Laser communication system and method of operation using multiple transmitters and multiple receivers with dispersive multiplexing in multimode fiber

• US 6,525,853 B1
• Filed: 09/15/1999
• Issued: 02/25/2003
• Est. Priority Date: 09/15/1999
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Stuart, Howard Roy
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/397,015
• Time in Patent Office: 1,259 Days
• Field of Search: 359/127, 359/124, 359/125, 359/130, 359/177, 385/18, 385/24
• US Class Current: 398/115
• CPC Class Codes: H04B 10/2581 Multimode transmission
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems

Abstract

A laser communication system includes transmitters and detectors coupled to a multimode fiber through “arms”, which can consist of N optical fibers joined to the main fiber through a 1×N fiber splitter. A set of N data streams is RF modulated onto RF carriers of identical frequency. RF modulated data streams are used to intensity modulate the N laser transmitters. N optical signals are combined onto the single multimode fiber for transmission to M multiple detectors, where M≧N. Each M detector receives power from all N transmitting lasers. The M detectors utilize direct optical detection to convert the received optical signal to a RF signal, which can be demodulated using standard RF techniques. The inherent modal-coupling diversity between the arms introduced by the optical system, when combined with modal dispersion in the multimode fiber, introduces a decorrelation in both the transmitted and received signal arrays to enhance signal throughput.

Claims

1. A laser communication system having increased signal throughput comprising:

a) means coupling N optical transmitters responsive to N data signals to a multimode fiber and introducing modal coupling diversity;

b) means transmitting an optical signal on the multimode fiber;

c) means coupling the multimode fiber to M detectors and introducing modal coupling diversity; and

d) means coupled to the M detectors for receiving and recovering the N data signals.

2. The laser communication system of claim 1 further comprising:

means for enhancing the transmitter and receiver modal coupling diversity.

3. The laser communication system of claim 1 further comprising:

means for combining N optical signals onto the multimode fiber.

4. The laser communication system of claim 3 further comprising:

means introducing modal diversity among the combined N optical signals.

5. The laser communication system of claim 1 further comprising:

means for splitting the optical signal from the multimode fiber to the M detectors.

6. The laser communication system of claim 5 further comprising:

means introducing modal coupling diversity among the split optical signals.

7. The laser communication system of claim 1 further comprising:

means varying the geometry of the transmitting optical transmitters to vary the mode power distribution of the N modulated data signals.

8. The laser communication system of claim 1 further comprising:

mean modulating the N data signals coupled to the N optical transmitters.

9. The laser communication system of claim 1 further comprising:

means for converting the split optical signals to electrical signals corresponding to the N data signals.

10. The laser communication system of claim 1 wherein all M detectors receive the same optical signals from the multimode fiber.

11. The laser communication system of claim 1 wherein the optical signal from the multimode fiber is split into N uncorrelated data signals.

12. The laser communication system of claim 1 wherein the M detectors is equal to or greater than the N data signals.

13. A laser communication system having increased signal throughput comprising:

a) N data signal sources;

b) means for modulating the N data signal sources;

c) means coupling each modulated data signal source to an optical transmitter;

d) means coupling each optical transmitter to a multimode fiber as a combined optical signal and introducing modal coupling diversity among the N transmitters;

e) means transmitting the optical signal on the multimode fiber and introducing modal dispersion;

f) means splitting the optical signal from the multimode fiber to M optical signal detectors and introducing modal coupling diversity among the M detectors; and

g) means coupled to the M detectors for recovering the N data signals from the optical signal.

14. In a laser communication system including N data signal sources coupled to optical transmitters coupled to multimode fiber for carrying an optical signal to M optical detectors, a method for increasing the signal throughput of the communication system, comprising the steps of:

a) modulating the N data signal sources onto identical RF carriers;

b) coupling the N modulated signal sources to N optical transmitters;

c) coupling the N optical transmitters to a multimode fiber and introducing modal coupling diversity between the transmitters;

d) transmitting an optical signal on the multimode fiber;

e) coupling the multimode fiber to M detectors for receiving the optical signal and introducing modal coupling diversity between the detectors; and

f) recovering the N data signals from the optical signal received by the M detectors.

15. The method of claim 14 further comprising the step of:

providing a combined output from the optical transmitters.

16. The method of claim 14 further comprising the step of:

providing a split optical signal from the multimode fiber to the M detectors.

17. The method of claim 14 further comprising the step of:

providing each M detector with the same signal from the multimode fiber.

18. The method of claim 14 further comprising the step of:

providing each M detector with N uncorrelated data signals.

19. The method of claim 14 further comprising the step of:

selecting the number of M detectors to be equal to or greater than the number of N data signals.

20. The method of claim 16 further comprising the step of:

converting the split optical signals into N electrical data signals.