Reduced-cross-talk coherent optical transmitter

Patent metadata

Field	Value
Publication number	US-10180588-B1
Application number	US-201816040121-A
Country	US
Kind code	B1
Filing date	Jul 19, 2018
Priority date	Jul 19, 2018
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

An electro-optical modulator includes a substrate comprising a first Mach-Zehnder modulator comprising a first waveguide and a second waveguide and a second Mach-Zehnder modulator comprising a first waveguide and a second waveguide. A first positive signal electrode is positioned on the substrate over the first waveguide of the first Mach-Zehnder modulator and a first negative signal electrode is positioned on the substrate over the second waveguide of the first Mach-Zehnder modulator. The first positive signal electrode and the first negative signal electrode are connected to a first differential signal input. A second positive signal electrode is positioned on the substrate over the first waveguide of the second Mach-Zehnder modulator and a second negative signal electrode positioned on the substrate over the second waveguide of the second Mach-Zehnder modulator. The second positive signal electrode and the second negative signal electrode are connected to a second differential signal input. A first ground electrode is positioned on the substrate between the first and second Mach-Zehnder modulators connected to ground potential. A second ground electrode is connected to ground potential and positioned on the substrate adjacent to the first Mach-Zehnder modulator such that the first positive signal electrode and the first negative signal electrode are between the second ground electrode and the first ground electrode. A third ground electrode is connected to ground potential and positioned on the substrate adjacent to the second Mach-Zehnder modulator such that the second positive signal electrode and the second negative signal electrode are between the third ground electrode and the first ground electrode. A plurality of first electrical connectors connect the first ground electrode to the second ground electrode and a plurality of second electrical connectors connect the first ground electrode to the third ground electrode. A spacing between at least two of the plurality of first electrical connectors is chosen to achieve a desired cross talk between an optical signal generated by the first Mach-Zehnder modulator and an optical signal generated by the second Mach-Zehnder modulator.

First claim

What is claimed is:

1. An electro-optical modulator comprising:
a) a substrate comprising a first Mach-Zehnder modulator comprising a first waveguide and a second waveguide and a second Mach-Zehnder modulator comprising a first waveguide and a second waveguide;
b) a first positive signal electrode positioned on the substrate over the first waveguide of the first Mach-Zehnder modulator and a first negative signal electrode positioned on the substrate over the second waveguide of the first Mach-Zehnder modulator, the first positive signal electrode and the first negative signal electrode being connected to a first differential modulation signal input;
c) a second positive signal electrode positioned on the substrate over the first waveguide of the second Mach-Zehnder modulator and a second negative signal electrode positioned on the substrate over the second waveguide of the second Mach-Zehnder modulator, the second positive signal electrode and the second negative signal electrode being connected to a second differential modulation signal input;
d) a first ground electrode positioned on the substrate between the first and second Mach-Zehnder modulators;
e) a second ground electrode positioned on the substrate adjacent to the first Mach-Zehnder modulator such that the first positive signal electrode and the first negative signal electrode are between the second ground electrode and the first ground electrode;
f) a third ground electrode positioned on the substrate adjacent to the second Mach-Zehnder modulator such that the second positive signal electrode and the second negative signal electrode are between the third ground electrode and the first ground electrode; and
g) a plurality of first electrical connectors connecting the first ground electrode to the second ground electrode and a plurality of second electrical connectors connecting the first ground electrode to the third ground electrode, wherein a spacing between at least two of the plurality of first electrical connectors is chosen to achieve a desired cross talk between an optical signal generated by the first Mach-Zehnder modulator and an optical signal generated by the second Mach-Zehnder modulator.

2. The electro-optic modulator of claim 1 wherein a spacing of at least two of the plurality of second electrical connectors is chosen to achieve the desired cross talk between the optical signal generated by the first Mach-Zehnder modulator and the optical signal generated by the second Mach-Zehnder modulator.

3. The electro-optic modulator of claim 1 wherein the plurality of first electrical connectors comprises an array of first electrical connectors.

4. The electro-optic modulator of claim 3 wherein the array of first electrical connectors comprises an array of first electrical connectors with a uniform spacing.

5. The electro-optic modulator of claim 1 wherein the plurality of second electrical connectors comprises an array of second electrical connectors.

6. The electro-optic modulator of claim 5 wherein the array of second electrical connectors comprises an array of second electrical connectors with a uniform spacing.

7. The electro-optic modulator of claim 1 wherein the spacing between at least two of the plurality of first electrical connectors comprises a spacing of about 250 microns.

8. The electro-optic modulator of claim 1 wherein at least one of the plurality of first electrical connectors comprises a bond wire.

9. The electro-optic modulator of claim 1 wherein at least one of the plurality of first electrical connectors comprises a via hole.

10. The electro-optic modulator of claim 1 wherein the substrate comprises a semiconductor material.

11. The electro-optic modulator of claim 10 wherein the semiconductor material comprises indium phosphide.

12. The electro-optic modulator of claim 1 wherein the first Mach-Zehnder modulator comprises an in-phase Mach-Zehnder modulator.

13. The electro-optic modulator of claim 11 wherein the second Mach-Zehnder modulator comprises a quadrature-phase Mach-Zehnder modulator.

14. The electro-optic modulator of claim 1 wherein the cross talk between the optical signal generated by the first Mach-Zehnder modulator and the optical signal generated by the second Mach-Zehnder modulator is less than −40 dB.

15. The electro-optic modulator of claim 1 wherein a modulation bandwidth of the optical signal generated by the first Mach-Zehnder modulator is greater than 10 GHz.

16. The electro-optic modulator of claim 1 wherein a modulation bandwidth of the optical signal generated by the first Mach-Zehnder modulator is greater than 25 GHz.

17. The electro-optic modulator of claim 1 wherein the spacing between at least two of the plurality of first electrical connectors is chosen to spoil a cavity resonance of the first Mach-Zehnder modulator, thereby improving a single channel signal integrity.

18. An IQ optical transmitter comprising:
a) an optical source;
b) an IQ modulator comprising:
i) a substrate comprising a first Mach-Zehnder modulator comprising a first waveguide and a second waveguide, the first Mach-Zehnder modulator having an input that is optically coupled to an output of the optical source, and a second Mach-Zehnder modulator comprising a first waveguide and a second waveguide, the second Mach-Zehnder modulator having an input that is optically coupled to the output of optical source;
ii) a first positive signal electrode positioned on the substrate over the first waveguide of the first Mach-Zehnder modulator and a first negative signal electrode positioned on the substrate over the second waveguide of the first Mach-Zehnder modulator, the first positive signal electrode and the first negative signal electrode being connected to a first differential signal input;
iii) a second positive signal electrode positioned on the substrate over the first waveguide of the second Mach-Zehnder modulator and a second negative signal electrode positioned on the substrate over the second waveguide of the second Mach-Zehnder modulator, the second positive signal electrode and the second negative signal electrode being connected to a second differential signal input;
iv) a first ground electrode positioned on the substrate between the first and second Mach-Zehnder modulators;
v) a second ground electrode positioned on the substrate adjacent to the first Mach-Zehnder modulator such that the first positive signal electrode and the first negative signal electrode are between the second ground electrode and the first ground electrode;
vi) a third ground electrode positioned on the substrate adjacent to the second Mach-Zehnder modulator such that the second positive signal electrode and the second negative signal electrode are between the third ground electrode and the first ground electrode; and
vii) a plurality of first electrical connectors connecting the first ground electrode to the second ground electrode and a plurality of second electrical connectors connecting the first ground electrode to the third ground electrode; and

c) an optical combiner with a first input coupled to an output of the first Mach-Zehnder modulator and a second input coupled to an output of the second Mach-Zehnder modulator and an output that provides an in-phase modulated optical signal in response to a first differential modulation signal applied to the first differential signal input and a quadrature modulated optical signal in response to a second differential modulation signal applied to the second differential signal input,
wherein a spacing between at least two of th

Assignees

• Finisar Corp

Inventors

• Lewen Robert
• Kaikkonen Andrei
• Daunt Christopher
• Chacinski Marek

Classifications

• G02F1/2257

  the optical waveguides being made of semiconducting material · CPC title

• G02F1/0121

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

• G02F1/025 Primary

  in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence) · CPC title

• G02F1/0316

  Electrodes · CPC title

• G02F2001/212

  Physics · mapped topic