JPH05249410

PURPOSE:To obtain an optical blanching/coupling device with a little insertion loss and without polarization dependency and suitable for duplex communication by an optical fiber in particular. CONSTITUTION:This element consists of an input port, an output port, input/ output port and a double refractive crystalline plate 101. Each port consists of the series of a double refractive crystalline part and optical activity crystalline parts divided into two stages of upper and lower, and further the input/ output port contains a Faraday element 102 between them. An incident optional polarization beam from the input port is divided into a normal light ray o1 and an abnormal light ray e1 and take upper and lower light paths and pass through the double refractive crystalline plate 101 as both normal light rays and outgo from the input/output port in an original polarization beam state. Further, the incident optional polarization beam from the input/output port is divided similarly, but since they pass through the double refractive crystalline plate 101 as the abnormal light rays by the action of the Faraday element 102, the optical activity crystalline part 108, their traveling directions are refracted and outgo not from the input port but from the output port in the original polarization state.