390 results about "Time-domain reflectometer" patented technology

Detecting a linear impairment in a cable under test by using a random signal transmitted down the cable. The impairment causes a reflected signal to be combined with the random signal. The combined signal extends over a plurality of sub-bands. A method and apparatus perform the steps of: (a) receiving the combined signal from a test point upstream from the impairment; (b) tuning to each sub-band and receiving a part of the combined signal within each sub-band; (c) determining an autocorrelation function of each part of the combined signal of each sub-band, to produce a plurality of autocorrelation functions; (d) combining the autocorrelation functions to form a combined function; (e) detecting the reflected signal from the combined function; and (f) determining, from the combined function, a time delay associated with the reflected signal and the distance from the test point to the impairment.

The present invention provides a system for determining downhole conditions including a time domain reflectometer (172) that is operable to generate a transmission signal and receive a reflected signal. A tubular (192) is positioned downhole in a downhole medium (214, 216, 218, 220, 222) and a waveguide (186), which is in electrical communication with the time domain reflectometer (172), is operably contacting the downhole (214, 216, 218, 220, 222). The waveguide (186) is operable to propagate the transmission signal and operable to propagate the reflected signal that is generated responsive to an electromagnetic property of the downhole medium (214, 216, 218, 220, 222).

A detector and a variable signal generator are coupled so that one or more specific changes in the output of the detector will cause a change in the characteristics of the generated signal. This change in signal characteristics is non-transient, the change remaining in effect until such time that another change in the detector output causes another change in the signal characteristic. The system can provide remote-end positive wire identification with no additional instrumentation at the remote end. When this invention is embodied in an already existing piece of test equipment, such as a multimeter or time domain reflectometer, there need be no additional hardware instrumentation at either end.

A time domain reflectometer having a first impedance when in a first test mode and a second impedance when in a second test mode. The first impedance is substantially the same as the nominal characteristic impedance of a network link cable not connected to a network and the second impedance is substantially different from the impedance of a network link cable that is terminated into a network. A method for measuring the length of a terminated network cable includes the steps of determining that the network cable is terminated at a network, selecting a test mode suitable for testing the terminated network cable, and performing time domain reflectometry testing on the terminated network cable.

Optical Time-Domain Reflectometer (OTDR) troubleshooting of a passive optical network (PON) can be enhanced by deploying cascaded splitters, at least some of which have multiple inputs. That is, at least some of the splitters in the PON have not only a first input coupleable to the optical line terminator (OLT) or output of another splitter but also a second input directly coupleable to an Optical Time-Domain Reflectometer (OTDR). Optical time-delay reflectometry can be performed upon a selected portion or segment of the PON by selecting a splitter and transmitting an optical test signal from the OTDR directly to the input of the selected splitter and analyzing the reflected signal.

A TDR for locating impairments in an HFC network is claimed. The network carries burst signals in an upstream band during burst intervals. The TDR comprises a transmitter, receiver, level detector, controller, accumulator, and probe detector. The transmitter transmits probe signals to the impairment, causing a reflection of the probe signals. Each probe signal is in the upstream band and has a bandwidth extending the width of the upstream band. The receiver receives the reflected probe signals during receiving intervals, and receives the burst signals during receiving intervals that overlap burst intervals. The level detector measures a level of the signals received during each receiving interval. The controller determines which of the receiving intervals are free of burst signals, based on the level measurement. The accumulator accumulates reflected probe signals received during intervals free of burst signals. The probe detector detects the impairment from the accumulated probe signals and estimates a time delay for the impairment. A distance to the impairment is estimated from the time delay.

The invention relates to a BOTDR (Brillouin Optical Time Domain Reflectometer) for calibrating optical power of reference light and a calibrating method thereof. The calibrating method comprises the following steps of: acquiring an electric signal of local reference light from a heterodyne photoreceiver on a basis of a traditional BOTDR for heterodyne coherent detection; transmitting the electric signal subjected to analog-to-digital conversion in a computer to be used as the optical power calibrating feedback quantity of the reference light; sending out an instruction by the computer to adjust the output power of a microwave source and change the optical power of the local reference light so that the difference between the optical power of the local reference light and the preset reference light power is smaller than a set value; calibrating the power; and detecting a BOTD signal. In the invention, the BOTDR in a working process can not be influenced by the working environment temperature, a microwave transmission line connecting the microwave source with an electro-optic modulator and different power responses of the electro-optic modulator on microwave signals of different frequencies, the error between the reference light power at different frequency points and the preset power is smaller than a set value, and the accurate measurement of the stress and the temperature is ensured.

Methods and systems for high-bandwidth time domain reflectometry include a printed circuit board (PCB) and a probe. The PCB includes at least one signal terminal connected to at least one signal via at least three guide terminals arranged around the at least one high-frequency signal terminal. At least one of the guide terminals is connected to at least one ground via. The probe includes at least one biased pin to contact the at least one signal terminal and at least three fixed guide pins arranged about the at least one biased pin to facilitate alignment of said at least one biased pin by first engaging at least one guide terminal area, such that the at least one mechanically biased pin is guided to the at least one contact point.

TDR (time domain reflection) technology may be used in optical domain or in electrical domain. For electrical TDR, single layer ITO glass may form a transmission line as a base TDR touch sensor. When the touch sensor is paired, the existing internal metal line of the display device may be reused as a TDR sensor and the ITO glass may be removed. When touched, the TDR profile is changed dynamically from baseline to the particular profile due to its dynamic impedance profile change across the display screen. Likewise, for optical TDR touch sensing, 2 dimensional optical slab waveguide is used to carry OTDR signal. When touched, the profile is changed due to this perturbation mainly by evanescent field changes on that particular position.

In a method and a corresponding apparatus for performing chaotic optical time domain reflectometer, the chaotic laser signal, generated by the chaotic laser transmitter, is split into probe signal I and reference signal II by a fiber coupler. Through an optical circulator, the probe signal I is launched into the test fiber and the echo light is converted into electrical signal by a photodetector and digitalized by an A/D converter. The reference signal II is converted into electrical signal by a photodetector and digitalized by another A/D converter. Two digital signals received from two A/D converters are correlated in a signal processing device to locate the exact position of faults in fibers. The result output is then displayed on a display device. This invention was developed to overcome the tradeoff between resolution and dynamic range of the pulse-based OTDR. This method can improve the dynamic range and spatial resolution significantly; enhance the anti-jamming capability and noise tolerance. Also it has merits of simple structure and lower cost.

A method and apparatus for sensing conditions in a subsurface geologic formation heated for the extraction of hydrocarbons is disclosed. A time domain reflectometer in conjunction with an open wire transmission line is employed in real time to determine impedance discontinuities in the geologic formation. These impedance discontinuities correspond to physical conditions in the geologic formation. The open wire transmission line can include pipes running into the subsurface geologic formation or other conductors, including a split tube well casing. The method may operate in the low frequency window for subsurface electromagnetic propagation.

The invention provides a method for simultaneously measuring distributed type temperatures and strain. A brillouin optical time domain reflectometer and a coherent light time domain reflectometer share the same optical path system and the same circuit system and serve as a sensing measurement system. The sensing measurement system works in a BOTDR mode and a COTDR mode in an alternate mode to measure a brillouin scattering spectrum and a Rayleigh scattering spectrum which are distributed along a single single-mode sensing optical fiber and detect the frequency shift of the brillouin scattering spectrum and the frequency shift of the Rayleigh scattering spectrum, a linear equation set in two unknowns about the temperature and the strain is set up according to the characteristic that the frequency shift of the two scattering spectra is in the linear relationship with the temperature and the strain, and the temperature and the strain of each position of the sensing optical fiber can be obtained by solving the equation set, and then the temperatures and the strain distributed along the whole sensing optical fiber can be obtained. According to the method, the complexity and the manufacturing cost of the system are greatly reduced, no special requirement for the brillouin frequency shift coefficient of the optical fiber exists, and the application range of the measurement system is enlarged.

An optical transceiver having an integrated optical time domain reflectometer monitoring unit and methods for using the same are disclosed. The disclosure relates to an optical transceiver comprising an optical device comprising a wavelength division multiplexing system (WDM), a data signal driver, a data signal limiting amplifier, and an optical time domain reflectometer (OTDR) data processing module. Furthermore, the optical transceiver is particularly advantageous in an optical line terminal (OLT) and/or a passive optical network (PON). The integrated OTDR data processing module can protect the optical transceiver, ensure successful monitoring data, simplify network wiring and decrease system and network costs by decreasing the number of OTDR modules and WDM units.

The invention discloses a spontaneous Brillouin scattering optical time domain reflectometer (BOTDR) based on a superconductive nanowire single-proton detector, which is characterized in that an optical pulse emitted by an optical pulse generating unit is coupled to a sensing optical fiber through a circulator, backward scattered light scattered from the sensing optical fiber is subjected to filtration of rayleigh scattering light through an optical filter unit to obtain Brillouin scattering light, a back scattering light signal is detected by the superconductive nanowire single-proton detector, an electric signal output from the superconductive nanowire single-proton detector is acquired and processed by a data acquiring and processing unit, and finally, a result is obtained through a certain demodulation relation. Compared with the traditional BOTDR, the BOTDR provided by the invention is used for carrying out data acquisition and processing by adopting the noise equivalent power (NEP) low/no-bandwidth-limit superconductive nanowire single-proton detector as a detection unit and adopting a single-proton counting technology.

A method for generating a broadband chaotic signal similar to white noise comprises the steps that beat frequency is carried out on two paths of chaotic lasers through an optical fiber coupler, the two paths of chaotic lasers are divided into two paths with the equal intensity, balanced detection is carried out on the two paths of optical signals, and a difference value signal is extracted and converted into a corresponding electric signal. A device for generating the broadband chaotic signal similar to the white noise comprises two chaotic laser emission devices, the optical fiber coupler and a balance detector. The optical frequencies of the chaotic laser emission devices are not equal, and an optical frequency difference is the spectral line width of the chaotic lasers. The chaotic signal generated through the method has the wide and flat frequency spectrum similar to that of the white noise, no rectilinear oscillation exists on the frequency spectrum, and periodicity caused when the chaotic lasers are generated through a time delay system can be thoroughly eliminated; the security of chaotic communication, the measurement accuracy of a radar and an optical time domain reflector, and the randomness of physical random numbers are improved. The method and device can be applied to the fields of communication, remote sensing, sensing and the like.

The invention provides a method of a multifrequency probe light time division multiplexing coherent light time domain reflectometer. The method is characterized in that: a detection light pulse being injected into a fiber being detected is multifrequency detection light pulse which generates time division multiplexing by utilizing sequential electric signal synchronization control phase modulator and light pulse modulator modulation; local oscillator light is single-frequency light, and power spectrum of the multifrequency detection light pulse is bilaterally symmetrical relative to local oscillator light frequency; 0 order frequency of the multifrequency detection light pulse is same with the local oscillator light frequency; modulation depth of the phase modulator is larger than 1; a backward scattering and/or reflection signal which the multifrequency light pulse of time division multiplexing is in mixes with the local oscillator light in a coherent detection module, both side are coherent and an intermediate frequency signal of time division multiplexing is output by a photoelectric detector; an intermediate frequency signal processing module amplifies an intermediate frequency signal of time division multiplexing detected by coherent detection, according to a characteristic of the intermediate frequency signal, a needed band pass filter is selected, the intermediate frequency signal is filtered, a subsequent circuit carries out real-time processing on a plurality of paths of intermediate frequency signals, and information of the fiber being detected is displayed.

An adaptive pulse width (APW) Time Domain Reflectometer (TDR) comprises an enhancement to the standard Pulse TDR by adjusting the effective pulse width as a function of time. Improved resolution for a large range of cable lengths is obtained, as well as allowing an all-in-one view of the processed return signal trace.

The invention discloses a phase-sensitive light time domain reflectometer based on a 120-degree difference interferometer. The reflectometer comprises a laser light source, a light pulse modulator, a first light amplifier, a first circulator, a second light amplifier, a second circulator, a fiber grating, the 120-degree difference interferometer, a first photoelectric detector, a second photoelectric detector, a third photoelectric detector, a data acquisition card and a data processing system. After light emitted by the laser light source is modulated to pulse light through the light pulse modulator, the pulse light is amplified through the first light amplifier, and then the pulse light goes into a second port from a first port of the first circulator so as to be injected into a sensing fiber; and the interferometer erected by use of a 3*3 coupler with a phase difference of 120 degrees is employed for performing distributed modulation on the phase of Rayleigh scattering light in the fiber and obtaining phase information along the fiber so that such information as vibration, temperature, strain and the like is sensed.

The invention relates to a characteristic impedance testing method, comprising the following steps: setting a test document; obtaining the position of a part to be tested; locating a probe of a time-domain reflectometer on the position of the part to be tested on a printing circuit board; obtaining the characteristic impedance of the part to be tested; analyzing the characteristic impedance of the part to be tested; and generating and storing test report. The invention further provides a characteristic impedance testing system; the characteristic impedance of the part on the printing circuit board can be automatically tested by utilizing the invention.