JP2021032734A - Measurement device - Google Patents

Abstract

To improve accuracy of a measurement device, eliminating impacts of wavelength dispersal.SOLUTION: A PM optical circulator 7 is configured to transmit wavelength sweep light incident from a second PM fiber 5 to a fourth PM fiber 8, and the wavelength sweep light entering into the fourth PM fiber 8 is configured to enter into a sixth PM fiber 11 via a polarization holding WDM coupler 9. One part of the wavelength sweep light entering into the sixth PM fiber 11 is configured to reflect in an opposite direction at an end surface of the sixth PM fiber 11 as reference light, and some of it passes through a lens 13 from the sixth PM fiber 11 to be emitted to a measurement object 100 as measurement light. Reflection light of the measurement light reflected upon the measurement object is configured to enter into the lens 13 and sixth PM fiber 11, and the reflection light entering into the sixth PM fiber 11 is configured to be transmitted to a seventh PM fiber 14 via the polarization maintaining WDM coupler 9 and PM optical circulator 7 with the reference light, and interference light of the reflection light with the reference light is detected by a first light receiver 15.SELECTED DRAWING: Figure 1

Description

The present invention relates to a measuring device that performs measurement using an optical frequency domain reflection measurement method (OFDR).

As a measuring device that performs measurement using the optical frequency domain reflection measuring method, a measuring device having the basic configuration shown in FIG. 6 is known (Patent Document 1).
In this measuring device, the wavelength sweep light source 641 sweeps the wavelength of the output light so that the frequency of the light changes linearly with time. A part of the light from the wavelength sweep light source 641 is branched by the optical coupler 642 and incident on the measurement interferometer 644. The light incident on the measurement interferometer 644 is branched by the optical coupler 643, and one of the branched lights is incident on the delay fiber 645 as reference light, and the other is incident on the measurement object 100 as measurement light via the lens 646. Incident.

The measurement light reflected by the measurement object 100 is incident on the measurement interferometer 644 again, and the measurement light reflected by the optical coupler 647 incident on the measurement object 100 and the reference light propagating through the delay fiber 645. Interferometric light is generated.

The interferometric light from the measuring interferometer 644 is heterodyne-detected by the receiver 648a and sampled by the A / D converter 649a.
When the change in the optical frequency in the wavelength sweep light source 641 is linear, the frequency of the beat signal obtained by the heterodyne detection is the light incident on the measurement object 100 and reflected, and the delayed light propagating on the delay fiber 645. It is proportional to the optical path difference. Therefore, the distance from the frequency of the beat signal to the measurement object 100 can be measured.

However, in reality, the wavelength sweep of the light output from the wavelength sweep light source 641 is non-linear, and modulation is superimposed. For this reason, the peak value of the spectrum of the heterodyne signal output from the measurement interferometer 644 is blurred and sideband waves are generated, which hinders high-precision measurement.

Therefore, a reference interferometer 651 is provided in addition to the measurement interferometer 644, and the light from the wavelength sweep light source 641 is branched by the optical coupler 642 and input to not only the measurement interferometer 644 but also the reference interferometer 651. The interferometric light generated by the reference interferometer 651 is heterodyne-detected by the receiver 648b and sampled by the A / D converter 649b.

The influence of the non-linearity and modulation of the wavelength sweep by the wavelength sweep light source 641 appears not only in the measurement interferometer 644 but also in the reference interferometer 651.
Therefore, the average length of the two paths from the wavelength sweep light source 641 to the receiver 648a via the measurement interferometer 644 and the two paths from the wavelength sweep light source 641 to the receiver 648b via the reference interferometer 651. The length is set so as to be approximately equal to the average length of the path, and in the controller 650 in the subsequent stage of the A / D converters 649a and 649b, measurement interference occurs at the timing when the signal strength from the reference interferometer 651 becomes 0. By resampling a total of 644 interferometric beat signals, it is possible to obtain a beat signal from which the non-linearity of wavelength sweep by the wavelength sweep light source 641 and the influence of modulation are removed.

Japanese Unexamined Patent Publication No. 2016-148539 Japanese Unexamined Patent Publication No. 2012-154790

In the measuring device shown in FIG. 6, the optical fiber length in the path from the wavelength sweep light source 641 to the receiver 648a through the delay fiber 645 and the receiver 648a from the wavelength sweep light source 641 via the reflection of the measurement object 100 If the length of the optical fiber in the path leading to The peak value of the spectrum varies, and the measurement accuracy deteriorates.

Further, since it is necessary to use a relatively expensive wavelength sweep light source 641 for measuring the distance of a single measurement point, the cost performance is not necessarily high as a measuring device.
Further, when the wavelength sweep of the wavelength sweep light source 641 is performed in the wavelength range of invisible light, the irradiation position (measurement point) of the measurement light on the measurement object 100 cannot be visually recognized, and the ease and safety of the measurement work are not sufficient. There was also the problem.

Therefore, an object of the present invention is to improve the measurement accuracy of a measuring device that performs measurement by the optical frequency domain reflection measuring method. At the same time, the present invention is a measuring device that performs measurement by the optical frequency domain reflection measuring method. The challenge is to improve the cost performance and measurement workability of the product.

In order to achieve the above object, the present invention includes a measuring device that performs measurement using wavelength sweeping light, which is wavelength sweeping light, a wavelength sweeping light source that emits the wavelength sweeping light, and a measurement interferometer block. It is a thing. The measurement interferometer block includes a first optical path configured by using an optical fiber, a second optical path configured by using an optical fiber, a third optical path configured by using an optical fiber, and the first optical path. It has an optical circulator connected to the first optical path, the second optical path, and the third optical path, a receiver, and a measuring unit. The optical circulator transmits the light transmitted from the first optical path to the optical circulator to the second optical path, and transmits the light transmitted from the second optical path to the optical circulator to the third optical path. Then, the first optical path transmits the wavelength sweep light emitted by the wavelength sweep light source to the optical circulator. The terminal optical fiber, which is an optical fiber constituting the end opposite to the end connected to the optical circulator of the second optical path, is a part of the wavelength sweep light transmitted from the optical circulator to the second optical path. It is emitted from the end face toward the object to be measured as measurement light into the space, and a part of the light is reflected as reference light by the end face of the end optical fiber. Light reflected by an object is incident. The second optical path transmits the reference light and the reflected light to the optical circulator, the receiver converts the light transmitted in the third optical path into a detection signal, and the measuring unit uses the measuring unit to convert the light transmitted through the third optical path into a detection signal. A beat signal due to interference between the reflected light and the reference light is extracted from the detection signal detected by the receiver, and the frequency of the extracted beat signal is calculated.

For reflection of the end face of the end optical fiber, for example, the end face of the ferrule attached to the end of the end optical fiber is flattened at right angles to the axis of the end optical fiber, or the end face of the ferrule is flattened by the end optical fiber. This can be achieved by polishing to a spherical surface that has a shaft as a normal.
According to such a measuring device, the wavelength sweep light that becomes the reflected light and the wavelength sweep light that becomes the reference light have the same path portion by the optical fiber that follows from the wavelength sweep light source to the receiver. Deterioration of measurement accuracy due to wavelength dispersion can be suppressed.

Here, in such a measuring device, an aiming light source that emits visible light is provided, and an aiming light optical fiber in which the visible light emitted by the aiming light source is incident on the measurement interferometer block, and aiming light. An optical coupler for aiming light may be provided in which the visible light transmitted by the optical fiber is superimposed in the second optical path so that the visible light is directed toward the end face of the terminal optical fiber.

By doing so, the irradiation position of the measurement light can be visually recognized from the visible light irradiated to the irradiation position of the measurement light, so that the measurement workability is improved.
Further, such a measuring device may be provided with a first optical coupler and a reference interferometer block. The reference interferometer block includes a first optical fiber, a second optical fiber, a third optical fiber having a length different from that of the second optical fiber, a fourth optical fiber, and a first optical fiber. A second optical coupler that branches the fiber into the second optical fiber and the third optical fiber, and a second optical fiber that couples the second optical fiber and the third optical fiber to the fourth optical fiber. It includes the optical coupler of No. 3 and an optical detector that converts the light transmitted by the fourth optical fiber into a reference signal. Further, the first optical coupler uses the wavelength sweep light emitted by the wavelength sweep light source as the wavelength sweep light directed to the first optical path of the measurement interferometer block and the first optical fiber of the reference interferometer block. Branches to the wavelength sweep light toward. Then, the measuring unit of the measurement interferometer block extracts a beat signal from the reference signal due to interference between the wavelength sweep light passing through the second optical fiber and the wavelength sweep light passing through the third optical fiber. Then, in synchronization with the extracted beat signal, the beat signal due to the interference between the reflected light and the reference light extracted from the detection signal detected by the receiver is sampled to generate sampling data, and the sampling data is analyzed. Then, the frequency is calculated.

Further, n (where n is an integer of 2 or more) of the measurement interferometer block and the wavelength sweep light are branched into the above measuring devices, and each of the branched wavelength sweep lights is supplied to each of the measurement interferometers. A branched optical system incident on the first optical path of the block may be provided.

Further, n (where n is an integer of 2 or more) of the measurement interferometer block and the wavelength sweep light are branched into the measuring device provided with the aiming light source, and each of the branched wavelength sweep lights is transferred to the measuring device. The first branch optical system incident on the first optical path of each measurement interferometer block and the visible light emitted by the aiming light source are branched, and each branched visible light is aimed at each measurement interferometer block. A second branch optical system incident on the optical fiber may be provided.

Further, in the measuring device provided with the reference interferometer block, n (where n is an integer of 2 or more) of the measuring interferometer blocks and the first optical path branched by the first optical coupler. A first-branch optical system may be provided in which the heading wavelength sweep light is branched and each branched wavelength sweep light is incident on the first optical path of each measurement interferometer block. The first optical coupler is a tap coupler, and the branch ratio of the tap coupler is such that the wavelength sweep light directed to the first optical path is larger than the wavelength sweep light directed to the first optical fiber. To do.

In this way, it is possible to perform multi-channel measurement for measuring multiple points by using a single wavelength sweep light source, and the cost performance of the measuring device is improved.
In addition, the present invention also includes, as a measuring device that performs measurement using wavelength-swept light, which is wavelength-swept light, a wavelength-swept light source that emits the wavelength-swept light, and n (where n is 2 or more). The measurement interferometer block (an integer of) and the branch optical system that branches the wavelength sweep light emitted by the wavelength sweep light source and injects each of the branched wavelength sweep lights into each measurement interferometer block. Is. Each measurement interferometer block irradiates the measurement object with wavelength sweep light incident from the branched optical system, and the wavelength sweep light reflected by the measurement object and the path followed by the reflected wavelength sweep light from the wavelength sweep light source. The frequency of the beat signal due to the interference is calculated by interfering with the wavelength sweep light that follows the paths of different path lengths.

According to such a measuring device, it is possible to perform multi-channel measurement for measuring multiple points by using a single wavelength sweep light source, and the cost performance of the measuring device is improved.

As described above, according to the present invention, it is possible to improve the measurement accuracy of the measuring device that performs the measurement by the optical frequency domain reflection measuring method.
In addition, according to the present invention, it is possible to improve the cost performance and measurement workability of the measuring device that performs the measurement by the optical frequency domain reflection measuring method.

It is a figure which shows the structure of the OFDR measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the end part of the ferrule which concerns on embodiment of this invention. It is a figure which shows the wavelength sweep of the wavelength sweep light source which concerns on embodiment of this invention. It is a figure which shows the other structural example of the OFDR measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the other structural example of the OFDR measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the conventional measuring apparatus.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows the configuration of the OFDR measuring device according to the present embodiment.
As shown in the figure, the OFDR measuring device includes a wavelength sweeping light source 1 and an aiming light source 2. The wavelength sweep light source 1 is, for example, a light source device that performs wavelength sweep with a center wavelength of 1550 nm, and the light output from the wavelength sweep light source 1 is invisible light. The aiming light source 2 is, for example, a light source device that outputs visible light having a wavelength of 635 nm.

Hereinafter, for convenience, the light emitted from the wavelength sweep light source 1 will be referred to as wavelength sweep light, and the light emitted from the aiming light source 2 will be referred to as aiming light.
The wavelength sweep light source 1 emits the wavelength sweep light to the first PM fiber 3, and the wavelength sweep light passing through the first PM fiber 3 is the PMTC 4 (polarization holding tap coupler 4) to the second PM fiber 5 and the third PM fiber 6. Branch. In addition, PM (Polarization Maintaining) represents polarization retention.

The wavelength sweep light incident on the second PM fiber 5 is sent to the PM optical circulator 7, the PM optical circulator 7 sends the wavelength sweep light incident on the second PM fiber 5 to the fourth PM fiber 8, and the wavelength incident on the fourth PM fiber 8. The sweep light is sent to the polarization-holding WDM coupler 9 (polarization-holding wavelength division multiplexing coupler 9).

On the other hand, the aiming light emitted from the aiming light source 2 passes through the fifth PM fiber 10 and enters the polarization-holding WDM coupler 9.
The polarization-holding WDM coupler 9 is wavelength-multiplexed between the wavelength sweep light incident from the 4th PM fiber 8 and the aiming light incident from the 5th PM fiber 10 and incident on the 6th PM fiber 11.
As shown in FIG. 2a, a ferrule 12 is attached to the tip of the sixth PM fiber 11, and the tip of the ferrule 12 is flat so that the end face is a plane perpendicular to the axis of the sixth PM fiber 11. ) It has been polished. A part of the light arriving at the end face of the 6th PM fiber 11 through the 6th PM fiber 11 is reflected by Fresnel reflection and travels in the 6th PM fiber 11 in the opposite direction. Here, in general, the reflection at the tip of the sixth PM fiber 11 when the surface is polished is a little over 3%.

Here, in order to increase the reflectance at the end face of the 6th PM fiber 11, as shown in FIG. 2b, a semitransparent mirror film is formed on the end face of the 6th PM fiber 11 by vapor deposition of a metal or dielectric multilayer film or the like. 121 may be formed.
Further, as shown in FIG. 2c, the tip end portion of the ferrule 12 may be polished so that the end face becomes a spherical surface having the axis of the sixth PM fiber 11 as a normal line by PC polishing or the like. Even in this way, a part of the light arriving at the end face of the 6th PM fiber 11 through the 6th PM fiber 11 is reflected and travels in the 6th PM fiber 11 in the opposite direction. Further, a semi-transparent mirror film may be formed on the spherically polished end face of the 6th PM fiber 11.

Returning to FIG. 1, a part of the wavelength sweep light incident on the 6th PM fiber 11 is reflected as reference light in the opposite direction at the end face of the 6th PM fiber 11 to which the ferrule 12 is mounted, and a part is reflected as the reference light in the 6th PM. It is emitted as measurement light from the end face of the fiber 11 into the space. Further, the aiming light incident on the 6th PM fiber 11 is also partially reflected in the opposite direction at the end face of the 6th PM fiber 11 to which the ferrule 12 is mounted, and a part is reflected in the space from the end face of the 6th PM fiber 11. It is emitted.

The wavelength sweep light and the aiming light emitted from the tip of the sixth PM fiber 11 into the space are converged on the measurement object 100 by the lens 13.
Here, the light converged on the measurement object 100 is coaxial with the wavelength sweep light, which is invisible light emitted from the wavelength sweep light source 1, and the aiming light, which is visible light emitted from the aiming light source 2. It becomes the combined light.

Therefore, the irradiation position of the measurement light can be visually recognized from the spot of light formed on the measurement object 100 by the aiming light which is the visible light.
The measurement object 100 reflects the wavelength sweep light and the aiming light converged by the lens 13, and the reflected light of the wavelength sweep light reflected by the measurement object 100 enters the sixth PM fiber 11 through the lens 13. It is sent to the PM optical circulator 7 through the polarization holding WDM coupler 9 and the fourth PM fiber 8.

Further, the reference light reflected by the end face of the 6th PM fiber 11 is also sent to the PM optical circulator 7 through the polarization holding WDM coupler 9 and the 4th PM fiber 8.
The PM optical circulator 7 sends the reflected light and the reference light incident from the 4th PM fiber 8 to the 7th PM fiber 14, and the reflected light and the reference light incident on the 7th PM fiber 14 are the first photoelectric conversion elements such as a photodiode. It is detected by the light receiver 15.

Here, interference occurs between the reflected light detected by the first light receiver 15 and the reference light, and the frequency of the beat signal of this interference is determined by the reference light from the wavelength sweep light source 1 to the first light receiver 15. The frequency becomes a frequency corresponding to the difference in the distance between the traced optical path and the optical path traced by the measured light from the wavelength sweep light source 1 to the first light receiver 15.

Since this difference in distance is twice the distance from the end face of the 6th PM fiber 11 to the object to be measured 100, the beat of the interference light with the measurement light included in the reflected light detected by the first receiver 15. By detecting the frequency of the signal, the distance to the object to be measured 100 can be measured.

Further, the PM fiber in the path followed by the reference light from the wavelength sweep light source 1 to the first receiver 15 and the PM fiber in the path followed by the measurement light from the wavelength sweep light source 1 to the first receiver 15. Since they are equal, the measurement light and the reference light are similarly affected by the wavelength dispersion of the optical fiber. Therefore, deterioration of measurement accuracy due to the difference in the influence of the wavelength dispersion of the optical fiber between the measurement light and the reference light is suppressed.

Further, since the optical system is configured to maintain the polarization of the wavelength sweep light emitted by the wavelength sweep light source 1, the two photoelectric conversion elements detect the light of opposite phase and amplify the difference. Even if the differential amplification detection is not performed, the detection with a good SN ratio can be performed by using the first light receiver 15 composed of one photoelectric conversion element.

Next, the wavelength sweep light branched to the third PM fiber 6 by the PMTC 4 is branched to the eighth PM fiber 17 and the ninth PM fiber 18 by the first PM coupler 16.
Here, the lengths of the 8th PM fiber 17 and the 9th PM fiber 18 are different. Further, the lengths of the 8th PM fiber 17 and the 9th PM fiber 18 pass through the wavelength sweep light source 1 to the second PM fiber 5 so as to eliminate the influence of the modulation superimposed on the waveform sweep of the wavelength sweep light source 1. The average length of the two paths of the wavelength sweep light to the first receiver 15 and the average length of the two paths of the wavelength sweep light from the wavelength sweep light source 1 to the second receiver 21 via the third PM fiber 6. Set so that and are approximately equal.

The wavelength sweep light incident on the 8th PM fiber 17 and the 9th PM fiber 18 is coupled to the 10th PM fiber 20 by the 2nd PM coupler 19, and the wavelength sweep light incident on the 10th PM fiber 20 and passed through the 8th PM fiber 17 and the first The wavelength sweep light that has passed through the 9PM fiber 18 is detected by the second light receiver 21, which is a photoelectric conversion element such as a photodiode.

Here, interference occurs between the two wavelength sweep lights detected by the second receiver 21, and the frequency of the beat signal of this interference is the difference in length between the 8th PM fiber 17 and the 9th PM fiber 18. It becomes the corresponding frequency.

The detection signal of the first light receiver 15 and the detection signal of the second light receiver 21 are output to the measuring device 30.
The first bandpass filter 31 (first BPF 31) of the measuring device 30 extracts a beat signal due to interference between the reference light and the measurement light from the detection signal of the first receiver 15 as a measurement beat signal, and extracts the beat signal as the measurement beat signal, and the second bandpass filter 32 (1st BPF 31). The second BPF 32) extracts a beat signal due to interference between the two wavelength sweep lights detected by the second receiver 21 from the detection signal of the second receiver 21 as a reference beat signal. If the beat signal due to the interference between the reference light and the measurement light or the beat signal due to the interference between the two wavelength sweep lights detected by the second receiver 21 is low frequency and can be extracted by the low-pass filter, the first A low-pass filter may be provided instead of the band-pass filter 31 and the second band-pass filter 32 to extract the beat signal.

The clock extraction unit 33 generates a sampling clock at a timing of a predetermined phase such as a zero cross point of the reference beat signal extracted by the second bandpass filter 32, and the A / D converter 34 is generated by the clock extraction unit 33. Using the sampling clock, the measurement beat signal extracted by the first bandpass filter 31 is sampled and stored in the memory 35 as sampling data.

The analysis unit 36 performs FFT or the like on the sampling data of the measurement beat signal stored in the memory 35 to calculate the frequency spectrum, and obtains and obtains the frequency of the measurement beat signal from the peak of the calculated frequency spectrum. The distance from the frequency to the object to be measured 100 is calculated.

In this way, by using the sampling data of the measurement beat signal sampled using the sampling clock synchronized with the reference beat signal extracted by the second bandpass filter 32 to calculate the frequency of the beat signal, the wavelength sweep light source 1 is used. Even if the frequency sweep (frequency change) is performed non-linearly as shown in FIG. 3a, the influence of the non-linearity is canceled by the reference beat signal appearing in the same manner as the measurement beat signal, and the measurement object 100 The frequency can be calculated according to the true distance to.

The difference in length between the 8th PM fiber 17 and the 9th PM fiber 18 is that the frequency of the sampling clock generated from the frequency of the reference beat signal is at least twice the maximum frequency of the measurement beat signal to be detected. To make it possible to reproduce the measurement beat signal below the maximum frequency from the sample data.

The embodiment of the present invention has been described above.
When the wavelength sweep light source 1 that performs the wavelength sweep linearly as shown in FIG. 3b is used, or the wavelength at which the wavelength sweep is performed linearly in the wavelength sweep light source 1 that performs the wavelength sweep linearly in a part of the wavelength range. When only the light in the range is used for the measurement, as shown in FIG. 4, the OFDR measuring device may be configured by excluding the portion related to the generation of the reference beat signal in the configuration shown in FIG. However, in this case, instead of the second bandpass filter 32 and the clock extraction unit 33, the measuring device 30 is provided with a clock generation unit 37 that generates a fixed frequency sampling clock and outputs it to the A / D converter 34. Provide.

Further, the OFDR measuring device shown in the above embodiment may be configured to perform multi-channel measurement for measuring a plurality of measurement points.
In this case, as shown in FIG. 5, the OFDR measuring device includes the wavelength sweeping light source 1 and the aiming light source 2 of the OFDR measuring device of FIG. 1, the first PM fiber 3, the PMTC 4, the third PM fiber 6, and the first PM coupler 16. The 8th PM fiber 17, the 9th PM fiber 18, the 2nd PM coupler 19, the 10th PM fiber 20, and the 2nd light source 21 are provided.

Further, the OFDR measuring device includes the second PM fiber 5, the PM optical circulator 7, the fourth PM fiber 8, the polarization holding WDM coupler 9, the fifth PM fiber 10, the sixth PM fiber 11, the ferrule 12, and the lens of the OFDR measuring device of FIG. Four sets of channel sets, which are a set of 13, the 7th PM fiber 14, the first light receiver 15, and the measuring device 30, are provided.

Here, the four blocks indicated by reference numerals A in FIG. 5 are blocks having the same internal configuration as that shown for the bottom block A.
Further, the 11 PM fiber 51 is provided, and the wavelength sweep light emitted from the wavelength sweep light source 1 to the first PM fiber 3 by the PMTC 4 is branched into the third PM fiber 6 and the 11 PM fiber 51. The branching ratio of PMTC4 is, for example, 9 for the branch to the 11th PM fiber 51 and 1 for the branch to the 3rd PM fiber 6.

Further, three PM couplers 52 for wavelength sweep light branching are provided, and the wavelength sweep light passing through the 11th PM fiber 51 is branched into four and incident on the second PM fiber 5 of each channel set.
Further, three PM couplers for aiming light 53 are provided, and the aiming light emitted from the aiming light source 2 is branched into four and incident on the fifth PM fiber 10 of each channel set.
Further, the detection signal of the second receiver 21 is input to the second bandpass filter 32 of the measuring device 30 of each channel set.
According to such an OFDR measuring device, a single wavelength sweep is performed by making each channel set measure the distance to the measuring point by making the irradiation position (measurement point) of the measurement light of each channel set different. Multi-channel measurement that measures a plurality of measurement points can be performed using the light source 1.

However, the clock extraction unit 33 of the measuring device 30 of each channel set may use one clock extraction unit 33 in common.
Further, although FIG. 5 shows a case where four measurement points are measured, the number of measurement points can be any number of two or more. In this case, the number of measurement points is n, the number of branches of the wavelength sweep light and the aiming light by the wavelength sweep light branching PM coupler 52 and the aiming light PM coupler 53 is n, and n channel sets are provided. , N measurement points are measured. In this case, if necessary, using PMTC or the like, the intensity of the wavelength sweep light emitted into the space from the tip of the 6th PM fiber 11 and the intensity of the aiming light are equal toward each measurement point. It is preferable to do

1 ... Wavelength sweep light source, 2 ... Aiming light source, 3 ... 1st PM fiber, 4 ... PMTC, 5 ... 2nd PM fiber, 6 ... 3rd PM fiber, 7 ... PM optical circulator, 8 ... 4th PM fiber, 9 ... Polarized light Retention WDM coupler, 10 ... 5th PM fiber, 11 ... 6th PM fiber, 12 ... Ferrule, 13 ... Lens, 14 ... 7th PM fiber, 15 ... 1st receiver, 16 ... 1st PM coupler, 17 ... 8th PM fiber, 18 ... 9th PM fiber, 19 ... 2nd PM coupler, 20 ... 10th PM fiber, 21 ... 2nd receiver, 30 ... Measuring device, 31 ... 1st band pass filter, 32 ... 2nd band pass filter, 33 ... Clock extraction unit , 34 ... A / D converter, 35 ... Memory, 36 ... Analysis unit, 37 ... Clock generation unit, 51 ... 11th PM fiber, 52 ... PM coupler for wavelength sweep light branching, 53 ... PM coupler for aiming light, 100 ... Object to be measured, 121 ... Mirror film.

Claims (8)

It is a measuring device that performs measurement using wavelength-swept light, which is wavelength-swept light.
A wavelength sweep light source that emits the wavelength sweep light and
Has a measuring interferometer block,
The measurement interferometer block
A first optical path constructed using an optical fiber and
A second optical path constructed using an optical fiber and
A third optical path constructed using an optical fiber and
An optical circulator connected to the first optical path, the second optical path, and the third optical path,
Receiver and
Has a measuring unit
The optical circulator transmits the light transmitted from the first optical path to the optical circulator to the second optical path, and transmits the light transmitted from the second optical path to the optical circulator to the third optical path. And
The first optical path transmits the wavelength sweep light emitted by the wavelength sweep light source to the optical circulator.
The terminal optical fiber, which is an optical fiber constituting the end opposite to the end connected to the optical circulator of the second optical path, is a part of the wavelength sweep light transmitted from the optical circulator to the second optical path. It is emitted from the end face toward the object to be measured as measurement light into the space, and a part of the light is reflected as reference light by the end face of the end optical fiber. Light reflected by an object is incident,
The second optical path transmits the reference light and the reflected light to the optical circulator.
The receiver converts the light transmitted in the third optical path into a detection signal and converts it into a detection signal.
The measuring unit is a measuring device characterized in that a beat signal due to interference between the reflected light and the reference light is extracted from the detection signal detected by the receiver and the frequency of the extracted beat signal is calculated. The measuring device according to claim 1.
A ferrule is attached to the end of the end optical fiber, and the end face of the ferrule is polished to a plane perpendicular to the axis of the end optical fiber or a spherical surface having the axis of the end optical fiber as a normal. A measuring device characterized by being present. The measuring device according to claim 1 or 2.
It has an aiming light source that emits visible light,
In the measurement interferometer block, the visible light emitted from the aiming light source is incident on the aiming optical fiber, and the visible light transmitted by the aiming optical fiber is transmitted by the visible light in the second optical path. A measuring device comprising an optical coupler for aiming light which is superimposed so as to face the end surface of the terminal optical fiber. The measuring device according to claim 1 or 2.
With the first optical coupler,
Has a reference interferometer block and
The reference interferometer block includes a first optical fiber, a second optical fiber, a third optical fiber having a length different from that of the second optical fiber, a fourth optical fiber, and a first optical fiber. A second optical coupler that branches the fiber into the second optical fiber and the third optical fiber, and a second optical fiber that couples the second optical fiber and the third optical fiber to the fourth optical fiber. It has 3 optical couplers and an optical detector that converts the light transmitted by the fourth optical fiber into a reference signal.
The first optical coupler directs the wavelength sweep light emitted by the wavelength sweep light source toward the wavelength sweep light directed to the first optical path of the measurement interferometer block and the wavelength sweep light directed to the first optical fiber of the reference interferometer block. Branches to wavelength sweep light
The measuring unit of the measurement interferometer block extracts a beat signal due to interference between the wavelength sweep light passing through the second optical fiber and the wavelength sweep light passing through the third optical fiber from the reference signal. Synchronized with the extracted beat signal, the beat signal due to the interference between the reflected light and the reference light extracted from the detection signal detected by the receiver is sampled to generate sampling data, and the sampling data is analyzed. A measuring device characterized by calculating the frequency. The measuring device according to claim 1 or 2.
With n (where n is an integer of 2 or more) the measurement interferometer blocks,
A measuring device characterized in that the wavelength sweep light is branched, and each of the branched wavelength sweep lights has a branched optical system that is incident on the first optical path of each measurement interferometer block. The measuring device according to claim 3.
With n (where n is an integer of 2 or more) the measurement interferometer blocks,
A first-branch optical system that branches the wavelength sweep light and incidents each of the branched wavelength sweep lights into the first optical path of each measurement interferometer block.
A measurement characterized in that the visible light emitted by the aiming light source is branched, and each branched visible light has a second branch optical system incident on the aiming optical fiber of each of the measurement interferometer blocks. apparatus. The measuring device according to claim 4.
With n (where n is an integer of 2 or more) the measurement interferometer blocks,
The first branch in which the wavelength sweep light directed to the first optical path branched by the first optical coupler is branched, and each branched wavelength sweep light is incident on the first optical path of each measurement interferometer block. Has an optical system
The first optical coupler is a tap coupler, and the branch ratio of the tap coupler is such that the wavelength sweep light directed to the first optical path is larger than the wavelength sweep light directed to the first optical fiber. A measuring device characterized by being present. It is a measuring device that performs measurement using wavelength-swept light, which is wavelength-swept light.
A wavelength sweep light source that emits the wavelength sweep light and
N measurement interferometer blocks (where n is an integer of 2 or more) and
It has a branched optical system that branches the wavelength sweep light emitted by the wavelength sweep light source and injects each of the branched wavelength sweep lights into each of the measurement interferometer blocks.
Each measurement interferometer block irradiates the measurement object with wavelength sweep light incident from the branched optical system, and the wavelength sweep light reflected by the measurement object and the path followed by the reflected wavelength sweep light from the wavelength sweep light source. A measuring device characterized in that it interferes with a wavelength sweeping light that follows a path having a different path length from the above, and calculates the frequency of a beat signal due to the interference.