Reduction of noise and polarization mode dispersion (PMD) based on optical polarization stabilizer in fiber transmission

• US 7,796,894 B1
• Filed: 07/30/2004
• Issued: 09/14/2010
• Est. Priority Date: 07/30/2003
• Status: Active Grant

• Current Assignee: Luna Innovations, Inc.
• Original Assignee: General Photonics Corporation (General Cable Corporation)
• Inventors: Yao, X. Steve
• Primary Examiner(s): Curs; Nathan M
• Application Number:
  US10/903,240
• Time in Patent Office: 2,237 Days
• Field of Search: 398/147, 398/148, 398/149, 398/150, 398/152, 398/158, 398/159, 398/160, 398/161, 398/26
• US Class Current: 398/159
• CPC Class Codes: H04B 10/2569 due to polarisation mode dispersion [PMD]

Abstract

This application describes devices and techniques for dynamically controlling polarization light at one or more locations along the optical transmission path to reduce optical noise and PMD in the optical signal. One device according to an implementation includes a polarization controller to receive an optical signal and operable to control polarization of the optical signal in response to a control signal, a fixed optical polarizer to receive output from the optical polarization controller and to produce an output optical signal, and a circuit to receive a fraction of the output optical signal from the fixed optical polarizer and operable to produce the control signal in response to an output power level of the output optical signal which controls the polarization controller to maximize the output power level.

Claims

1. An optical wavelength division multiplexing (WDM) communication system, comprising:

a fiber transmission line that receives a plurality of WDM optical signals at different WDM wavelengths;

an optical circulator having a first port coupled to the fiber transmission line to receive the WDM optical signals, a second port to output the received WDM optical signals and a third port to output light received at the second port;

a WDM demultiplexer coupled to the second port of the optical circulator to separate WDM optical signals output by the second port into separated WDM optical signals along different optical paths; and

a plurality of optical conditioning modules respectively coupled in the different optical paths, each optical conditioning module reconditioning a respective WDM optical signal and direct the reconditioned WDM optical signal back to the WDM demultiplexer which combines reconditioned WDM optical signals from the separate optical paths into the second port of the optical circulator which outputs the reconditioned WDM optical signals at the third port,

each optical conditioning module comprising;

a polarization controller coupled in a respective optical path for a respective WDM optical signal to control polarization of the WDM optical signal in response to a control signal;

a polarization beam splitter placed in the optical path downstream from the polarization controller to transmit light in a first polarization in the WDM optical signal as a first optical signal and to reflect light in a second polarization orthogonal to the first polarization in the WDM optical signal as a second optical signal;

a first optical detector to receive at least a portion of light of the first optical signal to produce a first detector signal;

a second optical detector to receive at least a portion of light of the second optical signal to produce a second detector signal;

a partial reflector located in one an optical path between the polarization beam splitter and one of the first and second optical detectors to reflect light back to the polarization beam splitter which directs the reflected light from the partial reflector to pass through the polarization controller to the WDM demultiplexer as a reconditioned WDM optical signal; and

a control circuit coupled to receive the first and second detector signals to produce the control signal to the polarization controller based on the received first and second detector signals to reduce noise and polarization mode dispersion in the reconditioned WDM optical signal.

2. The system as in claim 1, wherein the polarization controller comprises a plurality of adjustable polarization elements.

3. The system as in claim 2, wherein the adjustable polarization elements comprise piezo-electric elements.

4. The system as in claim 2, wherein the adjustable polarization elements comprise electro-ceramic elements.

5. The system as in claim 2, wherein the adjustable polarization elements comprise liquid crystal elements.

6. The system as in claim 2, wherein the adjustable polarization elements comprise solid state electro-optic elements.

7. The system as in claim 6, wherein the solid state electro-optic elements include lithium niobate crystals.