Method and apparatus for arbitrary spectral shaping of an optical pulse

• US 6,195,484 B1
• Filed: 09/22/1999
• Issued: 02/27/2001
• Est. Priority Date: 10/02/1997
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company), Massachusetts Institute of Technology
• Original Assignee: 3M Innovative Properties Company (3M Company), Massachusetts Institute of Technology
• Inventors: Haus, Hermann A., Brennan, James F. III, Chou, Patrick C., LaBrake, Dwayne L.
• Primary Examiner(s): Sanghavi, Hemang
• Application Number:
  US09/401,160
• Time in Patent Office: 524 Days
• Field of Search: 385/24, 385/37, 385/122, 385/10, 385/4, 359/326, 359/328, 359/333, 359/341, 359/130, 359/154, 359/572, 359/573, 359/574, 359/575, 372/25, 372/30, 372/102
• US Class Current: 385/37
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12109 Filter
• CPC Class Codes: G02B 2006/12138 Sensor
• CPC Class Codes: G02B 6/02095 Long period gratings, i.e. transmission gratings coupling light between core and cladding modes
• CPC Class Codes: G02B 6/02138 based on illuminating a phase mask
• CPC Class Codes: G02B 6/02147 Point by point fabrication, i.e. grating elements induced one step at a time along the fibre, e.g. by scanning a laser beam, arc discharge scanning G02B6/02133 and G02B6/02142 take precedence
• CPC Class Codes: G02B 6/02152 involving moving the fibre or a manufacturing element, stretching of the fibre G02B6/02147 takes precedence
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/274 based on light guide birefringence, e.g. due to coupling between light guides G02B6/105, G02B6/024 take precedence; mechanically induced birefringence G02F1/0134
• CPC Class Codes: G02B 6/29317 Light guides of the optical fibre type
• CPC Class Codes: G02B 6/29394 Compensating wavelength dispersion G02B6/29376 takes precedence; dispersion compensated optical transmission systems H04B10/2507
• CPC Class Codes: G02F 1/03 based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect G02F1/061 takes precedence
• CPC Class Codes: G02F 2202/20 LiNbO3, LiTaO3
• CPC Class Codes: G02F 2203/26 Pulse shaping; Apparatus or methods therefor
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108

Abstract

A method and an apparatus for stretching an optical pulse and shaping its spectrum. The method includes the step of: providing a an optical fiber element having a first long length fiber Bragg grating having a refractive index perturbation of varying periodicity. The optical pulse is launched into the fiber Bragg grating, wherein the Bragg grating reflects the pulse in a chromatically dispersed output. The reflected output is coupled with an optical modulator programmed to temporally modify the amplitude of the chromatically dispersed output to attenuate selected optical frequencies in a desired pattern. The apparatus for stretching and arbitrarily shaping the spectrum of an optical pulse with a desired wavelength resolution Δλ_res includes a routing optical device and an optical fiber element having a Bragg grating. The routing optical device routs energy between different waveguides, and has an input port to receive the optical pulse.

Claims

1. A method for stretching an optical pulse and shaping its spectrum, the method comprising the steps of:

a. providing a an optical fiber element having a first long length fiber Bragg grating having a refractive index perturbation of varying periodicity;

b. launching the optical pulse into the fiber Bragg grating, wherein the Bragg grating reflects the pulse in a chromatically dispersed output;

c. coupling the reflected chromatically dispersed output from the grating into an optical modulator; and

d. temporally modifying the amplitude of the chromatically dispersed output to attenuate selected optical frequencies.

2. The method of claim 1, where the step of providing a grating includes providing a grating having a chromatic dispersion capability between ±

10 ps/nm and 10 ns/nm.

3. The method of claim 1, where the optical pulse has less than 90% of its energy in a 10 MHz spectral range.

4. The method of claim 1, where the step of temporally modifying the amplitude of the chromatically dispersed output includes using an arbitrary waveform generator having at least 10 MHz bandwidth.

5. The method of claim 1, further comprising the step of recompressing the chromatically dispersed output after the step of temporally modifying the chromatically dispersed output.

6. The method of claim 5, where the step of recompressing the chromatically dispersed output includes launching the chromatically dispersed output into a fiber element having a second grating of opposite sign dispersion to that of the first grating.

7. The method of claim 5, where the step of recompressing the chromatically dispersed output includes launching the chromatically dispersed output into an opposite end of the optical fiber element.

8. The method of claim 7, further comprising the step of launching the chromatically dispersed output into an optical system that relies on nonlinear optical processes.

9. A pulse stretching and shaping apparatus for stretching and arbitrarily shaping the spectrum of an optical pulse with a desired wavelength resolution Δ

λ

_res;

a. a routing optical device that routs energy between different waveguides, the routing device having an input port, the input port receiving the optical pulse;

b. an optical fiber element having a long-length fiber Bragg grating optically coupled to the routing optical device, the Bragg grating having an increasing or decreasing periodicity, wherein

10. The apparatus of claim 9, further comprising an arbitrary waveform generator that temporally modifies the amplitude of the chromatically dispersed output to attenuate selected optical frequencies.

11. The apparatus of claim 9, the Bragg grating having a chromatic dispersion capability between ±

10 ps/nm and 10 ns/nm.

12. The apparatus of claim 9, where the Bragg grating is greater than 20 cm in length.

13. The apparatus of claim 9, where the grating is greater than 2 meters in length.

14. The apparatus of claim 9, where the grating is greater than 3.5 meters in length.

15. The apparatus of claim 9, where the routing optical device is a non-reciprocal optical device.

16. The apparatus of claim 15, where non-reciprocal optical device is an optical circulator.

17. The apparatus of claim 9, where the routing optical device is a device which couples energy from one waveguide to another.

18. An optical coherence tomography system including the apparatus of claim 9.

19. An interferometric optical fiber gyroscope including the apparatus of claim 9.

20. An optical fiber communication system including the apparatus of claim 9.