A control circuit for a fiber amplifier having a first stage pump and at least one second stage pump and method of controlling thereof is disclosed. The semi-light-shielding portion 102 is disposed in an outer region of the mask pattern and partially transmits the exposing light in an identical phase to the exposing light passing through the transparent portion 104. The bone plate has a through hole shaped like an hourglass which diameter matches that of the screw spherical head and is provided with multiple isolated protrusions. The lined trench is then filled with a metal fill material.