LINEARIZED OPTICAL DIGITAL-TO-ANALOG MODULATOR

• US 20170294968A1
• Filed: 10/20/2016
• Published: 10/12/2017
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: Ramot at Tel Aviv University Limited (Tel Aviv University)
• Original Assignee: Ramot at Tel Aviv University Limited (Tel Aviv University)
• Inventors: EHRLICHMAN, Yossef, AMRANI, Ofer, RUSCHIN, Shlomo
• Granted Patent: US 10,033,465 B2
• Time in Patent Office: Days
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/015 based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction G02F1/03 takes precedence
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 2203/19 linearised modulation; reduction of harmonic distortions
• CPC Class Codes: G02F 7/00 Optical analogue/digital converters
• CPC Class Codes: H03M 1/002 Provisions or arrangements for saving power, e.g. by allowing a sleep mode, using lower supply voltage for downstream stages, using multiple clock domains or by selectively turning on stages when needed
• CPC Class Codes: H03M 1/70 Automatic control for modifying converter range
• CPC Class Codes: H04B 10/2575 Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
• CPC Class Codes: H04B 10/25891 Transmission components H04B10/40 takes precedence
• CPC Class Codes: H04B 10/505 using external modulation
• CPC Class Codes: H04B 10/5055 using a pre-coder
• CPC Class Codes: H04B 10/516 Details of coding or modulation
• CPC Class Codes: H04B 10/541 Digital intensity or amplitude modulation
• CPC Class Codes: H04B 10/556 Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]

Abstract

A system for converting digital data into a modulated optical signal, comprises an electrically controllable device having M actuating electrodes. The device provides an optical signal that is modulated in response to binary voltages applied to the actuating electrodes. The system also comprises a digital-to-digital converter that provides a mapping of input data words to binary actuation vectors of M bits and supplies the binary actuation vectors as M bits of binary actuation voltages to the M actuating electrodes, where M is larger than the number of bits in each input data word. The digital-to-digital converter is enabled to map each digital input data word to a binary actuation vector by selecting a binary actuation vector from a subset of binary actuation vectors available to represent each of the input data words.

Claims

1. A method for converting digital electrical data into modulated optical streams, said method comprising

inputting into an optical modulator N bits of digital data in parallel, N being larger than 1;

using a digital to digital converter to map a set of N input values corresponding to said N bits of digital data to a set of M output values where M is larger than N and where the input and output values are not identical;

using the M output values to drive at least M electrodes, enabled to modulate at least an optical input optical stream to provide at least a modulated output optical stream.

2. The method of claim 1, wherein the M electrodes are distributed over a plurality of waveguide branches and are enabled to modulate unmodulated optical input streams coupled to the waveguide branches.

3. The method of claim 1, wherein each value of the set of M output values drives a single electrode of the M electrodes.

4. The method of claim 3, wherein each value of the set of M output values drives a single electrode on a single branch of a plurality of waveguide branches.

5. The method of claim 3, wherein each value of the set of M output values drives a single electrode on each of a plurality of waveguide branches.

6. A method for converting N bits of digital data input to at least a modulated optical stream and transmitting the at least modulated optical stream, the method comprising:

inputting the N bits of digital data input in parallel into an optical modulator where N>

1;

converting the N bits of digital data input to M bits of digital output using a digital to digital converter, where M>

N;

inputting at least an unmodulated optical stream into the optical modulator;

driving M electrodes that are enabled to modulate the at least unmodulated optical input stream to generate at least a modulated optical output stream using the M bits of digital output of the digital to digital converter; and

transmitting the at least a modulated optical output stream over at least an optical fiber.

7. The methods of claim 6, wherein the M electrodes are distributed over a plurality of waveguide branches and are enabled to modulate unmodulated optical input streams coupled to the waveguide branches.

8. The method of claim 6, wherein each bit of digital output drives a single electrode of the M electrodes.

9. The method of claim 8, wherein each bit of digital output drives a single electrode on a single branch of a plurality of waveguide branches.

10. The system of claim 8, wherein bit of digital output drives a single electrode on each of a plurality of waveguide branches.

11. A method of modulating and transmitting at least an optical signal over at least an optical fiber in response to N bits of digital data in parallel, the method comprising:

inputting the N bits of digital data into an optical modulator having a plurality of waveguides, each carrying an unmodulated optical signal;

converting the N bits of digital data to M bits of digital output, where M>

N and N>

1;

coupling, using an electrode actuating device that is associated with the modulator, the M bits of digital output to the unmodulated optical signals, said coupling enabling modulation of the optical signals, thereby generating modulated optical signals;

transmitting the modulated optical signals over at least an optical fiber.

12. The method of claim 11, wherein each bit of digital output drives a single electrode on a single waveguide.

13. The system of claim 11, wherein bit of digital output drives a single electrode on each of the plurality of waveguides.

14. A method of modulating an optical signal according to a predetermined QAM constellation in response to N bits of parallel digital data input, and transmitting the optical signal over an optical fiber, the method comprising:

inputting the N bits of digital data input into an optical modulator within a module also containing at least a light source, wherein the optical modulator comprises a plurality of waveguides for receiving one or more unmodulated optical signals and outputting one or more modulated optical signals;

converting the N bits of digital data input to M bits of digital output, where M>

N and N>

1, wherein a value of said M is selected to produce a Symbol Error Rate that is consistent with a performance graph matching the predetermined QAM constellation;

coupling, using an electrode actuating device that is associated with the modulator, the M bits of digital output to the one or more unmodulated optical signals, using M actuating electrodes, said coupling causing modulation of the one or more unmodulated optical signals; and

transmitting the one or more optical signals over one or more optical fibers.

15. The method of claim 14, wherein each bit of the M bits of digital output drives a single electrode on a single waveguide of the plurality of waveguides.

16. The method of claim 14, wherein each bit of the M bits of digital output drives a single electrode on each of the plurality of waveguide.

17. The method claim 14, wherein the light source comprises an optical laser.

18. The method claim 14, wherein the light source comprises a light emitting diode (LED).

19. The method of claim 18, wherein the waveguides are waveguide branches.

20. The method of claim 19, wherein each bit of the M bits of digital output drives a single electrode on a single waveguide branch of the plurality of waveguide branches.

21. The system of claim 19, wherein each bit of the M bits of digital output drives a single electrode on each of the plurality of waveguide branches.

22. The method claim 19, wherein the light source comprises an optical laser.

23. The method claim 19, wherein the light source comprises a light emitting diode (LED).

24. A method of modulating and transmitting an optical signal over an optical fiber in response to N bits of digital data, the method comprising:

inputting the N bits of digital data into a module containing an optical modulator, the optical modulator having at least one waveguide carrying an unmodulated optical signal;

converting the N bits of digital data to M actuating voltage outputs, where M>

N and N>

1;

coupling, using an electrode actuating device that is associated with the optical modulator, the M actuating voltage outputs to the unmodulated optical signal, said coupling enabling modulation of the unmodulated optical signal;

transmitting the modulated optical signal over the optical fiber.

25. The method of claim 24, wherein in the modulated optical signal is a quadrature amplitude modulated (QAM) signal.

26. The method of claim 24, wherein the modulated optical signal is a pulse amplitude modulated (PAM) optical signal.

27. A method of modulating an optical signal according to a predetermined QAM constellation in response to N bits of parallel digital data input, and transmitting the optical signal over an optical fiber, the method comprising:

inputting the N bits of digital data into an optical modulator within a module also containing at least a light source, wherein the modulator contains a plurality of waveguide branches for receiving at least an unmodulated optical signal and outputting at least a modulated optical signal;

converting the N bits of digital data input to M bits of digital output, where M>

N and N>

1;

coupling, using an electrode actuating device that is associated with the electronic input and the modulator, the M bits of digital output to the unmodulated optical signals using M actuating electrodes, said coupling causing modulation of the at least an unmodulated optical signal; and

transmitting the modulated optical signals over optical fibers;

wherein a value of said M and a disposition of the M actuating electrodes on the plurality of waveguide branches is selected to produce a Root Mean Square Error that is consistent with a performance graph matching the predetermined QAM constellation.

28. A method of modulating and transmitting an optical signal over an optical fiber in response to N bits of digital data, the method comprising:

inputting the N bits of digital data into a module containing an optical modulator, the optical modulator having at least one waveguide carrying an unmodulated optical signal;

converting the N bits of digital data to M digital bits, where M>

N and N>

1;

using an electrode actuating device that is associated with the optical modulator and is responsive to the M digital bits, modulating the unmodulated optical signal;

transmitting the modulated optical signal over the optical fiber.