Continuous carrier optical phase optometric measurement over coherent optical communication link

• US 10,148,352 B1
• Filed: 07/11/2017
• Issued: 12/04/2018
• Est. Priority Date: 07/11/2017
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Yang, Guangning, Chen, Jeffrey R.
• Primary Examiner(s): Vanderpuye, Ken N
• Assistant Examiner(s): Alagheband, Abbas H
• Application Number:
  US15/646,687
• Time in Patent Office: 511 Days
• Field of Search: 398 25, 398 66, 398 70
• CPC Class Codes: B64G 1/24 Guiding or controlling apparatus, e.g. for attitude control
• CPC Class Codes: B64G 1/66 Arrangements or adaptations of apparatus or instruments, not otherwise provided for
• CPC Class Codes: B64G 3/00 Observing or tracking cosmonautic vehicles
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/74 Systems using reradiation of electromagnetic waves other than radio waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 17/933 of aircraft or spacecraft
• CPC Class Codes: G08B 13/08 by opening, e.g. of door, of window, of drawer, of shutter, of curtain, of blind
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
• CPC Class Codes: H04B 10/079 using measurements of the data signal
• CPC Class Codes: H04B 10/503 Laser transmitters
• CPC Class Codes: H04B 10/61 Coherent receivers
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04J 14/00 Optical multiplex systems
• CPC Class Codes: H04L 7/0075 with photonic or optical means

Abstract

An apparatus for measuring a distance between a first and second terminal includes a frame counter for determining a number of data frames traversing a distance between the first terminal 105 and the second terminal, a frame bit counter for determining a number of data clock bits offset between a transmitted data frame and a concurrently received data frame, a data clock phase detector for determining a phase difference between an RF data clock for the transmitted data frame and an RF data clock for the concurrently received data frame, and an optical carrier phase detector for determining a phase difference between an optical carrier used to transmit the transmitted data frame and an optical carrier for the concurrently received data frame. The distance between the first and second terminal is determined from a round trip transit time T between the first and second terminals.

Claims

1. An apparatus for measuring a distance between a first and second terminal comprising:

a frame counter for determining a number of data frames traversing a distance between the first terminal 105 and the second terminal;

a frame bit counter for determining a number of data clock bits offset between a transmitted data frame and a concurrently received data frame;

a data clock phase detector for determining a phase difference between an RF data clock for the transmitted data frame and an RF data clock for the concurrently received data frame; and

an optical carrier phase detector for determining a phase difference between an optical carrier used to transmit the transmitted data frame and an optical carrier for the concurrently received data frame,

wherein the distance between the first and second terminal is determined from a round trip transit time T between the first and second terminals expressed as;

T=N_frame×

T_frame+N_bit×

T_bit+Δ

Data Clock Phase+Δ

Carrier Phase,

where N_frame is the number of frames traversing the distance between the first terminal 105 and the second terminal 110, T_frame is the frame period, N_bit is the number of RF data clock bits offset between the presently transmitted frame and the presently received data frame, T_bit is the period of the RF data clock, Δ

Data Clock Phase is the phase difference between the transmitted RF data clock and the received data clock, and Δ

Carrier Phase is the phase difference between the transmitted optical carrier and the received optical carrier.

2. The apparatus of claim 1, comprising an RF frequency synthesizer for generating the RF data clock.

3. The apparatus of claim 1, comprising a pattern generator for generating data for the data frames.

4. The apparatus of claim 1, comprising a source of communication data for generating data for the data frames.

5. The apparatus of claim 1, comprising an optical frequency synthesizer for generating the optical carrier.

6. The apparatus of claim 1, wherein the optical carrier is a coherent optical communications carrier.

7. The apparatus of claim 1, wherein the first terminal is a ground terminal and the second terminal is a space terminal.

8. The apparatus of claim 1, wherein the first and second terminals are located on different space craft.

9. The apparatus of claim 1, wherein the first and second terminals are located on different terrestrial bodies.

10. A method for measuring a distance between a first and second terminal comprising:

determining a number of data frames traversing a distance between the first terminal 105 and the second terminal;

determining a number of data clock bits offset between a transmitted data frame and a concurrently received data frame;

determining a phase difference between an RF data clock for the transmitted data frame and an RF data clock for the concurrently received data frame;

determining a phase difference between an optical carrier used to transmit the transmitted data frame and an optical carrier for the concurrently received data frame; and

calculating the distance between the first and second terminal from a round trip transit time T between the first and second terminals expressed as;

T=N_frame×

T_frame+N_bit×

T_bit+Δ

Data Clock Phase+Δ

Carrier Phase,

where N_frame is the number of frames traversing the distance between the first terminal 105 and the second terminal 110, T_frame is the frame period, N_bit is the number of RF data clock bits offset between the presently transmitted frame and the presently received data frame, T_bit is the period of the RF data clock, Δ

Data Clock Phase is the phase difference between the transmitted RF data clock and the received data clock, and Δ

Carrier Phase is the phase difference between the transmitted optical carrier and the received optical carrier.

11. The method of claim 10, comprising generating the RF data clock using an RF frequency synthesizer.

12. The method of claim 10, comprising generating data for the data frames using a pattern generator.

13. The method of claim 10, comprising generating data for the data frames using a source of communication data.

14. The method of claim 10, comprising generating the optical carrier using an optical frequency synthesizer.

15. The method of claim 10, wherein the optical carrier is a coherent optical communications carrier.

16. The method of claim 10, comprising locating the first terminal terrestrially and locating the second terminal in space.

17. The method of claim 10, comprising locating the first and second terminals on different space craft.

18. The method of claim 10, comprising locating the first and second terminals on different terrestrial bodies.