Amplitude mask, and apparatus and method for manufacturing long period grating filter using the same

• US 6,204,969 B1
• Filed: 12/08/1998
• Issued: 03/20/2001
• Est. Priority Date: 12/08/1997
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jang, Joo-nyung
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US09/207,584
• Time in Patent Office: 833 Days
• Field of Search: 359/3, 359/8, 359/34, 359/35, 359/577, 359/566, 359/569, 359/570, 359/900, 385/37
• US Class Current: 359/570
• 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
• 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: G03F 7/001 Phase modulating patterns, e.g. refractive index patterns
• CPC Class Codes: G03F 7/70283 Mask effects on the imaging process
• CPC Class Codes: Y10S 359/90 Methods

Abstract

An amplitude mask, and an apparatus and method for manufacturing a long period grating filter using the same, are provided. When a long period grating is manufactured by selectively passing laser light to an optical fiber, the amplitude mask periodically passes laser light to the optical fiber. The amplitude mask includes two masks having periodically alternating pass areas for passing the laser light and nonpass areas for preventing passing of the laser light, the two masks being continuously rotated in opposite directions. The period of the pass area thus continuously changes. In this mask, two masks each having a predetermined period are rotated in opposite directions, to thus provide an amplitude mask period depending on the angle of rotation. Thus, the period of the amplitude mask can be continuously changed.

Claims

1. An amplitude mask for periodically passing laser light to an optical fiber when a long period grating is manufactured by selectively passing the laser light to the optical fiber, comprising:

two masks having periodically alternating pass areas for passing the laser light and nonpass areas for preventing passing of the laser light; and

the two masks being rotatable over a continuous range in opposite directions such that the period of the pass area may be varied over a continuous range.

2. The amplitude mask as claimed in claim 1, the substrate material of each mask comprising a metal.

3. The amplitude mask as claimed in claim 1, the period (Λ

) of the amplitude mask being determined by the equation;

$\mathrm{\Lambda <br><br>}=\frac{2<br><br>{\mathrm{\Lambda <br><br>}}_0<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}}{\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\mathrm{\alpha <br><br>}}$

wherein Λ

₀ is the period of the mask, and α

is the angle of rotation of the two masks.

4. A long period grating filter manufacturing apparatus comprising:

a laser optical source for emitting laser light;

an amplitude mask portion whose period is controlled by overlapping two masks each having a predetermined period and rotating the two overlapped masks a predetermined angle, and which selectively passes the laser light to an optical fiber in which a long period grating is to be formed, according to the predetermined period; and

a rotator for rotating the two masks a predetermined angle in opposite directions.

5. The long period grating filter manufacturing apparatus as claimed in claim 4, further comprising:

a second optical source;

a detector for detecting a coupling peak of the long period grating filter from one of two ends of an optical fiber in which a long period grating has been formed, when light generated by the second optical source is incident upon the other of two ends of the optical fiber in which the long period grating has been formed; and

a controller for controlling the rotator to obtain a desired coupling peak wavelength by receiving a wavelength at the coupling peak from the detector.

6. The long period grating filter manufacturing apparatus as claimed in claim 4, the substrate material of each mask comprising a metal.

7. The long period grating filter manufacturing apparatus as claimed in claim 5, the period (Λ

) of the amplitude mask being determined as follows;

$\mathrm{\Lambda <br><br>}=\frac{2<br><br>{\mathrm{\Lambda <br><br>}}_0<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\alpha <br><br>}}{\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>2<br><br>\mathrm{\alpha <br><br>}}$

wherein Λ

₀ is the period of the mask, and α

is the angle of rotation of the mask.

8. A long period grating filter manufacturing apparatus comprising:

a laser optical source;

a mirror for changing the path of laser light emitted by the laser optical source;

a lens for adjusting the focus of laser light whose path has been changed;

an amplitude mask portion whose period is controlled by overlapping two masks each having a predetermined period and rotating the two overlapped masks a predetermined angle, and which selectively passes the laser light passed through the lens to an optical fiber in which a long period grating is to be formed, according to the predetermined period;

a detector for detecting a coupling peak of a long period grating filter formed on the optical fiber; and

a controller for controlling the period of the amplitude mask to obtain a desired coupling peak wavelength by receiving a wavelength at the coupling peak from the detector.

9. A method of manufacturing a long period grating filter, comprising the steps of:

overlapping two masks in each of which pass regions passed by laser light alternate with nonpass regions, and rotating the two masks in opposite directions;

irradiating the laser light to an optical fiber via the pass regions formed at predetermined periods in the two rotated masks and forming a long period grating on the optical fiber; and

measuring a coupling peak due to the long period grating by passing light through the optical fiber on which the long period grating has been formed, and controlling the angle of rotation at which the two masks are rotated so that the measured coupling peak is achieved at a desired wavelength.