# US 2016/0258808 A1 · Distributed optical sensing devices and methods performing a measurement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0258808 A1 - Document ID: US20160258808A1 - Status: Published application - Kind: A1 - Application number: 15/060,430 - Filed: 2016-03-03 - Published: 2016-09-08 - Earliest claimed: 2015-03-04 - Applicants: AiQ Dienstleistungen UG (haftungsbeschränkt) - Inventors: Gregor Cedilnik - Web page: https://patentgrep.com/patent/US20160258808A1 ## CPC - G01J 1/0425: {using optical fibers} - G01B 11/16: for measuring the deformation in a solid, e.g. optical strain gauge - G01D 5/25: Selecting one or more conductors or channels from a plurality of conductors or channels, e.g. by closing contacts - G01D 5/35364: {using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering} - G01J 1/42: using electric radiation detectors (optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10) - G01K 11/32: using changes in transmittance, scattering or luminescence in optical fibres - G01N 21/474: {Details of optical heads therefor, e.g. using optical fibres} - G01J 2001/4238: {Pulsed light} - G01K 11/324: using Raman scattering - G01N 2021/4742: {comprising optical fibres} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Distributed optical sensing devices are provided. The device may comprise a computing unit configured to receive signals indicative of an amount of light backscattered in an optical fiber and detected by a light detector; wherein the computing unit is further configured to correct the received signal for an amount of backscattered light undetected by the light detector due to dead time of the light detector. Or, the device may comprise a first light detector having a first light sensitivity and configured to detect light backscattered in a first distance range of an optical fiber; and a second light detector different to the first light detector and having a second light sensitivity being higher than the first light sensitivity, wherein the second light detector is configured to detect light backscattered in a second distance range of an optical fiber being farther away from the second light detector than the first distance range is away from the first light detector. Or, the device may comprise an optical fiber; a light source coupled to the optical fiber and configured to input a light pulse into the optical fiber; and at least one photon counting type detector. Then, either the detector has a dynamic range having an upper boundary and a lower boundary, being coupled to the optical fiber and being configured to measure light backscattered from a distance range of the optical fiber and to generate a signal indicative of the amount of the detected backscattered light, wherein the device is configured to restrict the generated signal to the dynamic range while maintaining a strength of the inputted light pulse, or alternatively, the detector has an input terminal optically coupled to the optical fiber and configured to receive the backscattered light pulse, and the device further comprises a variable attenuator arranged before the input terminal, wherein the distributed optical sensing device is configured to modify an attenuation of the backscattered light pulse during a single measuring cycle by the variable attenuator. ## Claims ### Claim 1 A distributed optical sensing device, the device comprising: a computing unit configured to receive signals indicative of an amount of light backscattered in an optical fiber and detected by a light detector; wherein the computing unit is further configured to correct the received signal for an amount of backscattered light undetected by the light detector due to dead time of the light detector. ### Claim 2 (depends on 1) The distributed optical sensing device according to claim 1, wherein the correction is calculated by a formula based on Poisson statistics. ### Claim 3 (depends on 2) The distributed optical sensing device according to claim 2, wherein the formula is given by: Nreal=−ln(1−Ncount·τ)/τ wherein Nreal is the real photon rate, Ncount is the counted photon rate; and τ is the detector effective dead time. ### Claim 4 (depends on 1) The distributed optical sensing device according to claim 1, wherein the correction is based on a modelled and/or empirically determined correction function and/or look-up table. ### Claim 5 (depends on 1) The distributed optical sensing device according to claim 1, wherein the received signal and/or a processed signal generated from the received signal is corrected. ### Claim 6 A distributed optical sensing device, the device comprising: a first light detector having a first light sensitivity and configured to detect light backscattered in a first distance range of an optical fiber; and a second light detector different to the first light detector and having a second light sensitivity being higher than the first light sensitivity, wherein the second light detector is configured to detect light backscattered in a second distance range of an optical fiber being farther away from the second light detector than the first distance range is away from the first light detector. ### Claim 7 (depends on 6) The distributed optical sensing device according to claim 6, wherein the second light detector is a photon counting type detector. ### Claim 8 (depends on 6) The distributed optical sensing device according to claim 6, further comprising an optical switch, wherein the optical switch is configured so that, in one switching state, the optical switch directs a Stokes shifted signal to one light detector and an anti-Stokes signal to the other light detector. ### Claim 9 (depends on 8) The distributed optical sensing device according to claim 8, wherein the optical switch is configured so that, in a second switching state, the optical switch directs an anti-Stokes signal to the one light detector and a Stokes shifted signal to the other light detector. ### Claim 10 (depends on 6) The distributed optical sensing device according to claim 6, further comprising a computing unit configured to receive signals indicative of an amount of light backscattered in an optical fiber and detected by the first and second light detectors; wherein the computing unit is further configured to correct the received signal for an amount of backscattered light undetected by the light detectors due to dead time of the light detector. ### Claim 11 (depends on 6) The distributed optical sensing device according to claim 6, wherein first distance range of the optical fiber and the second distance range have an overlap region. ### Claim 12 A distributed optical sensing device, comprising: an optical fiber; a light source coupled to the optical fiber and configured to input a light pulse into the optical fiber; and at least one photon counting type detector having a dynamic range having an upper boundary and a lower boundary, being coupled to the optical fiber and being configured to measure light backscattered from a distance range of the optical fiber and to generate a signal indicative of the amount of the detected backscattered light, wherein the distributed optical sensing device is configured to restrict the generated signal to the dynamic range while maintaining a strength of the inputted light pulse. ### Claim 13 (depends on 12) The distributed optical sensing device according to claim 12, wherein the restriction to the dynamic range is performed by shifting the dynamic range of the at least one photon counting type detector. ### Claim 14 (depends on 12) The distributed optical sensing device according to claim 12, wherein the shifting is performed by at least one of the measures out of the group consisting of switching operation parameter of the at least one photon counting type detector; adding a switchable attenuator into a light path of the distributed optical sensing device; and adding a variable attenuator into a light path of the distributed optical sensing device. ### Claim 15 (depends on 12) The distributed optical sensing device according to claim 12, wherein the restriction to the dynamic range is performed by unevenly splitting the inputted light and/or the backscattered light between at least two light detectors. ### Claim 16 (depends on 12) The distributed optical sensing device according to claim 12, further comprising a further light detector, configured to measure light backscattered from a further distance range of another optical fiber and to generate a signal indicative of the amount of the detected backscattered light, wherein the further distance range is closer to the light source than the distance range. ### Claim 17 (depends on 16) The distributed optical sensing device according to claim 16, wherein the at least one photon counting type detector and the optical fiber are part of a first sub-device and the further light detector and the another optical fiber are part of a second sub-device distinct from the first sub-device. ### Claim 18 (depends on 17) The distributed optical sensing device according to claim 17, wherein a first result determined from the first sub-device and a second result determined from the second sub-device are combined to a combined result. ### Claim 19 A distributed optical sensing device, comprising: an optical fiber; a light source coupled to the optical fiber and configured to input a light pulse into the optical fiber; at least one photon counting type detector having an input terminal optically coupled to the optical fiber and configured to receive the backscattered light pulse; and a variable attenuator arranged before the input terminal, wherein the distributed optical sensing device is configured to modify an attenuation of the backscattered light pulse during a single measuring cycle by the variable attenuator. ### Claim 20 (depends on 19) The distributed optical sensing device according to claim 19, wherein the attenuation is modified during a single pulse cycle. ### Claim 21 (depends on 20) The distributed optical sensing device according to claim 20, wherein the variable attenuator is configured to induce an attenuation decreasing according to a rate which correspond to a predetermined rate at which an attenuation induced by the optical fiber increases. ### Claim 22 A method of performing a measurement by a distributed optical sensing device, the method comprising: receiving a signal indicative of an amount of light backscattered in an optical fiber and detected by a light detector; and at least partially correcting the received signal for an amount of backscattered light undetected by the light detector due to dead time of the light detector. ### Claim 23 (depends on 22) The method according to claim 22, wherein the correction is calculated on the formula given by: Nreal=−ln(1−Ncount·τ)/τ wherein Nreal is the real photon rate, Ncount is the counted photon rate; and τ is the detector effective dead time. ### Claim 24 A method of performing a measurement by a distributed optical sensing device comprising an optical fiber, the method comprising: performing a first measurement wherein light of a light pulse backscattered in a first distance range of the optical fiber is measured by a first light detector having a first light sensitivity; performing a second measurement wherein light of the light pulse backscattered in a second distance range of the optical fiber is measured by a second light detector having a second light sensitivity being higher than the first light sensitivity, wherein the second distance range is farther away from the second light detector than the first distance range is away from the first light detector; and combining the first measurement and the second measurement to a combined measurement. ### Claim 25 (depends on 24) The method according to claim 24, further comprising: performing a calibration of at least one of the first light detector and the second light detector by using measurements of portions of the light pulse backscattered in a distance range of the optical fiber being part of the first distance range and the second distance range. ### Claim 26 A method of performing a measurement by a distributed optical sensing device comprising a photon counting type detector having a dynamic range having an upper boundary and a lower boundary and being coupled to an optical fiber, at least one photon counting type detector, being coupled to the optical fiber, the method comprising: measuring light of an inputted light pulse backscattered from a distance range of the optical fiber and generating a signal indicative of the amount of the detected backscattered light by the photon counting type detector, limiting the generated signal to the dynamic range while maintaining a strength of the inputted light pulse. ### Claim 27 A method of performing a measurement by a distributed optical sensing device comprising an optical fiber; a light source; and at least one photon counting type detector having an input terminal optically coupled to the optical fiber, wherein the method comprises: inputting a light pulse emitted by a light source into the optical fiber; attenuating, by a variable attenuator, a backscattered light portion of the light pulse backscattered in the optical fiber during a single measuring cycle before the backscattered light portion enters the input terminal of the at least one photon counting type detector. ### Claim 28 (depends on 27) The method according to claim 27, wherein the attenuation is varied during a single pulse cycle. ### Claim 29 (depends on 28) The method according to claim 28, wherein the variable attenuation is set so that an increasing attenuation caused by an increasing optical path through the optical fiber is compensated for. ### Claim 30 (depends on 27) The method according to claim 27, wherein the attenuation is varied between pulse cycles.