Arrayed hybrid filter/coupler device for in-service fibre line testing

An arrayed hybrid filter/coupler consisting of four waveguide-type wavelength-insensitive couplers and a thin dielectric filter has been developed for application to an in-service optical fibre testing system. The device was designed to combine a 1.31 mu m communication light and a 1.55 mu m test light with a ratio of 80:20%. The measured performance of a prototype device exhibited an excess loss of 0.6 dB, a return loss attenuation of >45 dB and a crosstalk attenuation for the test light of >60 dB.