| 摘要 |
PROBLEM TO BE SOLVED: To increase the incident light quantity to a light receiving element and to improve sensitivity by embodying an optical system which is free from light power loss in principle, to decrease noises by prohibiting the return light to a light emitting element 12 and to reduce the size over the entire part and a cost. SOLUTION: The light emitting element 12 and the light receiving element 14 as well as a polarization beam splitter 16, a Faraday rotator 18, a lens 20 and an optical waveguide element 22 are built into a single casing and are integrated. The light radiated from the light emitting element 12 is passed through the polarization beam splitter 16 by space propagation. The linearly polarized light rotated by the Faraday rotator 18 is coupled with the optical waveguide element 22. Conversely, the return light from the optical waveguide element 22 is passed through the Faraday rotator 18 by space propagation, is reflected by the polarization beam splitter 16 and is coupled with the light receiving element 14. The return light from the optical waveguide element 22 is coupled only with the light receiving element 14 and is not coupled with the light emitting element 12 by the control of the plane of polarization by the polarization beam splitter 16 and the Faraday rotator 18 which rotates the plane of polarization by 45 deg.. |
