Hitachi, Ltd.

Other

Hitachi Communication Technologies, Ltd.

Junya Kosaka

Takayuki Suzuki

Hiroyuki Nakano

Shinji Sakano

Tadashi Matsuoka

Daisuke Yoshida

Hideyuki Kuwano

Tetsushi Nakano

Ichiro Yokota

Toshiki Sugawara

Kazuo Aida

Kenro Sekine

Yoshiaki Sato

An optical transmission apparatus includes a demultiplexer for separating wavelength-division multiplexing light received from a first optical transmission line into signals of different wavelengths to transmit the signals to an outside and a multiplexer for multiplexing signals of different wavelengths received from the outside to transmit multiplexed signals to a second optical transmission line. An input check unit is provided for monitoring a power level of a signal separated by the demultiplexer and for providing an output indicative thereof. An output adjuster is provided for intercepting a signal from the outside so as to inhibit receipt of the signal from the outside by the multiplexer depending on the output of the input check unit.

Optical transmission equipment preventing malfunction in recovery from fault

In order to obtain optical transmission equipment for wavelength division multiplexing for providing a small inter-wavelength deviation regardless of a change in an input level, an amplification band is divided with wavelengths at inflection points in a wavelength gain characteristic of an impurity-doped fiber. The equipment includes an optical filter unit and a optical gain adjusting unit. The optical filter unit obtains filter characteristics associated with wavelength gain characteristics for a plurality of input levels by changing a temperature thereof. The optical gain adjusting unit includes a wavelength gain characteristic shift filter having a Peltier element for controlling the temperate of the optical filter unit.

Filter with variable transmission character, optical transmission equipment and method of optical transmission

An optical amplifier which amplifies a multiplexed signal light which is multiplexed with a plurality of signals having different wavelengths. The optical amplifier includes an optical amplifying medium which amplifies the multiplexed signal light and outputs amplified multiplexed signal light, a first light separator which separates light having a specific wavelength from at least a part of the multiplexed signal light output from the optical amplifying medium, a first light receiver which inputs the light having the specific wavelength separated by the first light separator and measures a strength of the specific wavelength light, and a controller which controls an output of the optical amplifying medium such that the strength of the specific wavelength light becomes a first predetermined value.

Optical amplifier

An optical amplification apparatus for adjusting optical power of wavelength-multiplexed signal light at respective wavelengths and for adjusting the optical output power at the respective wavelengths and a deviation of the optical output power between the wavelengths. An optical power adjusting unit for receiving inputted light having signal light at a plurality of different wavelengths (&#x3bb;, &#x3bb;, &#x3bb;, . . . , &#x3bb;) multiplexed thereon, amplifying or attenuating light at least one wavelength included in the received light independently of light at different wavelengths from the wavelength of the light, is provided before or after an optical amplifier unit for amplifying the light having the signal light at the plurality of different wavelengths multiplexed thereon. Further, a control unit is provided for controlling the gain of amplification or attenuation performed by the optical power adjusting unit and the gain of amplification performed by the optical amplifier unit, respectively.

Optical amplification apparatus

Dependence on wavelength makes it difficult to lengthen the distance while increasing the density of wavelength division multiplexing. An optical signal expander module for a group of wavelength bands in a transmission system is provided and configured to solve the problem of dispersion and to achieve both a longer distance and higher density of wavelength division multiplexing that can be traded off.

Optical transmission equipment and supervisory system thereof

An optical transmission device which reduces optical noise in an optical transmission system. The optical transmission device includes a core light amplifying unit, and a first buffer light amplifying unit for amplifying a first signal light from a first transmission path and an amplified second signal light from the core light amplifying unit. The first buffer light amplifying unit supplies the core light amplifying unit with the first signal light, and supplies the first transmission path with the amplified second signal light. Also provided is a second buffer light amplifying unit for amplifying a second signal light from a second transmission path and an amplified first signal light from the core light amplifying unit. The second buffer light amplifying unit supplies the core light amplifying unit with the second signal light, and supplies the second transmission path with the amplified first signal light.

Optical transmission device and optical transmission system employing the same

An optical transmission equipment for use in an optical transmission system, having an optical amplifier ( A), comprising: a first optical doped fiber ( A); a second optical doped fiber ( B); a third optical doped fiber ( C); an optical isolator ( ) of bringing loss in the optical signal, being provided between the first optical doped fiber and the second optical doped fiber; a dispersion compensator ( ) being provided between the second optical doped fiber and the third optical doped fiber; and a pumping light source ( ) being optically connected to so that the optical doped fibers ( A, B, C) are excited in common.

Optical amplifier, optical transmission equipment, optical transmission system, and method thereof

The objective is an optical transmission unit capable of coupling and branching signal lights of individual wavelengths at a data rate of 10 Gbits/s. In order to achieve the objective, DCFs are provided and proper values of dispersion compensation are given, so that different characteristics depending on the respective wavelengths to be coupled, split and pass through without being split are obtained. The signal lights are amplified by a plurality of low-excitation optical amplifiers to regain their light levels which are weakened due to using an optical coupler, branching filter and DCF together, thereby enabling a long-distance transmission.

Optical transmission system and optical coupler/branching filter

An optical amplifier includes an optical amplifying medium having a multiplexed light input thereto and providing an output of amplified multiplexed light, an excitation source which excites the optical amplifying medium; and at least one of a first monitor for monitoring the amplified multiplexed light from the optical amplifying medium and a second monitor for monitoring the multiplexed light input to the optical amplifying medium. An operation amount of the excitation source for the optical amplifying medium is controlled using a monitoring result output from at least one of said first and second monitors.

An optical transmission device which reduces optical noise in an optical transmission system. The optical transmission device includes a core light amplifying unit and a first buffer light amplifying unit for amplifying a first signal light from a first transmission path and an amplified second signal light from the core light amplifying unit. The first buffer light amplifying unit supplies the core light amplifying unit with the first signal light, and supplies the first transmission path with the amplified second signal light. Also provided is a second buffer light amplifying unit for amplifying a second signal light from a second transmission path and an amplified first signal light from the core light amplifying unit. The second buffer light amplifying unit supplies the core light amplifying unit with the second signal light, and supplies the second transmission path with the amplified first signal light.

An optical amplifier includes an optical amplification medium which has simultaneous inputs of a WDM signal light and a pumping light and amplifies the WDM signal light, a pumping light source, and an amplification characteristic supervisor part which evaluates the gain tilt of amplified WDM signal lights. The supervisor part is provided in advance with a record of the relation between the medium output light power and the pumping light power corresponding to the output light power in terms of a number of proper curves plotted for certain gain tilts, and adapted to select a proper curve which is nearest to the relation in operation between the power of the pumping light which is incident to the medium in operation and the resulting amplified output light power from among the recorded proper curves, thereby determining the gain tilt of the medium based on the selected proper curve.

Method and apparatus for monitoring and controlling gain tilt in an optical amplifier

A variable attenuator is inserted into an optical input part and a feedback control is performed so that an optical input to an amplifying optical fiber becomes constant. Further, a control for changing a total optical output and an optical input to the amplifying optical fiber is performed on the basis of channel number information obtained from a supervisory signal. When light to/from an intermediate optical component is detected and the absence of the component is detected, pumping is suppressed, thereby avoiding occurrence of an optical surge at the time of connection of the optical component and a signal indicative of detachment of the optical component is generated.

Growing community of inventors

Fujisawa, Japan

Junya Kosaka