Oki Electric Industry Co., Ltd.

Shigeru Shikii

Mikiya Suzuki

Akira Sasaki

Toshio Nakamura

Katsuhiro Ishimura

Yukihiro Ozeki

Shusei Aoki

Hirokazu Ishimatsu

Naomi Oohashi

An optical transmission system according to the present invention includes a connection confirming circuit for confirming connection of an input data signal, a test signal generator for generating a test signal, and a switching device on a transmitter side. The switching device selectively generates the input data signal from an output terminal in the case where the input data signal is detected by the connection confirming circuit , and the test signal when the input data signal is not detected. An output of the switching device is connected to an optical transmitter TX. On a receiver side, there is provided a determination circuit for receiving an optical signal from a transmission path and detecting the test signal to determine transmission characteristics of the transmission path on the basis of the test signal.

Optical transmission system and optical channel available quality measuring method

An EDFA is comprised of a pre-amp and a post-amp which are connected in series, a photocoupler a long wave pass filter (LWPF) and an LWPF controller The photocoupler is connected to an input-stage of the EDFA and enters the light signal in the LWPF controller The LWPF is located between the pre-amp and the post-amp and its cutoff wavelength is adjustable. A short-wavelength-part of the light signal which is amplified by the pre-amp is cut off by the LWPF The LWPF controller detects an input signal power of the input light signal and adjusts the cutoff wavelength of the LWPF based on the detected input signal power. Gain of light signals which are output from the post-amp are equalized ranging the extensive input signal power and covering wide signal-wavelength bands.

Optical fiber amplifier

Optical fiber amplifiers with a simple composition than can accurately flatten optical output power in a fixed range are provided. Main optical amplifiers and first gain equalizers connected to these amplifiers are disposed between input port and output port. The main optical amplifiers comprise first EDFs which function as first amplification optical fibers, pumping light sources for providing pumping to drive the first EDFs using amplification characteristics, and second isolators. It is preferable for the second isolators to be isolators that can eliminate optical pumping power. The first gain equalizers are comprised by second absorption EDF. This second EDF operates such that the gain of the optical signal decreases in a non-pumping state or in a slight pumping state. The amplification characteristics used by the first EDF to amplify the optical signal power are opposite to the absorption characteristics used by the second EDF to absorb the optical signal power. Therefore, by means of passing a Wavelength Division Multiplexing Signal (WDM) through the first and second EDFs, only the portion of the Wavelength Division Multiplexing Signal (WDM) output from the first EDF that corresponds to the signal amplified by the first EDF is absorbed while a Wavelength Division Multiplexing Signal (WDM) passes through the second EDF. Because of this, the gain of the Wavelength Division Multiplexing Signal (WDM) ultimately output from an optical fiber amplifier is flattened.

Optical fiber amplifier and output power flattening method of optical fiber amplifier

An optical amplifier that can easily cope with alteration of characteristics and whereby a prescribed characteristic can be obtained in a stable fashion. In an optical amplifier, a plurality of optical components including optical amplification media that amplify input signal light are cascade-connected. There are provided (1) a temperature adjustment member capable of changing the temperature of one or a plurality of optical components in accordance with a temperature control signal that is input, and (2) a characteristic control device that supplies in respect of the temperature adjustment member a control signal that controls a prescribed optical characteristic having temperature dependence in one or a plurality of optical components that are the subject of adjustment by the temperature adjustment member, being a prescribed optical characteristic that is demanded for the optical amplifier.

Optical component, optical amplifier and method of controlling optical amplifier characteristic

Provided is a planar lightwave circuit module in which the required optical components constituting an optical fiber amplifier and representing components other than amplifying optical fibers are formed into a unitary structure on a common substrate. This planar lightwave circuit module comprises signal light input ports, signal light output ports, and first and second connection ports. The first connection port is connected to the signal light output ports and to one end of an amplifying optical fiber. The second connection port is connected to the signal light input ports and to the other end of the amplifying optical fiber. Optical coupling means for feeding pumping light from an pumping source to the amplifying optical fiber are also provided in the form of waveguides or in integrated form. Amplifying optical fibers are connected from the outside to the first and second connection ports of this planar lightwave circuit module, yielding an optical fiber amplifier.

Planar lightwave circuit module and optical fiber amplifying device

There is provided an optical amplifier for reducing the optical output power difference and/or obtaining high output power across a wide wavelength band. The optical amplifier comprises a plurality of optical amplifier units connected in two or more stages. At least one of the optical amplifier units comprises a first optical component of a single input and N outputs that has an optical-demultiplexing function, and P units of optical amplification means for the individual amplification of light that is output from P (where 1&lE;P&lE;N) output terminals selected from the N (integer) output terminals of the first optical component. Second optical components are provided to the input side of the first optical component or between the output side of the first optical component and the input side of the optical amplification means. The second optical components are optical components having chromatic dispersion compensation functions, optical components having functions designed to compensate for wavelength dependency output power difference, or optical components demonstrating other required effects. The optical components are DCFs, FBGs, SMFs, optical filters, attenuators, or the like. The second optical components are provided nonselectively or selectively.

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Tokyo, Japan

Shigeru Shikii