Mach-Zehnder type optical modulator, optical transmission/reception system and control method of Mach-Zehnder type optical modulator

Patent metadata

Field	Value
Publication number	US-9459511-B2
Application number	US-201314394313-A
Country	US
Kind code	B2
Filing date	Apr 3, 2013
Priority date	Apr 27, 2012
Publication date	Oct 4, 2016
Grant date	Oct 4, 2016

Abstract

A Mach-Zehnder type optical modulator according to the present invention is characterized by: that it comprises a beam splitting unit for splitting input light into two component light beams, a first waveguide and a second waveguide for guiding respective ones of the split component light beams, a beam combining unit for combining together the component light beams guided respectively by the first and second waveguides and outputting the combined light, a plurality of electrodes which are formed into electrode pairs as a result of being arranged on the first and second waveguides in a symmetric and parallel manner, and driving units for differentially driving respective ones of the electrode pairs in accordance with the magnitude relationships between the voltage of an input signal and respective ones of threshold voltages set individually for the electrode pairs; and that, by thus being driven differentially, the plurality of electrodes each apply a voltage for modulating the input light to the waveguide on which they are arranged.

First claim

What is claimed is:

1. A Mach-Zehnder type optical modulator comprising:
a beam splitting unit for splitting input light into two component light beams;
a first waveguide and a second waveguide for guiding respective ones of the split component light beams;
a beam combining unit for combining together the component light beams guided respectively by said first and second waveguides and outputting the combined light;
a plurality of electrodes which are formed into electrode pairs as a result of being arranged on said first and second waveguides in a symmetric and parallel manner; and
driving units for differentially driving respectively correlated ones of said electrode pairs in accordance with the magnitude relationships between the voltage of an input signal and respective ones of threshold voltages set individually for the electrode pairs,
wherein,
by thus being driven differentially, said plurality of electrodes each apply a voltage for modulating said input light to the waveguide on which they are arranged, and
wherein
said threshold voltages set individually for the electrode pairs are designed to be values which compensate for nonlinearity of the extinction characteristic of said output light.

2. The Mach-Zehnder type optical modulator according to claim 1 , wherein said threshold voltages set individually for the electrode pairs are designed in a manner to set the relationships between the amplitude of said input signal and phases given respectively to the component light beams guided by said first and second waveguides to be of arcsine curves.

3. The Mach-Zehnder type optical modulator according to claim 1 , further comprising a threshold voltage table in which threshold voltages set individually for the electrode pairs are registered in advance, wherein
said driving units extract said threshold voltages from the threshold voltage table.

4. The Mach-Zehnder type optical modulator according to claim 1 , further comprising:
a detection unit for detecting the intensity of said output light; and
a control unit for determining said threshold voltages on the basis of the intensity obtained by said detection and outputting the determined threshold voltages to said driving units.

5. The Mach-Zehnder type optical modulator according to claim 4 , wherein said control unit comprises DACs (Digital-to-Analog Converters), and thereby outputs threshold voltages in the form of digital signals to respectively correlated ones of said driving units.

6. The Mach-Zehnder type optical modulator according to claim 1 , further comprising two adding units which are correlated respectively with two symmetrically arranged electrodes, each summing up output signals from two or more driving units, and output the summed signals respectively to the correlated electrodes.

7. The Mach-Zehnder type optical modulator according to claim 6 , further comprising amplitude adjustment units which are arranged between respective ones of said adding units and said two or more driving units correlated with the adding units, and optionally adjust the amplitudes of signals outputted from said two or more driving units and output the adjusted signals to respective ones of said adding units.

8. A method for controlling a Mach-Zehnder type optical modulator,
the Mach-Zehnder type optical modulator comprising:
a beam splitting unit for splitting input light into two component light beams;
a first waveguide and a second waveguide for guiding the split component light beams;
a beam combining unit for combining together the component light beams guided respectively by said first and second waveguides; and
a plurality of electrodes which are formed into electrode pairs as a result of being arranged on said first and second waveguides in a symmetric and parallel manner,
the method comprising:
differentially driving each of said electrode pairs in accordance with the magnitude relationship between the voltage of an input signal and a corresponding one of threshold voltages set individually for said electrode pairs; and
by thus differentially driving each of said electrode pairs, applying voltages for modulating said input light to the waveguides on which the electrode pairs are arranged,
wherein
said threshold voltages set individually for the electrode pairs are designed to be values which compensate for nonlinearity of the extinction characteristic of said output light.

9. An optical transmission/reception system including:
an optical transmitter comprising a Mach-Zehnder type optical modulator according to claim 1 , which outputs an optical signal modulated by the Mach-Zehnder type optical modulator;
a transmission line on which said optical signal propagates; and
an optical receiver which receives said optical signal via said transmission line.

Assignees

• Nec Corp

Inventors

• Noguchi Hidemi

Classifications

• H04B10/541

  Digital intensity or amplitude modulation · CPC title

• G02F2001/212

  Physics · mapped topic

• G02F1/0121

  Operation of devices; Circuit arrangements, not otherwise provided for in this subclass · CPC title

• G02F1/0316

  Electrodes · CPC title

• G02F2201/16

  series; tandem · CPC title