Abstract: An optical transmission apparatus is disclosed which comprises a light emitting element for outputting an optical output in order to transmit data, a current modulation circuit, a bias current generating circuit and a resistor circuit connected in parallel with the emitting element. The current modulation circuit supplies a binary modulated current to the emitting element in response to an input binary data to the transmitted, the bias current generating circuit provides a bias current to the emitting element and the resisor circuit, whereby said bias current is kept higher than a specified level.

Abstract: A star network optical transmission system comprising a star coupler as a center node, wherein a star coupler is provided with an optical fiber exhibiting a multimode transmission characteristic to an optical signal transmitted by said star coupler at an input portion and an output portion, an optical transmission apparatus having a laser with a wavelength of .lambda. as a light source, an up optical fiber exhibiting a single mode transmission characteristic to a wavelength of .lambda. connecting the optical transmission apparatus to the star coupler, an optical reception apparatus, and a down optical fiber exhibiting a multimode transmission characteristic at a wavelength .lambda. and connecting the optical reception apparatus to said star coupler.