JP5613371B2 - Test method, apparatus and system for optical fiber cord control - Google Patents

Description

  The present invention cancels polarization fluctuation noise existing in an optical fiber communication network in the construction and maintenance of the optical fiber communication network, and can identify the optical fiber regardless of whether the optical fiber is bent or not. The present invention relates to a control test method and apparatus and system.

  When constructing and maintaining an optical fiber communication network, it is necessary to grasp the optical fiber core to be worked on. This operation is called core contrast.

  FIG. 6 is an explanatory diagram showing a configuration of a conventional optical fiber core wire comparison test method. As shown in FIG. 6, test light is incident from a test light source 51 for controlling the core wire installed on the upper side of the optical fiber core wire 52 that needs to be controlled. A bend 54 is produced in the line to emit test light out of the optical fiber. This leakage light is detected by a PD (photodiode) 55. By using a longer wavelength than the communication light as the test light at this time, only the test light can be leaked without affecting the communication wavelength light. In addition, an optical coupler 4 that allows test light to enter and exit the optical line, or a test light blocking filter F that blocks only the test light and transmits the communication light immediately before the termination-side device 10 above the optical line. Is installed in advance, and the test light that has entered does not affect communication. 11 is an in-house device on the station side.

Mitsuo Kama, Hiroshi Aoyama, Hiroshi Tanaka, Yasuo Oda “Development of a bending-free optical fiber cord that makes optical wiring easy with DI sense” NTT Technical Journal, April 2006, p. 65-67 Takao Matsumoto, Ryo Nagase, Haruo Kano “Proposal of optical fiber type infinite rotation wavelength device and its application to optical wave technology” IEICE Transactions C, Vol. J70-C, No. 7, July 1987 pp. 1021-1030

  In recent years, with the advancement of technology, there is a problem that it is difficult to contrast the cores with the conventional method. That is a problem in which an optical fiber having bending resistance is invented, and the leakage light intensity due to bending is below the detection limit. Examples of the optical fiber having bending resistance include a hole assist fiber (HAF) that realizes an optical confinement effect. In these optical fibers, leakage light cannot be generated by a conventional method, and the cores cannot be controlled.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a test method, apparatus, and system for optical fiber core wire comparison, which enables a fiber core contrast even with an optical fiber having bending resistance by a simple optical fiber core wire comparison method. The purpose is to provide.

In order to achieve the above object, the optical fiber core wire comparison test method of the present invention has fixedly installed a periodic polarization change imparting portion bundled in a coil shape with a predetermined radius D on the optical fiber, Pulse light is incident from one side of the optical fiber, the polarization intensity in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulse light is measured, and one period of the measured polarization intensity The optical fiber length d ₂ is d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant , d ₁ : cladding diameter of the optical fiber )
It is characterized by performing a cardiac contrast based on

Further, the optical fiber core control test method of the present invention, previously installed a plurality of periodic polarization change imparted portion bundled coiled pre different songs diameter that defines the optical fiber fixedly, Pulse light is incident from one side of each optical fiber core, and the polarization intensity in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulse light is measured for each optical fiber core , The plurality of optical fiber cores are simultaneously contrasted based on a difference between the optical fiber cores in the measured periodic change in polarization intensity.

Further, the optical fiber core control test method of the present invention, an optical splitter connected to an optical fiber, bundled coiled different songs diameter predetermined to a plurality of splitters lower optical fiber which is branched by the optical splitter The periodic polarization change imparting unit is fixedly installed, pulse light is incident from one side of each splitter lower optical fiber, and the pulsed light is rearward by the periodic polarization change imparting unit of each splitter lower optical fiber. The polarization intensity of scattered light in the longitudinal direction of the optical fiber is measured for each of the splitter lower optical fibers, and based on the difference between the splitter lower optical fibers in the periodic change of the measured polarization intensity, It is characterized in that the optical fibers are simultaneously contrasted.

  Further, the present invention is characterized in that, in the optical fiber core wire contrast test method, a predetermined optical fiber is specified by releasing a bending distortion of a coil of a periodic polarization change imparting portion.

  The present invention is also characterized in that, in the optical fiber core wire contrast test method, when the periodic intensity change of the polarization component is superimposed, the periodic intensity change components of the plurality of polarization components are separated using Fourier transform. And

In addition, the optical fiber core wire comparison test device of the present invention includes a periodic polarization change imparting unit fixedly installed on an optical fiber and bundled in a coil shape with a predetermined curvature D , and an optical coupler from the optical fiber. A measuring apparatus for contrasting the core provided by branching, a light source for injecting a light pulse into the optical fiber provided in the measuring apparatus for controlling the core, and a measuring apparatus for controlling the core, A polarizer that extracts a polarization component in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulsed light, and a backscattered light that is provided in the measuring apparatus for contrast control and extracted by the polarizer A photoelectric conversion element that photoelectrically converts a polarization component in the longitudinal direction of the optical fiber, and an output from the photoelectric conversion element that is provided in the measuring device for contrast of the core wire, and the polarization intensity of the backscattered light in the longitudinal direction of the optical fiber Measure And, the optical fiber length d ₂ of one period of polarization intensities the measurement content
d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant)
And a computer for performing a contrast control based on the above.

In addition, the optical fiber cord control system according to the present invention includes a periodic polarization change imparting unit fixedly installed in an optical fiber and bundled in a coil shape with a predetermined curvature D , and a light from the optical fiber. A measuring device for contrasting a core provided by being branched by a coupler, a light source for injecting a light pulse into the optical fiber provided in the measuring device for controlling the core, and a measuring device for contrasting the core, A polarizer that extracts a polarization component in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulsed light, and a backscattered light that is provided in the measuring apparatus for contrast control and extracted by the polarizer A photoelectric conversion element that photoelectrically converts a polarization component in the longitudinal direction of the optical fiber, and an output from the photoelectric conversion element that is provided in the measuring device for contrast measurement of the optical fiber, and polarization of the backscattered light in the longitudinal direction of the optical fiber strength Was measured, the optical fiber length d ₂ of one period of polarization intensities the measurement content
d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant)
And a computer that performs contrast control on the basis of the data, and provides the computer with the core information / test instruction via the data transfer network and receives the test result / control core information from the computer via the data transfer network. And a terminal.

  The test method and apparatus and system for optical fiber core contrast according to the present invention can perform the core contrast regardless of the bending loss of the optical fiber, and the optical fiber core connected to the lower part of the optical splitter. A control can also be performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing a configuration of an optical fiber core wire comparison test apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a periodic polarization change imparting unit, 2 is a measuring device for contrast control, 3 is an optical fiber, 4 is an optical coupler, 5 is a light source such as a laser diode (LD), 6 is an optical coupler, and 7 is a photoelectric device. Conversion elements such as photodiodes (PD), 8 a polarizer, 9 a personal computer (PC), 10 a terminal device, 11 an in-house device, C an optical fiber cable, and F a filter.

  As shown in FIG. 1, a station-side in-house device 11 is connected to, for example, a subscriber-side end-side device 10 by an optical fiber 3 in a multi-core optical fiber cable C, and transmits communication light. The measuring device 2 for contrasting the core wire is for performing a core wire contrast test on the optical fiber 3, and is coupled to the optical fiber 3 using the optical coupler 4. In the measuring device 2 for controlling the core wire, the optical coupler 6 is connected to the branch line of the optical coupler 4, one branch line of the optical coupler 6 is connected to the PC 9 via the LD 5, and the other branch line of the optical coupler 6 is connected. Is connected to the PC 9 via the polarizer 8 and the PD 7.

  Test light (pulse light) transmitted from the LD 5 of the measuring device 2 for controlling the core wire enters the optical fiber 3 through the optical coupler 4. At this time, the test light is blocked by installing a filter F that transmits only the communication light in front of the terminal device 10. As a result, it is possible to perform a core-line contrast test without affecting communication.

  The optical fiber 3 is provided with a periodic polarization change imparting unit 1. The periodic polarization change imparting unit 1 is obtained by bundling an optical fiber 3 with a diameter D [m] in a coil shape. Since the optical fiber 3 is coiled, a refractive index difference is generated between the horizontal direction (p direction) in which no bending strain is applied and the vertical direction (s direction) in which the bending strain is applied. The s-wave and p-wave contained in the light traveling in the optical fiber 3 and the light scattered backwardly cause a difference in traveling speed in the optical fiber 3 due to the above-described relative refractive index difference.

  Therefore, the polarization state of the test light changes in the longitudinal direction of the optical fiber 3. Thereafter, the light scattered backward passes through the optical coupler 4 again and returns to the measuring device 2 for contrasting the core wires. The backscattered light entering the measuring device 2 for contrasting the core wire passes through the optical coupler 6 and is separated into the s or p polarized components by the polarizer 8 and the s component (or p component) is taken out and photoelectrically converted by the PD 7. Thereafter, the output from the PD 7 is input to the PC 9, synchronized with the LD 5 using the PC 9, the distance converted from the time from when the pulsed light is transmitted to the horizontal axis to the return to the measuring device 2 for contrast control, the vertical axis A waveform is drawn as an intensity change in the longitudinal direction of the optical fiber of the polarization component of s or p (hereinafter referred to as a polarization waveform). A cord contrast is performed based on the intensity change period of the polarization component.

At this time, the polarization change of the scattered light can be calculated using the Jones matrix.
The calculation formula is shown below.

と表す。Ｊｏｎｅｓ行列Ｔ_θ，εは First, assuming that the test light φ ₀ has linearly polarized light

It expresses. The Jones matrix T _{θ, ε} is

（但し、θ：入力角、ε：位相進みである。）
となり、ｓ成分を抽出するにはこれらに

(However, θ: input angle, ε: phase advance.)
To extract the s component,

を掛け合わせる。したがって、

Multiply Therefore,

となる。ここで、位相進みεはε＝２β・ｄ_２と変換できて、複屈折率差βは、

It becomes. Here, the phase advance ε can be converted to ε = 2β · d _2, and the birefringence difference β is

ｄ_１：クラッド径［ｍ］、ｄ_２：光ファイバ長［ｍ］、Ｃｆ：光ファイバ特性定数（材料、屈折率、波長等で決まる定数）、Ｄ：コイル径［ｍ］で表す。
以上から，φ_ｓの偏波強度Ｉ_ｓを求めると、

d ₁ : Cladding diameter [m], d ₂ : Optical fiber length [m], Cf: Optical fiber characteristic constant (constant determined by material, refractive index, wavelength, etc.), D: Coil diameter [m].
From the above, and determine the polarization intensity _{I s} of φ _s,

となる。
同様に、ｐ成分を抽出するには、Ｔ_ｓ，０を

It becomes.
Similarly, to extract the p component, T _{s, 0} is

に置き換えればよい。したがって、

Should be replaced. Therefore,

となる。
φ_ｐの偏波強度Ｉ_ｐを求めると、

It becomes.
When the polarization intensity I _p of φ _p is obtained,

となる。
ここで、β・ｄ_２＝πとすることで１周期の光ファイバ長ｄ_２を求めることができる。Ｉ_ｓ，Ｉ_ｐは供に絶対値で計算されるため、見かけ上１周期がπとなる。ｄ_２を計算すると
β＝Ｃ_ｆ（ｄ_１／Ｄ）^２を用いて、
ｄ_２＝（π／Ｃ_ｆｄ_１ ^２）×Ｄ^２となる。

It becomes.
Here, by setting β · d ₂ = π, the optical fiber length d ₂ of one cycle can be obtained. Since I _s and I _p are both calculated as absolute values, one period apparently becomes π. When d ₂ is calculated, β = C _f (d ₁ / D) ² is used,
d ₂ = (π / C _f d ₁ ² ) × D ²

From the above equation, the periodic polarization change applying unit 1 can determine an arbitrary intensity change period by predetermining the coil diameter D, and this optical fiber length d can be determined by the polarization waveform measured by the measuring device 2 for contrast control. By checking the intensity change period of _2, the cords can be contrasted.

FIG. 2 is a characteristic diagram showing a polarization waveform image according to the first embodiment of the present invention. For example, in the waveform shown in FIG. 2, it can be seen that the bending strain of the coil diameter D = 40 mm is applied because the period of the optical fiber length d ₂ = 0.6 m is generated.

  Although it is possible to contrast the optical fiber by external vibration or the like, the vibration change is canceled when the longitudinal intensity profile of the scattered light is averaged. If the first embodiment of the present invention is used, even if averaged, the change in polarization depends on the lengthwise direction, so that position detection is possible. Furthermore, this has an advantage that noise can be removed by averaging. If it is not perfect linear polarization, the amplitude will be small, but it is possible to make a similar comparison. Furthermore, it can be used not only for HAF but also for SMF (single mode type optical fiber).

  FIG. 3 is an explanatory diagram showing the configuration of an optical fiber core wire comparison test apparatus according to a second embodiment of the present invention. In FIG. 3, the same parts as those in FIG. In FIG. 3, 1-1 to 1-M are periodic polarization change imparting units, 10-1 to 10-M are termination-side devices, 12 is an optical splitter, 13-1 to 13-M are splitter lower optical fibers, F -1 to FM are filters.

  Since the test method for controlling an optical fiber core according to the embodiment of the present invention can apply a periodic change of scattered light corresponding to the coil diameter of the periodic polarization change applying units 1-1 to 1-M, It is also possible to use the optical fiber 12 at the bottom of the optical splitter 12 where light is equally divided. A method of contrasting the plurality of splitter lower optical fibers 13-1 to 13-M simultaneously will be described with reference to FIG.

  As shown in FIG. 3, the in-house device 11 is connected to the terminal side devices 10-1 to 10-M by the optical fiber 3, the optical splitter 12, and the splitter lower optical fibers 13-1 to 13-M, and transmits the communication light. ing.

  The measuring device 2 for controlling the core wire is for performing a core wire contrast test on the splitter lower optical fibers 13-1 to 13-M branched by the optical splitter 12, and includes LD5, optical coupler 6, PD7, It has a polarizer 8 and PC9. The measuring device 2 for contrasting a core wire is coupled to an optical fiber communication network using an optical coupler 4.

  Here, bent portions bundled in a coil shape with different diameters D-1 to DM are used for the periodic polarization change imparting portions 1-1 to 1-M of the splitter lower optical fibers 13-1 to 13-M. . However, these periodic polarization change imparting units 1-1 to 1-M adjust the installation position so that the distance from the optical splitter 12 is adjusted and the intensity change cycles do not overlap. Moreover, the bending diameter given to the periodic polarization change imparting units 1-1 to 1-M of the splitter lower optical fibers 13-1 to 13-M is recorded in the PC 9 corresponding to the core number.

  Test light (pulse light) is incident on the optical fiber line including the optical splitter 12 from above the optical splitter 12. The test light transmitted from the measuring device 2 for controlling the core wire is introduced into the optical fiber communication network by using the optical coupler 4, branched by the optical splitter 12, and then propagated through the lower optical fibers 13-1 to 13 -M of the splitter. .

  The light scattered by the splitter lower optical fibers 13-1 to 13 -M passes through the optical coupler 4 again and returns to the measuring device 2 for controlling the core wire. The scattered light intensity change in one polarization direction in the optical fiber 3 at this time is measured as in the first embodiment of the present invention.

  As an example, when optical fibers 13-1, 13-2, and 13-3 are allocated below the optical splitter 12, and periodic polarization change imparting units 1-1, 1-2, and 1-3 are respectively installed. think of. The scattered light below the optical splitter 12 at this time is measured as the optical fiber length-scattered light intensity in the same manner as in the first embodiment of the present invention.

FIGS. 4A and 4B are characteristic diagrams showing polarization waveform images according to the second embodiment of the present invention. In the waveform of FIG. 4A, the polarization intensity of the optical fiber lengths d ₂ -1, d ₂ -2, and d ₂ -3 corresponding to the periodic polarization change imparting units 1-1, 1-2, and 1-3. Change has occurred.

  Next, in the lower part of the optical splitter 12, for example, when the optical fiber 13-2 of the splitter lower optical fiber is contrasted, the bending distortion of the coil of the periodic polarization change imparting unit 1-2 of the optical fiber that is considered to be the optical fiber. Is released.

When the waveform is acquired again, the change in the polarization intensity of the optical fiber length d ₂ -2 period disappears as shown in FIG. 4B, and this disappeared optical fiber length d ₂ -2 period is recorded in advance. A predetermined optical fiber can be specified by confirming that the optical fiber core wire that matches the core wire number and has released the bending strain of the coil is 13-2.

  From the above work, if the second embodiment of the present invention is used, it is possible to perform the contrast control even at the lower part of the optical splitter.

  When the distance between the optical splitter 12 and the periodic polarization change applying units 1-1 to 1-M of the bending applying unit is close or equal, a waveform in which all polarization fluctuation periods are superimposed is obtained, and the period of the polarization component is obtained. The intensity change will be superimposed. In this case, M periodic changes are superimposed on the OTDR (optical pulse tester) waveform, but this part is Fourier transformed to separate the periodic intensity changing components of a plurality of polarization components, thereby determining whether or not there is a line. It is possible to confirm.

  The second embodiment of the present invention can be used in both SMF and HAF. Further, the second embodiment of the present invention can be similarly applied to a plurality of optical fiber core wires of a multi-core optical fiber cable.

  FIG. 5 is an explanatory diagram showing the configuration of a test system for controlling an optical fiber core according to a third embodiment of the present invention. In FIG. 5, the same parts as those in FIG. In FIG. 5, 14 is a mobile phone, 15 is the Internet, 16 is a core selection optical switch, and 17 is a measurement terminal.

  FIG. 5 shows a method of comparing the cores by operating only the measurement points in the field using the test method for controlling the cores according to the first embodiment of the present invention. Between the measuring device for control 2 and the optical coupler 4, a core selection optical switch 12 for introducing test light (pulse light) to the optical fiber network to be compared with the core is installed. The PC 9 of the measuring device 2 for controlling the core wire is connected to the measuring terminal 17 through the data transfer network including the Internet 15 and the mobile phone 14.

  That is, the measurement operator determines the diameter of the periodic polarization change imparting unit 1, creates a bundle in a coil shape, gives the intensity change periodic variation, and monitors the measurement instruction / result display at the measurement terminal 17. The measuring terminal 17 is connected to the Internet 15 using a mobile phone 14 or the like, and gives the core information / test instruction to the PC 9 in the measuring apparatus 2 for controlling the cores via the data transfer network. Test results and control core information are received via The measurement operator does not need to be in the equipment bureau, only the measurement point in the field where the control is performed.

  Similarly, in the case of the second embodiment of the present invention, the polarization intensity change monitor under the optical splitter can be performed at the work location, so that the operation in the equipment station can be omitted. It becomes possible to contrast the minds only by the operator.

  As described above, according to the embodiment of the present invention, it is possible to perform a core line contrast test that specifies a position in-service by detecting a periodic change of a specific polarization component of light.

  Thereby, it becomes possible to identify the position of the failure point of the optical fiber regardless of the presence or absence of bending resistance. Moreover, polarization fluctuation noise existing in the optical fiber communication network can be canceled by arbitrarily adding period information.

  Furthermore, it becomes possible to give a continuous periodic fluctuation, position detection by averaging can be performed, and the measurement dynamic range can be expanded.

  Even under the optical splitter, light can be scattered with different period changes in each optical fiber, and the optical fiber under the splitter can be distinguished on the measurement waveform. As a result, the control of the optical fiber below the optical splitter becomes possible.

  As described above, it is possible to provide a cord control test method, apparatus, and system capable of performing a stable cord control test in-service not only in HAF but also in SMF.

  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. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory view showing an optical fiber core wire comparison test apparatus according to a first embodiment of the present invention. It is a characteristic view which shows the polarization waveform image which concerns on the 1st Embodiment of this invention. It is composition explanatory drawing which shows the optical fiber core wire comparison test apparatus which concerns on the 2nd Embodiment of this invention. It is a characteristic view which shows the polarization waveform image which concerns on the 2nd Embodiment of this invention. It is composition explanatory drawing which shows the optical fiber core wire comparison test system which concerns on the 3rd Embodiment of this invention. It is composition explanatory drawing which shows the conventional test method for optical fiber core wire contrast.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Periodic polarization change provision part, 2 ... Measuring apparatus for optical fiber contrast, 3 ... Optical fiber, 4 ... Optical coupler, 5 ... Laser diode (LD), 6 ... Optical coupler, 7 ... Photodiode (PD), 8 DESCRIPTION OF SYMBOLS ... Polarizer, 9 ... Personal computer (PC), 10 ... Termination side device, 11 ... In-house device, C ... Optical fiber cable, F ... Filter.

Claims (7)

A periodic polarization change imparting unit that is bundled in a coil shape with a predetermined radius of curvature D is fixedly provided on the optical fiber, pulse light is incident from one side of the optical fiber, and the periodic polarization change imparting unit of the pulsed light The polarization intensity of the backscattered light in the optical fiber longitudinal direction is measured, and the optical fiber length d ₂ for one period of the measured polarization intensity is d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant , d ₁ : cladding diameter of the optical fiber )
A test method for optical fiber core contrast, characterized in that the core contrast is performed based on A plurality of periodic polarization change imparted portion bundled coiled pre different songs diameter that defines the optical fiber fixedly incident pulsed light from one side of each optical fiber, said pulsed light Measuring the polarization intensity of the backscattered light in the longitudinal direction of the optical fiber by each of the optical fiber cores, and the difference between the optical fibers in the periodic change of the measured polarization intensity And a plurality of optical fiber cores are simultaneously subjected to optical fiber contrast testing. An optical splitter connected to an optical fiber, fixedly provided with the light periodic polarization change imparted portion bundled coiled different songs diameter predetermined to a plurality of splitters lower optical fibers split by the splitter, the light Pulse light is incident from the upper part of the splitter, and the polarization intensity in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting part of each of the splitter lower optical fibers of the pulse light is measured for each of the splitter lower optical fibers. An optical fiber core-line contrast test method, wherein the plurality of splitter bottom optical fibers are simultaneously core-line-checked based on the difference between the splitter lower-side optical fibers in the measured periodic change in polarization intensity. . 4. The test method for controlling an optical fiber core according to claim 2 , wherein the predetermined optical fiber is specified by releasing the bending distortion of the coil of the periodic polarization change imparting unit. 4. The optical fiber core wire comparison device according to claim 2 , wherein when the periodic intensity change of the polarization component is superimposed, the periodic intensity change components of the plurality of polarization components are separated using Fourier transform. Test method. A periodic polarization change imparting unit fixedly installed in an optical fiber and bundled in a coil shape with a predetermined radius D;
A measuring device for contrasting a core provided by being branched from the optical fiber by an optical coupler;
A light source for injecting a light pulse into the optical fiber provided in the measuring apparatus for controlling the core wire;
A polarizer that is provided in the measuring apparatus for controlling the core wire and extracts a polarization component in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulsed light;
A photoelectric conversion element that is provided in the measuring device for contrast control of the core wire and photoelectrically converts a polarization component in the longitudinal direction of the optical fiber of the backscattered light extracted by the polarizer;
Provided in the measuring device for contrast control, the output from the photoelectric conversion element is input, the polarization intensity of the backscattered light in the longitudinal direction of the optical fiber is measured, and the light for one period of the measured polarization intensity The fiber length d ₂ is d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant , d ₁ : cladding diameter of the optical fiber )
And an optical fiber core wire test apparatus characterized by comprising: A periodic polarization change imparting unit fixedly installed in an optical fiber and bundled in a coil shape with a predetermined radius D;
A measuring device for contrasting a core provided by being branched from the optical fiber by an optical coupler;
A light source for injecting a light pulse into the optical fiber provided in the measuring apparatus for controlling the core wire;
A polarizer that is provided in the measuring apparatus for controlling the core wire and extracts a polarization component in the longitudinal direction of the optical fiber of the backscattered light by the periodic polarization change imparting unit of the pulsed light;
A photoelectric conversion element that is provided in the measuring device for contrast control of the core wire and photoelectrically converts a polarization component in the longitudinal direction of the optical fiber of the backscattered light extracted by the polarizer;
Provided in the measuring device for contrast control, the output from the photoelectric conversion element is input, the polarization intensity of the backscattered light in the longitudinal direction of the optical fiber is measured, and the light for one period of the measured polarization intensity The fiber length d ₂ is d ₂ = (π / C _f d ₁ ² ) × D ² (C _f : optical fiber characteristic constant , d ₁ : cladding diameter of the optical fiber )
A computer that performs mind line contrast based on
An optical fiber core comprising: a measurement terminal that gives optical fiber information / test instructions to the computer via a data transfer network and receives test results / control optical fiber information from the computer via the data transfer network Line control test system.

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