The Furukawa Electric Co., Ltd.

Kazunori Nakamura

Akira Fujisaki

Nobuyuki Kagi

Hijiri Nimura

Akira Oyobe

Haruki Ohgoshi

Yasumasa Sasaki

I Kou Tei

An optical amplification system capable of operating without being affected by the waveform of the incoming optical signal is provided for amplifying the optical signal in its optical waveguide by the effect of stimulated emission of a fluorescent substance induced by pumped light. According to a first aspect of the invention, an optical amplification system turns on its pumping source 8 when there is an optical signal s1 in the optical waveguide 5 whereas the pumping source 8 is kept off as long as no optical signal s1 is found in the optical waveguide 5 so that, when the pumping source 8 is turned on, pumped light from the pumping source 8 is fed to the optical waveguide 5 with a delay of time relative to the incoming optical signal s1. According to a second aspect of the invention, the inside of the optical waveguide 5 is constantly kept under an excited condition so that, when no optical signal s1 is found in the optical waveguide 5, dummy light s3 is fed to the optical waveguide 5, whereas no dummy light s3 is fed to the optical waveguide 5 once an optical signal s1 is introduced to the optical waveguide 5. With such an arrangement, since no optical amplification takes place at the rising edge of an incoming optical signal and hence the operation of optical amplification is not dependent on the waveform of the incoming optical signal, a safe and stable optical amplification system can be established.

Optical amplification system

Method of detecting an optical transmission line

There is provided a method of identifying a particular optical cable out of a plurality of similar optical cables in a simple, quick and accurate manner without requiring any significant additional cost. For identifying a particular optical cable C2 out of a plurality of optical cables C1 through C3 by means of a means for transmitting optical signals 11, a signal receiving/detecting means 13 and a signal applying device 16 and by utilizing the fluctuation in the level of optical signal due to the photoelastic effect that appears when external signals are applied to a cable carrying an optical signal, external signals are applied to the outer peripheral surface of each of the optical cable at a plurality of spots to boost the level of fluctuation of optical signal so that the particular optical cable can be identified without fail. Thus, the method of the present invention can be used to identify a particular optical cable out of a plurality of similar optical cables in an accurate and reliable manner by using a simple means of applying external signals.

Method of identifying a particular optical cable out of a number of

Quartz glass doped with rare earth element and production thereof

A sensing system using optical fibers having loss characteristics subject to variations of a signal light wave as a pumping light wave with a wavelength different from that of a pumping light wave is coupled into said optical fiber. Unlike conventional OTDRs that utilizes a light back scattering in an optical fiber, a sensing system using optical fibers according to the invention utilizes the light passing through an optical fiber as a detected signal in order to enhance the efficiency and effectiveness of the system and, therefore, it has a significantly improved S/N ratio and a dynamic range of measurement as compared with conventional OTDRs. Moreover, continuous light may be used for the signal light wave (detected signal) to increase the rate of light emission for detection and to reduce the time required for measurement.

Sensing system using optical fibers

Growing community of inventors

Yokohama, Japan

Kazunori Nakamura