Fiber-Optic Distributed Acoustic Sensor

Abstract

The present invention relates to an optical fiber acoustic sensor with improved acoustic signal measurement sensitivity, comprising: an optical circulator that outputs pulsed light, which is output from a light source and input to an input terminal, through an output terminal, and outputs light incident in reverse from the output terminal through a detection terminal; a sensing optical fiber connected to the output terminal of the optical circulator and installed to extend to a measurement target area; an acoustic focuser in which a plurality of sensing optical fibers are wound and at least one is disposed in the measurement target area to focus external acoustic signals; a light detection unit that detects Rayleigh scattered light, which is scattered from the sensing optical fiber and travels in reverse and input through the detection terminal; and a signal processing unit that measures positional vibration signals for acoustics received through the sensing optical fiber from the signal detected by the light detection unit. The acoustic focuser includes a cone antenna having a horn portion in which the inner diameter gradually narrows as it proceeds downward from the upper part where an opening is formed, and a vertical extension portion in which the inner diameter is extended equally from the bottom of the horn portion. According to this optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity, the sensing optical fiber is configured to respond sensitively to the focused acoustic signal, thereby improving the measurement sensitivity of the acoustic signal and providing the advantage of easy installation.

Description

Technology Field

[0001] The present invention relates to a fiber optic acoustic sensor, and more specifically, to a fiber optic acoustic sensor capable of improving the sensitivity of acoustic signal measurement. Background Technology

[0002] Various distributed fiber optic sensors that are installed and operated over long distances of approximately 10 km are disclosed, including Korean registered patent No. 10-1223105.

[0003] Distributed optical fiber sensors utilize scattering phenomena within optical fibers and measure the intensity of backscattered light that is reflected back differently depending on the physical quantity acting at a specific location in the optical fiber cable; they can be constructed to detect various physical quantities, such as deformation, in addition to temperature.

[0004] Among these distributed fiber optic sensors, there is a Distributed Acoustic Sensor (DAS) that utilizes Rayleigh scattering.

[0005] A fiber optic acoustic sensor is a sensor that measures scattered light generated from light traveling inside a fiber optic cable due to the non-uniform distribution of density within the fiber, and can obtain backscattered light proportional to the intensity of the pulsed light. Various such fiber optic acoustic sensors have been proposed, including Korean registered patent No. 10-1817295.

[0006] Meanwhile, conventional distributed optical fiber acoustic sensors are structured such that the sensing optical fiber is simply laid along the measurement target area, making it difficult to efficiently measure when the target sound is weak; therefore, a structure capable of improving measurement sensitivity is required. The problem to be solved

[0007] The present invention was devised to solve the above requirements, and aims to provide a fiber optic acoustic sensor that is easy to install and capable of improving acoustic signal measurement sensitivity so as to easily measure even weak acoustic signals. means of solving the problem

[0008] To achieve the above objective, the optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity according to the present invention comprises: a light source unit that generates and outputs pulsed light according to a control signal; an optical circulator that outputs pulsed light output from the light source unit and input to an input terminal through an output terminal, and outputs light incident in reverse from the output terminal through a detection terminal; a sensing optical fiber connected to the output terminal of the optical circulator and installed to extend to a measurement target area; an acoustic focuser in which the sensing optical fiber is wound in multiple ways and at least one is disposed in the measurement target area to focus external acoustic signals; and a light detection unit that detects Rayleigh scattered light that is scattered from the sensing optical fiber, travels in reverse, and inputs through the detection terminal. The device comprises a signal processing unit that controls the generation of pulsed light from the light source unit and measures positional vibration signals for sound received through the sensing optical fiber from a signal detected by the light detector unit based on the output time of the pulsed light; and the acoustic focuser includes a cone antenna having a horn portion in which the inner diameter gradually narrows as it proceeds downward from the upper part where an opening is formed, and a vertical extension portion in which the inner diameter is extended equally from the bottom of the horn portion.

[0009] According to one aspect of the present invention, the acoustic focus unit further comprises a unit housing coupled to the cone antenna so as to surround the area where the sensing optical fiber of the cone antenna is wound.

[0010] Preferably, the unit housing is equipped with a connector that supports the connection of the sensing optical fiber.

[0011] In addition, a winding mounting groove is formed along the circumferential direction on the outer surface of the cone antenna, which is drawn inward to provide a winding area for the sensing optical fiber.

[0012] In addition, the sensing optical fiber can be wound multiple times in a single layer without overlapping the winding mounting groove of the cone antenna.

[0013] Alternatively, the sensing optical fiber may be wound multiple times along the extension direction of the cone antenna while being overlapped in multiple layers in the winding mounting groove of the cone antenna.

[0014] Preferably, a protective cap coupled to the cone antenna is further provided to surround the winding mounting groove of the cone antenna from the outside.

[0015] According to one aspect of the present invention, the cone antenna has a coupling guide groove formed along the circumferential direction that is spaced apart from the winding mounting groove and inserted inwardly, and the protective cap has first and second semicircular dividing pieces, each having one end connected to rotate mutually around a hinge and surrounding the cone antenna, with the other end divided to be separated from each other; a fitting ring formed to protrude inwardly on the inner surface of the first and second semicircular dividing pieces to enter the coupling guide groove; and a locking part that mutually connects and separates the other end of the first and second semicircular dividing pieces opposite the hinge. Effects of the invention

[0016] According to the optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity of the present invention, the sensing optical fiber is configured to respond sensitively to a focused acoustic signal, thereby improving the measurement sensitivity of the acoustic signal and providing the advantage of easy installation. Brief explanation of the drawing

[0017] FIG. 1 is a drawing showing an optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity according to one embodiment of the present invention, and FIG. 2 is a perspective view showing the cone antenna of FIG. 1 extracted and illustrated, and FIG. 3 is a front view showing an acoustic focuser according to a second embodiment of the present invention, and FIG. 4 is a front view showing an acoustic focuser according to a third embodiment of the present invention, and FIG. 5 is a cross-sectional view of a cone antenna according to a fourth embodiment of the present invention, and FIG. 6 is a cross-sectional view of a cone antenna according to the fifth embodiment of the present invention, and FIG. 7 is a cross-sectional view of a cone antenna according to the 6th embodiment of the present invention, and FIG. 8 is a perspective view of the protective cap applied to FIG. 7. Specific details for implementing the invention

[0018] Hereinafter, an optical fiber acoustic sensor with improved acoustic signal measurement sensitivity according to a preferred embodiment of the present invention will be described in more detail with reference to the attached drawings.

[0019] FIG. 1 is a drawing showing an optical fiber acoustic sensor with improved acoustic signal measurement sensitivity according to one embodiment of the present invention, and FIG. 2 is a perspective view showing a cone antenna of FIG. 1.

[0020] Referring to FIGS. 1 and 2, the optical fiber acoustic sensor (100) according to the present invention comprises a light source unit (110), an optical circulator (120), a sensing optical fiber (130), a cone antenna (140), a light detection unit (160), and a signal processing unit (170).

[0021] The light source unit (110) generates and outputs pulsed light according to a control signal of the signal processing unit (170). The light source unit (110) may be constructed with a pulse generator (not shown) that generates pulses according to a driving control signal of the signal processing unit (170), and a light source that outputs pulsed light corresponding to the pulses output from the pulse generator.

[0022] In addition, the light source unit (110) can be configured to provide a portion of the generated pulsed light to the signal processing unit (170) to determine the time of pulsed light generation.

[0023] The light circulator (120) outputs pulsed light that is output from the light source unit (110) and input to the input unit (120a) through the output unit (120b), and outputs light that is incident in reverse from the output unit (120b) through the detection unit (120c).

[0024] One end of the sensing optical fiber (130) is connected to the output terminal (120b) of the optical circulator (120) and is installed to extend in series to the measurement target area, and in the sensitivity enhancement measurement area, it is installed in a pattern that is wound multiple times around the cone antenna (140) and extends in series.

[0025] The cone antenna (140) is formed by winding multiple sensing optical fibers (130) and arranging multiple units spaced apart from each other in the measurement target area, and is applied as an acoustic focuser capable of focusing external acoustic signals.

[0026] The cone antenna (140) has a structure having a horn portion (141) in which the inner diameter gradually narrows as it proceeds downward from the upper part where the opening (142) is formed, and a vertical extension portion (143) in which the inner diameter extends equally from the lower part of the horn portion (141).

[0027] A sensing optical fiber (130) is wound multiple times in close contact with the lower outer side of the cone antenna (140).

[0028] In this cone antenna (140), external sound is focused as it travels from the opening (142) downwards, and the sensing optical fiber (130) wound multiple times at the bottom increases the generation efficiency of Rayleigh scattered light by the focused sound, thereby improving measurement sensitivity and improving the coupling of the sensing optical fiber (130).

[0029] Meanwhile, an acoustic focuser capable of supporting the ease of connection of the cone antenna (140) illustrated as an acoustic focuser for focusing acoustic signals may be applied, and an example thereof is explained with reference to FIG. 3.

[0030] Referring to FIG. 3, the acoustic focus is provided with a unit housing (150) combined with the cone antenna (140) so as to surround the area where the sensing optical fiber (130) of the cone antenna (140) is wound.

[0031] The unit housing (150) is formed in a cylindrical shape having an internally closed receiving space so as to enclose a lower part of the horn portion (141) and a vertical extension portion (143). The unit housing (150) is constructed to protect the sensing optical fiber (130) and to easily connect the built-in sensing optical fiber (130) to an external sensing optical fiber (130).

[0032] At the bottom of the unit housing (150), a connector (160) is installed to support serial connection with the outside of an internal sensing optical fiber (130) that is wound around a cone antenna (140). Various known types of connectors capable of connecting optical fibers in series can be applied to the connector (160).

[0033] According to this structure, acoustic focusers having unit housings (150) are appropriately installed in each installation area, and sensing optical fibers (130) are connected in series from the outside through connectors (160), thus providing the advantage of easy laying and installation.

[0034] Unlike the illustrated example, as illustrated in FIG. 4, the unit housing (150) may be constructed to support fusion bonding of the internal sensing optical fiber (130) with the external sensing optical fiber (130). Reference numeral 165 is a protective tube coupled to protect the sensing optical fiber (130) serially bonded by fusion from the outside.

[0035] Meanwhile, on the outer surface of the cone antenna (140), a structure may be applied in which a winding mounting groove (146) that is drawn inward to provide a winding area of ​​the sensing optical fiber (130) as shown in FIG. 5 is formed in a ring shape along the circumferential direction.

[0036] In this case, the sensing optical fiber (130) can be installed by being wound multiple times along the extension direction of the cone antenna (140) while being vertically overlapped in multiple layers in the winding mounting groove (146) of the cone antenna (140) as shown in FIG. 5.

[0037] Alternatively, as shown in FIG. 6, the sensing optical fiber (130) may be installed in a single layer, without overlapping vertically in the winding groove (146) of the cone antenna (140), and wound multiple times along the extension direction of the cone antenna (140).

[0038] Additionally, as shown in FIGS. 7 and 8, a protective cap (170) may be applied to surround the winding mounting groove (146) of the cone antenna (140) from the outside, so as to protect the sensing optical fiber (130) mounted in the winding mounting groove (146) from the external environment, either separately from the unit housing or in a structure where the unit housing is not applied, and which is coupled to the cone antenna (140).

[0039] Additionally, on the outer surface of the cone antenna (140), two coupling guide grooves (148) are formed in the shape of ring grooves along the circumferential direction, spaced apart from each other above and below the winding mounting groove (146) along the extension direction of the cone antenna (140) and inserted inward.

[0040] The protective cap (170) is provided with first and second semicircular dividing pieces (171)(172), first and second fitting rings (175)(176), and a locking part (180).

[0041] The first and second semicircular segments (171) and (172) are formed in a semicircular shape, with one end each joined to rotate around the hinge (173) and surrounding the cone antenna (140), and the other end separated from each other.

[0042] The first and second fitting rings (175) (176) are formed in a ring shape so as to protrude inwardly to enter the coupling guide grooves (148) formed at the upper and lower ends of the inner circumference of the first and second semicircular split pieces (171) (172), respectively, which are spaced apart from each other.

[0043] The locking part (180) is configured to allow mutual connection and separation of the other ends opposite the hinge (173) of the first and second semicircular dividing pieces (171) (172).

[0044] The locking part (180) is constructed with a hook (182) that is rotatably coupled at one end to a rotation support pin (181) protruding from the outer side of the other end of the first semicircular dividing piece (171) and rotated, and a hook pin (182) that protrudes from the outer side of the second semicircular dividing piece (172) and into which the other end of the hook (182) can be inserted and locked.

[0045] The locking part (180) can be constructed to mutually combine and separate the first and second semicircular split pieces (171) (172) in various ways, unlike the structure shown.

[0046] As an example, the locking part (180) can be constructed so that the other ends of the first and second semicircular split pieces (171) (172) can be magnetically coupled to each other by magnetic force.

[0047] Meanwhile, the wound length of the sensing optical fiber (130) wound multiple times on the cone antenna (140) is applied as a length of at least twice the spatial resolution applied in the optical fiber acoustic sensor (100). Preferably, the wound length of the sensing optical fiber (130) wound multiple times on the cone antenna (140) is applied as a length of 2 to 10 times the spatial resolution applied in the optical fiber acoustic sensor (100).

[0048] Additionally, it is preferable that the sensing optical fiber (130) wound on the cone antenna (140) be constructed to be fixed by bonding it with a fixing material such as epoxy.

[0049] Additionally, the formation location of the winding inlet groove (146) of the cone antenna (140) can be appropriately applied to the upper, middle, lower, or vertical extension portion (143) of the horn portion (141), taking into consideration the installation environment, the measurement acoustic frequency band, the shape and size of the horn portion, etc.

[0050] The light detection unit (160) is connected to the detection unit (120c) of the optical circulator (120) to detect Rayleigh scattered light that is scattered from the sensing optical fiber (130), travels in reverse, and is output from the detection unit (120c), and provides a signal corresponding to the detected light to the signal processing unit (170).

[0051] Of course, the light detection unit (160) may have a wavelength filter applied to filter only the Rayleigh scattered light that is scattered from the sensing optical fiber (130), travels in reverse toward the optical circulator (120), and is output from the detection unit (120c) as an electrical signal.

[0052] The signal processing unit (170) controls the light source unit (110) to generate pulsed light from the light source unit (110). Based on the output time of the pulsed light from the light source unit (110), the signal processing unit (170) measures the vibration frequency and intensity of the sound received through the sensing optical fiber (130) from the signal detected by the light detector unit (160) at each location.

[0053] According to the optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity described above, the sensing optical fiber is configured to respond sensitively to the focused acoustic signal, thereby improving the measurement sensitivity of the acoustic signal and providing the advantage of easy installation. Explanation of the symbols

[0054] 110: Light source 120: Optical circulator 130: Sensing optical fiber 140: Cone antenna 160: Photodetector 170: Signal processing unit

Claims

Claim 1 delete Claim 2 A light source unit that generates and outputs pulsed light according to a control signal; an optical circulator that outputs pulsed light output from the light source unit and input to an input terminal through an output terminal, and outputs light incident in reverse from the output terminal through a detection terminal; a sensing optical fiber connected to the output terminal of the optical circulator and installed to extend to a measurement target area; and an acoustic focuser in which a plurality of the sensing optical fibers are wound and at least one is disposed in the measurement target area and capable of focusing an external acoustic signal; An optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity, comprising: a light detection unit that detects Rayleigh scattered light that is scattered from the sensing optical fiber, travels in reverse, and is input through the detection unit; and a signal processing unit that controls the generation of pulse light from the light source unit and measures positional vibration signals for acoustics received through the sensing optical fiber from a signal detected by the light detection unit based on the output time of the pulse light; wherein the acoustic focuser comprises a cone antenna having a horn portion in which the inner diameter gradually narrows as it proceeds downward from the upper part where an opening is formed, and a vertical extension portion in which the inner diameter is extended equally from the bottom of the horn portion; and further comprising a unit housing coupled to the cone antenna so as to surround the area where the sensing optical fiber of the cone antenna is wound. Claim 3 An acoustic signal measurement sensitivity-enhancing optical fiber acoustic sensor according to claim 2, characterized in that the unit housing is equipped with a connector that supports the connection of the sensing optical fiber. Claim 4 A light source unit that generates and outputs pulsed light according to a control signal; an optical circulator that outputs pulsed light output from the light source unit and input to an input terminal through an output terminal, and outputs light incident in reverse from the output terminal through a detection terminal; a sensing optical fiber connected to the output terminal of the optical circulator and installed to extend to a measurement target area; and an acoustic focuser in which a plurality of the sensing optical fibers are wound and at least one is disposed in the measurement target area and capable of focusing an external acoustic signal; An optical fiber acoustic sensor with enhanced acoustic signal measurement sensitivity, comprising: a light detection unit that detects Rayleigh scattered light that is scattered from the sensing optical fiber, travels in reverse, and is input through the detection unit; and a signal processing unit that controls the generation of pulse light from the light source unit and measures positional vibration signals for acoustics received through the sensing optical fiber from the signal detected by the light detection unit based on the output time of the pulse light; wherein the acoustic focuser includes a cone antenna having a horn portion in which the inner diameter gradually narrows as it proceeds downward from the upper part where an opening is formed, and a vertical extension portion in which the inner diameter is extended equally from the bottom of the horn portion, and wherein a winding mounting groove formed along the circumferential direction on the outer surface of the cone antenna is inwardly drawn in to provide a winding area for the sensing optical fiber. Claim 5 An acoustic signal measurement sensitivity-enhancing optical fiber acoustic sensor according to claim 4, characterized in that the sensing optical fiber is wound multiple times in a single layer so as not to overlap with the winding mounting groove of the cone antenna. Claim 6 An acoustic signal measurement sensitivity-enhancing optical fiber acoustic sensor according to claim 4, characterized in that the sensing optical fiber is wound multiple times along the extension direction of the cone antenna while being overlapped in multiple layers in the winding mounting groove of the cone antenna. Claim 7 An acoustic signal measurement sensitivity-enhancing optical fiber acoustic sensor, characterized in that, in claim 4, it further comprises a protective cap coupled to the cone antenna to surround the coiled mounting groove of the cone antenna from the outside. Claim 8 In claim 7, the cone antenna has a coupling guide groove formed along the circumferential direction that is spaced apart from the winding mounting groove and inserted inwardly, and the protective cap has first and second semicircular dividing pieces, each having one end connected to rotate mutually around a hinge and surrounding the cone antenna, with the other end divided to be separated from each other; a fitting ring formed to protrude inwardly on the inner surface of the first and second semicircular dividing pieces to enter the coupling guide groove; and a locking part that mutually connects and separates the other end of the first and second semicircular dividing pieces opposite the hinge; characterized by comprising: an acoustic signal measurement sensitivity enhancement type optical fiber acoustic sensor.

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