A confocal optical system comprising a scanning fiber is provided. The scanning fiber is a single-mode fiber of which a first end is shaped as a curved surface. The scanning fiber transmits illumination light to the first end. The illumination light is emitted toward an observation area. The illumination light emanates from the first end. The illumination light emanates from the first end striking a target area within the observation area. The first end receives at least one of reflected light and fluorescence from the target area. The reflected light is the illumination light reflected from the target area. The fluorescence is induced at the target area by illumination from the illumination light.