Tunable optical dispersion-slope compensation based on a nonlinearly-chirped bragg grating

• US 6,453,093 B2
• Filed: 01/08/2001
• Issued: 09/17/2002
• Est. Priority Date: 01/07/2000
• Status: Expired due to Fees

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Xie, Yong, Willner, Alan E., Pan, Zhongqi, Lee, Sanggeon
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US09/757,414
• Publication Number:
  US 20010048788A1
• Time in Patent Office: 617 Days
• Field of Search: 385/24, 385/1-12, 385/37-43, 385/122, 372/6, 372/27, 372/64, 372/96, 372/102, 359/188, 359/290
• US Class Current: 385/37
• CPC Class Codes: G02B 6/02085 characterised by the grating profile, e.g. chirped, apodised, tilted, helical
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02B 6/29317 Light guides of the optical fibre type
• CPC Class Codes: G02B 6/2932 comprising a directional router, e.g. directional coupler, circulator
• CPC Class Codes: G02B 6/29322 Diffractive elements of the tunable type G02B6/02195 takes precedence; optical modulation devices based on a change of the optical properties of the medium G02F1/00
• CPC Class Codes: G02B 6/29376 coupling light guides for controlling wavelength dispersion, e.g. by concatenation of two light guides having different dispersion properties dispersion managed optical transmission systems H04B10/25253
• CPC Class Codes: G02B 6/29394 Compensating wavelength dispersion G02B6/29376 takes precedence; dispersion compensated optical transmission systems H04B10/2507
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: H04B 10/25133 including a lumped electrical or optical dispersion compensator H04B10/2519, H04B10/2525 takes precedence
• CPC Class Codes: H04B 10/2519 using Bragg gratings

Abstract

Techniques for using a nonlinearly-chirped fiber Bragg grating to produce tunable dispersion-slope compensation.

Claims

1. A system, comprising:

a fiber grating formed in a fiber and configured to have a spatial grating pattern that changes nonlinearly along said fiber to exhibit up to at least a third-order nonlinear dispersion effect so as to produce a tunable dispersion slope; and

a grating control unit coupled to said fiber grating and operable to adjust a grating parameter of said fiber grating to tune both dispersion and dispersion slope produced by said fiber grating.

2. The system as in claim 1, wherein said grating control unit includes a fiber stretcher that changes a length of said fiber grating.

3. The system as in claim 1, wherein said fiber grating further includes a spatial sampling pattern that is formed in said fiber to overlap and modulate said spatial grating pattern to produce multiple Bragg reflection bands at different band center frequencies each with a tunable dispersion slope.

4. The system as in claim 3, wherein said spatial sampling pattern is selected to produce a band spacing between adjacent Bragg reflection bands that is different from a channel spacing between adjacent channels in multiple wavelength-division multiplexed (WDM) channels.

5. The system as in claim 3, wherein said spatial sampling pattern is selected to produce a band spacing between adjacent Bragg reflection bands that changes from channel to channel.

6. A system, comprising:

a fiber having a receiving end to a plurality of wavelength-division multiplexed (WDM) optical channels with a constant channel spacing in wavelength;

a fiber grating formed in said fiber and configured to have a spatial grating pattern that changes nonlinearly along said fiber to exhibit up to at least a third-order nonlinear dispersion effect and a spatial sampling pattern that overlaps with and modulates said spatial grating pattern to produce a plurality of Bragg reflection bands centered at different band center wavelengths that are spaced differently from said constant channel spacing, said fiber grating operable to produce a dispersion slope in each Bragg reflection band that is adjustable when a grating parameter is changed; and

a grating control unit coupled to said fiber grating and operable to adjust said grating parameter of said fiber grating to tune both dispersion and said dispersion slope produced by said fiber grating.

7. The system as in claim 6, wherein said Bragg reflection bands are evenly spaced from one another.

8. The system as in claim 6, wherein said Bragg reflection bands have a varying band spacing.

9. The system as in claim 6, wherein said grating control unit includes a fiber stretcher that changes a length of said fiber grating.

10. The system as in claim 6, further comprising a dispersion detection unit that is operable to measure dispersion and dispersion slope of each optical channel reflected by said fiber grating, wherein said grating control unit is operable to adjust said fiber grating in response to said measurement.

11. A method, comprising:

providing a fiber grating formed in a fiber and configured to have a spatial grating pattern that changes nonlinearly along said fiber to exhibit up to at least a third-order nonlinear dispersion effect and a spatial sampling pattern that overlaps with and modulates said spatial grating pattern to produce a plurality of Bragg reflection bands centered at different band center wavelengths, said fiber grating operable to produce a dispersion slope in each Bragg reflection band that is adjustable when a grating parameter is changed;

directing multiple optical channels into said fiber grating where channel wavelengths of different optical channels are respectively in different Bragg reflection bands and are respectively positioned differently with respect to respective band center wavelengths;

adjusting a grating parameter of said fiber grating to change dispersion slopes differently at respective different channel wavelengths to negate different dispersions and different dispersion slopes with respect wavelength in different channels.

12. The method as in claim 11, wherein said grating parameter includes a length of said fiber grating.

13. The method as in claim 11, further comprising:

measuring a change in dispersions and dispersion slopes of in said optical channels reflected from said fiber grating; and

further adjusting said grating parameter accordingly to negate said change in said dispersions and said dispersion slopes.

14. The method as in claim 11, wherein said optical channels transmit through a dispersive fiber system before entering said fiber grating, wherein dispersions and dispersion slopes of said dispersive fiber system are different for different channels and change over time.