OPTICAL TRANSCEIVER WITH VARIABLE DATA RATE AND SENSITIVITY CONTROL

• US 20150171961A1
• Filed: 12/18/2013
• Published: 06/18/2015
• Est. Priority Date: 12/18/2013
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: FEATHERSTON, JOHN, ARCHER, CHRISTOPHER A., CICCHIELLO, JAMES M.
• Granted Patent: US 10,038,497 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power
• CPC Class Codes: H04B 10/11 Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
• CPC Class Codes: H04B 10/40 Transceivers
• CPC Class Codes: H04B 10/6932 Bandwidth control of bit rate adaptation

Abstract

An optical communications system includes a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver. A main detector is coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem. An adaptive data rate processor monitors the electrical signal from the main detector to determine a current power level for the optical signal. The adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

Claims

1. An optical communications system, comprising:

a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver;

a main detector coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem; and

an adaptive data rate processor to monitor the electrical signal from the main detector to determine a current power level for the optical signal, wherein the adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

2. The optical communications system of claim 1, further comprising a control output for the adaptive data rate processor, wherein the adaptive data rate processor asserts the control output to dynamically adjust a sensitivity level of the main detector.

3. The optical communications system of claim 2, wherein the adaptive data rate processor employs the control output to dynamically adjust a bias voltage on the main detector to adjust the sensitivity level of the main detector.

4. The optical communications system of claim 3, wherein the main detector is an avalanche photo diode (APD) that operates between a range of Geiger mode for high sensitivity and low bias mode for low sensitivity, wherein the adaptive data rate processor dynamically adjusts the reverse bias voltage on the APD to select the mode.

5. The optical communications system of claim 1, wherein the modem transmits a packet of data indicating a data rate change to an optical transmitter that communicates the data rate change to a remote transceiver based on a command from the adaptive data rate processor.

6. The optical communications system of claim 5, wherein the modem negotiates a new data rate with the remote transceiver by exchanging data packets that indicate the new data rate.

7. The optical communications system of claim 1, wherein the adaptive data rate processor commands the modem to a new data rate based upon detecting a power level change from the current power level, wherein the new data rate is based upon a predetermined power threshold.

8. The optical communications system of claim 1, further an auxiliary detector to detect a power level of the optical signal and to generate an electrical output signal representing the power level.

9. The optical communications system of claim 8, wherein the auxiliary detector is an avalanche photo diode (APD) that operates between a range of Geiger mode for high sensitivity and low bias mode for low sensitivity, wherein the adaptive data rate processor dynamically adjusts the reverse bias voltage on the APD to select the mode.

10. The optical communications system of claim 1, wherein the adaptive data rate processor dynamically adjusts the data rate based upon system mode.

11. The optical communications system of claim 10, wherein the system mode includes a coarse pointing mode where transmitter and receiver terminals are directed to search for other communicating terminals, a mid-mode for acquisition where the transmitter and receiver terminals are localized to a region, and a tracking-mode where the transmitter and receiver terminal have locked positions for transmitting and receiving data between the terminals.

12. The optical communications system of claim 11, wherein the adaptive data rate processor dynamically adjusts the data rate if tracking between the terminals during the tracking mode degrades to support reentry into the coarse pointing mode or the mid-mode.

13. The optical communications system of claim 1, wherein the adaptive data rate processor dynamically adjusts the data rate based upon an estimated bit error rate (BER).

14. The optical communications system of claim 1, wherein the adaptive data rate processor dynamically adjusts the data rate independently between a header portion and a data portion of a data packet.

15. The optical communications system of claim 1, wherein the adaptive data rate processor dynamically adjusts the data rate independently for transmitted data packets while receiving data packets with different information rates from the transmitted data packets.

16. The optical communications system of claim 1, wherein the adaptive data rate processor dynamically adjusts the data rate by repeating bits in a redundant pattern within a header portion or a data portion of a data packet to signal an increase or a decrease in the data rate.

17. The optical communications system of claim 16, wherein a receiver of the data packet senses the redundant pattern to dynamically increase or decrease the data rate.

18. The optical communications system of claim 1, further comprising a separate communications channel that is established between transmitter and receiver terminals to negotiate data rate changes, wherein the separate communications channel includes at least one of an electrical link, a radio frequency (RF) link, and a fiber optic link.

19. An optical communications system, comprising:

a modulator/demodulator (modem) to transmit outgoing communications data and to receive incoming communications data in a transceiver;

a main detector coupled to the modem to convert an optical signal representing the incoming communications data to an electrical signal for the modem;

an auxiliary detector to detect a power level of the optical signal and to generate an electrical output signal representing the power level; and

an adaptive data rate processor to monitor the electrical output signal from the auxiliary detector to determine a current power level for the optical signal, wherein the adaptive data rate processor dynamically adjusts a data rate of the modem based on the determined current power level of the optical signal.

20. The optical communications system of claim 19, further comprising a control output for the adaptive data rate processor, wherein the adaptive data rate processor asserts the control output to dynamically adjust a sensitivity level of the main detector or the auxiliary detector.

21. The optical communications system of claim 20, wherein the adaptive data rate processor employs the control output to adjust a bias voltage on the main detector or the auxiliary detector to dynamically adjust the sensitivity level of the main detector or the auxiliary detector.

22. The optical communications system of claim 21, wherein the main detector or the auxiliary detector is an avalanche photo diode (APD) that operates between a range of Geiger mode for high sensitivity and low bias mode for low sensitivity, wherein the adaptive data rate processor dynamically adjusts the reverse bias voltage on the APD to select the mode.

23. The optical communications system of claim 19, wherein the modem transmits a packet of data indicating a data rate change to an optical transmitter that communicates the data rate change to a remote transceiver based on a command from the adaptive data rate processor.

24. The optical communications system of claim 23, wherein the modem negotiates a new data rate with the remote transceiver by exchanging data packets that indicate the new data rate.

25. The optical communications system of claim 19, wherein the adaptive data rate processor commands the modem to a new data rate based upon detecting a power level change from the current power level, wherein the new data rate is based upon a predetermined power threshold.

26. The optical communications system of claim 19, wherein the adaptive data rate processor dynamically adjusts the data rate based upon system mode.

27. The optical communications system of claim 26, wherein the system mode includes a coarse pointing mode where transmitter and receiver terminals are directed to search for other communicating terminals, a mid-mode for acquisition where the transmitter and receiver terminals are localized to a region, and a tracking-mode where the transmitter and receiver terminal have locked positions for transmitting and receiving data between the terminals.

28. The optical communications system of claim 27, wherein the adaptive data rate processor dynamically adjusts the data rate if tracking between the terminals during the tracking mode degrades to support reentry into the coarse pointing mode or the mid-mode.

29. The optical communications system of claim 19, wherein the adaptive data rate processor dynamically adjusts the data rate based upon an estimated bit error rate (BER).

30. The optical communications system of claim 19, wherein the adaptive data rate processor dynamically adjusts the data rate independently between a header portion and a data portion of a data packet.

31. The optical communications system of claim 19, wherein the adaptive data rate processor dynamically adjusts the data rate independently for transmitted data packets while receiving data packets with different information rates from the transmitted data packets.

32. The optical communications system of claim 19, wherein the adaptive data rate processor dynamically adjusts the data rate by repeating bits in a redundant pattern within a header portion or a data portion of a data packet to signal an increase or a decrease in the data rate.

33. The optical communications system of claim 32, wherein a receiver of the data packet senses the redundant pattern to dynamically increase or decrease the data rate.

34. The optical communications system of claim 19, further comprising a separate communications channel that is established between transmitter and receiver terminals to negotiate data rate changes, wherein the separate communications channel includes at least one of an electrical link, a radio frequency (RF) link, and a fiber optic link.

35. An optical communications method, comprising:

detecting, by a processor, a current power level of a received optical signal in an optical transceiver;

determining, by the processor, if the current power level of the received optical signal has changed from a previous power level;

adjusting, by the processor, a data rate for the optical transceiver if the current power level of the received optical signal has changed from the previous power level; and

adjusting, by the processor, a sensitivity level of at least one detector in the optical transceiver if the current power level of the received optical signal has changed from the previous power level.

36. The method of claim 35, further comprising transmitting a packet of data indicating the data rate change via a line-of-site path to a remote transceiver.