Patent ID: 6934478

Claim:
A bidirectional optical communication device for carrying out transmission and reception of an optical signal with use of one optical fiber having a curved end face as a transmission medium, comprising: a light emitting element for generating transmission light; a collection member for collecting transmission light emitted from the light emitting element and coupling the transmission light to the optical fiber; and a light receiving element for receiving reception light emitted from the optical fiber, wherein θ fb ≦0≦θ fa or θ fa ≦0≦θ fb is satisfied when angles of inclination θ fa and θ fb between an optical axis of the optical fiber and the transmission light after entering the optical fiber with a numerical aperture NA at an outermost periphery are expressed as follows: θ fa =Sin −1 [{n 0 Sin(θ L +Sin −1 ( NA )/ n 0 +θ T )}/ n f ]−θ T θ fb =Sin −1 [{n 0 Sin(θ L −Sin −1 ( NA )/ n 0 +θ T )}/ n f ]−θ T where θ L denotes an angle between an optical axis of transmission light prior to entering the optical fiber and an optical axis of the optical fiber, θ T denotes an angle between a perpendicular line of the optical fiber end face in a position where the transmission light is coupled to the optical fiber and an optical axis of the optical fiber, NA denotes a numerical aperture of the transmission light collected by the collection member prior to entering the optical fiber, n f denotes a refractive index of a core of the optical fiber, and n o denotes a refractive index of space through which the transmission light passes prior to entering the optical fiber.