Temperature compensated fiber bragg grating

• US 6,510,272 B1
• Filed: 08/28/2000
• Issued: 01/21/2003
• Est. Priority Date: 08/28/2000
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wiegand, Gordon
• Primary Examiner(s): Patel, Tulsidas
• Assistant Examiner(s): WEBB, BRIAN SCOTT
• Application Number:
  US09/649,494
• Time in Patent Office: 876 Days
• Field of Search: 385/136, 385/37
• US Class Current: 385/136
• CPC Class Codes: G02B 6/0218 using mounting means, e.g. by using a combination of materials having different thermal expansion coefficients

Abstract

An assembly and method for a fiber grating package comprising a rod having a first end and a second end and a coefficient of thermal expansion. A first end cap includes a first base having a first opening formed therein to receive the rod for movement of the first end cap along the rod to a first position adjacent to the first end of the rod. The first end cap further includes a first cantilever member extending from the first base and the first cantilever member has a first contact point thereon. A second end cap includes a second base having a second opening formed therein to receive said rod for movement of said second end cap along said rod to a second position adjacent to the second end of the rod. The second end cap further includes a second cantilever member extending from the second base and the second cantilever member has a second contact point thereon. The first end cap and the second end cap have a common rate of thermal expansion that is greater than the coefficient of thermal expansion of the rod. A portion of an optical fiber includes a Bragg grating, the portion of the optical fiber being attached between the first contact point and the second contact point. The portion of an optical fiber has a length defined by the distance between the first and second contact points, such that the length of the portion remains substantially unchanged in an operating range of temperature when the first end cap occupies the first position and the second end cap occupies the second position.

Claims

1. A fiber grating package comprising:

a cylindrical rod having a first end and a second end and a coefficient of thermal expansion;

a first end cap including a first base having a first opening formed therein to receive said cylindrical rod for movement of said first end cap along said cylindrical rod to a first position adjacent to said first end, said first end cap further including a first cantilever member extending from said first base said first cantilever member having a first contact point thereon;

a second end cap including a second base having a second opening formed therein to receive said cylindrical rod for movement of said second end cap along said cylindrical rod to a second position adjacent said second end, said second end cap further including a second cantilever member extending from said second base of said second end cap, said second cantilever member having a second contact point thereon, said first end cap and said second end cap having a common rate of thermal expansion that is greater than the coefficient of thermal expansion of said rod; and

a portion of an optical fiber including a Bragg grating, said portion attached between said first contact point and said second contact point, said portion having a length defined substantially by the distance between said first and second contact points, said length remaining substantially unchanged in an operating range of temperature, when said first end cap occupies said first position and said second end cap occupies said second position, said first cantilever member and said second cantilever member adapted for adjustment to tune the wavelength of said Bragg grating after attaching said portion of said optical fiber between said first and second contact points.

2. The fiber grating package as claimed in claim 1 wherein said cylindrical rod has a length less than 16 cm.

3. The fiber grating package as claimed in claim 1 wherein said cylindrical rod has a length less than 10 cm.

4. The fiber grating package as claimed in claim 1 wherein said cylindrical rod comprises a ceramic material.

5. The fiber grating package as claimed in claim 4 wherein said ceramic material has a coefficient of thermal expansion of about 0.4 ppm/°

C.

6. The fiber grating package as claimed in claim 4 wherein said ceramic material is selected from the group consisting of quartz, silica, and glass.

7. The fiber grating package as claimed in claim 1 wherein said first end cap and said second end cap comprise a metallic material.

8. The fiber grating package as claimed in claim 7 wherein said metallic material has a rate of thermal expansion of about 23 ppm/°

C.

9. The fiber grating package as claimed in claim 8 wherein said metallic material is aluminum.

10. The fiber grating package as claimed in claim 1 wherein said operating range of temperature is from about −

20°

C. to about 80°

C.

11. The fiber grating package as claimed in claim 1 wherein said operating range of temperature is from about −

5°

C. to about 70°

C.

12. The fiber grating package as claimed in claim 1 wherein said operating range of temperature is from about 0°

C. to about 60°

C.

13. A temperature compensated fiber support comprising:

a rod having a first end and a second end and a coefficient of thermal expansion;

a first end cap including a first base having a first opening formed therein to receive said cylindrical rod for movement of said first end cap along said cylindrical rod to a first position adjacent to said first end, said first end cap further including a first cantilever member extending from said first base said first cantilever member having a first contact point thereon for attachment of an optical fiber;

a second end cap including a second base having a second opening formed therein to receive said cylindrical rod for movement of said second end cap along said cylindrical rod to a second position adjacent said second end, said second end cap further including a second cantilever member extending from said second base of said second end cap, said second cantilever member having a second contact point thereon for attachment of said optical fiber, said first end cap and said second end cap having a common rate of thermal expansion that is greater than the coefficient of thermal expansion of said rod, said first cantilever member and said second cantilever member adapted for adjustment of said optical fiber after attachment to said first and second contact points.

14. A temperature compensated fiber support as claimed in claim 13 wherein said rod is an elongate cylinder.

15. A temperature compensated fiber support as claimed in claim 14 wherein said elongate cylinder has a length less than 10 cm.

16. A temperature compensated fiber support as claimed in claim 13 wherein said rod comprises a ceramic material.

17. A temperature compensated fiber support as claimed in claim 16 wherein said ceramic material is selected from the group consisting of quartz, silica, and glass.

18. A temperature compensated fiber support as claimed in claim 13 wherein said first end cap and said second end cap comprise a metallic material.

19. A method for assembling a fiber grating package, comprising the steps of:

providing a cylindrical rod having a first end and a second end and a coefficient of thermal expansion;

mounting a first end cap including a first base at a first position adjacent to said first end of said cylindrical rod, said first end cap further including a first cantilever member extending from said first base said first cantilever member having a first contact point thereon;

mounting a second end cap including a second base at a second position adjacent to said second end of said cylindrical rod, said second end cap further including a second cantilever member extending from said second base of said second end cap, said second cantilever member having a second contact point thereon, said first end cap and said second end cap having a common rate of thermal expansion that is greater than the coefficient of thermal expansion of said rod;

attaching a portion of an optical fiber including a Bragg grating between said first contact point and said second contact point, said portion having a length defined substantially by the distance between said first and second contact points; and

applying torsional force to at least one of said cantilever members to increase the distance between said cantilever member and said rod to tune said Bragg grating to a selected wavelength.

20. A method for assembling a fiber grating package, comprising the steps of:

providing a cylindrical rod having a first end and a second end and a coefficient of thermal expansion;

mounting a first end cap including a first base at a first position adjacent to said first end of said cylindrical rod, said first end cap further including a first cantilever member extending from said base said first cantilever member having a first contact point thereon;

securing said first end cap at said first position;

mounting a split end cap including a base member adjacent said second end of said rod, said split end cap further including a cantilever member extending from said base member of said split end cap and detachable therefrom, said cantilever member having a second contact point thereon, said first end cap and said split end cap having a common rate of thermal expansion that is greater than the coefficient of thermal expansion of said rod;

attaching a portion of an optical fiber including a Bragg grating between said first contact point and said second contact point;

tuning said portion to a selected wavelength corresponding to a length substantially defined by the distance between said first and second contact points;

maintaining said length;

detaching said base member from said cantilever member and separating said base member of said split end cap to a position separated from said first position such that said length of said portion remains substantially unchanged in an operating range of temperature; and

securely bonding said base member to said rod and said cantilever member to said base member to produce said wavelength tuned, temperature compensated fiber grating package.

21. A fiber grating package comprising:

a cylindrical rod having a first end and a second end and a coefficient of thermal expansion,

a first end cap including a first base having a first opening formed therein to receive said cylindrical rod said first opening being adapted to allow movement of said first end cap along said cylindrical rod to a first position adjacent to said first end, said first end cap further including a first cantilever member extending from said first base said first cantilever member having a first contact point thereon;

a second end cap including a second base having a second opening formed therein to receive said cylindrical rod, said second opening being adapted to allow movement of said second end cap along said cylindrical rod to a second position adjacent said second end, said second end cap further including a second cantilever member extending from said second base, said second cantilever member having a second contact point thereon, said first end cap and said second end cap having a common rate of thermal expansion that is greater than the coefficient of thermal expansion of said rod; and

an optical fiber connected to said first and second cantilever members at said first and second contact points respectively wherein the portion of said optical fiber extending between said first and second contact points comprises a Bragg grating and has a length, when said first end cap occupies said first position and said second end cap occupies said second position, said first cantilever member and said second cantilever member adapted for adjustment of said length of said optical fiber to tune the tension in said Bragg grating, said length after adjustment remaining substantially unchanged over temperatures within a range of −

5°

C. to 70°

C.