Nec Corporation

Norio Yanagi

Hiroaki Tanaka

Kenichi Nomura

Yasushi Hara

Takanori Fujisawa

A dummy bit elimination device in a coding apparatus for use in a submarine cable system. The dummy bit elimination device has a converter for eliminating only dummy bits from FEC (Forward Error Correction) code. The coding apparatus has an optical-to-electrical signal transducer, a demultiplexer, a coder for generating an FEC code, a multiplexer for multiplexing inputs, and an electrical-to-optical signal transducer. The dummy bit elimination device is inserted between the coder and the multiplexer so that the outputs of the coder are fed to the converter and an outputs of the converter are fed to the multiplexer.

Dummy bit elimination device and coding apparatus for FEC code word

A optical circuit includes a variable-wavelength optical notch filter having a notch wavelength, which receives optical WDM signals to allow an optical signal of the notch wavelength to be reflected and another optical signal to pass through. A control signal is detected from the optical WDM signals, and the notch wavelength of the variable-wavelength optical notch filter is controlled based on the control signal. The notch wavelength may be determined according to the control signal and is further controlled based on a signal level of a reflected optical signal reflected by the variable-wavelength optical notch filter such that the signal level of the reflected optical signal is maximized.

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Tokyo, Japan

Norio Yanagi