Real-number photonic encoding

Patent metadata

Field	Value
Publication number	US-10608663-B2
Application number	US-201916412242-A
Country	US
Kind code	B2
Filing date	May 14, 2019
Priority date	Jun 4, 2018
Publication date	Mar 31, 2020
Grant date	Mar 31, 2020

Abstract

Optical encoders for encoding signed, real numbers using optical fields are described. The optical fields may be detected using coherent detection, without the need for independent phase and amplitude control. This encoding technique enables the use of simple and non-ideal modulators (e.g., modulators that provide neither pure phase nor pure amplitude modulation) for high-precision encoding. A photonic system implementing optical encoding techniques may include a modulator configured to be driven by a single electrical modulating signal and a coherent receiver. An optical transformation unit optically coupled between the modulator and the coherent receiver may transform the phase and/or the intensity of the modulated optical field. The optical encoding techniques described herein may be used in a variety of contexts, including high-speed telecommunications, on chip-phase sensitive measurements for sensing, communications and computing, and optical machine learning.

First claim

What is claimed is:

1. A photonic system comprising:
a modulator configured to be driven by a single electrical modulating signal;
a coherent receiver; and
an optical transformation unit optically coupled between the modulator and the coherent receiver, wherein the optical transformation unit comprises:
a first array of interconnected variable beam splitters (VBSs) comprising a first plurality of optical inputs and a first plurality of optical outputs;
a second array of interconnected VBSs comprising a second plurality of optical inputs and a second plurality of optical outputs; and
a plurality of controllable optical elements, each of the plurality of optical elements coupling a single one of the first plurality of optical outputs of the first array to a respective single one of the second plurality of optical inputs of the second array.

2. The photonic system of claim 1 , further comprising an electronic encoder configured to encode a signed, real number onto the single electrical modulating signal.

3. The photonic system of claim 1 , wherein the modulator, the coherent receiver and the optical transformation unit are disposed on a common semiconductor substrate.

4. The photonic system of claim 1 , wherein the modulator is configured to modulate an optical input signal based on the single electrical modulating signal in accordance with an on-off keying (OOK) modulation scheme.

5. The photonic system of claim 1 , wherein the modulator is configured to modulate an intensity and a phase of an optical input signal based on the single electrical modulating signal.

6. The photonic system of claim 5 , wherein the modulator is configured to impart the single electrical modulating signal onto the intensity of the optical input signal.

7. The photonic system of claim 1 , wherein the modulator is configured to output a modulated optical signal and a reference signal including an optical carrier, and wherein the coherent receiver is configured to beat the modulated optical signal as transformed by the optical transformation unit with the reference signal.

8. The photonic system of claim 1 , wherein the coherent receiver comprises a local oscillator and a photodetector.

9. The photonic system of claim 1 , wherein the optical transformation unit comprises an optical fiber.

10. The photonic system of claim 1 , wherein each of the VBSs of the first and second array comprises a Mach-Zehnder interferometer comprising:
a first beam splitter;
a second beam splitter; and
a first phase modulator configured to modulate a phase of light of an optical mode that couples the first beam splitter and the second beam splitter.

11. The photonic system of claim 1 , wherein each of the plurality of controllable optical elements comprises a phase shifter.

12. The photonic system of claim 11 , wherein each of the plurality of controllable optical elements further comprises an amplitude modulator.

13. The photonic system of claim 1 , further comprising a power tree having an input and a plurality of outputs, one of the plurality of outputs being coupled to the modulator.

14. The photonic system of claim 1 , further comprising at least one digital-to-analog converter (DAC) configured to adjust one or more parameters of the first plurality of interconnected VBSs.

15. The photonic system of claim 1 , wherein each of the controllable optical elements comprises a variable attenuator and at least one phase shifter.

16. The photonic processor of claim 15 , wherein each of the variable attenuators of the controllable optical elements comprises a Mach-Zehnder interferometer.

17. A method for optically processing signed, real numbers, the method comprising:
providing a value representative of a first real number;
modulating, based on the value, a phase of an optical signal and an intensity of the optical signal, the modulating comprising driving a modulator using a single electrical modulating signal;
transforming the modulated optical signal;
mixing the transformed, modulated optical signal with a reference optical signal to obtain an electric output signal; and
obtaining a second value representative of a second real number based on the electric output signal,
wherein transforming the modulated optical signal comprises:
coupling a plurality of optical pulses to a first array of interconnected variable beam splitters (VBSs);
coupling each of a plurality of optical outputs of the first array to one of a plurality of controllable electro-optic elements; and
coupling each of a plurality of optical outputs of the plurality of controllable electro-optic elements to a second array of interconnected VBSs.

18. The method of claim 17 , wherein transforming the modulated optical signal further comprises modulating a phase of the modulated optical signal and an intensity of the modulated optical signal.

19. The method of claim 17 , wherein the mixing the transformed, modulated optical signal with the reference optical signal comprises mixing the transformed, modulated optical signal with the reference optical signal using a coherent receiver.

20. The method of claim 17 , further comprising transmitting the reference optical signal from the modulator to the coherent receiver.

21. The method of claim 17 , further comprising generating the reference optical signal having a wavelength substantially equal to a wavelength of the optical signal.

22. The method of claim 17 , wherein the modulator comprises a resonant modulator, and wherein the modulating comprises varying a resonance characteristic of the resonant modulator based on the single electrical modulating signal.

23. The method of claim 17 , further comprising setting a phase of the reference optical signal to a reference phase, and determining the second real number from the second value based on the reference phase.

24. The method of claim 23 , wherein determining the second real number from the second value based on the reference phase comprises accessing a look-up table (LUT) mapping real numbers based on reference phase values.

25. The method of claim 17 , wherein transforming the modulated optical signal comprises transmitting the modulated optical signal through an optical fiber.

26. A method for fabricating a photonic system comprising:
fabricating a modulator configured to be driven by a single electrical modulating signal;
fabricating a coherent receiver; and
fabricating an optical transformation unit optically coupled between the modulator and the coherent receiver, wherein fabricating the optical transformation unit comprises:
fabricating a first array of interconnected variable beam splitters (VBSs) comprising a first plurality of optical inputs and a first plurality of optical outputs;
fabricating a second array of interconnected VBSs comprising a second plurality of optical inputs and a second plurality of optical outputs; and
fabricating a plurality of controllable electro-optic elements, each of the plurality of electro-optic elements coupling a single one of the first plurality of optical outputs of the first array to a respective single one of the second plurality of optical inputs of the second array.

27. The method of claim 26 , wherein fabricating the modulator, coherent receiver and optical transformation unit comprises fabricating the modulator, coherent receiver and optical transformation unit on a common substrate.

Assignees

• Lighmatter Inc
• Lightmatter Inc

Inventors

• Gould Michael
• Bunandar Darius
• Gupta Shashank
• Harris Nicholas C

Classifications

• H04B10/25

  Arrangements specific to fibre transmission · CPC title

• H04B10/524

  Pulse modulation · CPC title

• H04L27/02

  Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation (H04L27/32 takes precedence) · CPC title

• H04L27/04

  Modulator circuits; Transmitter circuits · CPC title

• H03M5/02 Primary

  Conversion to or from representation by pulses · CPC title