JP5542255B2 - Optical fiber length expansion / contraction measurement and correction method and apparatus - Google Patents

Description

  The present invention relates to an optical fiber length change measurement and correction technique using a white interference method (low coherence interference method) and a pulse interference length measurement method.

  The optical fiber expands and contracts due to temperature changes. In long-distance signal transmission, there is a problem of signal delay (time shift) due to this expansion and contraction. In the conventional optical fiber length change measurement, the fiber expansion and contraction is measured by propagating a sine-type signal in the fiber with reference to a stabilized laser or an electrical RF source, and detecting the phase change. Even if you can measure the expansion and contraction, you cannot get the absolute length. A fiber stretcher is used to correct the fiber length, but there is a problem in reproducibility (repeatability) due to fiber hysteresis.

  As described in Patent Document 1, the inner surface shape of a narrow tube having a constriction shape with a length of 1 meter or more is measured with high accuracy on the order of microns by a non-contact measuring device using white interference method. There is a way.

  White interferometry is a method in which light from a white light source is split into reference light and measurement light by a half mirror, and the light reflected from the reference mirror by the reference mirror and the light reflected by the measurement light hitting the object are detected by a detector. However, when the reference mirror is moved and the optical path lengths of the measurement light and the reference light coincide with each other, interference fringes are seen. The interference fringe signal appears when the optical path difference between the object light and the reference light is within the coherence length of the light source, and becomes maximum when the optical path difference is zero.

  Since the maximum interference fringe contrast position corresponds to the surface height of the object and the peak position determination accuracy becomes the measurement accuracy, the optical path length of the reference light is scanned with high accuracy and the white interference fringe phase information is obtained. Measurement with metric accuracy is also possible.

  FIG. 8 is a diagram showing a configuration of a conventional pulse interference length measurement technique (optical comb technique). The white light interferometry can be applied when the reference optical path length and the measurement optical path length are substantially the same, but the pulse interferometry can be applied when there is a large difference between the reference optical path length and the measurement optical path length.

  In the pulse interference length measurement technique 1b, the light 15 from the pulse light source 2a is split into the reference light 15a and the measurement light 15b by the half mirror 6a or the like, and the reference light reflected light 15c is reflected by the reference mirror 10c. The detector 12c detects the light pulse 15e and the measurement light pulse 15f of the measurement light reflected light 15c obtained by reflecting the measurement light 15b by the mirror 10b. The optical path length of the measurement light 15b is determined by moving the reference mirror 10c. Interference fringes 14a can be seen at the point where the optical path length of the reference light 15a coincides with a certain length or the point where the optical path length of the measuring light 15b is an integral multiple of the pulse interval.

  Pulse lights are arranged at equal intervals on the spatial axis, the reference light pulse 15e interferes with any measurement light pulse 15f, and interference fringes 14 are observed. The interval between the measurement light pulses 15f is the speed of light / repetition frequency.

  Therefore, the present invention provides a method and apparatus for measuring the fiber absolute length by applying the white interference method and the pulse interference length measurement technology, and measuring the fiber expansion and contraction due to temperature drift etc. with high accuracy on the order of micrometers. The purpose is to do.

(1)
An interferometer unit that divides light from a light source into reference light and measurement light, a reference light scanner unit that returns the reference light divided by the interferometer unit to a reference mirror by reflecting it with a reference mirror, and the interferometer unit The measurement light that is connected with the optical fiber and divided by the interferometer unit is reflected by a mirror to return to the interferometer unit, and the reference light and measurement light returned to the interferometer unit are detected by a high-speed photodetector. An optical fiber length expansion / contraction measurement / correction device comprising: a detection unit that detects a reference light pulse and a measurement light pulse, and calculates a length of the optical fiber by measuring a time interval between the reference light pulse and the measurement light pulse by a computer. The configuration was as follows.
(2)
By dividing the light from the light source into reference light and measurement light and interfering the reference light and measurement light with each other, and by reflecting the reference light divided by the interferometer part with a reference mirror that changes the optical path length A reference light scanner unit that returns to the interferometer unit, and the measurement light that is connected to the interferometer unit with an optical fiber and is divided by the interferometer unit is reflected by a mirror via a fiber length correction mechanism that changes the optical path length. The measuring unit returning to the interferometer unit, and the computer detects the change amount of the interference signal while detecting the interference signal with the differential photodetector with respect to the reference light and the measurement light interfered with the interferometer unit. An optical fiber length expansion / contraction measurement / correction device is provided that includes a detection unit that corrects optical fiber expansion / contraction by operating the fiber length correction mechanism.
(3)
The light from the light source is divided into reference light and measurement light by the interferometer unit, the reference light divided by the interferometer unit is returned to the interferometer unit by being reflected by a reference mirror, and is divided by the interferometer unit. The reflected measurement light is reflected by a mirror through an optical fiber and returned to the interferometer unit. The reference light and measurement light pulse returned to the interferometer unit are detected by a high-speed photodetector with respect to the reference light and measurement light. The length of the optical fiber is calculated by measuring the time interval between the reference light pulse and the measurement light pulse.
(4)
Dividing the light from the light source into measurement light and reference light by an interferometer unit, together with the return a reference light split by the interferometer unit to the interferometer unit by reflecting the reference mirror for changing the optical path length, wherein The measurement light divided by the interferometer unit is reflected by a mirror through an optical fiber and through a fiber length correction mechanism that changes the optical path length, and then returned to the interferometer unit, and the reference light interfered by the interferometer unit While detecting the interference signal with the differential optical detector for the measurement light, the computer converts the change amount of the interference signal into the change amount of the fiber length, and corrects the optical fiber expansion and contraction by operating the fiber length correction mechanism. The optical fiber length expansion / contraction measurement / correction method is characteristic.

  By using the present invention, it is possible to perform accurate signal transmission / reception with minimal time deviation while performing highly accurate, high repetition and stable fiber length correction.

It is a figure which shows the structure of the optical fiber length measuring apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the optical fiber expansion-contraction measurement and correction apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the interferometer part of the optical fiber length expansion-contraction measurement and correction apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the reference light scanner part of the optical fiber length expansion-contraction measuring / correcting apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the fiber length correction | amendment mechanism of the optical fiber length expansion-contraction measurement / correction apparatus which concerns on Example 1 of this invention. It is a figure which shows the flow of the optical fiber length measuring method which concerns on Example 2 of this invention. It is a figure which shows the flow of the optical fiber expansion-contraction measurement and correction method which concerns on Example 2 of this invention. It is a figure which shows the structure of the conventional pulse interference length measurement technique (optical comb technique).

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an optical fiber length measuring apparatus according to a first embodiment of the present invention. The optical fiber length measurement device 1 includes a light source 2, an interferometer unit 6, a reference light scanner unit 7, a measurement unit 9, and a detection unit 12.

  The light source 2 and the fiber coupler 11 of the interferometer unit 6 are connected by an optical fiber 3. However, since the fiber circulator 5 is interposed between the light source 2 and the fiber coupler 11, the optical fibers 3 are connected by fiber connectors 4 and 4 a. The interferometer unit 6 and the reference light scanner unit 7 are connected by an optical fiber 3.

  The fiber coupler 11 of the interferometer unit 6 and the fiber coupler 11a of the measurement unit 9 are connected by an optical fiber 3, and a fiber length correction mechanism 8 is interposed between the fiber coupler 11 and the fiber coupler 11a.

  The fiber coupler 11 of the interferometer unit 6 and the fiber coupler 11b of the detection unit 12 are connected by an optical fiber 3, but the optical fibers 3 emitted from both are connected by a fiber connector 4b.

  The light source 2 is a device that supplies white light, and has CW (Continuous wave), spontaneous emission light (ASE (Amplified Spontaneous Emission)) or pulse light source, super luminescent diode (SLD), femto having a certain spectral width. A second laser.

  The optical fiber 3 is a light transmission path made of quartz glass or plastic with high transmittance, and propagates the light 15 from the light source 2, the reference light 15a, the measurement light 15b, and the like to each part. It consists of a core of the core part and a clad outside thereof, and light is propagated only to the core by making the refractive index of the core higher than that of the clad.

  The fiber connectors 4, 4 a, and 4 b are connection members that connect the optical fibers 3 and cause light propagation. The fiber connector 4 connects the optical fiber 3 from the light source 2 and the optical fiber 3 on the light source 2 side of the fiber circulator 5. The fiber connector 4 a connects the optical fiber 3 on the light source 2 side of the fiber coupler 11 and the optical fiber 3 on the fiber coupler 11 side of the fiber circulator 5. The fiber connector 4 b connects the optical fiber 3 on the detection unit 12 side of the fiber coupler 11 and the optical fiber 3 from the detection unit 12.

  The fiber circulator 5 is a device that propagates and circulates input light, output light, and return light through different paths. The light 15 from the light source 2 is sent to the interferometer unit 6, and the reference light reflected light 15 c and the measurement light reflected light 15 d from the interferometer unit 6 are sent to the detection unit 12.

  The interferometer unit 6 is means for causing the reference light 15a and the measurement light 15b to interfere with each other, and uses the fiber coupler 11. The light 15 from the light source 2 is divided into the reference light 15 a and the measurement light 15 b by the fiber coupler 11, the reference light 15 a is sent to the reference light scanner unit 7, and the measurement light 15 b is sent to the measurement unit 9 and returned from the reference light scanner unit 7. The reference light reflected light 15c and the measurement light reflected light 15d are caused to interfere with each other and sent to the detection unit 12.

  The reference light scanner unit 7 is means for changing the optical path length of the reference light 15a coming from the interferometer unit 6 and reading the amount of change. The reference light 15a reflected by the reference light scanner unit 7 is returned to the interferometer unit 6 as reference light reflected light 15c.

  The measurement unit 9 sends the measurement light 15b from the interferometer unit 6 to the fiber coupler 11a via the fiber length correction mechanism 8, and after dividing the transmission signal 15g by the fiber coupler 11a, the measurement light 15b is sent to the fiber collimator 9a. To the mirror 10.

  When the transmission signal 15g is input from the fiber coupler 11b of the detection unit 12 and sent to the interferometer unit 6, the transmission signal 15g is sent to the measurement unit 9 together with the measurement light 15b. Therefore, the transmission signal 15g is separated in the fiber coupler 11a. Output.

  The fiber length correction mechanism 8 is a device having a function of changing the optical path length on the measurement light 15 b side in accordance with the amount of change in the length of the optical fiber 3.

  The fiber collimator 9a includes a lens and a fiber holder, and is a member having a function of converting divergent light emitted from the optical fiber 3 into parallel light. The measurement light 15b is reflected by the mirror 10 and used to make the measurement light reflected light 15d incident.

  The mirror 10 is an optical element that reflects incident light. A CCP (corner cube prism) may be used. Since it is only necessary to apply the measurement light 15b to the measurement object and detect the reflected measurement light reflected light 15d, an optical element or the like is used as the measurement object.

  The fiber couplers 11, 11a, and 11b are devices that serve as beam splitters. The fiber coupler 11 splits the light 15 from the light source 2 into reference light 15a and measurement light 15b. The fiber coupler 11a divides and outputs the transmission signal 15g sent together with the measuring light 15b. The fiber coupler 11 b divides the flow of the reference light reflected light 15 c and the measurement light reflected light 15 d sent from the interferometer unit 6 to the detector 12 and the flow of the transmission signal 15 g sent to the interferometer unit 6.

  Since the reference light reflected light 15c and the measurement light reflected light 15d interfered by the interferometer unit 6 are sent to the fiber circulator 5 and the fiber coupler 11b, the detection unit 12 transmits the reference light reflected light from each of the fiber circulator 5 and the fiber coupler 11b. 15c and measurement light reflected light 15d are detected by the high-speed photodetector 12a and processed by the computer 14 via the analog-digital converter 13.

  The high-speed light detector 12a is a device that detects the reference light reflected light 15c or the measurement light reflected light 15d at high speed. Since the reference light reflected light 15c and the measurement light reflected light 15d are analog signals, they are digitized by the analog-to-digital converter 13 and then input to the computer 14.

  The analog-digital converter 13 is an electric circuit that converts an analog signal into a digital signal. The computer 14 is a processing device that processes various signals and controls the reference light scanner unit 7 and the fiber length correction mechanism 8.

  The computer 14 is used to read the difference in detection time (ΔT) between the reference light pulse 15e and the measurement light pulse 15f, which is caused by the difference in fiber length between the reference light 15a side and the measurement light 15b side.

  When the fiber length (L) is obtained from this time and the known fiber refractive index (n), the speed of light in vacuum is c, and L = c × ΔT / n.

  FIG. 2 is a diagram illustrating a configuration of the optical fiber expansion / contraction measurement / correction apparatus according to the first embodiment of the present invention. The optical fiber expansion / contraction measurement / correction device 1a also includes a light source 2, an interferometer unit 6, a reference light scanner unit 7, a measurement unit 9, and a detection unit 12.

  In the optical fiber expansion / contraction measurement / correction apparatus 1a, the high-speed photodetector 12a of the detection unit 12 is replaced with a differential photodetector 12b, and the computer 14 controls the fiber length correction mechanism 8 of the measurement unit 9. The differential photodetector 12b is a device that converts an optical interference signal into an electrical signal.

  Using the computer 14, the position of the reference light scanner unit 7 at the time of detecting the peak of the interference fringes 14a is read. The peak position fluctuation is monitored and measured as fiber expansion and contraction. The measured expansion / contraction amount is a deviation from the initial position, and is corrected by the fiber length correction mechanism 8.

  FIG. 3 is a diagram illustrating the structure of the interferometer unit of the optical fiber length expansion / contraction measurement / correction apparatus according to the first embodiment of the present invention. The interferometer unit 6 includes a light splitting unit, a reference light transmitting / receiving unit, a measuring light transmitting / receiving unit, and an optical interference unit.

  The light splitting means is means for splitting the light 15 from the light source 2 into the reference light 15a and the measuring light 15b, and the fiber coupler 11 is provided with a half mirror having a beam splitter function.

  By connecting the input terminal of the fiber coupler 11 and the light source 2 with the optical fiber 3, the light 15 enters the fiber coupler 11, and the light 15 is divided into the reference light 15a and the measurement light 15b.

  The reference light transmission / reception means is means for sending the reference light 15a to the reference light scanner unit 7 and receiving the reference light reflected light 15c. The reference light output / input terminal of the fiber coupler 11 and the reference light scanner unit 7 are connected by the optical fiber 3. The reference light 15a and the reference light reflected light 15c are allowed to pass through.

  The measurement light transmission / reception means is means for sending the measurement light 15b to the measurement unit 9 and receiving the measurement light reflected light 15d. The measurement light output / input terminal of the fiber coupler 11 and the measurement unit 9 are connected by the optical fiber 3, and the measurement light 15b. And the measurement light reflected light 15d is passed.

  The optical interference means is means for sending the interfered reference light reflected light 15c and measurement light reflected light 15d to the detection unit 12, and connects the output terminal of the fiber coupler 11 and the detection unit 12 with the optical fiber 3, and is connected with a half mirror or the like. The reference light reflected light 15c and the measurement light reflected light 15d are caused to interfere with each other and output to the detection unit 12.

  FIG. 4 is a diagram illustrating the structure of the reference light scanner unit of the optical fiber length expansion / contraction measurement / correction apparatus according to the first embodiment of the present invention. The reference light scanner unit 7 includes a stage table 7a, a fiber collimator 9b, a reference mirror 10a, a linear motion stage 16, a reflective optical element 17, a linear scale 18, a scale head 19, a constant temperature and pressure vessel 20, and the like.

  A linear motion stage 16 and a linear scale 18 are installed on the stage table 7 a, and the stage table 7 a is stored in a constant temperature and pressure vessel 20. A reflective optical element 17 and a scale head 19 are placed on the linear motion stage 16, and the linear motion stage 16 can move back and forth along the linear scale 18.

  The optical fiber 3 from the interferometer unit 6 is connected to the fiber collimator 9 b, the reference light 15 a is incident on the reference light scanner unit 7, and the reference light reflected light 15 c is emitted toward the interferometer unit 6. .

  The direction of the incident reference light 15a is changed by the reflective optical element 17 and is irradiated toward the reference mirror 10a. The reference light reflected light 15c reflected by the reference mirror 10a passes through the same path from the reflective optical element 17 to the fiber collimator 9b.

  By reciprocating the reflective optical element 17 on the stage table 7a by the linear motion stage 16, the optical path length of the reference light 15a can be changed. The reflective optical element 17 changes the traveling direction of the reference light 15a, and uses a right-angle prism mirror or a CCP (corner cube prism).

  The linear scale 18 gives a position on the stage table 7 a, and the scale head 19 reads the position of the reflective optical element 17 on the stage table 7 a from the linear scale 18. The constant-temperature pressure tank 20 keeps the temperature and pressure of the reference light scanner unit 7 constant, and suppresses fluctuations in the optical path length due to atmospheric fluctuations.

  FIG. 5 is a diagram illustrating the structure of the fiber length correction mechanism of the optical fiber length expansion / contraction measurement / correction device according to the first embodiment of the present invention. The fiber length correction mechanism 8 includes a stage table 8a, a fiber collimator 9c, a fiber collimator 9d, a linear motion stage 16a, a linear scale 18a, a scale head 19a, a constant temperature and pressure vessel 20a, and the like.

  The linear motion stage 16a is installed on the stage table 8a, and the stage table 8a is stored in the constant temperature and pressure vessel 20a. A fiber collimator 9c and a scale head 19a are mounted on the linear motion stage 16a, and the linear motion stage 16a can move back and forth along the linear scale 18a.

  The optical fiber 3 from the interferometer unit 6 is connected to the fiber collimator 9c, and the measurement light 15b enters the fiber length correction mechanism 8, and the measurement light reflected light 15d is emitted toward the interferometer unit 6. The

  The fiber collimator 9d is connected to the optical fiber 3 to the measurement unit 9, the measurement light 15b is emitted to the measurement unit 9, and the measurement light reflected light 15d is incident into the fiber length correction mechanism 8.

  The incident measurement light 15b is irradiated from the fiber collimator 9c toward the fiber collimator 9d. The incident measurement light reflected light 15d is irradiated from the fiber collimator 9d toward the fiber collimator 9c. By reciprocating the fiber collimator 9c on the stage table 8a by the linear motion stage 16a, the optical path length of the measuring light 15c can be changed.

  The linear scale 18a gives a position on the stage table 8a, and the scale head 19a reads the position of the fiber collimator 9c on the stage table 8a from the linear scale 18a. The constant-temperature pressure tank 20a keeps the temperature and pressure of the fiber length correction mechanism 8 constant, and suppresses fluctuations in the optical path length due to atmospheric fluctuations.

  An amount corresponding to the fiber expansion / contraction amount (deviation from the initial position) measured by the computer 14 is adjusted by the movement of the linear motion stage 16a, and is corrected so that the interference signal peak returns to the initial position.

  FIG. 6 is a diagram illustrating a flow of the optical fiber length measurement method according to the second embodiment of the present invention. The optical fiber length measurement method 21 includes the steps of white light source irradiation 22, reference optical path length fixing 23, pulse detection 24, time interval measurement 25, and fiber length calculation 26.

  The light source irradiation 22 irradiates the light 15 from the light source 2, sends the light 15 to the interferometer unit 6 through the optical fiber 3, and divides the light 15 into the reference light 15 a and the measurement light 15 b by the interferometer unit 6. 15 a is sent to the reference light scanner unit 7 and the measuring light 15 b is sent to the measuring unit 9.

  The reference optical path length fixing 23 fixes the optical path length of the reference light 15 a in the reference light scanner unit 7.

  The pulse detector 24 sends the reference light reflected light 15c returned from the reference light scanner unit 7 to the interferometer unit 6 and the measurement light reflected light 15d returned from the measuring unit 9 to the interferometer unit 6 to the detecting unit 12, and the reference light The pulse 15e and the measurement light pulse 15f are detected.

  The time interval measurement 25 is performed by measuring the difference in detection time between the reference light pulse 15e and the measurement light pulse 15f caused by the difference in fiber length between the reference light 15a side and the measurement light 15b side by the high-speed photodetector 12a of the detection unit 12. read.

  The fiber length calculator 26 determines the fiber length from the difference in detection time between the reference light pulse 15e and the measurement light pulse 15f and the known fiber refractive index.

  FIG. 7 is a diagram illustrating a flow of the optical fiber expansion / contraction measurement / correction method according to the second embodiment of the present invention. Optical fiber expansion / contraction measurement / correction method 21a includes white light source irradiation 22, reference optical path length scan 27, interference signal detection 28, interference signal peak position change confirmation 29, fiber length change conversion 30, fiber length change adjustment 31, It consists of the steps of fiber length correction mechanism stage movement 32 and interference signal peak position confirmation 33.

  In the reference light path length scan 27, the reference light scanner unit 7 moves the linear motion stage 16 so that the reference light 15a is reflected by the reference mirror 10a via the reflective optical element 17 and returned as reference light reflected light 15c. Read the optical path length.

  The interference signal detection 28 sends the reference light reflected light 15c returned from the reference light scanner unit 7 to the interferometer unit 6 and the measurement light reflected light 15d returned from the measuring unit 9 to the interferometer unit 6 to the detecting unit 12 for reference. The position where the interference fringes 14a of the light 15a and the measurement light 15b appear is detected as an initial position.

  The interference signal peak position change confirmation 29 reads the position in the reference light scanner unit 7 when the peak of the interference fringe 14a is detected, and monitors the change amount of the interference signal peak position by the differential photodetector 12b of the detection unit 12.

  The fiber length change amount conversion 30 obtains the change amount of the fiber length to be corrected according to the change amount of the interference signal peak position when the differential photodetector 12b detects the change of the interference signal peak position.

  In the fiber length change adjustment 31, the computer 14 of the detection unit 12 instructs the fiber length correction mechanism 8 to operate by instructing the adjustment amount according to the converted change.

  The fiber length correction mechanism stage movement 32 moves the linear motion stage 16 a of the fiber length correction mechanism 8 provided in the measurement unit 9 to correct the deviation from the initial position due to the expansion and contraction of the optical fiber 3.

  The interference signal peak position confirmation 33 confirms that the interference signal peak position has returned to the initial position. By returning to the interference signal peak position change confirmation 29 and repeating, correction is performed whenever expansion or contraction occurs.

DESCRIPTION OF SYMBOLS 1 Optical fiber length measurement apparatus 1a Optical fiber expansion-contraction measurement and correction apparatus 1b Pulse interference measurement technique 2 Light source 2a Pulse light source 3 Optical fiber 4 Fiber connector 4a Fiber connector 4b Fiber connector 5 Fiber circulator 6 Interferometer section 6a Half mirror 7 Reference light scanner section 7a stage table 8 fiber length correction mechanism 8a stage table 9 measurement unit 9a fiber collimator 9b fiber collimator 9c fiber collimator 9d fiber collimator 10 mirror 10a reference mirror 10b mirror 10c reference mirror 11 fiber coupler 11a fiber coupler 11b fiber coupler 12 detection unit 12a High-speed photodetector 12b Differential photodetector 12c Detector 13 Analog to digital converter 14 14a Interference fringe 15 light 15a reference light 15b measurement light 15c reference light reflected light 15d measurement light reflected light 15e reference light pulse 15f measurement light pulse 15g transmission signal 16 linear motion stage 16a linear motion stage 17 reflective optical element 18 linear scale 18a linear Scale 19 Scale head 19a Scale head 20 Constant temperature pressure tank 20a Constant temperature pressure tank 21 Optical fiber length measurement method 21a Optical fiber expansion / contraction measurement / correction method 22 Light source irradiation 23 Reference optical path length fixing 24 Pulse detection 25 Time interval measurement 26 Fiber length calculation 27 Reference Optical path length scan 28 Interference signal detection 29 Interference signal peak position change confirmation 30 Fiber length change conversion 31 Fiber length change adjustment 32 Fiber length correction mechanism stage movement 33 Interference signal peak position confirmation

JP 2011-017615 A

Claims (2)

By dividing the light from the light source into reference light and measurement light and interfering the reference light and measurement light with each other, and by reflecting the reference light divided by the interferometer part with a reference mirror that changes the optical path length A reference light scanner unit that returns to the interferometer unit, and the measurement light that is connected to the interferometer unit with an optical fiber and is divided by the interferometer unit is reflected by a mirror via a fiber length correction mechanism that changes the optical path length. The measuring unit returning to the interferometer unit, and the computer detects the change amount of the interference signal while detecting the interference signal with the differential photodetector with respect to the reference light and the measurement light interfered with the interferometer unit. An optical fiber length expansion / contraction measurement / correction device comprising a detection unit that corrects optical fiber expansion / contraction by operating the fiber length correction mechanism in terms of Dividing the light from the light source into measurement light and reference light by an interferometer unit, together with the return a reference light split by the interferometer unit to the interferometer unit by reflecting the reference mirror for changing the optical path length, wherein The measurement light divided by the interferometer unit is reflected by a mirror through an optical fiber and through a fiber length correction mechanism that changes the optical path length, and then returned to the interferometer unit, and the reference light interfered by the interferometer unit While detecting the interference signal with the differential optical detector for the measurement light, the computer converts the change amount of the interference signal into the change amount of the fiber length, and corrects the optical fiber expansion and contraction by operating the fiber length correction mechanism. Optical fiber length expansion / contraction measurement and correction method.

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