Optical communications system

Patent metadata

Field	Value
Publication number	US-12348253-B2
Application number	US-202318151934-A
Country	US
Kind code	B2
Filing date	Jan 9, 2023
Priority date	Jan 10, 2022
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

An adaptive receiver comprising a current buffer, an inverter-based transimpedance that receives input from the current buffer, an average current control loop that feeds back from the inverter-based transimpedance to the current buffer, a variable gain circuit that receives input from the inverter-based transimpedance, a differential voltage amplifier that receives input from the variable gain circuit, an automatic gain control loop that feeds back from the differential voltage amplifier to the inverter-based transimpedance and variable gain circuit, and a differential buffer that receives input from the differential voltage amplifier.

First claim

What is claimed is:

1. An adaptive receiver, comprising:
a current buffer;
an inverter-based transimpedance that receives input from the current buffer;
an average current control loop that feeds back from the inverter-based transimpedance to the current buffer;
a variable gain circuit that receives input from the inverter-based transimpedance;
a differential voltage amplifier that receives input from the variable gain circuit;
an automatic gain control loop that feeds back from the differential voltage amplifier to the inverter-based transimpedance and variable gain circuit; and
a differential buffer that receives input from the differential voltage amplifier.

2. The adaptive receiver of claim 1 , further comprising an offset cancellation loop that feeds back from the differential voltage amplifier to the variable gain circuit.

3. The adaptive receiver of claim 2 , wherein the offset cancellation loop comprises:
a low-pass filter;
a second differential amplifier; and
a second differential transadmittance amplifier.

4. The adaptive receiver of claim 1 , wherein the variable gain circuit comprises:
a differential transadmittance amplifier that converts input voltage to current; and
a differential transimpedance amplifier that converts the current back to voltage.

5. The adaptive receiver of claim 4 , wherein the variable gain circuit comprises Miller capacitances to decrease total capacitance at output of the differential transadmittance amplifier.

6. The adaptive receiver of claim 1 , wherein the current buffer receives input current from a photodiode in an optical receiver.

7. The adaptive receiver of claim 1 , wherein the differential buffer outputs a recovered radio frequency signal.

8. The adaptive receiver of claim 7 , wherein the recovered radio frequency signal comprises a number of baseband signals.

9. The adaptive receiver of claim 1 , wherein the average current control loop comprises:
a low-pass filter; and
an amplifier.

10. The adaptive receiver of claim 1 , wherein the automatic gain control loop comprises:
a peak detector; and
an integrator.

11. The adaptive receiver of claim 1 , wherein the inverter-based transimpedance comprises a voltage-controlled, variable gain, inverter-based transimpedance amplifier.

12. A receiver system, that comprises:
an optical receiver comprising a photodiode;
an adaptive receiver that receives an input current from the photodiode, wherein the adaptive receiver comprises:
a feedback-controlled current buffer;
a voltage-controlled inverter-based transimpedance that receives input from the feedback-controlled current buffer;
a current control loop configured to feed back from the voltage controlled inverter-based transimpedance to the feedback-controlled current buffer and that automatically subtracts excessive average current of the photodiode from the input current;
a variable gain circuit that receives input from the voltage-controlled inverter-based transimpedance;
a differential voltage amplifier that receives input from the variable gain circuit;
an automatic gain control loop configured to feed back from the differential voltage amplifier to the voltage controlled inverter-based transimpedance and variable gain circuit;
a differential voltage amplifier that receives input from the variable gain circuit;
a differential buffer that receives input from the differential voltage amplifier and outputs a recovered radio frequency signal; and
a number of demodulators that demodulate the recovered radio frequency signal into respective baseband signals.

13. The receiver system of claim 12 , further comprising an offset cancellation loop that feeds back from the differential voltage amplifier to the variable gain circuit.

14. The receiver system of claim 13 , wherein the offset cancellation loop comprises:
a low-pass filter;
a second differential amplifier; and
a second differential transadmittance amplifier.

15. The receiver system of claim 12 , wherein the variable gain circuit comprises:
a differential transadmittance amplifier that converts input voltage to current; and

a differential transimpedance amplifier that converts the current back to voltage.

16. The receiver system of claim 12 , wherein the current control loop comprises:
a low-pass filter; and
an amplifier.

17. The receiver system of claim 12 , wherein the automatic gain control loop comprises:
a peak detector; and
an integrator.

18. An adaptative receiver, comprising:
a current buffer that receives input current from a photodiode;
a variable gain transimpedance amplifier connected to output of the current buffer;
an average current control feedback loop from the variable gain transimpedance amplifier back to the current buffer;
a differential transadmittance amplifier connected to output of the variable gain transimpedance amplifier;
a differential transimpedance amplifier connected to output of the differential transadmittance amplifier;
first and second capacitors connected between input and output of the differential transimpedance amplifier;
a differential voltage amplifier connected to output of the differential transimpedance amplifier;
an automatic gain control feedback loop from the differential voltage amplifier to the variable gain transimpedance amplifier and differential transimpedance amplifier; and
a differential buffer connected to output of the differential voltage amplifier.

19. The adaptive receiver of claim 18 , further comprising an offset cancellation feedback loop from the differential voltage amplifier to the differential transimpedance amplifier.

20. The adaptive receiver of claim 18 , wherein the differential buffer outputs a recovered radio frequency signal to a number of demodulators.

21. A communications system that comprises a receiver configured to convert a modulated coherent optical signal to a number of radio frequency signals encoding data, wherein the receiver comprises:
a current buffer;
an inverter-based transimpedance that receives input from the current buffer;
an average current control loop that feeds back from the inverter-based transimpedance to the current buffer;
a variable gain circuit that receives input from the inverter-based transimpedance;
a differential voltage amplifier that receives input from the variable gain circuit;
an automatic gain control loop that feeds back from the differential voltage amplifier to the inverter-based transimpedance and variable gain circuit;
a differential buffer that receives input from the differential voltage amplifier;
an optical receiver that generates an electrical current in response to receiving the modulated coherent optical signal; and
an adaptive circuit connected to the optical receiver, wherein the adaptive circuit is configured to execute the following:
recover a radio frequency signal from the electrical current;
adjust for changes in the modulated coherent optical signal caused by variation in received optical intensity occurring during propagation of the modulated coherent optical signal; and
output the radio frequency signal.

22. The communications system of claim 21 , wherein the optical receiver comprises:
a receiver telescope;
adaptive optics;
an optical amplifier;
an optical bandpass filter; and
a photodiode.

23. The communications system of claim 21 , further comprising an optical transmitter configured to generate the modulated coheren

Assignees

• Boeing Co
• California Inst Of Techn

Inventors

• Hunt Jeffrey H
• Aghlmand Fatemeh
• Emami Azita

Classifications

• H04B10/616

  Details of the electronic signal processing in coherent optical receivers · CPC title

• H04B10/27

  Arrangements for networking · CPC title

• H04B10/6165

  Estimation of the phase of the received optical signal, phase error estimation or phase error correction · CPC title

• H04B10/6164

  Estimation or correction of the frequency offset between the received optical signal and the optical local oscillator · CPC title

• H04B1/18

  Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H) · CPC title