Hybrid direct-modulated/external modulation optical transceiver

Patent metadata

Field	Value
Publication number	US-10116390-B2
Application number	US-201615185487-A
Country	US
Kind code	B2
Filing date	Jun 17, 2016
Priority date	Jun 19, 2015
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

Aspects of a method and system for feedback during optical communications are provided. In one embodiment, a system for optical communications comprises a predistortion module, a feedback subsystem, a transmit optical subsystem, and an external modulator. The predistortion module is operable to receive an input digital signal and modify the input digital signal to produce a digital predistorted signal. The transmit optical subsystem is operable to generate an optical signal from the digital predistorted signal. The modification of the input digital signal is dynamically controlled by the feedback subsystem according to one or more characteristics of the optical signal as determined by the feedback subsystem. The amplitude of the external modulator output is also dynamically controlled by the feedback subsystem.

First claim

What is claimed is:

1. A system for optical communications, comprising:
a predistortion module operable to modify an input digital signal to produce a digital predistorted signal;
a transmit optical subsystem operable to generate an optical signal from the digital predistorted signal, wherein the optical signal generated from the digital predistorted signal comprises an amplitude shift according to the modification;
a feedback subsystem operable to determine one or more characteristics of the optical signal, the feedback subsystem being operable to control the modification applied to the input digital signal by the predistortion module according to the one or more characteristics of the optical signal; and
an external modulator operable to modulate the optical signal, the amplitude of a modulated optical signal produced by the external modulator being controlled by the feedback subsystem to counteract the amplitude shift of the optical signal.

2. The system of claim 1 , wherein the one or more characteristics of the optical signal comprise a nonlinear relationship between the digital predistorted signal and the optical signal.

3. The system of claim 1 , wherein the feedback subsystem is operable to determine the modification of the input digital signal that reduces a dispersion characteristic of an optical channel.

4. The system of claim 1 , wherein the one or more characteristics of the optical signal comprise a temperature dependency.

5. The system of claim 1 , wherein the feedback subsystem comprises a backside monitor photodiode.

6. The system of claim 1 , wherein the one or more characteristics of the optical signal are dependent on a temperature of a laser diode in the transmit optical subsystem, wherein the temperature is determined according to a plurality of Volterra series coefficients and a comparison between the optical signal and an expected signal.

7. The system of claim 1 , wherein the feedback subsystem is operable to determine the one or more characteristics according to the modulated optical signal.

8. The system of claim 1 , wherein the feedback subsystem comprises a model extraction module operable to determine an optical channel model based on a feedback path in the transmit optical subsystem.

9. The system of claim 1 , wherein a high-speed, high-bandwidth photodiode intermittently monitors the external modulator.

10. A method for optical communications, wherein the method comprises:
modifying an input digital signal to produce a digital predistorted signal;
generating an optical signal from the digital predistorted signal, wherein the optical signal generated from the digital predistorted signal comprises an amplitude shift according to the modification;
determining one or more characteristics of the optical signal;
controlling the modification applied to input digital signal according to the one or more characteristics of the optical signal; and
controlling an external modulation of the optical signal to counteract the amplitude shift of a modulated optical signal, wherein the control of the external modulation is based on the modification of the input digital signal that produces the digital predistorted signal.

11. The method of claim 10 , wherein the method comprises estimating a dispersion of the digital predistorted signal over an optical channel.

12. The method of claim 10 , wherein the method comprises determining a temperature according to a predetermined behavior of the optical signal and updating the modification applied to input digital signal according to the temperature.

13. The method of claim 10 , wherein determining one or more characteristics of the optical signal comprises intermittently monitoring an external modulator using a high-speed, high-bandwidth photodiode.

14. The method of claim 10 , wherein determining one or more characteristics of the optical signal comprises modelling the modulation of the optical signal.

15. The method of claim 10 , wherein determining one or more characteristics of the optical signal comprises determining the modification of the input digital signal that compensates for dispersion over an optical fiber.

16. A non-transitory machine-readable storage having stored thereon, a computer program having at least one code section for enabling optical communications, the at least one code section being executable by a machine for causing the machine to perform operations comprising:
modifying an input digital signal to produce a digital predistorted signal, the digital predistorted signal being used by a transmit optical subsystem for generating an optical signal, wherein the optical signal generated from the digital predistorted signal comprises an amplitude shift according to the modification;
determining one or more characteristics of the optical signal;
controlling the modification applied to input digital signal according to the one or more characteristics of the optical signal; and
controlling an external modulation of the optical signal to counteract the amplitude shift of a modulated optical signal, wherein the control of the external modulation is based on the modification of the input digital signal that produces the digital predistorted signal.

17. The non-transitory machine-readable storage of claim 16 , wherein the at least one code section is executable to perform the operation of determining a dispersion of the digital predistorted signal over an optical channel.

18. The non-transitory machine-readable storage of claim 17 , wherein the at least one code section is executable to perform the operation of determining a temperature according to a predetermined behavior of the optical signal and updating the modification applied to input digital signal according to the temperature.

19. The non-transitory machine-readable storage of claim 16 , wherein the at least one code section is executable to intermittently monitor an external modulator according to the output of a high-speed, high-bandwidth photodiode.

20. The non-transitory machine-readable storage of claim 16 , wherein the at least one code section is executable to determine the modification of the input digital signal that compensates for dispersion over an optical fiber.

Assignees

• Maxlinear Inc

Inventors

• Ling Curtis
• Anandakumar Anand
• Spyropoulos Ioannis

Classifications

• H04B10/2507

  for the reduction or elimination of distortion or dispersion · CPC title

• H04B10/25133

  including a lumped electrical or optical dispersion compensator (H04B10/2519, H04B10/2525 takes precedence) · CPC title

• H04B10/6911

  Photodiode bias control, e.g. for compensating temperature variations · CPC title

• H04B10/516

  Details of coding or modulation · CPC title

• H04B10/58

  Compensation for non-linear transmitter output · CPC title