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(Nikkei BP Group)

(No.1 High-Tech News Site in Japanese)

  • NEC, Tohoku, NTT Technology Miniaturizes Optical Devices
  • September 17, 1998 (TOKYO) -- NEC Corp., Tohoku University and NTT Opto-electronics Laboratories jointly developed a technique to separate optical signals with different wavelengths.
    This will lead to miniaturization of optical communication circuits by one hundredth.

    An optical device, "photonic crystal," which was developed by Professor Shojiro Kawakami at Tohoku University, is used to separate such optical signals. This crystal is made of 0.2-micrometer alternate layers of highly refractive silicon and less-refractive SiO2. Each layer is honeycombed so that it possesses a 3-dimensional structure.

    An optical signal with an angle of incidence at this optical device is refracted by more than 60 degrees when its wavelength is changed from 0.99 to 1.0 micrometer. NEC calls that effect the "super prism effect." The refraction angle for a usual silicon prism is less than 1 degree under the same condition.

    Further, for a given wavelength it was observed that the refraction angles were changed from 0 to +/-90 degrees when the angles of incidence were changed from 0 to 12 degrees.

    Much attention has been paid to a wavelength division multiplexing (WDM) system that sends multiple optical signals with different wavelengths with a single optical fiber as a practical high-speed communication method today.

    Since the new optical device enables optical signals with different wavelengths to be separated, NEC is considering applying the device to the WDM system as an add/drop multiplexer.

    The size of such equipment will be about one-hundredth that of equipment in use at present. NEC aims to put it into commercial use five years from now.

    (Nikkei Electronics)

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    Updated: Wed Sep 16 18:42:57 1998 PDT