JPS57174946A - Bidirectional optical transmission method - Google Patents

Abstract

PURPOSE:To enable to realize bidirectional optical transmission with low loss, by spatially separating two linearly polarized optical beam at an input terminal of an optical fiber without inducing any loss. CONSTITUTION:The plane of polarization of an oscillated optical beam of a semiconductor laser 1 is matched to one plane of polarization of a polarized beam split prism 11. In this case, the oscillated optical beam from the laser 1 is made parallel at a lens 5 and transmitted to the prism 11 in the plane of polarization in parallel with this paper. This plane of polarization is matched to e.g., the major axis of an index ellipsoid of an optical fiber 13 and introduced to the fiber 13 via a lens 7. Similarly, at another end of the fiber 13, the plane of polarization of oscillated light from a semiconductor laser 2 is adjusted so as to match with minor axis of the index ellipsoid of the fiber 13. Thus, the polarized light incident to the fiber 13 from the laser 1 keeps linearity also at the emission side and is made incident to a photodetector 4 straightforward without being incident to the laser 2, and similarly the oscillated light of the laser 2 is made incident to a photodetector 3.