JP7006964B2 - Optical fiber type measuring device and optical fiber type measuring method - Google Patents

Description

The present invention relates to an optical fiber type measuring device and an optical fiber type measuring method.

Conventionally, an optical fiber type measuring device capable of measuring a refractive index and a temperature using an optical fiber is known (see, for example, Patent Document 1).

As shown in FIG. 16, this optical fiber type measuring device includes an incident optical fiber 100 having one end connected to a light source (not shown) and a first light guide connected to the other end of the incident optical fiber 100. The body 200, the intermediate optical fiber 300 having one end connected to the first light guide 200, the second light guide 400 connected to the other end of the intermediate optical fiber 300, and the second light guide 400. The structure is provided with an emission optical fiber 500 in which one end is connected and the other end is connected to a detector (not shown).

The incident optical fiber 100, the intermediate optical fiber 300, and the emitted optical fiber 500 each have a core having a predetermined thickness, and the first light guide body 200 and the second light guide body 400 are the same as these cores. Because the diameter of the material is larger than that of the core, the light incident on the first light guide body 200 from the incident optical fiber 100 and the light incident on the second light guide body 400 from the intermediate optical fiber 300. It causes light to diffract.

The diffracted light generated by the first light guide body 200 is totally reflected on the peripheral surface of the first light guide body 200, and a goose henshen shift occurs at the time of this total reflection, so that the periphery of the first light guide body 200 is generated. The phase change is to occur according to the refractive index of. Since the diffracted light detected by the detector changes due to this phase change, it is possible to measure the change in the refractive index.

Similarly, the diffracted light generated by the second light guide body 400 is also totally reflected on the peripheral surface of the second light guide body 400, and a goose henschen shift occurs during this total reflection, so that the second light guide body is a second light guide body. A phase change occurs according to the refractive index around the 400, but if a silicone resin coating 410 whose refractive index changes depending on the temperature is provided on the peripheral surface of the second light guide 400, the change in temperature can be measured. It has become.

JP-A-2015-203692

However, in the conventional optical fiber type measuring device, in order to obtain the maximum possible interference strength so that the change can be easily detected, it is necessary to cause a plurality of total reflections in the first light guide body and the second light guide body. Therefore, the lengths of the first light guide and the second light guide tend to be long.

Therefore, normally, the first light guide and the second light guide are often used as 10 mm or more, and cannot be used for measuring a region smaller than 10 mm, for example, a droplet.

The present inventors have come up with the present invention while conducting research and development to shorten the first light guide body and the second light guide body so that they can be used for measurement in a smaller area.

In the optical fiber type measuring device of the present invention, a light source, an incident optical fiber having one end connected to the light source, a light guide body connected to the other end of the incident optical fiber, and one end to the light guide body. In an optical fiber type measuring device having an emission optical fiber connected to the other end and having the light guide as a sensor, the incident optical fiber and the exit optical fiber are single-mode fibers. The light guide body is an optical fiber having a core having a diameter smaller than that of the core of the incident optical fiber and the core of the emitting optical fiber and having a length of 1 mm or less. The light incident on the light guide body spreads in the clad centering on the small diameter core and propagates through the light guide body, and at the same time, the outer peripheral portion of the light guide body is perpendicular to the optical axis as the boundary region. Of the light in the phase state that satisfies the standing condition in the plane, the light having the waveform with the maximum light intensity at the center of the light guide and the light with the minimum light intensity at the center of the light guide. It is characterized in that light having a wavelength having a waveform is formed, and the light at the center of the light guide is output from the emission optical fiber .

Further, the optical fiber type measuring device of the present invention is also characterized in that the light incident on the light guide body from the incident optical fiber is used as the light guide propagating light spread in the cladding of the light guide body. Furthermore, the light guide propagating light is light in a phase state that satisfies the standing condition with the outer peripheral edge of the light guide body as a boundary, and has a waveform in which the light intensity becomes maximum (peak) at the center position of the light guide body. It is also characterized by the presence of light having a wavelength of the above and light having a waveform having a minimum light intensity (dip) at the center position of the light guide.

Further, in the optical fiber type measuring device of the present invention, a reflecting surface is provided on the end surface of the light guide connected to the incident optical fiber, and the light incident on the light guide from the incident optical fiber is reflected by the reflecting surface to be incident. A part of the optical fiber is used as an outgoing optical fiber, and the light reflected by the reflecting surface is guided to an optical directional coupler provided in the middle of the incident optical fiber, and the optical directional coupler and the detector are connected to the optical fiber. It is connected by.

Further, in the optical fiber type measuring device of the present invention, a light source, an incident optical fiber having one end connected to the light source, a first light guide body connected to the other end of the incident optical fiber, and the first light guide body thereof. An intermediate optical fiber having one end connected to the light guide, a second light guide connected to the other end of the intermediate optical fiber, and one end connected to the second light guide to connect the other end to the detector. In an optical fiber type measuring device having a first light guide body and a second light guide body as sensors, the second light guide body is a core of an intermediate optical fiber and an optical fiber for emission. The optical fiber has a core having a diameter smaller than that of the core, and the first light guide body is made of the same material as the core of the incident optical fiber.

Further, in the first light guide body, the diffracted light of the light incident on the first light guide body from the incident optical fiber is totally reflected only once on the peripheral surface of the first light guide body and is incident on the intermediate optical fiber. It is also characterized by the length of the light.

A light source, an incident optical fiber having one end connected to this light source, a light guide connected to the other end of the incident optical fiber, and one end connected to this light guide and the other end connected to a detector. Light guided from the light source through the incident optical fiber is incident on the light guide body using the light emitted from the light guide body, and the light emitted from the light guide body is used to form the light guide body. In an optical fiber type measuring method for measuring fluctuations in surrounding physical quantities, the incident optical fiber and the emitted optical fiber are single-mode fibers, and the light guide is used as the core of the incident optical fiber and the emission. By making the optical fiber having a core having a diameter smaller than that of the optical fiber core and having a length of 1 mm or less, the light incident on the light guide from the incident optical fiber is centered on the small diameter core. Of the light in a phase state that spreads in the cladding and propagates through the light guide and satisfies the standing condition in a plane perpendicular to the optical axis whose outer peripheral portion is the boundary region, the light guide. Light having a waveform wavelength that maximizes the light intensity at the center of the body and light having a waveform wavelength that minimizes the light intensity are formed at the center of the light guide, and the light at the center of the light guide forms light. It is characterized in that it is output from the emission optical fiber.

According to the present invention, the light guide body can be made shorter, and an optical fiber type measuring device that can be used for measurement in a small area can be obtained.

It is explanatory drawing of the optical fiber type measuring apparatus of 1st Embodiment. It is a graph of the spectrum of the optical fiber type measuring apparatus of 1st Embodiment. It is a graph of the spectrum of the optical fiber type measuring apparatus of 1st Embodiment. It is explanatory drawing of the optical fiber type measuring apparatus of 2nd Embodiment. It is explanatory drawing of the optical fiber type measuring apparatus of 2nd Embodiment. It is a graph of the spectrum of the optical fiber type measuring apparatus of 2nd Embodiment. It is a graph which shows the temperature-wavelength correlation obtained from the relationship between the wavelength and the temperature of the spectrum dip of FIG. It is a graph which shows the temperature-light intensity change correlation obtained from the relationship between the wavelength and the temperature of the spectrum dip of FIG. It is explanatory drawing of the optical fiber type measuring apparatus of 3rd Embodiment. It is explanatory drawing of the transformation example of the 1st light guide body. It is a graph of the spectrum of the 1st light guide body in the optical fiber type measuring apparatus of 3rd Embodiment. It is a graph of the spectrum of the 1st light guide body in the optical fiber type measuring apparatus of 3rd Embodiment. It is a graph of the spectrum of the optical fiber type measuring apparatus of 3rd Embodiment. It is an enlarged view of the main part of FIG. It is a graph of the spectrum of the optical fiber type measuring apparatus of 3rd Embodiment. It is explanatory drawing of the conventional optical fiber type measuring apparatus.

<First Embodiment>
As shown in FIG. 1, the optical fiber type measuring device of the present embodiment includes a light source (not shown), an incident optical fiber 10 having one end connected to the light source, and the other end of the incident optical fiber 10. It is an optical fiber type measuring device including a light guide body 40 connected to the light guide body 40 and an optical fiber 50 for emission, one end of which is connected to the light guide body 40 and the other end of which is connected to a detector (not shown). The light guide body 40 is a sensor body, and changes in the refractive index around the light guide body 40 can be detected. Further, when the surface of the light guide body is provided with a film whose refractive index changes depending on the temperature, it can be used as a temperature sensor. When the surface of the light guide is provided with a film whose refractive index changes depending on the humidity, it can be used as a humidity sensor. When the surface of the light guide is provided with a film whose refractive index changes depending on the gas concentration, it can be used as a gas sensor.

The detector measures the intensity of the light incident through the exit optical fiber 50. In particular, the intensity of the light is measured by irradiating the laser beam from the light source while appropriately changing the wavelength, and it is possible to detect the change in the refractive index from these data.

The incident optical fiber 10 and the emitted optical fiber 50 are single-mode fibers. In this embodiment, an optical fiber having a core diameter of about 8.2 μm and a clad diameter of 125 μm is used.

The light guide body 40 is an optical fiber having a core 10a of the incident optical fiber 10 and a core 40a having a diameter smaller than that of the core 50a of the emitting optical fiber 50. In this embodiment, an optical fiber having a core diameter of about 2 μm and a clad diameter of 125 μm is used.

When the core 40a of the light guide body 40 is made smaller than the core 10a of the optical fiber 10 for incident light in this way, the light incident on the light guide body 40 from the incident side optical fiber 10 has a sufficiently small diameter of the light guide body 40. It spreads in the clad 40b centering on the core 40a of the above, propagates through the light guide body 40, and is output from the optical fiber 50 on the exit side.

The light that has spread to the clad 40b by the light guide 40 has the outer peripheral portion of the fiber as the boundary region in the plane perpendicular to the optical axis, and is the central part of the light in the phase state that satisfies the standing condition in this plane. There are light having a wavelength with a waveform that maximizes the light intensity (peak) and light having a wavelength having a waveform that minimizes the light intensity (dip) at the center. Then, it was newly found that the light having this peak / dip is output from the emission side optical fiber 50. In this way, the light that has spread to the clad 40b of the light guide body 40 and has a peak / dip is referred to as "light guide body propagating light".

In the boundary region of the outer peripheral portion of the light guide body 40, since the optical electric field seeps out of the light guide body 40, the inside of the light guide body 40 is affected by the refractive index outside the light guide body 40. The phase of the propagating light changes. By detecting this phase change from the output light, the refractive index outside the light guide body 40 can be measured.

Since the phase change in the light propagating body of the light guide body is determined by the component perpendicular to the optical axis of the light guide body 40, it has a feature that the length dependence of the light guide body 40 hardly appears. In the case where the intensity of the light is increased or weakened by the interference at the end of the conventional optical fiber for emission, the phase change of the propagated light changes depending on the length of the sensor unit, so the wavelength of the spectrum dip that makes the spectrum smaller is the length of the sensor unit. Will depend on it. However, this structure is characterized in that the length dependence of the fiber of the sensor unit hardly appears due to the mechanism of generating the light guide propagating light, which is light having a peak / dip that does not depend on interference at the end of the optical fiber for emission. Will occur. However, it has been found that the use of this light guide body propagating light is affected by the optical axis and radial non-uniformity of the fibers constituting the light guide body 40 as the light guide body 40 becomes longer. , It is desirable that the light guide body 40 is as short as 2 mm or less. FIG. 2 shows the measured values of the spectrum when the length of the light guide body 40 is changed from 0.91 mm to 1.07 mm.

As shown in FIG. 2, depending on the length of the light guide body 40, the wavelength position where the spectrum becomes deeper and the spectrum dip becomes smaller changes. However, it can be seen that the change in the position where the spectral dip occurs is small. The reason why the wavelength position where the spectral dip is deepest changes depending on the length of the light guide 40 is unknown at this time. However, it is shown that the wavelength can be selected by adjusting the length of the light guide body 40.

FIG. 3 shows the spectral changes when the length of the light guide body 40 is 1.07 mm and the surroundings of the light guide body 40 are air, pure water, and ethanol. As shown in FIG. 3, it was confirmed that the spectral dip shifts to the long wavelength side as the refractive index increases in the order of air → pure water → ethanol, and it can be used as a refractive index sensor.

Further, when a film whose refractive index changes depending on temperature, humidity, pressure, gas concentration, etc. is formed on the outer peripheral surface of the light guide body 40, the change in the refractive index of this film can be detected, so that various sensors can be detected. Can be configured. That is, if the refractive index of the film changes with temperature, it can be used as a temperature sensor. If the refractive index of the film changes with humidity, it can be used as a humidity sensor. If the refractive index of the film changes with pressure, it can be used as a pressure sensor. If the refractive index of the film changes depending on the gas concentration, it can be used as a gas sensor.

<Second Embodiment>
In the first embodiment described above, the light incident on the light guide 40 from the incident optical fiber 10 is transmitted to the exit optical fiber 50, but as shown in FIG. 4, the end face of the light guide 40'is transmitted. It is also possible to provide a reflecting surface 41'to reflect the light incident on the light guide 40' from the incident optical fiber 10'.

That is, as shown in FIG. 5, an optical directional coupler 63 is provided in the middle portion of the incident optical fiber 10', one end is connected to the light source 61, and the optical directional coupler 63 is provided in the middle portion. A light guide 40'is connected to the other end of the intervening incident optical fiber 10', and a part of the incident optical fiber 10'is used as an exit optical fiber at the reflecting surface 41' of the light guide 40'. The reflected light is guided to the optical directional coupler 63 in the middle of the incident optical fiber 10', and the other end of the connecting optical fiber 50'in which one end is connected to the optical directional coupler 63 is detected by the detector 62. It is connected to the optical fiber type measuring device.

Here, the incident optical fiber 10'and the connecting optical fiber 50'are single-mode fibers. In this embodiment, an optical fiber having a core diameter of about 8.2 μm and a clad diameter of 125 μm is used.

The light guide body 40'forms a reflective surface 41'by depositing a metal film on the end surface facing the incident optical fiber 10'. In this embodiment, the reflective surface 41'is formed of a gold film.

Also in this embodiment, the core 40a'of the light guide body 40'is smaller than the core 10a' of the incident optical fiber 10'. That is, as in the case of the first embodiment, the light incident on the light guide body 40'from the incident optical fiber 10'is the clad of the light guide body 40' centering on the core 40a' of the light guide body 40'. It spreads widely in 40b', propagates in the light guide body 40', and is reflected by the reflecting surface 41'. In the present embodiment, the core diameter of the light guide body 40'is about 2 μm, the clad diameter of the light guide body 40' is 125 μm, and the length of the light guide body 40'is 0.96 mm.

Further, in the present embodiment, as shown in FIG. 4, a silicone resin film 42' whose refractive index changes depending on the temperature is provided around the light guide body 40'. The silicone resin coating 42'may also be provided on the reflective surface 41'.

In this way, the light guide body 40'is covered with a silicone resin coating 42' to enable temperature measurement, and the change in the spectral dip when the air temperature is changed from room temperature to around -50 ° C is shown in FIG. Shown in.

From FIG. 6, the temperature-wavelength correlation of FIG. 7 can be obtained from the relationship between the wavelength and the temperature of the spectral dip, and the temperature can be estimated from the wavelength of the spectral dip.

Alternatively, focusing on the wavelength 1588.88 nm in FIG. 6, the temperature-light intensity change correlation of FIG. 8 can be obtained from the change in light intensity at this wavelength, and the temperature can be estimated from the change in spectrum intensity.

In this embodiment, the film 42'is made of a silicone resin whose refractive index changes depending on the temperature. However, by using a film whose refractive index changes according to a predetermined physical quantity, a sensor capable of measuring a predetermined physical quantity can be used. can do. For example, when the film has a refractive index that changes with humidity, such as a silica gel film, it can be used as a humidity sensor. When the film has a refractive index that changes depending on the gas concentration, such as a so-called sensitive film, it can be used as a gas sensor.

<Third Embodiment>
As shown in FIG. 9, the optical fiber type measuring device of the present embodiment includes a light source (not shown), an incident optical fiber 10 "with one end connected to the light source, and an incident optical fiber 10". The first light guide 20 "connected to the other end, the intermediate optical fiber 30" connected to one end of the first light guide 20 ", and the second guide connected to the other end of the intermediate optical fiber 30". It is an optical fiber type measuring device equipped with an optical body 40 "and an emission optical fiber 50" having one end connected to the second light guide body 40 "and the other end connected to a detector (not shown). In the present embodiment, the first light guide body 20 "and the second light guide body 40" are sensor bodies.

The incident optical fiber 10 ", the intermediate optical fiber 30" and the outgoing optical fiber 50 "are single-mode fibers. In this embodiment, an optical fiber having a core diameter of about 8.2 μm and a clad diameter of 125 μm is used. There is.

The second light guide body 40 "has a smaller diameter than the core 30a" of the intermediate optical fiber 30 "on the incident side and the core 50a" of the optical fiber 50 "for emission, like the light guide body 40 of the first embodiment described above. It is an optical fiber having a core 40a ". In this embodiment, an optical fiber having a core diameter of about 2 μm and a clad diameter of 125 μm is used.

Since the second light guide body 40 "of this embodiment is the same as the light guide body 40 of the first embodiment described above, overlapping description will be omitted.

The first light guide body 20 "is made of the same material as the core 10a" of the incident optical fiber 10 ", and has a larger diameter than the core 10a" of the incident optical fiber 10 ", so that the incident optical fiber 10" is used. It is determined that the light incident on the first light guide body 20 "is diffracted.

Here, the first light guide body 20 "has a columnar shape having the same diameter as the incident optical fiber 10" and the intermediate optical fiber 30 ", but it does not necessarily have to have a columnar shape having the same diameter. As shown in a), the first light guide body may be expanded in diameter from the incident optical fiber 10 "to the intermediate optical fiber 30". Here, the intermediate optical fiber 30 "is the incident optical fiber. The diameter may be larger than 10 ", or as shown in FIG. 10 (b), the first light guide may have a diameter larger than that of the incident optical fiber 10" or the intermediate optical fiber 30 ", and conversely. As shown in FIG. 10 (c), the diameter may be smaller than that of the incident optical fiber 10 "or the intermediate optical fiber 30", or as shown in FIG. 10 (d), the first light guide body is incident. The diameter may be reduced from the optical fiber 10 "to the intermediate optical fiber 30". Further, the first light guide body does not have to have a circular cross section, but has an elliptical shape or a polygonal shape. May be good.

Similarly, the second light guide body 40 "may not have a cylindrical shape, but may have an appropriate diameter shape so that a spectral dip that is easy to measure can be easily obtained.

In the optical fiber type measuring device of the present embodiment, since the length of the second light guide body 40 "can be shortened, it is possible to measure a small area.

Further, in the first light guide 20 ", the diffracted light of the light incident on the first light guide 20" from the incident optical fiber 10 "is totally reflected only once on the peripheral surface of the first light guide 20". The length can be shortened by making the length incident on the intermediate optical fiber 30 ". That is, the optical fiber type measuring device of the present embodiment can measure a small area.

In particular, assuming that the core diameter of the incident optical fiber 10 "and the intermediate optical fiber 30" is about 8.2 μm, the clad diameter is 125 μm, and the diameter dimension of the first light guide 20 ”is 125 μm, the first light guide 20 It is a condition that the length of "is within 2 mm and is totally reflected only once on the peripheral surface of the first light guide body 20" and is incident on the intermediate optical fiber 30 ". When the length of the first light guide body 20 "is set to around 2 mm, the wavelength position where the spectral dip is deepest is measured. The results are shown in FIG. 11.

As shown in FIG. 11, it was confirmed that a steep spectral dip appeared when the length of the first light guide body 20 "was 1.83 mm, and a gradual change spectral dip appeared before and after that. Since the spectral dip did not appear when the length of the optical body 20 "was set to 1 mm or less, the length of the first light guide body 20" needs to be 1 mm or more, while the second one. As described in the first embodiment, the light guide body 40 "can have a spectral dip that can be used for measurement even at 1 mm or less (see FIG. 2). Therefore, when it is desired to make the light guide body smaller, the first The second light guide 40 "is more effective as a sensor body than the light guide 20".

FIG. 12 shows the spectral changes when the length of the first light guide body 20 "is 1.83 mm and the surroundings of the first light guide body 20" are air, pure water, and ethanol. .. As shown in FIG. 12, it was confirmed that the spectral dip shifts to the long wavelength side as the refractive index increases in the order of air → pure water → ethanol, and it can be used as a refractive index sensor.

In the case of an optical fiber type measuring device provided with the first light guide body 20 "and the second light guide body 40" as in the present embodiment, the spectrum dip caused by the first light guide body 20 "and the first 2 It is desirable that the spectral dip caused by the light guide 40 "is sufficiently separated. This can be easily adjusted by adjusting the shape of the first light guide body 20 "or the second light guide body 40".

As shown in FIG. 9, in the optical fiber type measuring device of the present embodiment, a coating film 42 "whose refractive index changes depending on the temperature is provided around the second light guide body 40". Specifically, the coating film 42 "can be produced by using a silicone resin. Instead of forming the coating film 42" whose refractive index changes depending on the temperature, for example, a silica gel film or a gas whose refractive index changes depending on the humidity is used. A sensitive film whose refractive index changes by adsorption may be used.

FIG. 13 shows a change in the spectrum when the temperature is changed from 30 to 80 ° C. in the air using an optical fiber type measuring device in which the second light guide body 40 "is provided with a silicone resin film 42". .. Here, as the incident optical fiber 10 ", the intermediate optical fiber 30", and the emitted optical fiber 50 ", a single mode fiber having a core diameter of about 8.2 μm and a clad diameter of 125 μm is used. The body 20 "uses a columnar optical fiber made of the same material as the core of the incident optical fiber 10", having an outer diameter of 125 μm and a length of 1.83 mm. The second light guide body 40 "has a core diameter. Is about 2 μm, the clad diameter is 125 μm, and an optical fiber with a length of 1,07 mm is used.

In FIG. 13, the spectrum dip near the wavelength of 1490 nm is the spectrum dip obtained from the interference caused by the first light guide body 20 ", and the spectrum dip near the wavelength 1280 nm is caused by the second light guide body 40". It is a spectral dip.

FIG. 14 is an enlarged view of FIG. 13 having a wavelength of around 1280 nm. As shown in FIG. 14, the wavelength of the spectral dip is shifted depending on the temperature, and the temperature can be measured by using this.

Further, in FIG. 15, the temperature was fixed at 30 ° C., and the surroundings of the first light guide body 20 "and the second light guide body 40" were used as air, pure water, and ethanol. The spectral change of the case is shown. As shown in FIG. 15, as the refractive index increases in the order of air → pure water → ethanol, the spectral dip obtained from the interference caused by the first light guide 20 ”with a wavelength of around 1490 nm shifts while the wavelength shifts. There is no change in the spectral dip due to the second light guide 40 "near around 1280 nm. From this, it can be seen that the refractive index and the temperature can be measured completely independently.

As another embodiment, the light guide body 40'of the second embodiment may be used instead of the second light guide body 40 "of the third embodiment.

10,10', 10 "optical fiber for incident
10a, 10a', 10a "core
20 "1st light guide
30 "intermediate fiber optic
30a "core
40,40'Light guide
40 "2nd light guide
40a, 40a', 40a "core
40b clad
41'Reflective surface
42', 42 "film
50, 50 "optical fiber for emission
50a, 50a "core
50'Connecting optical fiber
61 Light source
62 Detector
63 Optical directional coupler

Claims (7)

Light source and
An incident optical fiber with one end connected to this light source,
A light guide connected to the other end of this incident optical fiber,
In an optical fiber type measuring device provided with an optical fiber for emission in which one end is connected to the light guide and the other end is connected to a detector, and the light guide is used as a sensor.
The incident optical fiber and the emitted optical fiber are single-mode fibers.
By making the light guide body an optical fiber having a core having a diameter smaller than that of the core of the incident optical fiber and the core of the outgoing optical fiber and having a length of 1 mm or less.
The light incident on the light guide from the incident optical fiber spreads in the clad centering on the small-diameter core and propagates through the light guide, and the outer peripheral portion of the light guide becomes a boundary region. Of the light in the phase state that satisfies the standing condition in the plane perpendicular to the optical axis, the light having the waveform having the maximum light intensity at the center of the light guide and the center of the light guide. Formes light with a waveform wavelength that minimizes the light intensity.
An optical fiber type measuring device characterized in that light at the center of the light guide is output from the emission optical fiber. The optical fiber type measuring device according to claim 1, wherein the core diameter of the light guide body is about 2 μm. The optical fiber type measuring device according to claim 1 or 2, wherein the core diameters of the incident optical fiber and the emitted optical fiber are about 8.2 μm. A reflective surface is provided on the end surface of the light guide body connected to the incident optical fiber, and the light incident on the light guide from the incident optical fiber is reflected by the reflective surface.
A part of the incident optical fiber is used as the emitted optical fiber, and the light reflected by the reflecting surface is guided to an optical directional coupler provided in the middle of the incident optical fiber.
The optical fiber type measuring device according to any one of claims 1 to 3, wherein the optical directional coupler and the detector are connected by an optical fiber. Light source and
An incident optical fiber with one end connected to this light source,
A light guide connected to the other end of this incident optical fiber,
With an optical fiber for emission, one end of which is connected to this light guide and the other end of which is connected to the detector.
Using,
An optical fiber that incidents light guided from the light source through the incident optical fiber onto the light guide and measures fluctuations in the physical amount around the light guide using the light emitted from the light guide. In the formula measurement method
The incident optical fiber and the emitted optical fiber are single-mode fibers.
By making the light guide body an optical fiber having a core having a diameter smaller than that of the core of the incident optical fiber and the core of the outgoing optical fiber and having a length of 1 mm or less.
The light incident on the light guide from the incident optical fiber spreads in the clad centering on the small-diameter core and propagates through the light guide, and the outer peripheral portion of the light guide becomes a boundary region. Of the light in the phase state that satisfies the standing condition in the plane perpendicular to the optical axis, the light having the waveform having the maximum light intensity at the center of the light guide and the center of the light guide. Formes light with a waveform wavelength that minimizes the light intensity.
An optical fiber type measurement method characterized in that light at the center of the light guide is output from the emission optical fiber. The optical fiber type measuring method according to claim 5, wherein the core diameter of the light guide body is about 2 μm. The optical fiber type measuring method according to claim 5 or 6, wherein the core diameter of the incident optical fiber and the outgoing optical fiber is about 8.2 μm.

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