COHERENT OPTICAL TRANSCEIVER AND COHERENT COMMUNICATION SYSTEM AND METHOD FOR SATELLITE COMMUNICATIONS

• US 20080025728A1
• Filed: 10/04/2007
• Published: 01/31/2008
• Est. Priority Date: 07/02/2003
• Status: Active Grant

• Current Assignee: CeLight, Inc.
• Original Assignee: CeLight, Inc.
• Inventors: Shpantzer, Isaac, Kazi, Sabera
• Granted Patent: US 7,840,144 B2
• Time in Patent Office: Days
• US Class Current: 398/104
• CPC Class Codes: H04B 10/118 specially adapted for satellite communication
• CPC Class Codes: H04B 10/40 Transceivers
• CPC Class Codes: H04B 10/61 Coherent receivers

Abstract

An optical transceiver is provided for optical communications with additive noise compensation. The system and method are disclosed for the additive noise cancellation, which is typically a vibration noise, caused by moving platform, where the transceiver is located. The transceiver comprises an additive noise sensor and a digital signal processing (DSP) unit which implements variable step size technique to adjust the filter weight in the least square estimate of the noise signal. In the preferred embodiment the digital signal processing is applied both at the transmission and the receiving side. The optical device is packed for ground-satellite and inter-satellite communications applications with resistance to high-energy X-rays, gamma rays and cosmic rays. The optical device sustains its operation characteristics under launch load.

Claims

1. An optical system comprising:

an optical receiver receiving a phase modulated optical signal and producing a digital data output signal;

a first means for measuring an additive phase noise at a receiver site and providing a first correction signal;

a digital signal processing unit correcting the digital data output signal basing on the first correction signal.

2. The system of claim 1, further comprising:

the optical receiver is a coherent optical receiver, in which the phase modulated optical signal is mixed a local oscillator signal.

3. The system of claim 2, wherein the coherent optical receiver includes 90-degrees optical hybrid.

4. The system of claim 1, wherein the first means includes an accelerometer.

5. The system of claim 1, further comprising:

a light source generating an initial optical beam;

a second means for evaluating an additive phase noise at a transmitter side and providing a second correction signal; and

a phase modulator providing a modulation of the initial optical beam with data;

the phase modulator providing a correction of the modulation basing on the second correction signal and transmitting the phase modulated optical signal towards the optical receiver.

6. The system of claim 5, wherein the second means includes an accelerometer.

7. The system of claim 5, wherein the modulation is QPSK or QAM modulation.

8. The system of claim 1, wherein the noise is associated with vibration of a platform, on which the light source is positioned.

9. The system of claims 1, wherein the correction uses an active noise control.

10. The system of claims 1, wherein the correction uses a digital filter and adaptively adjusts the filter parameters.

11. The system of claim 10, wherein the filter parameters include weights.

12. The system of claim 10, wherein the filter parameters are selected to minimize the mean-square value of an error signal, which is a difference between the digital data output signal and the first correction signal.

13. The system of claim 1, further comprising

a protective coating covering the coherent receiver, the first means and the digital signal processing unit to shield them from hard radiation.

14. The system of claim 1, implemented over all types of networks, including intersatellite, ground-satellite, free-space optical links, short haul and long haul terrestrial, submarine, and metro fiber networks.

15. A method for an optical signal transmission, comprising:

receiving a phase modulated optical signal encoded with data;

mixing the phase modulated signal with a local oscillator signal;

recovering a data stream from the phase modulated signal;

correcting the data stream in a digital signal processing unit basing on an active noise control technique; and

outputting corrected data.

16. The method of claim 15, further comprising:

mixing the data stream in the digital signal processing unit with a correcting signal from a sensor.

17. The method of claim 15, wherein:

the active noise control technique uses a digital filter and adaptively adjusts the filter parameters.

18. The method of claim 17, wherein:

the filter parameters include weights.

19. The method of claim 18, wherein:

the weights adjustment is based on the mean-square value of an error signal, the error signal being a difference between the data stream and a correcting signal.

20. The method of claim 15, implemented over all types of an optical signal transmission, including optical communications, remote sensing and LADARs.