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US 7,031,042 B2Granted
Signal converter for converting digital input signal to optical modulation signal
AssigneeHitachi Cable, Ltd.
InventorMasaki Ogura
Life of this patent
Estimating the term…
Abstract
A signal converter for converting a digital input signal to an optical modulation signal includes a pilot signal-superimposing circuit which superimposes a pilot signal on a bias control signal, a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator, a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal through a frequency deviation signal obtained from the monitor signal, and a second feedback system for providing the bias control the bias signal through a multiplying frequency deviation signal obtained from the monitor signal.
Claims14
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein:
- the first feedback system comprises a first mixer for multiplying the pilot signal and the monitor signal;
- a first low pass filter for providing the frequency deviation signal based on a low frequency component obtained from an output of the first mixer;
- and a first differential amplifier for providing the amplitude control signal in accordance with a difference between an output of the first low pass filter and a first reference signal.
7 more elements
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein:
- the second feedback system comprises a first oscillator for generating a multiplying frequency corresponding to a multiplication of the frequency of the pilot signal;
- a second mixer for multiplying an output of the first oscillator and the monitor signal;
- a second low pass filter for providing the multiplying frequency deviation signal based on a low frequency component obtained from an output of the second mixer;
- and a second differential amplifier for providing the bias control signal in accordance with a difference between an output of the second low pass filter and a second reference signal.
8 more elements
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein:
- the second feedback system comprises a second oscillator for generating the frequency of the pilot signal;
- a band pass filter for providing a harmonic wave contained in the pilot signal;
- a third mixer for multiplying the harmonic wave and the monitor signal;
- a third low pass filter for providing a multiplying frequency deviation signal based on a low frequency component obtained from an output of the third mixer;
- and a third differential amplifier for providing the bias control signal in accordance with a difference between an output of the third low pass filter and a third reference signal.
9 more elements
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein the second feedback system comprises a first oscillator for generating a twofold frequency of the frequency of the pilot signal.
4 more elements
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein the second feedback system comprises a second oscillator for generating the frequency of the pilot signal.
4 more elements
A signal converter for converting a digital input signal to an optical modulation signal, comprising:
- a Mach-Zehnder type optical modulator to be supplied with the digital input signals controlled in amplitude, and a bias signal for providing the optical modulation signal;
- a pilot signal-superimposing circuit for superimposing a pilot signal of a frequency on a bias control signal;
- a monitor circuit for providing a monitor signal by receiving a part of the optical modulation signal supplied from the optical modulator;
- a first feedback system for providing an amplitude control signal to control an amplitude of the digital input signal in accordance with a frequency deviation signal obtained from the monitor signal;
- and
- a second feedback system for providing the bias control signal to control the bias signal in accordance with a multiplying frequency deviation signal obtained from the monitor signal,
- wherein the second feedback system comprises:
- a first oscillator for generating a signal for interior reference of a twofold frequency of the frequency of the pilot signal;
- and
- a second oscillator for generating the frequency of the pilot signal.
7 more elements
Dependencies are inferred from the claim text.