Optical transmitter and optical transmission method

• US 8,879,925 B2
• Filed: 12/08/2011
• Issued: 11/04/2014
• Est. Priority Date: 12/13/2010
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Akiyama, Yuichi, Hoshida, Takeshi
• Primary Examiner(s): Bello, Agustin
• Application Number:
  US13/314,590
• Publication Number:
  US 20120148260A1
• Time in Patent Office: 1,062 Days
• Field of Search: 398182-201
• US Class Current: 398/193
• CPC Class Codes: H04B 10/505 using external modulation
• CPC Class Codes: H04B 10/588 in external modulation systems

Abstract

An optical transmitter includes: a digital signal processor to generate a drive signal from input data; a controller to control an amplitude or power of the drive signal according to information relating to the digital signal processing of the digital signal processor; and an optical modulator to modulate input light with the drive signal controlled by the controller to generate an optical signal.

Claims

1. An optical transmitter, comprising:

a digital signal processor configured to generate a drive signal from input data;

a controller configured to equalize an amplitude or power of the drive signal by controlling the amplitude or power of the drive signal to be substantially constant at a specified amplitude or power according to information relating to the digital signal processing of the digital signal processor; and

an optical modulator configured to modulate input light with the drive signal equalized by the controller to generate an optical signal, wherein

the digital signal processor includes a polarization scrambler to apply polarization rotation to the drive signal, and

the controller equalizes the amplitude or power of the drive signal according to an angle of polarization rotation applied by the polarization scrambler.

2. The optical transmitter according to claim 1, wherein the controller equalizes the amplitude or power of the drive signal with reference to amplitude or power of the drive signal at which an angle of polarization rotation applied by the polarization scrambler is zero.

5. The optical transmitter according claim 1, wherein the controller equalizes the amplitude of the drive signal to a specified amplitude with which the optical modulator operates in an optimal state.

6. The optical transmitter according to claim 1, wherein the optical transmitter receives instruction information which provides an instruction for the digital signal processing,

the digital signal processor generates the drive signal from the input data according to the instruction information, and

the controller equalizes the amplitude or power of the drive signal according to the instruction information.

7. The optical transmitter according to claim 1,

further comprising an oscillation controller to configured the drive signal to oscillate at a specified frequency,

wherein

the digital signal processor includes a polarization scrambler to apply polarization rotation to the drive signal, and

when an angle of polarization rotation applied by the polarization scrambler is zero or π

, the controller equalizes the amplitude or power of the drive signal according to a component of the specified frequency or a component of a frequency which is an integral multiple of the specified frequency included in the optical signal output from the optical modulator.

8. The optical transmitter according to claim 7, wherein when an angle of polarization rotation applied by the polarization scrambler is zero or π

, the controller equalizes the amplitude or power of the drive signal so as to maximize the component of a frequency which is twice the specified frequency included in the optical signal output from the optical modulator.

3. An optical transmitter, comprising:

a digital signal processor configured to generate a drive signal from input data;

a controller configured to equalize an amplitude or power of the drive signal by controlling the amplitude or power of the drive signal to be substantially constant at a specified amplitude or power according to information relating to the digital signal processing of the digital signal processor; and

an optical modulator configured to modulate input light with the drive signal equalized by the controller to generate an optical signal, wherein

the digital signal processor includes a mapper to generate the drive signal from the input data according to a specified modulation scheme, and

the controller equalizes the amplitude or power of the drive signal according to the modulation scheme.

4. An optical transmitter, comprising:

a digital signal processor configured to generate a drive signal from input data;

a controller configured to equalize an amplitude or power of the drive signal by controlling the amplitude or power of the drive signal to be substantially constant at a specified amplitude or power according to information relating to the digital signal processing of the digital signal processor; and

an optical modulator configured to modulate input light with the drive signal equalized by the controller to generate an optical signal, wherein

the digital signal processor includes a distortion equalizer to apply distortion to the drive signal to compensate for chromatic dispersion of an optical transmission line for transmitting the optical signal, and

the controller equalizes the amplitude or power of the drive signal according to the chromatic dispersion of the optical transmission line.

9. An optical transmission method, comprising:

generating a drive signal from input data and performing polarization scrambling to apply polarization rotation to the drive signal in digital signal processing;

equalizing an amplitude or power of the drive signal by controlling the amplitude or power of the drive signal to be substantially constant at a specified amplitude or power according to information relating to the digital signal processing; and

modulating an input light with the equalized drive signal to generate an optical signal,

wherein the amplitude or power of the drive signal is equalized according to an angle of polarization rotation by the polarization scrambling.