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

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.

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.

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.