Fujitsu Corporation

Taiki Kobayashi

Hiroyuki Itou

Susumu Kinoshita

Shinya Inagaki

Tadashi Okiyama

Yasushi Sugaya

Miki Onaka

Hiroyuki Itoh

Norifumi Shukunami

Terumi Chikama

Yoshihito Onoda

Chihiro Ohshima

Norifumi c/o Fujitsu Hokkaido Digital Technology Limited Shukunami

Hiroyuki Fujitsu Hokkaido Digital Technology Limited Itoh

An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by &#x394;, the controller controls a level of the light received by the second optical amplifier to change by approximately &#x2212;&#x394;. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

Gain and signal level adjustments of cascaded optical amplifiers

An optical amplification device which includes first and second optical amplifiers, and a controller. The first optical amplifier receives a light and amplifies the received light. The second optical amplifier receives the light amplified by the first optical amplifier, and amplifies the received light. When a level of the light received by the first optical amplifier changes by &Dgr;, the controller controls a level of the light received by the second optical amplifier to change by approximately &minus;&Dgr;. In various embodiments, the controller causes the sum of the gains of the first and second optical amplifiers to be constant. In other embodiments, the optical amplification device includes first and second optical amplifier and a gain adjustor. The gain adjustor detects a deviation in gain of the first optical amplifier from a target gain, and adjusts the gain of the second optical amplifier to compensate for the detected deviation.

An optical amplifier of a wavelength-division multiplexing transmission system that includes a pre-stage optical amplifying unit and a post stage optical amplifying unit. The pre-stage optical amplifying unit has a rare-earth element doped optical fiber and a pump light source for inputting a pump light to the rare-earth element doped optical fiber. The post-stage optical amplifying unit has a second rare-earth element doped optical fiber and a pump light source for inputting a pump light to the second rare-earth element doped optical fiber. The pre-stage optical amplifying unit and the post-stage optical amplifying unit are optically connected by a detachable optical coupling device. In addition, a gain equalizing unit, positioned on an output side of the optical fibers, compensates for wavelength-dependency of a gain characteristic of the optical fibers.

Optical amplifier

An optical amplifying module having an internal pumping source is provided. WDM signal light obtained by wavelength division multiplexing a plurality of optical signals allocated to different wavelength channels is supplied to the optical amplifying module. An output power from the internal pumping source is adjusted so that the optical amplifying module provides a gain for the WDM signal light. A booster module having an external pumping source for supporting the gain is connected to the optical amplifying module. An output power from the external pumping source is set according to the number of channels of the WDM signal light. This method allows easy response to a change in the number of channels of the WDM signal light.

Method, apparatus, and system for optical amplification

Disclosed herein is an optical amplifier including an optical amplifying medium, a pumping source, an optical filter, and a control unit. Signal light is supplied to the optical amplifying medium. The pumping source supplies pump light to the optical amplifying medium so that the optical amplifying medium provides a gain band including the wavelength of the signal light. The optical filter is optically connected between the optical amplifying medium and the pumping source, and has wavelength selectivity depending upon temperature. The control unit controls the temperature of the optical filter according to a control signal given to the control unit. The wavelength characteristic of gain in the gain band provided by the optical amplifying medium changes according to the power of the signal light and the power and center wavelength of the pump light. When the temperature of the optical filter changes, the wavelength selectivity of the optical filter changes, so that the center wavelength of the pump light changes. Accordingly, the gain tilt of the optical amplifier can be adjusted.

Optical amplifier and system including the same

A wavelength division multiplexed (WDM) optical signal amplifier which amplifies optical signals having different wavelengths with minimized deviations in their respective output power levels, while maintaining the total optical output at a constant power level. An optical splitter, disposed at the output of the amplifier, splits off a fraction of the amplified WDM optical output signal for feedback purposes. This WDM optical feedback signal is subjected to a wavelength division demultiplexer, where the optical components contained in the signal are demultiplexed into separate optical feedback signals each having a different wavelength. A plurality of optical power level detectors detect the optical power levels of the individual optical feedback signals. Based on the detected optical power levels, a controller adjusts the individual output power levels of the plurality of electrical-to-optical converters, so that the optical power levels detected by the optical power level detectors will coincide with each other.

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Kawasaki, Japan

Taiki Kobayashi