An optical device includes a light emitting element emitting light signal, a light coupling lens and a light receiving element. The light coupling lens includes a light input surface, a light output surface adjacent to the light input surface and a plurality of total reflective surfaces connected to the light input surface and the light output surface. The light input surface includes a first aspheric protrusion facing the light emitting element. The light output surface includes a second aspheric protrusion. Light signal emitted from the light emitting element enters the light coupling lens and collimated by the first aspheric protrusion to be parallel light signal. The parallel light signal is reflected by the total reflective surface and then collimated by the second aspheric protrusion to be convergent light signal. The light receiving element receives the convergent light signal.