Unidirectional absolute optical attenuation measurement with OTDR

摘要

Devices and methods for optical measurements in point-to-point and point-to-multipoint networks, e.g. like PON networks with splitters are described in which reflected power from some known reflections at the end of the lines is used to determine the attenuation and stability of the attenuation of each line. Also a reference reflection is used at the beginning of the network so that an absolute loss measurement between the points of reflection and the reference reflection can be made. In a further aspect wavelength selective stable reflections and reflectors are used, to provide reflections in a wavelength range that does not interfere with normal operation.

主权项

1. A monitoring device for monitoring absolute loss between two points in an optical network, said optical network comprising an optical transmission path having a head end and at least one remote end, the optical network carrying data traffic using at least light of a first wavelength, wherein the monitoring device comprises:
an optical signal returning device at a first location in the optical network; a reference optical signal returning device at a second location in the optical network; optical test equipment for communicating with the head end, the optical test equipment optically connected to the optical network at a location spaced apart from at least the first location and configured to:
send a test signal at a test wavelength, different from the first wavelength; andreceive a first returning signal from the optical signal returning device and a second returning reference signal from the reference optical signal returning device, both the first returning signal and the second returning reference signal being derived from the test signal; andcompare the first returning signal and the second returning reference signal to derive therefrom a value related to the absolute loss between the first and second locations in the optical network, wherein at least one of the optical signal returning device and the reference optical signal returning device is a wavelength selective device, wherein the test signal travels with the data signal remains spaced apart from the reference optical signal returning device.