The Furukawa Electric Co., Ltd.

The Tokyo Electric Power Company, Incorporated

Haruki Ogoshi

Masaru Fukushima

Masahito Morimoto

Akira Fujisaki

Hijiri Nimura

Shintaro Sentsui

Mitsuo Miyazaki

Morinobu Mizutani

Yoshio Tashiro

Yoshihiro Emori

Osamu Aso

Masateru Tadakuma

Atsushi Ogino

Isamu Oshima

Katsuya Kurotori

Hiroki Tachibana

Isamu Ohshima

A light source for Raman amplification to Raman-amplify signal light includes: plural incoherent light sources that output incoherent light; plural pumping light sources that output second-order pumping light; an optical fiber for Raman amplification to Raman-amplify the incoherent light with the second-order pumping light, and outputs the amplified incoherent light; and an output unit connected to the optical transmission fiber, receiving the amplified incoherent light, and outputting the amplified incoherent light as first-order pumping light having a wavelength that Raman-amplifies the signal light to the optical transmission fiber.

Light source for Raman amplification, light source system for Raman amplification, Raman amplifier, and Raman amplifying system

In an optical amplifier having a plurality of rare earth doped optical fibers in a multi-stage, there are provided one or more optical variable attenuator means, and an attenuation amount control means for changing an optical attenuation amount of the optical variable attenuator means on the basis of temperature of the rare earth doped optical fibers or an environmental temperature. In an optical amplifier having a plurality of rare earth doped optical fibers in a multi-stage, between the rare earth doped optical fibers, there are provided a replaceable optical part, one or more optical variable attenuator means, and an attenuation amount control means for changing an optical attenuation amount of the optical variable attenuator means on the basis of temperature of the rare earth doped optical fibers or an environmental temperature. In an optical amplifier having a plurality of rare earth doped optical fibers in a multi-stage, one or more externally controllable optical variable attenuator means are provided, and an optical attenuation amount of the optical variable attenuator means is varied with intensity of input optical signal to the optical amplifier and intensity of output optical signal from the optical amplifier.

Optical amplifier

An optical transmitter provided with a supercontinuum light source,which is composed of an optical amplifier,made by using a polarization maintaining amplification fiber,and a polarization maintaining fiber,which has a length of at least a specified value, is connected to the output side of the optical amplifier,and emits light having a continuous wave and a stable plane of polarization, a polarization maintaining optical demultiplexer,which takes out a light with a desired wavelength from the continuous wave light, and an external modulator,which superposes desired information upon the light with the desired wavelength.

Optical transmitter

A method of manufacturing an optical filter that can restrain the wavelength dependence of the gain of an optical amplifier. The input signal light power, output power of pump light source (,), and the output signal light power of an optical amplifier (,) are set to the power values used for optical communication systems, and the total power of the simulation input light of a plurality of wavelengths (&lgr;1, &lgr;2, . . . &lgr;n) from light sources (,) and an input light (probe light) from light sources (,) are set equal to the total power of the input signals of a plurality of wavelengths used in wavelength division multiplex transmission systems. In this condition, the input light are multiplexed and are launched into optical amplifier (,), and the amount of attenuation is variably adjusted so that the output power from optical amplifier (,) in correspondence to the probe light will be within the range determined by the maximum and minimum of the output power corresponding to the simulation input light to determine the attenuation amount corresponding to the wavelength of the probe light. The above operation is repeated upon varying the wavelength of the probe light, and loss spectrum of the optical filter is set to the loss spectrum of the attenuation amounts in one-to-one correspondence with the respective wavelengths.

Optical filter, manufacturing method thereof, and optical amplifier equipped with said optical filter

An optical fiber amplifier can maintain its optical power output above a level exceeding +20 dBm and a low noise figure if the input optical signal shows a high power level. It comprises a front stage amplifying optical fiber 11 doped with a rare-earth element and arranged in a front stage 10A thereof and a back stage amplifying optical fiber 12 also doped with a rare-earth element and arranged in a back stage 10B thereof, wherein the front stage amplifying optical fiber 11 is provided at the signal light input terminal 13 thereof with a first optical coupler 14 for coupling signal light and excitation light in a same direction and at the signal light output terminal 15 thereof with a second optical coupler 16 for coupling signal light and excitation light in opposite directions and the back stage amplifying optical fiber 12 is provided at the signal light input terminal 19 thereof with a third optical coupler 21 for coupling signal light and excitation light in opposite directions, the first, second and third optical couplers 14, 16 and 21 being connected respectively to a first excitation light source 17 for generating excitation light with the 1,480 nm wavelength, a second excitation light source 18 for generating excitation light with the 980 nm wavelength and a third excitation light source 22 for generating excitation light with the 1,480 nm wavelength.

High-output and low-noise optical fiber amplifier

A method to obtain polarization characteristics of an optical transmission medium is disclosed. Sequentially plural different states of polarized light are launched into the optical transmission medium. Intensities of light emerging from the optical transmission medium through combinations of optical elements are measured to obtain Stokes parameters from which Stokes vectors describing the emerging light corresponding to each of the plural sequentially launched states of polarization are obtained; for at least three different launched states of polarization, descriptors are used of these launched states of polarization and the Stokes vectors describing the corresponding emerging light to calculate a Jones matrix which mathematically models the changes that the launched light when described in terms of a Jones vector is subject to when passing through the optical transmission medium; and, the Jones matrix is used to describe the polarization characteristics of the optical transmission medium.

Method and apparatus for measuring the polarization characteristics of

A method of manufacturing an optical filter that can restrain the wavelength dependence of the gain of an optical amplifier. The input signal light power, output power of pump light source (8), and the output signal light power of an optical amplifier (4) are set to the power values used for optical communication systems, and the total power of the simulation input light of a plurality of wavelengths (.lambda.1, .lambda.2, . . . .lambda.n) from light sources (1a) and an input light (probe light) from light sources (1m) are set equal to the total power of the input signals of a plurality of wavelengths used in wavelength division multiplex transmission systems. In this condition, the input light are multiplexed and are launched into optical amplifier (4), and the amount of attenuation from light source (1m) to the input end (14) of optical amplifier (4) is variably adjusted so that the output power from optical amplifier (4) in correspondence to the probe light will be within the range determined by the maximum and minimum of the output power corresponding to the simulation input light to determine the attenuation amount corresponding to the wavelength of the probe light. The above operation is repeated upon varying the wavelength of the probe light, and loss spectrum of the optical filter is set to the loss spectrum of the attenuation amounts in one-to-one correspondence with the respective wavelengths.

Optical filter, manufacturing method thereof and optical amplifier

An Er-doped optical fiber amplifier is adapted to increase the length of transmission path by raising the intensity of pumped light. In an Er-doped optical fiber amplifier 1 for amplifying signal light by means of an Er-doped optical fiber 7, using a 1,530 nm band pumping source 8, 1,530 nm band pumped light is Raman-amplified by a 1,430 nm-1,450 nm band light source 9 on the transmission path of an optical fiber 5.

Er-doped optical fiber amplifier

There is provided an optical telecommunications method that can externally modulate a plane of polarization without producing any null point. According to the invention, in an optical telecommunications system for externally modulating the plane of polarization of the light being transmitted through an optical fiber for the transmission of a polarized wave signal by externally applying a signal to modify the state of polarization, the source of light for the transmission of a polarized wave signal is a fiber ring laser.

Optical telecommunications system

An apparatus and method for optical telecommunication includes introducing a laser beam emitted from a light source at a first station into an optical fiber, providing an ultrasonic wave obtained by modulating a voice signal by a signal-applying-device at a work section to the optical fiber, modulating a polarized light passing through the optical fiber in amplitude and frequency, receiving the polarized light with the shifted wave plane at a light-receiving section in a second station, detecting at the light-receiving section in the second station the polarized light which has been modulated by the signal-applying device in the work section, and demodulating the polarized light to obtain a voice signal.

Method and apparatus for polarized optical telecommunications using

A technique for identifying an optical transmission medium from a plurality of single-mode-type optical transmission media by using longitudinal middle portions of the media as an identification section by first exciting a particular optical transmission media by means of a polarized light, next applying either an electromagnetic action or a mechanical action to the particular optical transmission medium to modulate the polarized light and then identifying the particular optical transmission medium based on the deviation of the polarized plane of the polarized light.

Growing community of inventors

Tokyo, Japan

Haruki Ogoshi