Single-mode fiber-optic directional couplers

A new design of Y-type end-fused single-mode fiber directional couplers has been suggested and its optimum parameters to obtain losses of 0,5–1 dB have been determined. A technique has been developed for fabricating such couplers by electric arc fusion of single-mode fibers with thin claddings. Excess loss in these couplers splitting into two channels is 1—3 dB and the value is in good agreement with calculations. Cross-talk attenuation between reverse channels exceeds 60 dB, which is an indication of high directivity of the couplers. It has been found by experiments that the developed couplers maintain the state of polarization of the propagating radiation.