Fujitsu Corporation

Nippon Telegraph and Telephone Corporation

Keiko Takeda

Shinya Inagaki

Kenji Tagawa

Kazuya Sasaki

Sakae Yoshizawa

Koji Okamura

Hisayoshi Ikeda

Kaoru Moriya

Osamu Oyama

Nahoko Mase

Hiroshi Onaka

Norifumi Shukunami

Masayoshi Shigihara

Akihiko Ichikawa

Sinya Inagaki

Etsugo Yoneda

Shigeharu Maeda

Junko Shiraha

Kenji Ikenaga

Eiji Kinoshita

Akifumi Hirose

Matsudou Takahashi

Miyuki Hieda

An optical dropping apparatus and an optical add/drop multiplexer capable of dropping optical signals of an arbitrary wavelength from a WDM optical signal. The apparatus comprises a generating means for occurring four-wave mixing, a dropping means for dropping light of a predetermined wavelength, and a controlling means for controlling the wavelength of a pump light which is occurred four-wave mixing at the generating means. This apparatus is able to change the wavelength of the optical signals to be dropped, by changing the wavelength of the pump light.

Optical dropping apparatus and optical add/drop multiplexer

An optical amplifying fiber including a clad, a first core provided inside the clad and containing Ge, a second core provided inside the first core and containing Er and Al, and a third core provided inside the second core and containing Ge. The second core has a refractive index higher than that of the clad, and the first and third cores have refractive indexes each of which is higher than that of the second core. Since the third core having the high refractive index is provided at a central portion, it is possible to make smaller a mode field diameter and hence to improve a conversion efficiency of pumping light into signal light. Further, since the second core contains Al as an amplification band width increasing element, it is possible to sufficiently ensure a wide amplification band width.

Solution doping method of making an optical amplifying fiber

An optical amplifier which suppresses the occurrence of a nonlinear optical phenomena, such as four-wave mixing. The optical amplifier includes an optical fiber doped with a rare earth element, and a light source providing excitation light to the fiber so that a wavelength division multiplexed (WDM) light is amplified as the WDM light travels through the fiber from a first point to a second point along the fiber. A third point exists along the fiber between the first and second points at which a power of the WDM light substantially reaches a level producing a nonlinear optical phenomenal. A first portion of the fiber is between the first point and the third point, and a second portion of the fiber is between the third point and the second point. The second portion suppresses the occurrence of the nonlinear optical phenomena as compared to the first portion. The second portion can have various different constructions to provide the required suppression effect.

Optical fiber amplifier using optical fiber having a portion which suppresses nonlinear optical phenomena

With a dispersion compensating fiber 1, a dispersion compensating fiber material having a dispersion characteristic which is opposite to a dispersion characteristic of an optical transmission path, is formed with a rare-earth element doped region limited to an output side predetermined range of the full length of the fiber, while an input side region 1n is not doped with a rare-earth element. Due to this construction, signal light is amplified inside the doped region 1d even with low power excitation light, so that insertion losses in the dispersion compensating fiber are compensated. Moreover, by providing the dispersion compensating fiber between two stage optical amplifying sections, the noise factor for the overall optical amplifying section is reduced.

Dispersion compensating fiber and optical amplifier using same

An electronic photo album editing apparatus in which photo images are set on a mount displayed on a screen of a display unit so that an electronic photo album can be edited. The electronic photo album editing apparatus includes an image reading unit for reading photo images. The editing apparatus also includes an input unit for inputting the photo images read by the image reading unit and for setting a name of a photo group to which the photo images belong and a management unit for managing to what photo group the photo images input by the input unit belong. Further, a display controller for causing, with reference to information obtained by the management unit, photo images belonging to a specified photo group to be displayed on the screen and an editing unit for editing an electronic photo album using photo images displayed on the screen are also included in the electronic photo album editing apparatus.

Electronic photo album editing apparatus

An optical amplifying fiber including a center core region doped with erbium, aluminum, and phosphor, and a ring region doped with erbium and aluminum, the ring region being radially spaced a given distance from the center core region.

Optically amplifying fiber and optical fiber amplifier

Optical amplifying fiber and process of producing the same

There is provided a picture-forming device which is capable of easily drawing an arrow having a desired shape on a display screen of a display device, such as a CRT. The picture-forming device is capable of setting a basic shape of an arrow to be used in picture-forming. The basic shape of the arrow set is stored. When arrow display conditions indicative of a position, a direction, and a length of the arrow are entered via the display screen, data of the basic shape of the arrow and data of the arrow display conditions are synthesized, to display an image data thus synthesized, on the display screen.

Picture forming device

Picture plane data of a picture plane file is converted to picture plane data of a GIF file format on a frame unit basis by a picture plane data forming module. A list display picture plane in which a plurality of miniature picture planes are arranged is formed from scenario data and the image data of all frames by a list display picture plane forming module. Further, on the basis of the scenario data of a scenario file, a frame converting module forms scenario data of an HTML file format for switching to each frame picture plane by the selection of the miniature picture plane in the list display picture plane and the switching among the frame picture planes.

Apparatus and method for converting presentation data

In an optical amplifier for amplifying a signal light by propagating the signal light and a pumping light in a rare earth element doped fiber doped with a rare earth element, a diameter of a rare earth element doped portion of the rare earth element doped fiber is gradually reduced in a direction of propagation of the pumping light. With this construction, an adverse rare earth element doped area which does not contribute to optical amplification, but rather attenuates the pumping light, can be eliminated to thereby provide an optical amplifier having increased amplification efficiency.

Optical amplifier

An optical fiber amplifier employs an optical fiber and an optical coupler. The optical fiber has a core and a clad. The core has an erbium-aluminum-doped center and an erbium-doped annular section. The optical coupler guides signal light and pump light to the optical fiber, which amplifies the signal light using the pump light. The center of the core corresponds to a section where the field diameter of the signal light overlaps that of the pump light. The annular section is outside the field diameter of the pump light. The amplifier provides a required gain without employing optical parts such as filters. The signal light has a wavelength in the 1.5-micrometer band, and the pump light has a wavelength, in the 1.45-micrometer band, corresponding to the absorption band of erbium. The present invention may further employ pump light having a wavelength in the 0.98-micrometer band. The optical fiber may be doped with erbium and aluminum only in an annular section around the center of the core, to prevent a gain drop near a wave length of 0.98 micrometers.

Optical fiber amplifier

Disclosed is an optical amplifier, wherein efficient optical amplification of signal light of 1.3 .mu.m band is made achievable by optically exiting a doped fiber doped with Pr (praseodymium) alone, or together with other rare earth element, or a similar optical waveguide arrangement, and then supplying the optical waveguide arrangement with the signal light.

Optical amplifier for 1.3 .mu.m band

A high-output optical transmitter including a rare earth-doped fiber. The optical transmitter includes a signal light source for outputting signal light having a first predetermined plane of polarization and a pumping light source for outputting pumping light having a second predetermined plane of polarization. The plane of polarization of the signal light from the signal light source is rotated 45 degrees by a Faraday rotator such that the plane of polarization of the signal light output from the Faraday rotator and the pumping light are perpendicular to each other. The signal light from the Faraday rotator and the pumping light from the pumping light source are polarization-coupled by a polarization coupler and the combined light is introduced into the rare earth-doped fiber.

Optical transmitter including rare earth-doped fiber

An optical fiber amplifier in which light generated within an Er doped optical fiber by spontaneous emission is eliminated or suppressed. By inserting a wavelength demultiplexer in the Er doped optical fiber, the light generated within the optical fiber by spontaneous emission can be effectively eliminated. As an alternative, the Er doped optical fiber is arranged in a coil form with a predetermined radius of curvature to thereby effectively eliminate light due to spontaneous emission on the longer wavelength side than the signal light. Further, by doping the center portion of the core of an optical fiber with aluminum and the whole body of the core uniformly with erbium, it is made possible to suppress the generation of light by spontaneous emission without causing an adverse effect on the amplification performance of the signal light.

An optical fiber doped with Er is provided at its both end portions with a pair of 1.25 .mu.m band reflecting filters such that the distance therebetween becomes the resonator length for a light beam of 1.25 .mu.m band. When a pumping light beam of a wavelength of 0.8 .mu.m band is introduced into the optical fiber, laser oscillation at 1.25 .mu.m band is produced, whereby the energy level of Er in an excited state is lowered and a signal light beam of a wavelength of 1.55 .mu.m band can be optically amplified with high efficiency. Another fiber optic amplifier in which a pair of 0.98 .mu.m band reflecting filters are disposed at both end portions of an optical fiber doped with Yb and Er such that the distance therebetween becomes the resonator length for a light beam of 0.98 .mu.m band is also disclosed.

Growing community of inventors

Kawasaki, Japan

Keiko Takeda