An optical signal emitter includes a transmitting lens; a lens supporting portion, extending from an edge of the transmitting lens to defined a containing space surrounded by the transmitting lens and the lens supporting portion; a lens carrier, for carrying the transmitting lens and the lens supporting portion, wherein a coupling surface is defined on the lens carrier and at least a part of the lens supporting portion is coplanar with the lens carrier with respect to the coupling surface; a light transmitter, disposed in the containing space and coaxially with the transmitting lens, so as to define an light transmission path for light passing through coupling surface by an alignment between the light transmitter and the transmitting lens; at least one engagement portion, disposed on the coupling surface; at least one magnet, disposed on the lens carrier.