High speed MMF (multi-mode fiber) transmissions via orthogonal wavefronts

• US 10,090,958 B2
• Filed: 07/06/2015
• Issued: 10/02/2018
• Est. Priority Date: 09/21/2011
• Status: Active Grant

• Current Assignee: Spatial Digital Systems Inc
• Original Assignee: Spatial Digital Systems Inc
• Inventors: Chang, Donald C. D.
• Primary Examiner(s): Wolf, Darren E
• Application Number:
  US14/791,556
• Publication Number:
  US 20160006532A1
• Time in Patent Office: 1,184 Days
• Field of Search: None
• CPC Class Codes: B64U 2101/20 for use as communications relays, e.g. high-altitude platforms
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence
• CPC Class Codes: H04B 10/2581 Multimode transmission
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/18502 Airborne stations
• CPC Class Codes: H04B 7/18504 Aircraft used as relay or high altitude atmospheric platform
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations
• CPC Class Codes: H04B 7/18523 Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service arrangements specially adapted for satellite broadcast receiving H04H40/90; picture transmission via satellite H04N1/00103; television transmission via satellite H04N7/20
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: H04J 14/00 Optical multiplex systems
• CPC Class Codes: H04J 14/005 Optical Code Multiplex
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0307 Multiplexers; Demultiplexers
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 25/03891 Spatial equalizers MIMO diversity systems H04B7/0413

Abstract

A system is provided for high speed optical fiber data transmission by generating artificial wavefronts along multiple paths exhibiting spatial mutual orthogonality. Multiple independent signal streams are “structured” over a group of different propagation paths that are coherently organized by wavefront multiplexing and dc-multiplexing techniques. Therefore, signal streams with enhanced throughput and reliability may be fully recovered at destinations via embedded diagnostic signals and optimization loops. Multiple optical channels are matched with multiple orthogonal wavefronts created by a signal pre-processor. A receiving end signal post-processor dynamically aligns propagation paths via diagnostic signals and orthogonality of the propagation wavefronts electronically. The multiple optical channels are coherently bonded into a single virtual channel, thereby increasing data bandwidth while reducing interference and unwanted multi-path effects. The wavefront multiplexing and de-multiplexing functions may be performed in a dedicated signal processor or may reside in a general-purpose microprocessor located in the user terminal.

Claims

1. A system comprising:

a first processor having N first input ports and N first output ports, N being a positive integer greater than 1, for receiving concurrently N first signals at the N first input ports, performing an N-to-N wavefront multiplexing transform on the N first signals and outputting concurrently N first wavefront multiplexed signals at the N first output ports such that the N first wavefront multiplexed signals are orthogonal to one another and each of the N first wavefront multiplexed signals is a respective linear combination of the N first signals; and

a first set of optical modulators coupled to the first processor, for converting the N first wavefront multiplexed signals into first optical mode groups for transmission in a multi-mode fiber,

wherein the respective linear combination is a sum of products of the N first signals at the N first input ports and corresponding wavefront components of the N-to-N wavefront multiplexing transform.

2. The system of claim 1, wherein the N first signals comprise at least one known pilot code signal or at least one ground signal or both.

3. The system of claim 1 further comprising a time-division de-multiplexer coupled to M first input ports of the N first input ports, M being a positive integer greater than or equal to 1 and smaller than N, the time-division de-multiplexer receiving and transforming a data signal into M first signals of the N first signals.

4. The system of claim 1 further comprising:

a second processor having N second input ports and N second output ports, N being a positive integer greater than 1, for receiving concurrently N second signals at the N second input ports, performing an N-to-N wavefront multiplexing transform on the N second signals and outputting concurrently N second wavefront multiplexed signals at the N second output ports such that the N second wavefront multiplexed signals are orthogonal to one another and each of the N second wavefront multiplexed signals is a respective linear combination of the N second signals; and

a second set of optical modulators coupled to the second processor, for converting the N second wavefront multiplexed signals into second optical mode groups for transmission in the multi-mode fiber,

wherein the first and second sets of optical modulators are transmitting respectively the first and second optical mode groups simultaneously to the multi-mode fiber.

5. The system of claim 4, wherein the first optical mode groups correspond respectively to the second optical mode groups.

6. The system of claim 4, wherein the second processor and the second set of optical modulators are not located at a same site as the first processor and the first set of optical modulators.

7. The system of claim 1 further comprising:

a time-division multiplexer coupled to the N first outputs, for multiplexing the N first wavefront multiplexed signals into L multiplexed signals, L being a positive integer smaller than N, and for outputting the L multiplexed signals to the first set of optical modulators.

18. The system of claim 1 further comprising:

a mode-group diversity multiplexer coupled to the first set of optical modulators to multiplex the first optical mode groups for transmission in the multi-mode fiber.

8. A system comprising:

a set of optical demodulators for receiving optical mode groups from a multi-mode fiber and converting the optical mode groups into electrical signals;

a bank of adaptive filters coupled to the set of optical demodulators, for filtering the electrical signals and outputting concurrently N filtered signals, N being a positive integer greater than 1; and

a first processor coupled to the bank of adaptive filters, the processor having N input ports and N output ports, receiving concurrently the N filtered signals at the N input ports, performing an N-to-N wavefront demultiplexing transform on the N filtered signals and outputting concurrently N wavefront demultiplexed signals at the N output ports such that the N wavefront demultiplexed signals are orthogonal to one another and each of the N wavefront demultiplexed signals is a respective linear combination of the N filtered signals;

wherein the N filtered signals correspond to N signals that result from performing an N-to-N wavefront multiplexing transform on a set of input signals at a transmitting site, and wherein the N-to-N wavefront demultiplexing transform is an inverse of the N-to-N wavefront multiplexing transform, and

wherein the respective linear combination is a sum of products of the N filtered signals at the N input ports and corresponding wavefront components of the N-to-N wavefront demultiplexing transform.

9. The system of claim 8, wherein the set of input signals comprises at least one known pilot code signal and wherein at least one of the N wavefront demultiplexed signals comprises a corresponding at least one recovered pilot code signal.

10. The system of claim 9 further comprising an optimization processor coupled to the bank of adaptive filters for dynamically modifying coefficients of the adaptive filters such that differences between the at least one recovered pilot code signal and the at least one known pilot code signal are minimized.

11. The system of claim 8 further comprising a time-division multiplexer coupled to the first processor for combining some of the N wavefront demultiplexed signals into a recovered signal.

12. The system of claim 8 further comprising:

a mode-group diversity de-multiplexer coupled to the set of optical de-modulators to de-multiplex the optical mode groups.

13. The system of claim 8 further comprising a signal de-multiplexer coupled to one of the N output ports of the first processor to receive and demultiplex a respective one of the N wavefront demultiplexed signals into a second recovered signal and a recovered pilot code signal.

14. The system of claim 9 further comprising a cost function generator coupled to the first processor and to the optimization processor for generating performance indexes based on the at least one recovered pilot code signal and the at least one known pilot code signal, and outputting the performance indexes to the optimization processor.

19. The system of claim 12, wherein the set of optical demodulators comprises:

at least one dual-polarization quadrature phase-shift-key demodulator coupled to the mode-group diversity de-multiplexer and outputting the electrical signals to the bank of adaptive filters.

15. A system comprising:

a time-division de-multiplexer for converting a first data stream into a set of concurrent first data signals;

a signal multiplexer for converting a second data stream and at least one pilot code signal into a second data signal; and

a processor coupled to the time-division de-multiplexer and the signal multiplexer, the processor having N input ports and N output ports, N being a positive integer greater than 1, for receiving concurrently N input signals at the N input ports, the N input signals including the concurrent first data signals and the second data signal, performing an N-to-N wavefront multiplexing transform on the N input signals and outputting concurrently N wavefront multiplexed signals at the N output ports such that the N wavefront multiplexed signals are orthogonal to one another and each of the N wavefront multiplexed signals is a respective linear combination of the N input signals; and

a set of optical modulators coupled to the processor, for converting the N wavefront multiplexed signals into optical mode groups for transmission in a multi-mode fiber,

wherein the respective linear combination is a sum of products of the N input signals at the N input ports and corresponding wavefront components of the N-to-N wavefront multiplexing transform.

16. The system of claim 15, wherein some of the N input ports are grounded.

17. The system of claim 15, wherein the set of optical modulators comprises:

at least one dual-polarization quadrature phase-shift-key modulator coupled to the N output ports of the processor for receiving the N wavefront multiplexed signals and outputting optical data streams.

20. The system of claim 15 further comprising:

a mode-group diversity multiplexer coupled to the set of optical modulators to multiplex the optical mode groups for transmission in the multi-mode fiber.