Nippon Telegraph and Telephone Corporation

Fujikura Limited

Osaka Prefecture University Public Corporation

Shimane University

Ando Electric Company

University Public Corporation Osaka

National University Corporation Shimane University

Hiroji Masuda

Makoto Shimizu

Kazuo Aida

Shinichi Aozasa

Hirotaka Ono

Noboru Takachio

Makoto Yamada

Yutaka Miyamoto

Shoichiro Matsuo

Katsuhiro Takenaga

Junichi Kani

Kiyoshi Nakagawa

Kentaro Ichii

Kenichi Suzuki

Atsushi Mori

Hiroto Kawakami

Shingo Kawai

Naoto Sato

Ken-Ichi Suzuki

Kyouzou Tsujikawa

Yoshiki Nishida

Tadashi Sakamoto

Seiji Nogiwa

Kenji Sato

Tatsuhiko Takatsu

A plurality of coresis disposed around the center axis of a first claddingin a state in which an inter-core distance &#x39b; of cores adjacent to each other is equal, a refractive index nof the coreis provided higher than a refractive index nof the first cladding, and the refractive index nof the first claddingis provided higher than a refractive index nof a second cladding. Moreover, 5.8&#x2266;&#x39b;/MFD(2&#x3bb;c/(&#x3bb;c+&#x3bb;op))&#x2266;8 is satisfied, where the inter-core distance is defined as &#x39b;, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as &#x3bb;c, and a wavelength of communication light incident on the coreis defined as &#x3bb;op.

Amplifying optical fiber and optical amplifier

The first claddinghas a two-layer structure formed of a solid inner layerA passed through the center axis of the first claddingand an outer layerB enclosing the inner layerA and the plurality of coreswith no gap. A refractive index nof the coreis provided higher than refractive indexes nand nof the inner layerA and the outer layerB, the refractive indexes nA and nB of the inner layerA and the outer layerB are provided higher than a refractive index nof the second cladding, and the refractive index nof the inner layerA is provided lower than the refractive index nof the outer layerB.

An inline repeater that uses a forward-pumped DRA that can use a pumping light source such as an FBG pumping light source and a fiber laser, which are the most commonly used, and an optical fiber communication system are realized. The optical fiber communication system comprises silica fiber as a gain medium for Raman amplification to amplify a signal light; a pumping light source that emits a pumping light that co-propagates through the silica fiber in the same direction as the signal light; and a multiplexer disposed between the silica fiber and the pumping light source that multiplexes the signal light and the pumping light, with the multiplexer being provided with a means to multiplex the signal light input thereto having a wavelength longer than the zero-dispersion wavelength of the silica fiber and the pumping light emitted from the pumping light source, and the pumping light source being equipped with a means to emit pumping light, with the longest wavelength of the pumping light being shorter than the shortest wavelength of the signal light by a frequency difference on the low-frequency side of 13.7 to 30 THz.

Inline repeater and optical fiber communication system

An optical amplifier includes a rare-earth doped optical fiber or rare-earth doped optical waveguide serving as an amplification medium where rare-earth ions have been doped in its core and/or clad, an excitation mechanism for exciting the amplification medium, and a plurality of optical resonator that causes laser oscillation at a plurality of wavelengths of amplified spontaneous emission light produced in the amplification medium.

Optical amplifier having a constant gain profile

An optical amplifier includes a rare-earth doped optical fiber or rare-earth doped optical waveguide serving as an amplification medium where rare-earth ions have been doped in its core and/or clad, an excitation mechanism for exciting the amplification medium, an optical resonator that causes laser oscillation at one or more wavelength of spontaneous emission light produced and amplified in the amplification medium, a monitoring mechanism that monitors a power of at least one light selected from a power of at least one light with at least one prescribed wavelength band selected from the light inputted to the amplification medium and a power of at least one light selected from a power of at least one light with at least one prescribed wavelength band selected from the light outputted from the amplification medium, and a control unit that controls the excitation mechanism based on a value from monitoring mechanism.

Optical amplifier

An optical fiber communication system is provided which uses remote pumping that is capable of improving pumping efficiency and reducing a noise figure. A coupler () of a linear repeater () couples signal light to pumping light outputted from a pumping light source (). The outputted signal light and pumping light reach a linear repeater () through transmission fibers (to) and remote pumping modules (F andR). A coupler () of the linear repeater () couples the signal light to the pumping light supplied from a pumping light source (), to output the signal light and the pumping light to the transmission fiber (). The remote pumping module (F) divides the pumping light propagated in the transmission fiber (), from the signal light. The remote pumping moduleF branches the divided pumping light in two directions with a predetermined ratio. After branching, each of the branched pumping light is coupled to the signal light to be supplied to both ends of an erbium-doped fiber. The remote pumping module (R) is similar in structure to the remote pumping module (F).

Optical fiber communication system using remote pumping

An optical amplifier capable of holding the gain profile of the optical amplifier constant includcs a rare-earth doped optical waveguide serving as an amplification medium, a pump light source for exciting the amplification medium, one or more control light source, a monitor, and a control unit. A control method is also provided for using the amplifier for holding the gain profile of the optical amplifier constant by, for example, controlling the control light source so that the calculated gain is matched with a prescribed value or an externally decided value.

The present invention relates to a white light source. This white light source comprises a plurality of amplified spontaneous emission light generating sections each comprising at least an active fiber. At least two of the amplified spontaneous emission light generating sections are connected together in series. The plurality of amplified spontaneous emission light generating sections generate amplified spontaneous emission lights having at least partially overlapping wavelength ranges. Furthermore, a white light source of the present invention includes amplified spontaneous emission light generating sections each comprising at least an active fiber. At least one of the amplified spontaneous emission light generating sections comprises a mirror. If the white light source includes a plurality of amplified spontaneous emission light generating sections, at least two of the plurality of amplified spontaneous emission light generating sections are connected together in series to generate amplified spontaneous emission lights having at least partially overlapping wavelength ranges.

White light source

This invention relates to the following four structures for attaining a flat gain spectrum over a wide wavelength region. The first structure relates to a Raman amplifier where a tellurite fiber is pumped with two wavelengths having a predetermined difference. The second structure relates to a Raman amplifier or an optical communication system employing a tellurite fiber and a silica fiber. The third structure relates to an optical fiber amplifier employing an Erbium-doped tellurite fiber of which Erbium concentration is low. The fourth structure relates to an optical fiber amplifier employing a rare-earth doped fiber such as the Erbium-doped fiber and a tellurite fiber.

Optical fiber amplifier and optical communication system using the same

An optical fiber amplifier with a high conversion efficiency, which is capable of using the pump light in the wavelength band that can be emitted by the laser diode, is formed by an amplification optical fiber containing thulium at least in a core, to which a signal light is to be entered, and a pump light input unit configured to enter at least one pump light with a wavelength in a range of 1320-1520 nm, or more preferably 1320-1480 nm, into the amplification optical amplifier.

Thulium-doped fiber amplifier using pump light for improving conversion efficiency in a S-band

An optical amplifier is implemented which can reduce its size and cost by using a smaller number of components. Signal light coupled by an optical combiner with pump light fed from a pumping light source is incident on an EDF (erbium-doped fiber) to be pumped and amplified by the pump light, is emitted from the EDF to be incident on a second optical circulator and output from its second port, passes through an optical component to be fed back to the second optical circulator and launched into the EDF from the second optical circulator, passes through the EDF again in the direction opposite to the first passing direction followed by passing through the optical combiner, and is output from the third port of a first optical circulator.

Optical amplifier and optical fiber communication system using the amplifier

In the optical amplifier an optical divider based on long wavelength (or short wavelength) transmission type dielectric multi-layer filter divides input signal light according to wavelengths, and amplifying sections disposed in parallel and having different respective wavelength amplification regions respectively amplify light signals emitted from the optical divider, and an optical combiner based on long wavelength (or short wavelength) transmission type dielectric multi-layer filter combines light signals output from the respective amplifying sections. In another configuration of the optical amplifier, input signal light is divided using an optical divider based on a dielectric multi-layer filter of a long wavelength (or short wavelength) transmission type, and output signals from the divider are filtered using an optical filter connected in series to a short wavelength (or long wavelength) amplifier generating a loss in the long wavelength (or short wavelength) region of the light signals. Interference noise caused by residual reflection components in the dielectric multi-layer filter is thus suppressed, thereby increasing the bandwidth of useable wavelengths in the signal light.

An optical amplifier having a two-stage construction using an erbium doped fiber (EDF) as a gain medium. The erbium dopant concentration is 1000 ppm, and the unsaturated absorption coefficient of the signal beam at 1550 nm is 1 dB/m. The length of the EDF,-,is 10 m, and the length of the EDF,-,is 70 m. The excitation light sources,-,and,-,are semiconductor lasers of 1.53 &mgr;m, and the excitation light power is 100 mW. Multiplexers,-,and,-,are inductive multi-layer film filters, and the gain equalizer,-,is a Fourier filter. The peak loss of the Fourier filter is 17 dB. The gain of the EDF,-,is 25 dB, and the gain of the EDF,-,is 15 dB. Two optical isolators are installed on a pre-stage amplifier, and one on a post-stage amplifier in order to prevent laser oscillation.

Optical amplifier and transmission system using the same

The purpose of the invention is to offer an optical-frequency-stabilized light source with high accuracy and stability of the optical frequency. An optical splitter 8 splits output light from a local light source 7 into two beams. An optical detector 2 detects beat signals formed by the superimposition of the optical frequency difference between the local light source 7 and the output light, and a rectifier 3 rectifies the beat signal. A time measuring circuit 4 measures the time at which the beat signal was obtained. A frequency measuring circuit 5 measures the beat frequency. A CPU 6 outputs the deviation between the output light from the local light source 7 and the target optical frequency. A Fabry-Perot etalon transmission detection circuit 11 outputs an electrical signal corresponding to the optical frequency of the output light from an optical splitter 9. A control circuit 12 controls the optical frequency of the local light source 7 such that the electrical signal always matches the electrical signal corresponding to the target optical frequency. A Fabry-Perot etalon control circuit 10 corrects the relationship between the output electrical signal and the optical frequency of the light input to the Fabry-Perot etalon transmission detection circuit 11.

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Mito, Japan

Hiroji Masuda