There are provided methods and systems that enable the use of the backscattering pattern produced by an optical fiber in an OTDR trace as a signature (also referred to herein as the “RBS fingerprint”) to recognize an optical fiber. It was found that it may be difficult to obtain repeatable signatures as those are sensitive to the wavelength of the OTDR laser source and the temperature of the fiber. OTDR methods and systems that are adapted to compare the backscattering pattern in a more repeatable manner are therefore provided. Once the repeatability issue is overcome, such signature can be used for identification purposes and enable new applications.

The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Brillouin scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.

An optical test system capable of accurately measuring a loss of each mode at each position of an optical fiber which propagates a plurality of modes is provided. An optical fiber loss measuring apparatus for measuring using an OTDR technique includes a crosstalk suppressing light input unit that inputs light of a different mode different from the predetermined mode, the different mode causing crosstalk to the probe light, to the target optical fiber to be measured through the near end as crosstalk suppressing light at a second frequency obtained by giving a frequency that is equivalent to a Brillouin frequency shift of the predetermined mode to a first frequency, a light separating unit that removes light of the second frequency from light that is output from the target optical fiber to be measured through the near end to separate light of the first frequency, and a propagation mode loss measuring unit that measures an intensity of the separated light to measure a loss of each propagation mode at each position of the target optical fiber to be measured.

The present invention has an object to provide an optical fiber test method and an optical fiber test apparatus for measuring a mode dependent loss and an inter-modal crosstalk in a fundamental mode and a first higher-order mode at a connection point of a few-mode fiber. In the optical fiber test method and test apparatus according to the present invention, the mode dependent loss and the inter-modal crosstalk in the fundamental mode and the first higher-order mode at the connection point are calculated by using an approximation expression of an inter-modal coupling efficiency that is obtained in approximating electric field distributions of the fundamental mode and the first higher-order mode in a few-mode fiber by Gaussian function and Hermite Gaussian function.

An arrangement for distributed acoustic sensing and sensor integrity monitoring is adapted to operate in a first operation mode and in a second operation mode. In the first operation mode, the arrangement injects a first light pattern (and successively injects a second light pattern having substantially the same wavelength, both light patterns generated using a light launching module, into the fiber; determines a backscatter change between first backscatter dependent light and second backscatter dependent light detected by the detector, to determine a time change of a characteristic of the fiber. In the second operation mode, the arrangement injects another first light pattern and successively another second light pattern; to determine a backscatter average of other first backscatter dependent light and other second backscatter dependent light detected by the detector, to determine a static characteristic of the fiber.

Aspects of the present disclosure describe amplifier dynamics compensation through feedback control for distributed fiber sensing systems, methods, and structures employing Brillouin optical time-domain reflectometry.

A bidirectional optical repeater having two unidirectional optical amplifiers and a supervisory optical circuit connected to optically couple the optical ports thereof. In an example embodiment, the supervisory optical circuit provides one or more pathways therethrough for supervisory optical signals, each of these pathways having located therein a respective narrow band-pass optical filter. The supervisory optical circuit further provides one or more pathways therethrough configured to bypass the corresponding narrow band-pass optical filters in a manner that enables backscattered light of any wavelength to cross into the optical path that has therein the unidirectional optical amplifier directionally aligned with the propagation direction of the backscattered light.

Systems and methods include detecting a fast fiber transient on a span based on analyzing power data, wherein the power data is for any of optical wavelengths of traffic channels, optical service channel (OSC) wavelengths, and telemetry from a network element; and responsive to detecting the fast fiber transient, causing an optical time domain reflectometer (OTDR) trace on the span with a specific configuration based on the fast fiber transient.

An Optical Time Domain Reflectometer (OTDR) module obtains Optical Return Loss (ORL) of a fiber plant. Calibration information is obtained of at least internal OTDR reflections associated with the OTDR module. The OTDR module is connected to the fiber plant. An ORL response is measured due to reflections of an ORL signal transmitted from the OTDR module along the fiber plant, and a peak OTDR response is measured in response to reflections of an OTDR signal transmitted from the OTDR module along the fiber plant. A corrected ORL response of the fiber plant is determined by: using the measured peak OTDR response (e.g., peak value or area under the peak) and the calibration information to calculate the calculated ORL due to internal reflections, and then adjusting the measured ORL response by the calculated ORL to represent the corrected ORL of the fiber plant.

The purpose of the present invention is to provide a device for optical frequency domain reflectometry and a method thereof that can measure a reflectance distribution with less spatial resolution degradation due to a phase noise, without using a wideband receiving system even when a long-distance measurement is performed. The device for optical frequency domain reflectometry according to the present invention is provided with a delay optical fiber for delaying a local light by a prescribed time, and obtains information on a relative delay of a backscattered light from an optical fiber under measurement with respect to the local light and information on the positivity and the negativity of a beat frequency by measuring an in-phase component and a quadrature component of a beat signal obtained by multiplexing the backscattered light from the optical fiber under measurement and the local light delayed by the delay optical fiber, so as to obtain a reflectance distribution in a longitudinal direction of the optical fiber under measurement based on these pieces of information.