COHERENT DUAL PARAMETRIC FREQUENCY COMB FOR ULTRAFAST CHROMATIC DISPERSION MEASUREMENT

• US 20140253915A1
• Filed: 03/05/2014
• Published: 09/11/2014
• Est. Priority Date: 03/05/2013
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: ATAIE, Vahid, KUO, Ping Piu, RADIC, Stojan
• Granted Patent: US 9,625,351 B2
• Time in Patent Office: Days
• US Class Current: 356/300
• CPC Class Codes: G01M 11/333 using modulated input signals
• CPC Class Codes: G01M 11/338 by measuring dispersion other than PMD, e.g. chromatic dispersion
• CPC Class Codes: G01N 21/41 Refractivity; Phase-affecting properties, e.g. optical path length G01N21/21 takes precedence
• CPC Class Codes: H04B 10/07951 Monitoring or measuring chromatic dispersion or PMD

Abstract

A wide-band optical frequency comb is provided to estimate an optical phase shift induced in a dispersive material. In contrast to the conventional techniques that rely on a single tunable laser for extracting the dispersion parameter at different frequencies, the wide-band optical frequency comb uses multiple comb lines for simultaneously evaluating the dispersion induced phase shifts in different frequencies. Since the frequency response of the dispersive material is a phase function, a phase associated with each comb line passed through the material represents a discrete measure of the material frequency response.

Claims

1. A method for measurement of chromatic dispersion in an optical material, comprising:

using a wide-band optical frequency comb to estimate an optical phase shift induced in the optical material.

2. The method of claim 1, wherein the wide-band optical frequency comb is a dual-phase locked optical frequency comb comprising a probe comb and a reference comb, wherein the probe comb and the reference comb have difference frequency offset spacings.

3. The method of claim 1, wherein the wide-band optical frequency comb comprises more than 10 lines.

4. The method of claim 1, wherein the wide-band optical frequency comb comprises approximately 100 lines with a spacing of approximately 1 nanometer (nm).

5. The method of claim 1, further comprising utilizing multiple comb lines of the wide-band optical frequency comb at the same time to estimate optical phase shifts at different frequencies.

6. The method of claim 5, further comprising mapping the estimated optical phase shift of each received comb line to a corresponding comb line of an electrical signal separated by a frequency-spacing mismatch.

7. The method of claim 6, further comprising estimating the chromatic dispersion in a single cycle of frequency-spacing mismatch.

8. A device for measurement of chromatic dispersion in an optical material, comprising:

a laser source;

a dual-phase locked optical frequency comb for receiving an optical signal from the laser source and providing an input into a first end of the optical material, the input comprising a plurality of comb lines;

a detector at a second end of the optical material for converting received optical comb lines into electrical comb lines; and

a processor for determining a phase shift in the electrical comb lines.

9. The device of claim 8, wherein the dual-phase locked optical frequency comb comprises a probe comb and a reference comb, and wherein the probe comb and the reference comb have difference frequency offset spacings.

10. The device of claim 8, wherein the wide-band optical frequency comb comprises more than 10 lines.

11. The device of claim 8, wherein the wide-band optical frequency comb comprises approximately 100 lines with a spacing of approximately 1 nanometer (nm).

12. The device of claim 8, wherein the plurality of comb lines is configured to estimate optical phase shifts at different frequencies at the same time.

13. The device of claim 12, wherein the processor determines the phase shift by mapping an estimated optical phase shift of each comb line to a corresponding electrical comb line separated by a frequency-spacing mismatch.

14. The device of claim 13, wherein the chromatic dispersion is estimated in a single cycle of frequency-spacing mismatch.

15. A method for calculating chromatic dispersion in an optical material, comprising:

collecting target paths and calibrator paths for a single cycle of a received frequency comb spacing mismatch;

extracting phase information of frequency points; and

determining a dispersion profile from the extracted frequency points.

16. The method of claim 15, further comprising collecting target paths and calibrator paths by performing a fast Fourier transform (FFT) on the collected target paths and calibrator paths to reconstruct an instantaneous spectrum of the received frequency comb.

17. The method of claim 15, further comprising extracting phase information by subtracting phases of calibrator FFT coefficients from target path coefficients.