Optical transmitter, optical transmission apparatus, and optical modulation method

Patent metadata

Field	Value
Publication number	US-2019020418-A1
Application number	US-201816030312-A
Country	US
Kind code	A1
Filing date	Jul 9, 2018
Priority date	Jul 14, 2017
Publication date	Jan 17, 2019
Grant date	—

Abstract

An optical transmitter includes, an optical modulator that multilevel-modulates light outputted from a light source, and a processor that outputs a first drive voltage for driving the optical modulator according to an amplitude component when transmission data is symbol-mapped and a second drive voltage for driving the optical modulator according to a phase component when the transmission data is symbol-mapped. A phase shift of phase modulation by the second drive voltage outputted from the processor is greater than 0 and less than π/2.

First claim

What is claimed is:

1 . An optical transmitter comprising:
an optical modulator configured to multilevel-modulate light outputted from a light source; a processor configured to output a first drive voltage for driving the optical modulator according to an amplitude component when transmission data is symbol-mapped and a second drive voltage for driving the optical modulator according to a phase component when the transmission data is symbol-mapped; and a phase shift of phase modulation by the second drive voltage outputted from the processor configured to be greater than 0 and less than π/2.

2 . The optical transmitter according to claim 1 , wherein the optical modulator outputs an optical signal having a waveform including a modulated light spectrum carrying the transmission data and a carrier spectrum protruding at an edge of the modulated light spectrum.

3 . The optical transmitter according to claim 1 , wherein the processor outputs the first drive voltage based on the intensity of the carrier spectrum and the amplitude component.

4 . The optical transmitter according to claim 1 , wherein the optical modulator includes an amplitude modulator and a phase modulator connected in series.

5 . The optical transmitter according to claim 1 , wherein the optical modulator is one Mach-Zehnder optical modulator.

6 . The optical transmitter according to claim 5 , wherein the processor outputs the first drive voltage in a differential mode and outputs the second drive voltage in a common mode.

7 . The optical transmitter according to claim 6 , wherein the processor outputs the first drive voltage to an RF terminal and outputs the second drive voltage to a DC terminal.

8 . The optical transmitter according to claim 1 , wherein the processor includes:
a setting circuit that sets a carrier-to-signal power ratio; a first drive voltage determination circuit that determines the first drive voltage based on the carrier-to-signal power ratio, the transmission data, and a modulation scheme; and a second drive voltage determination circuit that determines the second drive voltage based on the carrier-to-signal power ratio, the transmission data, and the modulation scheme.

9 . The optical transmitter according to claim 2 , wherein the processor includes:
a setting circuit that sets a carrier-to-signal power ratio; and a first drive voltage determination circuit that calculates the intensity of the carrier spectrum and the intensity of the modulated light spectrum based on the carrier-to-signal power ratio and determines the first drive voltage from the intensity of the carrier spectrum and the intensity of the modulated light spectrum.

10 . The optical transmitter according to claim 9 , wherein the first drive voltage determination circuit calculates the amplitude modulation amount of the transmission data based on the intensity of the modulated light spectrum, the transmission data, and the modulation scheme.

11 . The optical transmitter according to claim 4 , wherein the amplitude modulator is a directly modulated laser.

12 . An optical transmission apparatus comprising:
a first optical amplifier and a second optical amplifier; an optical receiver coupled to the first optical amplifier, configured to receive light of a targeted reception wavelength from the first optical amplifier; and an optical transmitter coupled to the second optical amplifier, configured to include an amplitude modulator to which a first drive voltage is applied and a phase modulator to which a second drive voltage is applied, the phase modulator being connected in series with the amplitude modulator, output an optical signal having a waveform including a modulated light spectrum in which transmission data outputted from the transmitter is modulated and a carrier spectrum protruding at an edge of the modulated light spectrum.

13 . An optical modulation method in an optical transmission apparatus, the method comprising:
generating an optical signal by which a phase shift of phase modulation by a second drive voltage is greater than 0 and less than π/2, based on a first drive voltage for driving an optical modulator according to an amplitude component when transmission data is symbol-mapped and the second drive voltage for driving the optical modulator according to a phase component when the transmission data is symbol-mapped.

14 . The optical modulation method according to claim 13 , wherein the optical signal having a waveform includes a modulated light spectrum carrying the transmission data and a carrier spectrum protruding at an edge of the modulated light spectrum.

15 . The optical modulation method according to claim 13 , comprising:
calculating an amplitude modulation amount of a transmission data and a phase modulation amount of the transmission data based on the intensity of the modulated light spectrum, the transmission data, and the modulation scheme; determining the first drive voltage for driving the optical modulator according to the amplitude modulation amount of the transmission data; and determining the second drive voltage for driving the optical modulator according to the phase modulation amount of the transmission data.

Assignees

• Fujitsu Ltd

Inventors

• Yamauchi Tomohiro
• Oyama Tomofumi
• Tanimura Takahito
• Huang Guoxiu
• Hoshida Takeshi

Classifications

• H04B10/5561

  Digital phase modulation · CPC title

• H04B10/5161

  Combination of different modulation schemes · CPC title

• H04B10/541 Primary

  Digital intensity or amplitude modulation · CPC title

• G02F1/225

  in an optical waveguide structure · CPC title

• G02F1/212

  Mach-Zehnder type · CPC title