A New Optical Fiber Line Testing Function for Service Construction Work That Checks for Optical Filters Below an Optical Splitter in a PON

In this paper, we propose a new function for construction work undertaken to install optical fiber lines for services in a passive optical network (PON). This paper describes a novel measurement technique designed to check for optical filters located in front of an optical network unit in branched optical fiber regions in PONs with outside optical splitters. The purpose is to determine whether an optical fiber is ldquoliverdquo or ldquounused.rdquo The features of our proposed technique are the use of test lights operating at two different wavelengths and a nondestructive macrobending technique. By comparing the difference between the reflected powers of the two wavelengths, we can determine the presence of a filter at the end of a fiber line. Furthermore, we describe an enhanced estimation analysis method that uses two photodetectors installed symmetrically in the detection part and an analysis procedure for detecting only a test light reflected from the fiber end. We also demonstrate the performance of the enhanced analysis method experimentally and confirm that it can be employed to detect an optical filter installed at the end of an optical fiber line.