Disclosed is an apparatus for measuring convergence using a fiber Bragg
grating sensor measuring slight deformation, capable of measuring the
convergence such as the inclination or the gravitational acceleration of
a measurement target including a bridge or a tunnel by measuring the
deformation of the fiber Bragg grating sensor when the measurement target
is inclined or vibrated, as well as a measurement method using the
apparatus. The apparatus includes a main body that is installed on a
measurement target; a fixture that is fixedly installed at the front of
the main body; a rotator that is horizontally installed apart from the
fixture at a predetermined distance and is rotatably installed in the
main body using a bearing; an optical fiber that is adhered to upper
outer surfaces of the fixture and the rotator so as to maintain a
horizontally tensioned state and has optical terminals installed on
opposite ends thereof; a fiber Bragg grating sensor that is installed on
the optical fiber between the fixture and the rotator; and a bob that is
vertically connected with a lower portion of the rotator by a support
having a predetermined length. The apparatus is installed on the
measurement target after setting a reference value and then calculates a
quantity of displacement caused by variation of the ground, so that
values of angular displacement and gravitational acceleration
displacement are measured.