Optical side input/output circuit and optical connector

An optical side input/output circuit comprising:

• a grating portion in which a fiber Bragg grating that reflects light of a desired wavelength is formed in a core of a step-index optical fiber, the light of the desired wavelength being of light propagating in the core;
• and
• a tap portion that is disposed at a stage before the grating portion in a propagation direction of the light, and is provided with a tap waveguide that outputs a reflected light reflected by the grating portion from a side surface of the optical fiber;
• wherein the tap portion is configured such that the tap waveguide extends from outside the optical fiber, passes through a cladding of the optical fiber, and connects to the core, and wherein an angle formed between the core and the tap waveguide on a side opposite to the grating portion is an acute angle.