75results about "Reflectometers using simulated back-scatter" patented technology

A modular fiber optic interferometry control system and method for extracting information from superimposed waves is disclosed. The system comprises a first module for converting a radio frequency input to a multiplexed binary data stream, a second module for correlating a pseudo random number (PRN) reference with a received PRN code modulated backscattered signal, and a third module comprising control logic. In some embodiments the system further comprises one or more of a fourth module for generating a power stream, a fifth module for event interrogation, and a sixth module for noise reduction.

A method of determining the gain characteristic of a Raman amplifier includes the steps of launching a pump light signal into a fiber; preliminary adjusting the power of the pump light signal to a value that lies in a range where the amplified spontaneous emission noise originating from the pump light signal is substantially proportional to the on / off gain provided by the power of the pump light signal; monitoring the power of the amplified spontaneous emission noise signal; varying the power of the pump light signal; measuring a variation in the power of the amplified spontaneous emission noise signal corresponding to the pump power variation; and determining the gain characteristic of the amplifier from the relative variation in pump power and the measured variation in noise power.

Raman amplifier systems and methods with an integrated Optical Time Domain Reflectometer (OTDR) for integrated testing functionality include an amplifier system, an OTDR and telemetry subsystem, and a method of operation. The OTDR and telemetry subsystem is configured to operate in an OTDR mode when coupled to a line in port and to operate in a telemetry mode when coupled to a line out port. The OTDR and telemetry subsystem enables on-demand fiber testing while also operating as a telemetry channel that is both a redundant optical service channel (OSC) and provides a mechanism to monitor Raman gain over time. The OTDR and telemetry subsystem minimizes cost and space by sharing major optical and electrical components between the integrated OTDR and other functions on the Raman amplifier.

A method for measuring Brillouin backscattering from an optical fibre (18), comprises frequency mixing a first signal with a frequency f B (t) representative of the Brillouin frequency shift in backscattered light received from a deployed optical fibre with a second signal at a frequency f i (t) that varies in time in the same manner as a Brillouin shift previously measured from the fibre to produce a difference signal with a difference frequency iF(t) that has a nominally constant value corresponding to the situation where the received light has a Brillouin shift that matches the previously measured shift. The difference signal is acquired and processed to determine properties of the Brillouin shift and corresponding physical parameters producing the shift. The frequency mixing can be carried out. optically or electrically. Techniques for acquisition of the difference signal include the use of parallel frequency measurement channels and fast rate digital sampling.

A method of providing Raman amplification in an optical fiber sensing system, comprises generating a probe pulse of light and launching the pulse into a sensing optical fiber, generating pump light at a shorter wavelength and modulating it to produce a time-varying intensity profile, and launching the pump light into the sensing fiber. such that the intensity of the launched pump light during launch of the probe pulse is different from the intensity at other times. Raman amplification of backscattered light produced by the probe pulse as it propagates along the fiber is achieved, as is amplification of the probe pulse if the pump power is non-zero during launch of the probe pulse.

An apparatus for measuring the characteristics of an optical fiber is provided. An optical pulse generator generates, from a coherent light, first and second optical pulses having a time interval which is equal to or shorter tan a life time of an acoustic wave in the optical fiber. A detector couples the coherent light with a Brillouin backscattered light which includes first and second Brillouin backscattered lights belonging to the first and second optical pulses respectively, thereby generating an optical signal. The detector further converts the optical signal into an electrical signal. A signal processor takes the sum of the electrical signal and a delay electrical signal which is delayed from the electrical signal by a delay time corresponding to the time interval, thereby generating an interference signal, and finds the characteristics of the optical fiber based on the interference signal.

optical fiber characteristic measuring device comprising a coherent light supply device, a light pulse generating device, a wave mixing device, a opto-electrical converting device, and a processing device, is provided such that parts have the frequency characteristic for corresponding to low frequency component for an opto-electrical converting device and a processing section so as to reduce the cost of the circuits.

A method of distributed and dynamical Brillouin sensing in optical fibers is provided herein. The method includes the following stages: deriving average characteristics of an optical fiber along its length; generating a variable frequency probe signal, such that the variable frequency is tailored to match, at specified points along the fiber, the respective average characteristics; injecting the variable frequency probe signal to a first end of the optical fiber and a periodic pulse signal to a second end of the optical fiber, wherein the injecting is synchronized such that a stimulated Brillouin scattering is carried out at each one of the specified points along the optical fiber, such that a frequency difference between the probe signal and the pump signal matches the average characteristics of the fiber; and measuring occurrences of the stimulated Brillouin scattering, to yield data indicative of strain and temperature at all points along the optical fiber.

The invention discloses a Brillouin optical time domain analyzer relevant to a chaotic laser, which is an optical fiber Brillouin optical time domain analyzer made according to the chaotic laser relevant principle, the coherent amplification Brillouin scattered light, the temperature effect and the optical time domain reflection principle. In the analyzer, the same chaotic laser device serves as the local reference light source and the pump signal light source of the Brillouin optical time domain analyzer. According to the chaotic laser relevant principle, the chaotic laser has an ultra-wide frequency width; signal light and local light are relevantly processed to obtain a high spatial resolution, so that the reliability of the sensor can be effectively improved, the spatial resolution can reach the centimeter level, the number of pump photons entering the sensing optical fiber is increased, the signal to noise ratio of the sensor system is 10dB, and the measurement length of the sensor can reach 50km; and the same chaotic laser device is adopted to serve as the local reference light source and the pump signal light source of the Brillouin optical time domain analyzer, thereby solving the problem of locking a narrow-band detection laser and a narrow-band pump laser, and improving system stability.

In an optical amplifier of the present invention, an input light is supplied to one end of an optical fiber connected to an output port, and the power of a light In an opposite direction which is input to the output port from the one end of the optical fiber, is measured, thereby obtaining a stimulated Brillouin scattering (SBS) occurrence threshold in the optical fiber based on the measurement result. Then, using the SBS occurrence threshold, a relation been the input light power and an occurrence amount of the self phase modulation (SPM) or the like in the optical fiber is obtained to be reflected on a control of the optical amplifier, so that an occurrence of the SPM or the like in the optical fiber is suppressed. As a result, It becomes possible to accurately measure, with a simple configuration, the nonlinear optical properties of the optical fiber actually connected to the output port of the optical amplifier, so that the optical S / N ratio degradation due to a nonlinear optical effect can be effectively suppressed.

Fiber light amplifiers adapted for high power application are provided. In embodiments of the invention, the light signal to be amplified is coupled to a cladding mode of an active waveguide region which is cladding doped. The amplified light is coupled to an output fiber have waveguiding properties matching those of the active cladding of the active waveguide region. In other embodiments, two or more amplifying stages are provided coupled by a wavelength selective loss element which couples the Stokes wave co-propagating with the signal to be amplified out of the signal guiding mode prior to the onset of SRS.

A long-distance polarization and phase-sensitive reflectometry based on random laser amplification for extending a sensing distance includes a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by unilateral pumps, a long-distance polarization and phase-sensitive reflectometry of a distributed Raman amplification based on optical fiber random lasers generated by bilateral pumps, and a long-distance polarization and phase-sensitive reflectometry of a Raman amplification based on a combination of optical fiber random lasers generated by unilateral pumps and a common Raman pump source, which are applied in optical fiber perturbation sensing and have a capability of greatly improving a working distance of a sensing system and a high practicability.

An arrangement for providing real-time, in-service OTDR measurements in an optical communication system utilizing distributed Raman amplification. One or more of the laser diodes used to provide the pump light necessary to create optical gain is modified to also generate short duration pulses that ride above or below the conventional pump light. These short duration pulses (which co-exist with the pump light within the optical fiber) are used in performing OTDR measurements, with a conventional processing system used to evaluate reflected pulses and create the actual OTDR measurements.

A method is provided for measurement of dispersion or other optical and mechanical properties within a waveguide by inducing four-photon mixing at different locations within the waveguide by timing a pump signal to counter-collide with and abruptly amplify or attenuate one or both of a probe pulse and a signal pulse at each location. The measurement of the components of the resulting mixing signal created by each collision is used to calculate dispersion defined by the location at which the collision occurred. By combining the measurements from all of the locations, a spatial map of dispersion or other optical or mechanical properties within the waveguide can be generated.

Systems and methods for characterizing an optical fiber performed in part by an optical node in an optical line system include performing one or more measurements to characterize the optical fiber with one or more components at the optical node, wherein the one or more components perform functions during operation of the optical node and are reconfigured to perform the one or measurements independent of the functions; and configuring the optical node for communication over the optical fiber based on the one or more measurements. The one or more components can include any of an Optical Service Channel (OSC), an Optical Time Domain Reflectometer (OTDR), and an optical amplifier. The configuring can include setting a launch power into the optical fiber based on the one or more measurements.

An apparatus for measuring the characteristics of an optical fiber is provided. An optical pulse generator generates, from a coherent light, first and second optical pulses having a time interval which is equal to or shorter tan a life time of an acoustic wave in the optical fiber. A detector couples the coherent light with a Brillouin backscattered light which includes first and second Brillouin backscattered lights belonging to the first and second optical pulses respectively, thereby generating an optical signal. The detector further converts the optical signal into an electrical signal. A signal processor takes the sum of the electrical signal and a delay electrical signal which is delayed from the electrical signal by a delay time corresponding to the time interval, thereby generating an interference signal, and finds the characteristics of the optical fiber based on the interference signal.

In Raman gain slope measurement method and device measures Raman gain slope which is a value obtained by normalizing a gain generated by Raman amplification caused by pump light incident on an optical fiber by optical power of the pump light in question. The method and device measures the power of noise light and operates based on a relationship between the optical power of pump light incident on an optical fiber and the optical power of the measured noise light generated by the application of the pump light, Raman gain slope of the optical fiber in question is thus calculated.

A modular fiber optic interferometry control system and method for extracting information from superimposed waves is disclosed. The system comprises a first module for converting a radio frequency input to a multiplexed binary data stream, a second module for correlating a pseudo random number (PRN) reference with a received PRN code modulated backscattered signal, and a third module comprising control logic. In some embodiments the system further comprises one or more of a fourth module for generating a power stream, a fifth module for event interrogation, and a sixth module for noise reduction.

The present invention relates to a spectral measurement apparatus and measurement method utilizing Brillouin scattering, which judge the state of the temperature or strain of an optical fiber more quickly. The spectral measurement apparatus comprises a light source, an analysis section, and an anomaly judgment section. The light source outputs pumping light and probe light. The pumping light and probe light thus output are caused to enter in opposite directions to the sensing fiber. The analysis section analyzes the gain received by the probe light as a result of the Brillouin scattering. The anomaly judgment section judges the state relating to the temperature or strain of the sensing fiber on the basis of the analysis result of the analysis section. The frequency difference υ between the pumping light and probe light is set within a predetermined frequency difference setting range. The frequency difference setting range is a range which includes the frequency difference at which the peak value of the reference gain spectrum of the gain received by the probe light is obtained when the temperature or strain of the sensing fiber is in the reference state and is set at or below the line width of the reference gain spectrum

A method of simultaneously specifying the wavelength dispersion and nonlinear coefficient of an optical fiber. Pulsed probe light and pulsed pump light are first caused to enter an optical fiber to be measured. Then, the power oscillation of the back-scattered light of the probe light or idler light generated within the optical fiber is measured. Next, the instantaneous frequency of the measured power oscillation is obtained, and the dependency of the instantaneous frequency relative to the power oscillation of the pump light in a longitudinal direction of the optical fiber is obtained. Thereafter, a rate of change in the longitudinal direction between phase-mismatching conditions and nonlinear coefficient of the optical fiber is obtained from the dependency of the instantaneous frequency. And based on the rate of change, the longitudinal wavelength-dispersion distribution and longitudinal nonlinear-coefficient distribution of thee optical fiber are simultaneously specified.

According to the invention, these aims are achieved by means of a sensor, suitable for sensing one or more properties of one or more structures, the sensor comprising, a first optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a second optical propagation path which is configurable to cooperate with a structure whose properties are to be sensed; a third optical propagation path; a means for amplifying a signal which propagates in the third optical propagation path, so that the signal is amplified before it begins propagation along the second optical propagation path, and a means to prevent the propagation of signals from the second optical propagation path to the third optical propagation path. There is further provided a corresponding method of sensing.

An integrated fiber interferometry interrogator for generating superimposed waves is disclosed. The system is optimized for efficiency and vibration attenuation. The system comprises an optical light source for generating a first signal, a first signal splitter which splits the first signal into a reference signal and an interrogation signal, optical modulators for modulating the signals, a fiber coupler connected to a fiber under test, an isolator, a circulator with a plurality of connections for directing the signals, a signal mixer for mixing the signals into superimposed waves, and photo diodes for receiving the superimposed waves.

A distortion of a device under test (such as an optical fiber) can be precisely measured. There is provided a distortion measuring device including a signal processing unit 32 having a Brillouin scattered light spectrum recording unit 322a which records a spectrum of Brillouin scattered light generated in an optical fiber as a result of supplying incident light, a Rayleigh scattered light spectrum recording unit 322b which records a spectrum of Rayleigh scattered light generated in the optical fiber as a result of supplying the incident light, a deconvolution unit 324 which derives a Brillouin gain spectrum of the optical fiber based on the recorded spectrum of the Brillouin scattered light and the recorded spectrum of the incident light, a peak frequency deriving unit 326 which derives a peak frequency at which the derived Brillouin gain spectrum takes the maximum value, and a distortion deriving unit 328 which derives a distortion of the optical fiber based on the derived peak frequency.

A method and a system for adjusting the sensitivity of an optical sensor are provided. A first beam of light in an optical fiber is separated into first and second portions propagating therethrough at a first speed. A second beam of light is directed into the optical fiber to interact with the first beam of light such that the first and second portions propagate through the optical fiber at a second speed. The propagation speed in turn influences the sensitivity of the optical sensor.

The invention relates to the technical field of optical time domain reflectometer, and provides a detection method and device for high-dynamic-range optical time domain reflection. The device comprises a Raman laser and an OTDR detection laser, which are respectively connected to a WDM, wherein a light outlet of the WDM is connected to a light inlet of a circulator; a light receiving and light signal processing module is connected to a light outlet of the circulator; the light receiving and light signal processing module is further connected to a control module; the control module is used forcontrolling a driving pin of the Raman laser, and controlling the Raman laser to emit at least two light pulses with a time interval in a detection time period according to the relevant information ofreflection light. According to a multi-pulse solution, the light pulses can be amplified and detected through forward Raman light pulses, the Raman light pulses can be continuously sent through the Raman laser after the OTDR detection laser is closed in order to directly amplify and detect back Rayleigh scattering light signals or Fresnel reflection light signals generated by the light pulses.

A test pulse is generated from a first and a second test light beam pulse with different wavelengths, with a predetermined time difference applied between the first and the second test light beam pulse. A circulator inputs the test pulse to a trunk fiber of a measurement target fiber line. A reflected light is extracted which is output from an input end of the trunk fiber. A filter extracts stimulated Brillouin backscattered light. A receiver receives and converts the scattered light into an electrical signal. A processing device carries out the signal to determine in which of N branched fibers the stimulated Brillouin scattered light is generated, while varying a time difference between the first and the second test pulse.

A method and a system for ultimately fast frequency-scanning Brillouin optical time domain analysis are provided herein. The method may include: simultaneously launching two pairs each having a pulsed pump wave and a counter-propagating constant wave (CW) probe wave, into an optical fiber, wherein the pulsed pumps have orthogonal States of Polarization (SOPs), and wherein the two CW probe waves have a same SOP; scanning common pump-probe frequency difference, over a frequency range that encompasses a respective Brillouin Gain Spectrum (BGS) and current and expected spectral shifts of the BGS along the optical fiber; deriving, a local Brillouin Frequency Shift (BFS), in a distributed manner along the optical fiber, which is defined as the pump-probe frequency difference which maximizes the Brillouin gain on the BGS; and determining strain and / or temperature in a distributed manner along the optical fiber, based on the respective local BFS.