Bidirectional optical communication device and bidirectional optical communication apparatus

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
• θfb≦0≦θfa or θfa≦0≦θfb
• is satisfied when angles of inclination θfa and θfb 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:
• θfa=Sin−1 [{n0 Sin(θL+Sin−1(NA)/n0+θT)}/nf]−θT θfb=Sin−1 [{n0 Sin(θL−Sin−1(NA)/n0+θT)}/nf]−θT
• where θL denotes an angle between an optical axis of transmission light prior to entering the optical fiber and an optical axis of the optical fiber, θT 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, nf denotes a refractive index of a core of the optical fiber, and no denotes a refractive index of space through which the transmission light passes prior to entering the optical fiber.