EML bias control system

Patent metadata

Field	Value
Publication number	US-9479263-B2
Application number	US-201414243984-A
Country	US
Kind code	B2
Filing date	Apr 3, 2014
Priority date	Apr 3, 2014
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

Systems and methods of minimizing distortion produced when modulating an optical signal using an electrical signal.

First claim

The invention claimed is:

1. A system comprising:
a modulator that has a first input for receiving an optical signal from an optical transmitter, a second input for receiving an electrical signal used by the modulator to modulate the optical signal, and an output for outputting a modulated optical signal, the modulator having a variable bias; and
a controller that measures distortion from the electrical signal input to the second input of the modulator and uses the distortion measured from the electrical signal input to vary the bias of the modulator, wherein the distortion measured from the electrical signal input is measured independently from distortion in the outputted modulated optical signal.

2. The system of claim 1 where the modulator is free from being operatively connected to a coupler.

3. The system of claim 1 where the controller selects a bias of the modulator that minimizes distortion produced by the modulator.

4. The system of claim 3 where the distortion minimized by the controller is a second order distortion.

5. The system of claim 3 where the distortion minimized by the controller is higher than a second order distortion.

6. The system of claim 1 where the optical transmitter is a laser integrally formed with the modulator.

7. The system of claim 1 where the modulated optical signal is output to a fiber optic network delivering content from a selected one of a head end to a node and a node to a head end.

8. A system comprising:
a transmitter having a modulator that has a first input for receiving an optical signal from a laser, a second input for receiving an electrical signal used by the modulator to modulate the optical signal, and an output for outputting a modulated optical signal, the modulator having a variable bias; and
a controller that receives distortion produced by the modulator and uses the distortion as feedback to control the bias of the modulator, where the distortion is measurable at the second input independently from distortion in the outputted modulated optical signal,
where the control of the bias of the modulator based on the distortion measurable at the second input is free from including a coupler operatively connected to the output of the modulator.

9. The system of claim 8 where the controller measures distortion from the electrical signal to the second input of the modulator and uses the measured distortion to vary the bias of the modulator.

10. The system of claim 8 where the controller selects a bias of the modulator that minimizes distortion produced by the modulator.

11. The system of claim 10 where the distortion minimized by the controller is a second order distortion.

12. The system of claim 10 where the distortion minimized by the controller is higher than a second order distortion.

13. The system of claim 8 where the laser is integrally formed with the modulator.

14. The system of claim 8 where the modulated optical signal is output to a fiber optic network delivering content from a selected one of a head end to a node and a node to a head end.

15. A method comprising:
modulating an optical signal from an optical transmitter by using an electrical signal;
delivering the modulated signal to a transmission network, the modulated signal having a distortion product reflected back in to the electrical signal;
measuring the distortion product from the electrical signal used to modulate the optical signal, wherein the distortion measured from the electrical signal is measured independently from distortion in the modulated optical signal;
using the distortion product measured from the electrical signal to minimize the distortion product.

16. The method of claim 15 including the step of splitting the electrical signal into a first path used to modulate the optical signal and a second path used to measure the distortion product.

17. The method of claim 15 where the optical signal is modulated by a modulator having a selectively variable bias, the method including the step of using the measured distortion product to vary the bias.

18. The method of claim 17 where the bias is varied to minimize the distortion product.

19. The method of claim 16 where an RF tap splits the electrical signal into the first and second paths, respectively.

20. The method of claim 15 where the distortion product is higher than a first order distortion.

Assignees

• Arris Entpr Inc

Inventors

• Schemmann Marcel
• Chasmawala Shamsuddin

Classifications

• G02F1/0123

  Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops · CPC title

• H04B10/58 Primary

  Compensation for non-linear transmitter output · CPC title

• H04B10/516

  Details of coding or modulation · CPC title

• H04B10/50572

  to control the modulating signal amplitude including amplitude distortion · CPC title

• G02F1/0327

  Operation of the cell; Circuit arrangements (G02F1/05 takes precedence) · CPC title