Contents Introduction
Recently, a long wavelength band (L-band) that extends to 1625 nm has begun to be used for WDM transmission [3] and a 10 Gbit/s WDM system is being introduced into metropolitan networks. An optical fiber line testing system is essential for reducing maintenance costs and Improving service reliability in optical access networks. We have already developed and introduced such a system called AURORA (AUtomatic optical fibeR OpeRAtions support system) [1] [2], and use the 1650 nm wavelength band for maintenance in accordance with ITU-T recommendation L.41 [2] [4]. With a view to monitoring optical fiber cables transmitting L-band communication light, an attractive way of separating the 1650 nm band test light from the L-band communication light is to use a chirped fiber Bragg grating (FBG) filter because of its steep optical spectrum [2]. However, multi-reflections degrade the accuracy of the OTDR mesurement when FBG filters are installed at either end of an optical fiber line [5]. In this paper, we design and evauate an extended optical fiber line testing system that employs a new L/U-band crossed optical waveguide coupler in a planar lightwave circuit (PLC) with a multi-array design and demonstrate the in-service line testing of 10 Gbit/s L-band transimission.
