input optical signal, the powers of optical signals on the input and output sides of an optical amplifier are monitored totally or individually to control the powers of optical signals of the output optical signal of the optical amplifier so that they may be fixed equally. The apparatus includes an entire input light detection section for monitoring the power of the entire input optical signals on the input side of the optical amplifier, an individual output light detection section for monitoring the powers of the output optical signals on the output side of the optical amplifier, an optical amplifier output adjustment section for adjusting the output of the optical amplifier, and a control section for controlling the optical amplifier output adjustment section based on results of detection by the entire input light detection section and the individual output light detection section so that the powers of the output optical signals on the output side of the optical amplifier may be fixed equally.

Multi-wavelength optical batch amplification apparatus

Spontaneous emission occurring in association with direct optical amplification using an erbium-doped optical fiber is modulated with an auxiliary signal, such as a supervisory signal, for transmission of the auxiliary signal. In a first aspect of the invention, the output of an optical amplifier is passed through a variable optical band-pass filter whose transmission characteristic is varied in accordance with the auxiliary signal, to modulate the spontaneous emission component contained in the optical amplifier output. In a second aspect of the invention, the output of the optical amplifier is separated by an optical branching device into a main optical signal and part of the spontaneous emission. The separated spontaneous emission component is modulated by being passed through a variable optical band-pass filter whose transmission characteristic is varied in accordance with the auxiliary signal, and then, the modulated spontaneous emission component is wavelength-division multiplexed with the main optical signal.

Auxiliary-signal transmission system

A control apparatus for an optical amplifier such as an erbium-doped optical-fiber (EDF) amplifier suppresses overshooting of ALC control at power on and at the time of input light restoration from an off condition, while ensuring quick starting. At power on and at the time of input light restoration from an off condition, an idling current (IDC) reference value generating circuit generates an IDC reference voltage that increases to a value sufficiently greater than a value in a normal operating condition with a time constant corresponding to a rise time of the EDF, and thereby controls a laser diode for pumping the EDF. The voltage may be set to a value larger than the value in the normal operating condition for a predetermined period of time by using a timer.

Control apparatus for optical amplifier

An optical amplifier amplifies a wavelength division-multiplexed optical input signal composed of optical signals having different wavelengths such that the output level of each of the optical signal is always optimized and such that the difference between the gains of the amplifier on the optical signals is minimized when the number of optical signals is two. The output level of the amplifier is controlled according to the number of the optical signals, to optimize the output level of each of the optical signals.

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

A drive circuit drives an electronic device that converts electric power into light or heat energy. The drive circuit has a switch connected to the electronic device in series, and a control circuit for providing, in response to an input control signal, a pulse modulation signal for controlling the switch. The frequency of the pulse modulation signal is higher than the response frequency of the electronic device. Alternatively, the drive circuit may have first to fourth switches disposed on both sides of the electronic device, for passing a current in different directions through the electronic device, and a control circuit for controlling the switches to change the direction and magnitude of the average of the current flowing through the electronic device in response to an input control signal.

Growing community of inventors

Kawasaki, Japan

Michikazu Shima