Abstract: A multi-branch optical network testing method (or device) is provided to perform a fault isolation test on an optical network that branches off at a branch point by a number of optical lines having terminal ends respectively. Herein, optical pulses are input to the optical network, from which they are returned as reflection beams. Then, response beams corresponding to mixture of the reflection beams are converted to OTDR waveform data representing a waveform whose optical power gradually decreases in accordance with a distance from an OTDR measurement device and which has a number of reflection peaks. The OTDR waveform data are subjected to logarithmic conversion to produce logarithmic waveform data representing a logarithmic waveform. An approximation method of least squares is effected on the logarithmic waveform data to produce an approximation line, which crosses the logarithmic waveform at points of intersection corresponding to Fresnel reflection points.

Abstract: A testing device performs testing on a multistage multi-branch optical network, which contains optical lines (such as optical fibers) that are connected together at connection points (e.g., optical couplers) in a multistage multi-branch manner. An OTDR measurement device uses software to perform fault determination with respect to the multistage multi-branch optical network. Herein, optical pulses are input to an input end of the multistage multi-branch optical network, wherein they are reflected at certain portions of the optical lines and the connection points while propagating through the optical lines. Then, reflected beams are returned to the input end and are mixed together as response light, which is measured by the OTDR measurement device. The response light is converted to a plurality of digital waveform data representing a measured waveform, which is then divided into multiple ranges on the basis of the Fresnel reflection points and connection points.

Abstract: A multi-branched optical line testing apparatus can automatically detect a faulty line in multi-branched optical lines and the distance to the fault point. An optical pulse is introduced to the branch point of optical fibers and is reflected inside the respective optical fibers. The waveform of the returning response light is analyzed by an optical time-domain reflectometer (OTDR) measuring apparatus to detect a fault in the respective optical fibers and to determine the fault point. The OTDR measuring apparatus periodically converts the response light which is returned from the respective optical fibers into a digital waveform data group, calculates the attenuation ratios of the respective optical fibers by performing separation analysis of the digital waveform data group, and determines the faulty line and the position of the fault point based on the change of the attenuation ratio of the respective optical fibers.