QUADRATURE PHASE-SHIFT KEYING MODULATOR AND PHASE SHIFT AMOUNT CONTROLLING METHOD FOR THE SAME
First Claim
1. A quadrature phase shift keying modulator comprising:
- a first modulator which performs phase-shift keying modulation of input light with a first driving signal that is based on first data;
a second modulator which performs phase-shift keying modulation of input light with a second driving signal that is a driving signal based on second data and is different from the first driving signal in eye crossing percentage;
a phase shifting unit which performs phase shift processing in such a manner that a second optical signal, which is phase-shift keying modulated with a first optical signal being phase-shift keying modulated by said first modulator, and a second optical signal, which is phase-shift keying modulated by said second modulator, form a phase difference of π
/2 therebetween; and
a combining unit which combines the first optical signal and the second optical signal, which are subjected to the phase shift processing performed by said phase shifting unit, and hereby outputs quadrature phase-shift keying modulated light,said quadrature phase shift keying modulator being constructed in such a manner that an average light output power of the quadrature phase-shift keying modulation light output from said combining unit changes in accordance with a phase difference between a component of the first optical signal and a component of the second optical signal after being combined by said combining unit by means of applying driving signals different in eye crossing percentage by said first modulator and said second modulator, respectively,said quadrature phase shift keying modulator further comprising;
a power monitor which monitors an average light output power of the quadrature phase-shift keying modulation light output from said combining unit; and
a phase shift controlling unit which performs feedback control of the phase shift amount in said phase shifting unit based on the average light output power monitored by said power monitor.
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Abstract
The improved quadrature phase shift keying modulator has a structure such that the average light output power of phase-shift keying modulation light output from the combining unit is changed according to the phase difference between the first and the second optical signal after being combined by means of applying driving signals different in eye crossing percentage by the first modulator and the second modulator, respectively, and has a power monitor monitoring the average light output power of quadrature phase-shift keying modulated light and a phase shift controlling unit which performs feedback control of the phase shift amount in the phase shifting unit based on the average light output power monitored by the power monitor.
31 Citations
10 Claims
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1. A quadrature phase shift keying modulator comprising:
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a first modulator which performs phase-shift keying modulation of input light with a first driving signal that is based on first data; a second modulator which performs phase-shift keying modulation of input light with a second driving signal that is a driving signal based on second data and is different from the first driving signal in eye crossing percentage; a phase shifting unit which performs phase shift processing in such a manner that a second optical signal, which is phase-shift keying modulated with a first optical signal being phase-shift keying modulated by said first modulator, and a second optical signal, which is phase-shift keying modulated by said second modulator, form a phase difference of π
/2 therebetween; anda combining unit which combines the first optical signal and the second optical signal, which are subjected to the phase shift processing performed by said phase shifting unit, and hereby outputs quadrature phase-shift keying modulated light, said quadrature phase shift keying modulator being constructed in such a manner that an average light output power of the quadrature phase-shift keying modulation light output from said combining unit changes in accordance with a phase difference between a component of the first optical signal and a component of the second optical signal after being combined by said combining unit by means of applying driving signals different in eye crossing percentage by said first modulator and said second modulator, respectively, said quadrature phase shift keying modulator further comprising; a power monitor which monitors an average light output power of the quadrature phase-shift keying modulation light output from said combining unit; and a phase shift controlling unit which performs feedback control of the phase shift amount in said phase shifting unit based on the average light output power monitored by said power monitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A phase shift amount controlling method for a quadrature phase-shift keying modulator including:
- a first modulator which is operable to output a first optical signal obtained by means of phase-shift keying modulation of input light with application of a first driving signal thereto;
a second modulator which is operable to output a second optical signal obtained by means of phase-shift keying modulation of input light with application of a second driving signal thereto;
a phase shifting unit which performs phase shift processing in such a manner that the first optical signal and the second optical signal form a phase difference of π
/2 therebetween; and
a combining unit which combines the first optical signal and the second optical signal, which are subjected to the phase shift processing performed by said phase shifting unit and hereby outputs quadrature phase-shift keying modulation light, said method comprising;applying driving signals different in eye crossing percentage by said first modulator and said second modulator, respectively, and hereby changing an average light output power of phase-shift keying modulation light output from said combining unit in accordance with a phase difference between the first optical signal and the second optical signal formed by the phase shift processing; monitoring an average light output power of the phase-shift keying modulation light output from said combining unit; and performing feedback control of the phase shift amount in said phase shifting unit based on the monitored average light output power.
- a first modulator which is operable to output a first optical signal obtained by means of phase-shift keying modulation of input light with application of a first driving signal thereto;
Specification