Apparatus for manufacturing long-period fiber gratings and apparatus for manufacturing two-band long-period fiber gratings using the same

• US 6,201,911 B1
• Filed: 08/19/1999
• Issued: 03/13/2001
• Est. Priority Date: 08/19/1998
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jang, Joo-nyung
• Primary Examiner(s): Palmer, Phan T. H.
• Application Number:
  US09/377,184
• Time in Patent Office: 572 Days
• Field of Search: 385/37, 385/11, 385/33, 385/12, 385/34, 385/16, 385/10, 385/129, 385/123, 359/248, 372/20, 372/50, 372/6, 372/108, 430/5, 430/290, 430/321, 436/172
• US Class Current: 385/37
• CPC Class Codes: G02B 6/02095 Long period gratings, i.e. transmission gratings coupling light between core and cladding modes
• CPC Class Codes: G02B 6/02142 based on illuminating or irradiating an amplitude mask, i.e. a mask having a repetitive intensity modulating pattern

Abstract

An apparatus for manufacturing a long-period fiber grating and a two-band long-period fiber grating manufacturing apparatus using the same are provided. The apparatus includes a light source for generating the UV laser light, a mirror for reflecting the UV laser light generated in the light source at a predetermined angle and changing the traveling path thereof, a lens for focusing the laser light whose traveling path is changed by the mirror, a dispersing unit for dispersing the laser light passed through the lens, and an amplitude mask positioned between the dispersing unit and the optical fiber, and having a transmission region in which the dispersed laser light is periodically transmitted to the optical fiber. The bandwidth of a long-period fiber grating can be adjusted by adjusting the size of a laser beam irradiated into an optical fiber. Also, amplitude masks can be easily manufactured at low cost and damage threshold power thereof is high.

Claims

1. An apparatus for manufacturing a long-period fiber grating from an optical fiber, comprising:

a UV laser light source for generating UV laser light;

a cylindrical lens for focusing the UV laser light onto the optical fiber;

a dispersing unit between the cylindrical lens and the fiber, said dispersing unit having a focus, for dispersing the UV light exiting the cylindrical lens;

an amplitude mask having a plurality of transmission regions and non-transmission regions spaced at a transmission periodicity, said amplitude mask positioned between the dispersing unit and the optical fiber at a first distance from the optical fiber; and

a slit located between the amplitude mask and the optical fiber, said slit having a slit width along the optical fiber.

2. The apparatus of claim 1, further comprising:

said dispersing unit being a concave lens.

3. The apparatus of claim 2, further comprising:

said concave lens being a plano-concave lens.

4. The apparatus of claim 1, said amplitude mask comprising a thin metal substrate.

5. The apparatus of claim 4, the transmission region of said amplitude mask being formed by CO₂ laser or chemical etching.

6. The apparatus of claim 1, further comprising a controller connected to said amplitude mask for controlling said first distance.

7. The apparatus of claim 1, further comprising:

a light source on one end of the optical fiber and a measuring unit on the other end of the optical fiber, for measuring a coupling peak of the long-period fiber grating.

8. The apparatus of claim 7, further comprising:

a controller connected to the amplitude mask and to the measuring unit, for controlling said first distance as a function of the measured coupling peak.

9. The apparatus of claim 1, further comprising:

a mirror between the UV laser light source and the cylindrical lens, for reflecting the UV laser light into the cylindrical lens.

10. The apparatus of claim 1, further comprising:

the value of said first distance being given by the formula;

$\mathrm{\Lambda <br><br>}=\frac{{\mathrm{\Lambda <br><br>}}_0<br><br>\left(x+y\right)}{x}$

where y is said first distance, x is the distance from the focus of the first dispersing unit to the optical fiber, Λ

₀ is the transmission periodicity of the amplitude mask, and Λ

is the periodicity of the fiber grating.

11. An apparatus for manufacturing a multiple band long-period optical fiber grating, comprising:

a UV laser light source for generating UV laser light;

a beam splitter for splitting the laser light into a first portion which is reflected and a second portion which is not reflected;

a first cylindrical lens for focusing the first portion of the UV laser light onto a first region of the optical fiber;

a first dispersing unit between the first cylindrical lens and the optical fiber, said first dispersing unit having a focus, for dispersing the UV light exiting the first cylindrical lens;

a first amplitude mask having a plurality of transmission regions and non-transmission region spaced at a first transmission periodicity, said first amplitude mask positioned between the first dispersing unit and the optical fiber at a first distance from the optical fiber;

a first slit located between the first amplitude mask and the optical fiber, said slit having a first slit width along the optical fiber;

a mirror for reflecting the second portion of the UV laser light;

a second cylindrical lens receiving the light reflected by the mirror, for focusing the reflected second portion of the UV laser light onto the optical fiber in a second region adjacent to said first region;

a second dispersing unit between the second cylindrical lens and the optical fiber, said second dispersing unit having a focus, for dispersing the UV light exiting the second cylindrical lens;

a second amplitude mask having a plurality of transmission regions and non-transmission region spaced at a second transmission periodicity, said second amplitude mask positioned between the second dispersing unit and the optical fiber at a second distance from the optical fiber; and

a second slit located between the second amplitude mask and the optical fiber, said slit having a second slit width along the optical fiber.

12. The apparatus of claim 11, further comprising:

said first transmission periodicity being equal to said second transmission periodicity.

13. The apparatus of claim 11, further comprising:

said first and second dispersing units each being concave lenses.

14. The apparatus of claim 11, further comprising:

said first and second amplitude masks each comprising a thin metal substrate.

15. The apparatus of claim 11, further comprising:

a controller attached to said first and second amplitude masks for controlling said first and second distances.

16. The apparatus of claim 11, further comprising:

a light source on one end of the optical fiber and a measuring unit on the other end of the the optical fiber, for measuring coupling peaks of the long-period optical grating.

17. The apparatus of claim 16, further comprising:

a controller connected to said first and second amplitude masks and to the measuring unit, for controlling said first and second distances as a function of the measured coupling peaks.

18. A method of manufacturing a long-period fiber grating, comprising the steps of:

directing a UV laser light beam through a cylindrical lens oriented with the focal point on an optical fiber, and then passing the light from the cylindrical lens through a dispersing unit having a focus, for increasing the beam size;

passing the light from the dispersing unit through an amplitude mask having a transmission periodicity and oriented at a distance from the optical fiber to irradiate a region of the optical fiber around the focal point of the first cylindrical lens; and

passing the light from a first amplitude mask through a fu-st slit having a first slit width to irradiate a region of the optical fiber.

19. The method of claim 18, said step of directing a UV laser light beam comprising reflecting the laser light beam using a mirror.

20. The method of claim 18, further comprising:

controlling said distance of the amplitude mask from the fiber using a controller.

21. The method of claim 20, further comprising:

measuring the coupling peaks of light passed through the fiber from a light source at one end to a measuring unit at the other end during the manufacture of the long-period grating; and

adjusting said first distance using the controller so that a measured coupling peak occurs at a desired wavelength.

22. The method of claim 18, further comprising:

using a hydrogen-loaded germanium-doped optical fiber as the optical fiber.

23. The method of claim 18, further comprising:

setting the first distance to the value determined using the formula;

$\mathrm{\Lambda <br><br>}=\frac{{\mathrm{\Lambda <br><br>}}_0<br><br>\left(x+y\right)}{x}$

where y is the first distance, x is the distance from the focus of the first dispersing unit to the optical fiber, Λ

₀ is the transmission periodicity of the first amplitude mask, and Λ

₀ is the periodicity of the first band of the fiber grating.

24. A method of manufacturing a multiple band long-period fiber grating, comprising the steps of:

splitting a UV laser beam into two portions in approximately a 1;

1 ratio;

directing one portion of the UV laser light through a first cylindrical lens oriented with the focal point on an optical fiber, and then passing the light from the cylindrical lens through a first dispersing unit having a focus, for increasing the beam size;

passing the light from the first dispersing unit through a first amplitude mask having a first periodicity and oriented at a first distance above the optical fiber;

passing the light from a first amplitude mask through a first slit having a first slit width along the length of the optical fiber to irradiate a region of the optical fiber around the focal point of the first cylindrical lens;

directing the second portion of the UV laser light through a second cylindrical lens oriented with the focal point on a region of the optical fiber adjacent to the focal point of the first cylindrical lens, and then passing the light from the second cylindrical lens through a second dispersing unit having a focus, for increasing the beam size; and

passing the light from the second dispersing unit through a second amplitude mask having a second periodicity and oriented at a second distance above the optical fiber and through a second slit having a second slit width, to irradiate a region of the optical fiber around the focal point of the second cylindrical lens.

25. The method of claim 24, further comprising:

controlling the first and second distances using a controller.

26. The method of claim 25, further comprising:

measuring the coupling peaks of light passed through the fiber from a light source at one end to a measuring unit at the other end during the manufacturing of the two band long-period fiber grating; and

adjusting the position of the first amplitude mask using the controller so that a measured coupling peak occurs at a desired wavelength.

27. The method of claim 24, said step of directing the second portion of the light comprising reflecting the second portion using a mirror.

28. The method of claim 27, further comprising:

setting the first distance to the value determined using the formula;

$\mathrm{\Lambda <br><br>}=\frac{{\mathrm{\Lambda <br><br>}}_0<br><br>\left(x+y\right)}{x}$

where y is the first distance, x is the distance from the focus of the first dispersing unit to the optical fiber, Λ

₀ is the transmission periodicity of the first amplitude mask, and Λ

is the periodicity of the first band of the fiber grating.

29. The method of claim 24, further comprising:

using a hydrogen-loaded germanium doped optical fiber as the optical fiber.

30. The method of claim 24, further comprising:

the first period of the first amplitude mask being equal to the second period of the second amplitude mask.

31. The method of claim 24, further comprising:

adjusting the first and second slit widths to determine the first and second bandwidths of the two-band fiber grating.