Fusion splicer and fusion splicing method

A fusion splicer for fusion-splicing a first end face that is an end face of a first optical fiber having a plurality of cores with a second end face that is an end face of a second optical fiber having a plurality of cores, the fusion splicer comprising:

• a first holding unit configured to hold the first optical fiber in a state where the first end face faces the second end face;
• a second holding unit configured to hold the second optical fiber in a state where the second end face faces the first end face;
• a screen disposed between the first end face and the second end face, the screen including a light guide portion through which only light emitted from one of the plurality of cores of the first optical fiber can pass, and a light shielding portion that shields light that does not pass through the light guide portion;
• a light source configured to cause test light to enter the first optical fiber;
• a first measurement device configured to measure an intensity of leakage light leaking from the second optical fiber out of the test light emitted from the first end face and incident on the second end face;
• discharge electrodes configured to heat the first end face and the second end face;
• a first driving unit configured to adjust a position of the first holding unit and a first angle that is a rotation angle about an axis of the first optical fiber;
• a second driving unit configured to adjust a position of the second holding unit and a second angle that is a rotation angle about an axis of the second optical fiber;
• and
• a third driving unit configured to adjust a position of the screen such that the light guide portion is aligned with one of the plurality of cores of the first optical fiber in an axial direction of the first optical fiber, and to retract the screen from a position between the first end face and the second end face.