Nec Corporation

Masao Morie

Kouichi Suzuki

A skew adjustment method and a digital coherent receiver which can achieve skew adjustment without using a fixed pattern for skew detection are provided. A digital coherent receiver () includes: a chromatic dispersion adder () that adds chromatic dispersion to the optical multiplexed signal; a skew adjuster () that sets a quantity of skew adjustment for each of the plurality of channel signals obtained by detecting the optical multiplexed signal; and a skew controller () that is configured to, while monitoring signal quality of a reception signal obtained from the plurality of channel signals skew-adjusted, search for a quantity of skew adjustment at which the signal quality is made better.

Digital coherent receiver and skew adjustment method thereof

A coherent optical module includes an optical power monitor configured to monitor power of a wavelength multiplexed signal, a local oscillator configured to output a local oscillation light with an optical power corresponding to the monitored power of the wavelength multiplexed signal, a coherent receiver configured to receive an optical signal from the wavelength multiplexed signal by an interference with the local oscillation light, and a converter configured to convert the received optical signal to an electrical signal.

Coherent optical receiver device and coherent optical receiving method

A coherent optical receiver device includes a first unit configured to output local oscillation light having a predetermined wavelength, a second unit configured to receive an optical signal to have been inputted by making the optical signal interfere with the local oscillation light, a third unit configured to process electrically the optical signal received by the second unit, a fourth unit configured to monitor at least a part of power of the optical signal, and a fifth unit configured to control power of the local oscillation light output by the first unit depending on an optical power monitored by the fourth unit.

In an optical transmission system using an RZ code, in order to improve the quality of the modulated transmission signal, an RZ optical modulator includes an RZ carver that outputs a optical pulse train of the RZ code, a polarization adjustment device which improves and outputs a polarization extinction ratio of optical pulse train outputted from the RZ carver and an optical modulator which modulates and outputs the optical pulse train outputted from a polarization adjustment device.

RZ optical modulator and RZ optical modulation method

In a coherent optical receiver device, the control process for keeping received signals in high quality is complicated, therefore, a coherent optical receiver device according to an exemplary aspect of the invention includes a coherent optical receiver receiving input signal light; an input power monitor obtaining input power information determined on the basis of the power of the input signal light; a local oscillator connected to the coherent optical receiver; and a controller connected to the coherent optical receiver, the input power monitor, and the local oscillator; wherein the coherent optical receiver comprises a 90-degree hybrid circuit, a photoelectric converter, and an amplifier; the input power monitor is disposed in the optical path of the input signal light in a stage preceding the amplifier; and the controller obtains the input power information from the input power monitor and controls the power of local oscillation light output from the local oscillator on the basis of the input power information.

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Tokyo, Japan

Masao Morie