JP2018194372A - Optical fiber position searching device and program - Google Patents

Abstract

To provide an optical fiber position searching device and program for searching for the position or path of an existing optical fiber that can hardly be visually checked or touched with a hand.SOLUTION: An optical fiber vibrates due to that an elastic wave outputted to a space collides with the optical fiber, and phase modulation or polarization modulation is added to test light passing through a vibration-added portion due to slight extension/shrinkage of the optical fiber. When the phase modulation of test light is utilized, the distance from an elastic wave generated part to a point where the elastic wave collided with the optical fiber by a coherent OTDR or coherent OFDR that analyzes vibration by a phase change or a spectral response of reflected or scattered light. When the polarization modulation of test light is utilized, the distance from the elastic wave generated part to the point where the elastic wave collided with the optical fiber by a polarization OTDR or polarization OFDR that analyzes a change in the polarized state of reflected or scattered light.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a facility search technique for specifying the position and route of a wired optical fiber cable.

  Conventionally, as a technique for searching for the position of a cable, for example, as in Non-Patent Document 1, an AC or DC magnetic field for searching is made conductive for a conductive cable (a metal cable or an optical fiber cable having a conductor). There is a technology for applying to and detecting a cable. On the other hand, for an optical fiber cable that does not have a conductor, it is mainly a means for confirming the presence or absence of disconnection. For example, as shown in Non-Patent Document 2, visible light having a wavelength of about 600 nm to 800 nm is incident on the optical fiber. However, there is a technique for visually recognizing the position of the cable by visually recognizing the leaked light generated at the stressed portion or the connecting portion of the optical fiber cable.

  On the other hand, as a technique for measuring the shape of an optical fiber cable, an optical fiber cable incorporating an optical fiber having a plurality of cores is used. Using a material that regularly twists a plurality of cores in an optical fiber as described in Reference 4, the strained and strained directions are measured with high accuracy in a distributed manner. Techniques for measuring in the original are known.

NTT InfraNet Technology Introduction “Investigation of buried object position / state (position / state)”, http: // www. nntinf. co. jp / service / management / (searched on April 27, 2017) NTT AT Technology Introduction “Optical Fiber Continuity Checker”, http: // keytech. ntt-at. co. jp / fiberoptic / prd_0043. html (Search April 27, 2017) J. et al. P. Moore, et al. , “Shape sensing using multicore fiber optic cable and parametric curve solutions”, Optics Express vol. 20 no. 3 pp. 2967 E. M.M. Lally, et al. , “Fiber optic shape sensing for monitoring of flexible structures”, Proc. of SPIE Vol. 8345 83352Y-1

  In communication buildings and data center buildings of telecommunications carriers, the number of optical fiber facilities used for wiring between many optical service subscribers and servers is steadily increasing. When performing, it is necessary to search for the position and route of a specific optical fiber cable. For example, if the detailed position of the optical fiber is unknown, the removal work itself may cause an accident that affects the communication in the fiber optic cable during communication. To avoid this, it is necessary to check the optical fiber cable. is there. However, there is a problem that this operation requires a large operation and cost.

  Furthermore, the optical fiber cable normally used in such communication buildings is an aramid fiber reinforced cable in which an aramid fiber or the like is vertically attached to an optical fiber, and since there is no electrical conductivity, a search technique using a magnetic field in the background art is It cannot be applied. In addition, the search technique using a visible light source is not limited to a place where a cable is present at a visible position and a leaked portion can be confirmed, and it is practically impossible to know the route. For example, in such a space, there are many cases of non-exposed wiring such as wiring in a double floor, a route on a wiring rack using a cable wiring conduit, and wiring in a wall, and thus cannot be applied. The shape measurement technique based on high-precision strain measurement in the background art cannot be applied to a normal optical fiber search because a special optical fiber or device is necessary for the detection principle. Thus, with the existing background art, it is difficult to solve the above problems.

  Accordingly, an object of the present invention is to provide an optical fiber position search apparatus and program for searching for the position and route of an existing optical fiber that is difficult to touch visually or by hand to solve the above-described problems.

  In order to achieve the above object, an optical fiber position search apparatus according to the present invention emits an elastic wave such as a sound wave into the air, and generates vibration generated in the optical fiber when the elastic wave collides with the optical fiber. The distance between the elastic wave generator and the location where the elastic wave collided with the optical fiber was measured.

Specifically, the optical fiber position search apparatus according to the present invention is:
Signal generating means for generating an elastic wave signal;
An elastic wave generating unit that generates an elastic wave based on the elastic wave signal generated by the signal generating unit and outputs the generated elastic wave to the air;
A light reflection measuring unit that enters test light into one end of the optical fiber to be measured, and obtains the polarization or phase information of the test light from the return light from each point of the optical fiber to be measured every time;
A clock signal generation unit that generates a clock signal that synchronizes generation of the elastic wave and incidence of the test light on the optical fiber to be measured;
A propagation delay time for the elastic wave to reach each point of the optical fiber to be measured is calculated from a change in the polarization or the phase information acquired every time, and the elastic wave generator and the optical fiber to be measured are calculated. A signal processing unit for calculating the distance to each point of
Is provided.

  When the elastic wave output to the space collides with the optical fiber, the optical fiber vibrates, and phase modulation or polarization modulation is applied to the test light transmitted through the vibration applying portion by slight expansion and contraction of the optical fiber. When using phase modulation of test light, the distance between the elastic wave generator and the location where the elastic wave collided with the optical fiber in a coherent OTDR or coherent OFDR that analyzes vibration with the phase change or spectral response of reflected or scattered light Measure. When using the polarization modulation of the test light, it is necessary to analyze the change in the polarization state of the reflected or scattered light by using the polarized wave OTDR or the polarized wave OFDR to the point where the elastic wave collides with the optical fiber. Measure distance.

  Therefore, the present invention can provide an optical fiber position search device that searches for the position and path of an existing optical fiber that is difficult to touch visually or by hand.

Further, the elastic wave generation unit of the optical fiber position search apparatus according to the present invention outputs the elastic wave from at least two output points in a three-dimensional space, and the signal processing unit is output from the output point. It is preferable that the distance between the output point and each point of the measured optical fiber is calculated based on each of the elastic waves, and the position of each point of the measured optical fiber in the three-dimensional space is specified.
With such a configuration, the position and route of the wired optical fiber cable can be specified three-dimensionally.

  It is preferable that the elastic wave generator of the optical fiber position search device according to the present invention outputs a low frequency sound of 100 Hz or less as the elastic wave. Low-frequency sound has a relatively small attenuation constant with respect to a physical barrier such as a wall and has low directivity, so that it can be specified even if an optical fiber cable is wired in a corner or a hidden place in a room.

  It is preferable that the signal generation unit of the optical fiber position search apparatus according to the present invention assigns a different frequency or code string to the elastic wave signal for each output point of the elastic wave generation unit. Whether the acquired information is modulated by elastic waves or noise can be easily identified, and search accuracy is improved.

  The signal processing unit of the optical fiber position search apparatus according to the present invention is configured such that the difference between the polarization or the phase information at a measurement point and the polarization or the phase information at a point on the light reflection measurement unit side of the measurement point Is preferably calculated as the change of the polarization or the phase information.

  When vibration due to elastic waves is applied on the test light incident side of the optical fiber, the test light propagating through the optical fiber after the vibration applying portion is in a modulated state, and the influence is transmitted to the far end side. For this reason, after obtaining the polarization or phase component at each point of the optical fiber, the influence is reduced by taking the difference of the polarization or phase component between adjacent points in the distance direction on the optical fiber.

  The program according to the present invention is a program for causing a computer to function as the signal processing unit of the optical fiber position path searching device. The signal processing unit of the optical fiber position search apparatus according to the present invention can be realized by a computer and a program, and can be recorded on a recording medium or provided through a network.

  The present invention can provide an optical fiber position search apparatus and program for searching for the position and route of an existing optical fiber that is difficult to touch visually or by hand.

It is a figure explaining the optical fiber position search apparatus which concerns on this invention. It is a figure explaining the principle of the optical fiber position search apparatus which concerns on this invention. It is a figure explaining the calculation of the calculation process part of the optical fiber position search apparatus which concerns on this invention. It is a figure explaining the procedure which searches the position of an optical fiber using the optical fiber position search apparatus which concerns on this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  FIG. 1 is a diagram illustrating an optical fiber position search apparatus 301 according to the present embodiment. The optical fiber position search device 301 can specify the position and path of the optical fiber 1 to be measured wired in the three-dimensional space 0.

The optical fiber position search device 301 includes:
A signal generator 3 for generating an elastic wave signal;
An elastic wave generation unit 2 that generates an elastic wave based on the elastic wave signal generated by the signal generation unit 3 and outputs the elastic wave to the air;
A light reflection measuring unit 4 that enters test light into one end of the optical fiber 1 to be measured, and obtains polarization or phase information of the test light from the return light from each point of the optical fiber 1 to be measured at each time;
A clock signal generator 5 for generating a clock signal for synchronizing the generation of the elastic wave and the incidence of the test light on the optical fiber 1 to be measured;
The propagation delay time for the elastic wave to reach each point of the measured optical fiber 1 is calculated from the change in polarization or phase information acquired every time, and each point of the elastic wave generator 2 and the measured optical fiber 1 is calculated. A signal processing unit 6 that calculates the distance between
Is provided.

  The elastic wave generator 2 only needs to generate an elastic wave that propagates in the air with respect to the signal input from the signal generator 3. Although the details will be described separately, the position of the elastic wave generator 2 can be set arbitrarily, and the position and path of the optical fiber 1 to be measured are not dependent on the position of the elastic wave generator 2. Can be identified.

  In the present embodiment, a case where a sound source that generates a low-frequency sound having a relatively small attenuation constant and low directivity, for example, 100 Hz or less, is used as the elastic wave generator 2 with respect to a physical barrier such as a wall. . This low frequency sound has an advantage that it is relatively less noisy than high frequency sound than the loudness characteristic of the human ear. For this reason, an acoustic speaker specialized in low frequency characteristics such as a subwoofer can be used as the elastic wave generator.

  The light reflection measuring unit 4 receives test light from one end of the measured optical fiber 1 and analyzes the reflected light or scattered light at each point on the measured optical fiber 1 to add to the measured optical fiber 1. It is a measuring device which analyzes the vibration which was done. Typical principles of the light reflection measuring unit 4 include OTDR (Optical Time Domain Reflexometry) and OFDR (Optical Frequency Domain Reflexometry).

  The vibration detection utilizes the fact that phase modulation or polarization modulation is applied to the test light transmitted through the vibration applying portion by slight expansion and contraction of the optical fiber to which vibration is applied. When utilizing phase modulation of test light, means such as coherent OTDR or coherent OFDR that analyze vibrations with a phase change or spectral response of reflected or scattered light is used. When using polarization modulation of test light, means such as polarization OTDR or polarization OFDR for analyzing changes in the polarization state of reflected or scattered light are used.

  A low frequency sound is generated from the elastic wave generator 2 via the signal generator 3 in accordance with the clock signal of the clock signal generator 5. At the same time, it is assumed that the test light is incident on the light reflection measuring unit 4 by the clock signal and the measurement is repeatedly performed. That is, in the light reflection measurement unit 4, the phase or polarization state at each point of the measured optical fiber 1 is sampled in time.

  The elastic wave generated from the elastic wave generator 2 propagates in the three-dimensional space 0 and reaches the optical fiber 1 to be measured. FIG. 2 shows how the elastic wave arrives. Since an acoustic wave with low directivity propagates from the elastic wave generator 2 ideally like a spherical wave, it reaches each point of the optical fiber 1 to be measured after an elapsed time corresponding to the distance from the elastic wave generator 2. To do. Since the elastic wave is a physical vibration of air, the optical fiber 1 to be measured starts to vibrate at the same frequency as the elastic wave when receiving the elastic wave. The light propagating through the optical fiber due to this vibration changes the polarization component or phase of the power. The light reflection measurement unit 4 records the polarization or phase information at each point of the measured optical fiber 1 with respect to the elapsed time from the clock and outputs the information to the signal processing unit 6.

  It is assumed that the speed of light in the optical fiber is sufficiently faster than the propagation speed of the elastic wave in the air, and the temperature is almost constant in the three-dimensional space 0 in which the speed of the elastic wave is measured. From the polarization or phase information of each point of the measured optical fiber 1 recorded by the light reflection measuring unit 4, the signal processing unit 6 calculates the time at which the elastic wave with respect to the time of the clock signal reaches each point of the measured optical fiber 1, That is, the elastic wave propagation delay time is analyzed. That is, the signal processing unit 6 can calculate how far each point of the measured optical fiber 1 is from the elastic wave generating unit 2.

Therefore, the procedure for specifying the position of the measured optical fiber 1 in the three-dimensional space 0 using the optical fiber position searching device 301 is the following two steps.
(Procedure M1)
The light reflection measuring unit 4 measures how far each point of the optical fiber 1 to be measured is from the elastic wave generating unit 2.
(Procedure M2)
The position in the three-dimensional space 0 is specified based on the measured distance from the elastic wave generator 2 at each point of the measured optical fiber 1.

  First, the procedure M1 will be described. The conditions of the light reflection measurement unit 4 will be described with respect to the distance measurement from the elastic wave generation unit 2 of the optical fiber 1 to be measured by the light reflection measurement unit 4. As already described, the parameters to be measured are parameters that vary due to vibrations such as a phase change of scattered light, a response spectrum change, and a polarization state change at each point of the measured optical fiber 1.

  Assuming that the length of one side of the three-dimensional space 0 is 100 m at the maximum and the velocity (sound velocity) of the elastic wave is 330 m / s, the maximum propagation time of the elastic wave is approximately 100 m ÷ 330 m / s≈300 ms. If the measurement is performed for 1 second, the elastic wave is sufficiently transmitted to the entire room and the state can be measured. Further, assuming that an optical fiber is wired in the entire room and assuming that the fiber length is about 300 m, the reciprocation time of the optical fiber in the light reflection measuring unit 4 is 3 μs. This means that polarization or phase information at each point of the optical fiber 1 to be measured cannot be acquired at a higher speed. If the detection accuracy of the elastic wave propagation delay time to be measured is about 100 μs, the positional accuracy in the three-dimensional space 0 is 3 cm from a speed of 330 m / s. If the distance resolution on the optical fiber of the light reflection measuring unit 4 is 10 cm, the recognition accuracy of the object is about 10 cm. This means that the position of the optical fiber having a length of 10 cm can be grasped with an error of about 3 cm.

From the above example, the performance required for the light reflection measuring unit 4 is as follows.
(Condition 1) The distance resolution of the light reflection measuring unit 4 is equal to or smaller than the required recognition accuracy of the object (Condition 2) Required positional accuracy in the three-dimensional space 0 ÷ elastic wave in space From the propagation velocity (sound velocity) × 2, the acquisition period of polarization or phase information at each point of the optical fiber 1 to be measured of the light reflection measuring unit 4 is equal or short. Note that “× 2” in condition 2 is Nyquist This is because of a request by the sampling theorem.

  First, OTDR is considered as a specific measurement principle. If the recognition accuracy of the object is 10 cm, the pulse width is 1 ns because the distance resolution is 10 cm or less. Assuming that the length of the fiber to be measured is 300 m and the round trip time is 3 μs, the fact that the pulse can travel back and forth and the waveform of the entire optical fiber can be measured means a maximum interval of 3 μs. This satisfies the condition 2 that it is smaller than half of the time change interval 100 μs to be measured. These conditions can be sufficiently realized by OTDR.

  Next, consider OFDR. The OFDR measures the frequency for a certain period of time and then performs Fourier transform to separate the frequencies to separate scattered light at each point of the optical fiber. The distance resolution of OFDR is determined by the frequency sweep width, and is 10 cm at 1 GHz. If the frequency sweep speed is γ (Hz / s) and the measurement time is 50 μs or less, a frequency sweep of about 20 THz / s is required to achieve 10 cm resolution. This is a range that can be easily realized by using a wavelength variable light source.

  As described above, even the OTDR or OFDR can operate as the light reflection measuring unit 4, but the elastic wave propagation is performed by the signal processing unit 6 from the polarization or phase information at each point of the optical fiber 1 to be measured of the light reflection measuring unit 4. In calculating the delay time, it is necessary to consider the following.

  Since the optical fiber position search apparatus 301 needs to perform vibration measurement from one end of the optical fiber 1 to be measured, the principle such as OTDR or OFDR described above is used for the light reflection measurement unit 4. In these measurements, when vibration due to elastic waves is applied on the test light incident side of the optical fiber 1 to be measured, the test light transmitted through the optical fiber 1 to be measured is modulated. To the far end. In order to avoid this, after obtaining the polarization or phase component at each point of the optical fiber 1 to be measured, a difference in polarization or phase is taken between adjacent points in the distance direction on the optical fiber. It is necessary to process based on That is, the signal processing unit 6 calculates the difference between the polarization or phase information at the measurement point and the polarization or phase information at the point on the light reflection measurement unit 4 side of the measurement point, and sets the change in the polarization or phase information. .

  Note that, as a method for measuring the elastic wave propagation delay time in the signal processing unit 6, the signal generation unit 3 may be able to perform measurement more easily by modulating the elastic wave signal. When no modulation is applied to the elastic wave signal, since the elastic wave propagation delay time is measured only by the presence or absence of the phase difference due to the elastic wave, that is, the impulse response, the change in other noise and phase difference is small. Measurement error.

  On the other hand, if the signal generation unit 3 performs amplitude or phase modulation on the elastic wave signal and adds some code string, the signal processing unit 6 can obtain a mutual relationship between the polarization or phase information of the test light and the signal applied to the signal generation unit 3. By observing the correlation, it is possible to calculate the delay time difference with a signal having the same polarization or phase information. It is possible to increase the measurement accuracy of the elastic wave propagation delay time performed by the signal processing unit 6.

  As will be described later, when the elastic wave is output from two or more points, the signal generator 3 gives a different frequency or code string to the elastic wave signal for each output point of the elastic wave generator 2. It is preferable. It can be easily determined whether the elastic wave from which output point is the polarization or phase information given to the test light.

  The light reflection measuring unit 4 that satisfies the above conditions can measure the arrival time of the elastic wave and the distance from the elastic wave generating unit 2 at each point of the measured optical fiber 1.

ここで、弾性波伝搬速度をＶ、弾性波伝搬遅延時間をｔとしている。 Next, the procedure M2 will be described.
By taking a coordinate system in which the point of the measured optical fiber 1 is (x, y, z) and the position (elastic wave output point) of the elastic wave generator 2 is (X, Y, Z), the measured light The distance r between each point of the fiber 1 and the elastic wave generator 2 can be written as follows.

Here, the elastic wave propagation velocity is V, and the elastic wave propagation delay time is t.

  The elastic wave generator 2 outputs elastic waves from at least two output points in the three-dimensional space, and the signal processing unit 6 outputs the output points and the optical fiber to be measured based on the elastic waves output from the output points. The distance to each point is calculated, and the position of each point of the measured optical fiber 1 in the three-dimensional space is specified. If the number 1 is only one, it is impossible to specify the position (x, y, z) of each point of the measured optical fiber 1. Therefore, the position (x, y, z) of each point of the measured optical fiber 1 can be solved by creating a plurality of equations 1 using a plurality of elastic wave generators 2 and solving the simultaneous equations.

  At this time, the calculation method differs depending on the number of elastic wave generating units 2 (number of output points). Actually, it is not necessary to prepare a plurality of elastic wave generators 2, and one elastic wave generator 2 may be moved and measured a plurality of times.

(1) When the number of output points of the elastic wave generator 2 is four The parameters to be obtained are the position (x, y, z) of each point of the optical fiber 1 to be measured. Since the number 1 which is the distance to the part 2 is non-linear, four equations are necessary to determine one solution. Therefore, the case where there are four basic output points of elastic waves will be described first.

  The elastic wave generator 2 is arranged at four arbitrary positions on the three-dimensional space 0. Although the position in the three-dimensional space 0 is arbitrary, in order to simplify the calculation of the positional relationship between the four points, the four elastic wave generators 2 are A, B, C, and D, and the positions are A (0 , 0, 0), B (X, 0, 0), C (0, Y, 0), and D (0, 0, Z). Since A is (0, 0, 0), this is a coordinate system based on the elastic wave generator 2.

と表せる。以下の計算は２乗して√を消して行う。
数２−数３、数２−数４、数２−数５を計算すると、

となり、一意に被測定光ファイバ１の位置が決定する。 If the distance (rA, rB, rC, rD) between the position (x, y, z) of the measured optical fiber 1 and each elastic wave generator 2 is calculated from the delay time, the distances rA, rB, rC and rD are

It can be expressed. The following calculation is performed by squaring and eliminating √.
When calculating Equation 2 to Equation 3, Equation 2 to Equation 4, Equation 2 to Equation 5,

Thus, the position of the optical fiber 1 to be measured is uniquely determined.

  However, as it is, the coordinate system is represented by coordinates based on the elastic wave generator 2, and the positional relationship and distance between the elastic wave generator 2 and the measured optical fiber 1 are grasped for position recognition. There is a possibility that the installation position of the elastic wave generator 2 may be limited in practice.

  For this reason, it is necessary to convert the obtained coordinate system based on the elastic wave generator 2 to a coordinate system based on the optical fiber 1 to be measured. This procedure will be described below.

  In the actual measurement, since the optical fiber is directly connected when the test light is incident on the optical fiber 1 to be measured from the light reflection measuring unit 4, the test light incident end of the optical fiber 1 to be measured is a light reflection measurement. Exposed in the same place as part 4 where it is exposed and can be touched. For this reason, the incident point l0 = (x0, y0, z0) of the measured optical fiber 1 is used as a reference.

  First, adjust the origin. The origin moves in parallel from the elastic wave generator 2A (0, 0, 0) to the incident point l0 = (x0, y0, z0) of the optical fiber 1 to be measured. This can be done by subtracting l0 = (x0, y0, z0) from each calculated point (x, y, z) of the optical fiber.

  Next, the angle is converted. This is also converted so as to be independent of the position of the elastic wave generator 2 as in the case of the origin. However, since the direction itself has no physical meaning, a coordinate system of an arbitrary angle may be used. However, the conversion itself is necessary in order to indicate which direction (x, y, z) is obtained in the three-dimensional space 0 in a form independent of the elastic wave generator 2. Here, the following coordinate system is considered. The four elastic wave generators 2 may be placed in any way, but in reality, it is easier to think that the z-axis is oriented in the vertical direction. That is, it is considered that the vertical z-axis is not converted, but the x-axis and y-axis are converted.

  For example, the outer product of the direction from the incident point 10 of the measured optical fiber 1 to the next next point 11 and the plane formed by the z axis, that is, the direction from 10 to 11 and the z axis is calculated as the new x axis. . Again, there is no particular meaning in how to set this axis, but this is done to simplify the calculation, and in order to grasp the direction of (x, y, z) that would have been obtained without this conversion. This is an essential conversion for eliminating the dependency of the position of the elastic wave generator 2.

と表せる。φは回転角度である。 The correspondence of this conversion is shown in FIG. Hereinafter, the calculation after the origin is translated by drawing the incident point l0 = (x0, y0, z0) of the optical fiber 1 to be measured will be described. For a general three-dimensional Cartesian coordinate system, the z-axis is the same.

It can be expressed. φ is the rotation angle.

となるので、２つのベクトルの外積をとり、その長さを１に合わせると

と表せる。このベクトルが新しいｘ軸を弾性波発生部２を基準とした座標系で表した形となる。新しいｙ軸はｚ軸とｘ軸の外積なので

と同じように表せる。 Next, the x-axis is converted. The new x-axis is the outer product of the direction from l0 to the next point l1 and the z-axis. The direction from l0 to l1 is (x1−x0, y1−y0, z1−z0), and this is set as (x ′, y ′, z ′). The length of (x ′, y ′, z ′) is Δl by definition. The angle α between the l1-l0 vector and the z-axis is calculated using the inner product

So, if you take the outer product of two vectors and set the length to 1,

It can be expressed. This vector has a new x-axis expressed in a coordinate system with the elastic wave generator 2 as a reference. Because the new y-axis is the outer product of the z-axis and the x-axis

It can be expressed in the same way as

と表せる。これらをまとめると

となる。 Since these expressions are x-axis and y-axis in the new coordinate system,

It can be expressed. Putting these together

It becomes.

の式で弾性波発生部２の位置に依存しない座標系（ｘ’’，ｙ’’，ｚ’’）に変換できる。 From the above calculation, the conversion from the coordinate system based on the elastic wave generator 2 to the coordinate system based on the incident point of the optical fiber 1 to be measured is first performed by subtracting the coordinates of the incident point of the optical fiber 1 to be measured. Move the origin and then rotate around the z axis,

Can be converted into a coordinate system (x ″, y ″, z ″) independent of the position of the elastic wave generator 2.

  As already described, a new coordinate axis in this conversion is arbitrary and is not limited to this calculation method. The z-axis is not limited to being common in the vertical direction, and the coordinate conversion may be calculated using Euler angles, which are conversions in an arbitrary orthogonal coordinate system. Polar coordinate display with the incident point of the measurement optical fiber 1 as the origin may be used. It is possible to convert from the coordinate system based on the elastic wave generator 2 by any calculation method.

(2) In the case where the number of output points of the elastic wave generator 2 is three In this case, Equations 2 to 8 in the case where the number of the elastic wave generator 2 is four, Equations 5 and 8 do not exist, and In the equations 6 and 7, x and y are determined in the same way. Even if an attempt is made to obtain z by substituting x and y obtained in Equations 6 and 7 in any one of Equations 2 to 4, the expression is non-linear, so that ± arbitrary remains. For this reason, the fact that the optical fiber 1 to be measured is a continuous object is used here.

  The incident point l0 = (x0, y0, z0) at which the test light enters the optical fiber 1 to be measured to be calculated is used. At this point, x0 and y0 are already known from equations (6) and (7). It is necessary to determine whether z0 is ±. At this time, the incident point l0 is in a place where it can be seen at the same place as the light reflection measuring unit 4 as already described. For this reason, z0 is uniquely specified by assuming an environment where z0> 0 is clear, for example, assuming that 23 elastic wave generators are placed at the end of the three-dimensional space 0 or placed on the floor. It is possible. Thereby, the incident point l0 = (x0, y0, z0) of the measured optical fiber 1 is determined.

と書ける。数１５に数２と既知の点ｌ０の測定結果

を代入すれば

と書ける。ここで、ｒｌＡ、ｒ０Ａは点ｌ、点ｌ０の弾性波発生部２Ａとの距離である。数１７に数６と数７を代入すればｚに関して線形な式となり、ｚが一意に求められる。 Next, calculation is performed for a point l = (x, y, z) adjacent to the incident point of the optical fiber 1 to be measured. Again, x and y are already known by calculation. Here, it is assumed that l and l0 are separated by a length corresponding to the distance resolution (distance sampling interval) Δl on the optical fiber of the light reflection measuring unit 4. Δl is a known parameter determined by the measurement method. In the range shorter than Δl, the approximation is that the optical fiber is a straight line, but since the length is about the same as the resolution of the optical measurement method performed by the light reflection measurement unit 4, it is a reasonable approximation that does not lead to measurement degradation. It is. Considering this condition, the relationship between l and l0 is

Can be written. Measurement result of equation 2 and equation 2 and known point l0

If you substitute

Can be written. Here, rlA and r0A are distances between the point l and the point l0 from the elastic wave generator 2A. Substituting Equations 6 and 7 into Equation 17 yields a linear expression with respect to z, and z is uniquely obtained.

  By the above calculation, l = (x, y, z) can be calculated uniquely, and the points adjacent to this point can also be calculated sequentially, and the positions of all the points on the measured optical fiber 1 from the elastic wave generator 2 can be calculated. It can be measured. Also in this case, the incidence point l0 = (x0, y0, z0) of the optical fiber 1 to be measured, which has already been calculated, as in the case of four elastic wave generators 2, and the direction to the adjacent point should be used as a reference. Thus, the position of the optical fiber 1 to be measured can be converted into a coordinate system based on the incident point, and can be expressed in a form independent of the position of the elastic wave generator 2 in the three-dimensional space 0.

(3) When the number of output points of the elastic wave generating unit 2 is two When the elastic wave generating unit 2 is two, only the above Equations 2, 3, 6, and 11 are obtained. In this case, Equations 2, 6, and 11 may be solved simultaneously and calculated sequentially from the incident point 10 of the optical fiber 1 to be measured. However, as already explained, in these three equations, either y or z is not determined by ±. In particular, in this case where there are only two elastic wave generating portions 2, ± of y or z is not determined at all points other than the incident point 10 of the optical fiber 1 to be measured. For this reason, on the assumption that two elastic wave generators are placed at the end of the three-dimensional space 0 or placed on the floor, the entire wiring path to be specified of the measured optical fiber 1 is, for example, y> 0 or z> By setting the environment where 0 is clear, the position of the fiber can be uniquely specified. In addition, as already explained, by using the position of the incident point 10 of the measured optical fiber 1 and the direction to the adjacent point as a reference, it can be expressed in a form independent of the position of the elastic wave generator 2. The same.

  By the above procedure, the path and position of the optical fiber in the space can be specified using the plurality of elastic wave generators 2 and the distances of the respective points of the measured optical fiber 1 measured by the light reflection measuring unit 4. In addition, the number of elastic wave generators 2 only needs to be at least two, but this is not explained when there are five or more. However, the number of expressions representing conditions increases, and in addition to the calculation in the case of four, the numerical accuracy is improved. Calculation that reduces the error.

  In the present embodiment, no specific condition is given to all the elastic waves at the plurality of elastic wave generators 2 or their positions. For example, if the signals are the same, measurement may be performed sequentially. If an application such as changing the frequency of the elastic wave from the wave generating unit 2 by the elastic wave generating unit 2 or arranging the code string so as to be orthogonal to the elastic wave generating unit 2, a plurality of elastic wave generating units 2 Applications such as simultaneous measurements are also conceivable.

FIG. 4 is a diagram for explaining a procedure for searching for the position of the optical fiber using the optical fiber position searching apparatus 301. When searching for the position of an optical fiber,
(Step S1)
The elastic wave generator 2 is installed at an arbitrary position. In addition, when installing the elastic wave generation | occurrence | production part 2 in multiple places, the elastic wave generation | occurrence | production part 2 is installed in the place where it is in the relationship of the position matched to the orthogonal coordinate system. The position in the three-dimensional space 0 does not matter.
(Step S2)
A clock is transmitted from the clock signal generation unit 5, and an elastic wave generation signal is transmitted from the signal generation unit 3 to the elastic wave generation unit 2 in accordance with the clock. Test light is incident on the optical fiber 1 and the phase change, spectral response change or polarization fluctuation of the backscattered light is measured.
(Step S3)
From the backscattered light waveform measured by the light reflection measuring unit 4, the elastic wave arrival time at each point of the measured optical fiber 1 is recorded and output to the signal processing unit 6.
(Step S4)
Based on the interval between each position of each elastic wave generator and the measured optical fiber, the signal processing unit 6 calculates the position of each position relative to the incident point of the measured optical fiber 1.
(Step S5)
When a plurality of elastic wave generators 2 are installed, steps S2 and S3 are repeated by the number of elastic wave generators 2.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiment examples may be appropriately combined.

(Effect of the invention)
As described above, with the technology of the present invention, vibrations caused by elastic waves that pass through walls and the like are intentionally caused in the optical fiber to be searched, and this is detected by a reflectometer, so that it can be detected in the walls and floors. It is possible to identify and visualize optical fiber paths that cannot be seen or touched, such as when many core wires are converging into bundles. As a result, it is possible to contribute to the efficiency of searching for communication equipment such as equipment renewal during the operation of an optical fiber line and prevention of damage accidents to the communication equipment.

0: Three-dimensional space in which optical fibers are wired 1: Optical fiber to be measured 2: Elastic wave generation unit 3: Signal generation unit 4: Light reflection measurement unit 5: Clock signal generation unit 6: Signal processing unit 301: Optical fiber Location search device

Claims (6)

Signal generating means for generating an elastic wave signal;
An elastic wave generating unit that generates an elastic wave based on the elastic wave signal generated by the signal generating unit and outputs the generated elastic wave to the air;
A light reflection measuring unit that enters test light into one end of the optical fiber to be measured, and obtains the polarization or phase information of the test light from the return light from each point of the optical fiber to be measured every time;
A clock signal generator for generating a clock signal that synchronizes generation of the elastic wave and incidence of the test light on the optical fiber to be measured;
A propagation delay time for the elastic wave to reach each point of the optical fiber to be measured is calculated from a change in the polarization or the phase information acquired every time, and the elastic wave generator and the optical fiber to be measured are calculated. A signal processing unit for calculating the distance to each point of
An optical fiber position search device. The elastic wave generator outputs the elastic waves from at least two output points in a three-dimensional space,
The signal processing unit calculates a distance between the output point and each point of the measured optical fiber based on each of the elastic waves output from the output point, and the measured optical fiber in the three-dimensional space The position of each point is specified, The optical fiber position search apparatus of Claim 1 characterized by the above-mentioned.   The optical fiber position path searching device according to claim 1, wherein the elastic wave generating unit outputs a low frequency sound of 100 Hz or less as the elastic wave.   The said signal generation part gives a different frequency or code sequence to the said elastic wave signal for every said output point of the said elastic wave generation part, Claim 3 or Claim 3 which quotes Claim 2 characterized by the above-mentioned. Optical fiber position path searching device. The signal processing unit
The difference between the polarization or the phase information at the measurement point and the polarization or the phase information at a point on the light reflection measurement unit side of the measurement point is calculated, and the change in the polarization or the phase information is calculated. The optical fiber position path searching device according to any one of claims 1 to 4.   The program for functioning a computer as the said signal processing part of the optical fiber position path search apparatus in any one of Claim 1 to 5.

Images