Polarization-OTDR for measuring characteristics of optical fibers
AssigneeEXFO Electro-Optical Engineering Inc.
InventorMichel Leblanc
Life of this patent
Estimating the term…
Abstract
In a method of polarization optical time-domain reflectometer (P-OTDR) for measuring a parameter of an optical transmission path, for example an optical fiber, by transmitting pulses of light into the path and measuring the state of polarization of backscattered light against distance, statistical analysis of the degree of polarization (DOP) of the backscattered signal is used to detect sections of an optical transmission path for which mode-coupling behaviour (long h) leads to high PMD. Preferably, successive DOP measurement are taken with different state of polarization, SOP, for the P-OTDR light source.
Claims18
A method of measuring characteristics of an optical path comprising the steps of:
- transmitting a first series of polarized optical signal pulses into the path, each of the pulses having a length that is long compared with a beat length of the optical path and having a first state of polarization (SOP);
- transmitting at least a second series of pulses into the path, the pulses of said second series each having a length substantially equal to the length of the pulses of the first series but having a second state of polarization that differs significantly from the state of polarization of the pulses of said first series of pulses when the first and second states of polarization are represented on the Poincaré sphere;
- measuring, and averaging over a prescribed period of time, intensity of backscattered light corresponding to each of the first and second series of pulses;
- deriving, from said intensity measurements, a degree of polarization (DOP) signature comprising a degree of polarization with respect to distance along the path for each of the first and second states of polarization;
- and
- analyzing said DOP signatures to determine variations in polarization mode dispersion (PMD) along the length of the path.
Apparatus for measuring optical characteristics of an optical path, such as an optical fiber, comprises:
- means for transmitting a first series of polarized optical signal pulses into the path, each of the pulses having a length that is long compared with a beat length of the optical path and having a first state of polarization (SOP);
- means for transmitting at least a second series of pulses into the path, the pulses of said second series each having a length substantially equal to the length of the pulses of the first series but having a second state of polarization that differs significantly from the state of polarization of the pulses of said first series of pulses when the first and second states of polarization are represented on the Poincaré sphere;
- means for measuring, and averaging over a prescribed period of time, intensity of backscattered light corresponding to each of the first and second series of pulses;
- means for deriving, from said intensity measurements, a DOP signature comprising a degree of polarization with respect to distance along the path for each of the first and second states of polarization;
- and
- means for analyzing said DOP signatures to determine variations in polarization mode dispersion (PMD) along the length of the path.
Dependencies are inferred from the claim text.