JP5684776B2 - Optical power monitoring device, manufacturing method, and optical power monitoring method - Google Patents

Description

  The present invention relates to an optical power monitoring device and an optical power monitoring method for monitoring the power of light propagating through an optical fiber. The present invention also relates to a manufacturing method for manufacturing such an optical power monitor device.

  An optical fiber is widely used as a transmission medium for transmitting laser light used for communication and processing. Also, an optical power monitor device is used to monitor the power of output light output from the optical fiber. The power of the output light detected by the optical power monitor device is used, for example, to adjust the intensity of light incident on the optical fiber or to detect a failure occurring in the optical fiber.

  As a typical configuration of the optical power monitoring device, (1) a configuration in which a part of output light output from the output end face of the optical fiber is taken out and its power is measured by a light receiving element, and (2) from the side surface of the optical fiber A configuration in which the power of leaked light is measured by a light receiving element. When it is difficult to add a configuration such as a light receiving element near the output end face of an optical fiber, such as a processing fiber laser, the latter configuration is adopted. Usually, the power of leakage light leaking from the side surface of the optical fiber is proportional to the power of output light output from the output end surface of the optical fiber. For this reason, even in the latter configuration, it is possible to calculate the power of the output light from the magnitude of the photocurrent output from the light receiving element.

  As a prior art document disclosing the latter configuration, for example, Patent Document 1 is cited. Patent Document 1 discloses a configuration in which the power of light leaked from an optical fiber in the vicinity of a fusion point is measured by a light receiving element disposed in the vicinity of the fusion connection point.

Japanese Patent Laid-Open No. 10-224304 (released on August 21, 1998)

  When the configuration described in Patent Document 1 is adopted, the temperature of the light receiving element varies due to heating due to leakage light leaking from the fusion point of the optical fiber or a change in environmental temperature. For this reason, even if the intensity of light incident on the light receiving element is constant, the magnitude of the photocurrent output from the light receiving element varies. For example, if the sensitivity of the light receiving element has a negative temperature characteristic, the magnitude of the photocurrent output from the light receiving element when the temperature of the light receiving element rises even if the intensity of light incident on the light receiving element is constant When the temperature of the light receiving element decreases, the magnitude of the photocurrent output from the light receiving element increases.

  As described above, when the magnitude of the photocurrent output from the light receiving element fluctuates even though the intensity of the light incident on the light receiving element is constant, the optical fiber is calculated from the magnitude of the photocurrent output from the light receiving element. It is difficult to accurately specify the intensity of light propagating through the light. In particular, this problem becomes more serious as the output of the fiber laser becomes higher.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical power monitoring device capable of accurately identifying the power of light propagating through an optical fiber even if the temperature of the light receiving element changes. Is to realize.

  In order to solve the above problems, an optical power monitoring device according to the present invention is a resin in which a section of an optical fiber including a fusion point is embedded, and has a temperature characteristic with a negative refractive index, and A light receiving element for detecting leakage of light leaking from the optical fiber to the resin at the fusion point, wherein the light receiving element has a negative temperature characteristic. The light receiving element has a z axis parallel to the optical axis of the optical fiber, the z coordinate of the fusion point is 0, and the z coordinate of the center point of the light receiving surface of the light receiving element is z1. (Z1> 0), the intensity distribution of the light leakage on a straight line passing through the center point of the light receiving surface of the light receiving element and parallel to the z axis when the temperature of the resin coincides with an upper limit value of a predetermined temperature range The z coordinate of the point where the peak of is formed is z0 (z0> ) As are arranged so as to satisfy the condition z1> z0, it is characterized.

  In order to solve the above-described problem, a manufacturing method according to the present invention is a resin in which a section of an optical fiber including a fusion point is embedded, and has a temperature characteristic with a negative refractive index, and An optical power monitoring device that detects light leaking from the optical fiber at the fusion point using a light receiving element having a negative temperature characteristic in a resin having a refractive index equal to or higher than the refractive index of the cladding of the optical fiber. In the manufacturing method, the z-axis is parallel to the optical axis of the optical fiber, the z-coordinate of the fusion point is 0, the z-coordinate of the center point of the light receiving surface of the light receiving element is z1 (z1> 0), and the resin The peak of the intensity distribution of the light leakage is formed on a straight line passing through the center point of the light receiving surface of the light receiving element and parallel to the z axis when the temperature coincides with the upper limit value of the predetermined temperature range. Assuming that the z coordinate of is z0 (z0> 0), the condition 1> z0 includes disposing step of disposing the light-receiving element so as to satisfy the, characterized in that.

  According to the optical power monitoring device, when the temperature of the resin rises, the point at which the intensity distribution peak is formed approaches the light receiving element, and the intensity of light leakage incident on the light receiving element increases. For this reason, a decrease in sensitivity of the light receiving element due to a temperature rise is compensated. Further, when the temperature of the resin is lowered, the point where the peak of the intensity distribution is formed moves away from the light receiving element, and the intensity of light leakage incident on the light receiving element is reduced. For this reason, an increase in sensitivity of the light receiving element due to a temperature decrease is compensated. Therefore, even if the temperature of the light receiving element changes, the power of light propagating through the optical fiber can be specified with high accuracy. The optical power monitor device manufactured by the above manufacturing method also has the same effect.

  In the optical power monitoring device according to the present invention, the light receiving element has a peak of the intensity distribution of the light leakage on the straight line when the refractive index of the resin matches the refractive index of the cladding of the optical fiber. It is preferable that the z coordinate of is set to satisfy the condition z1> z ′ where z ′ (z ′> z0).

  According to said structure, arrangement | positioning of the said light receiving element can be defined, without specifying the peak of the said intensity distribution obtained when the temperature of the said resin corresponds with the upper limit of the predetermined temperature range.

  In the optical power monitoring device according to the present invention, it is preferable that the optical power monitoring device further includes a scatterer interposed between the resin and the light receiving element and randomizing a propagation direction of the light leakage.

  According to the above configuration, it is possible to accurately specify the power of light propagating through the optical fiber even when a positional deviation occurs in the relative position between the fusion point and the light receiving element. .

  In the optical power monitor device according to the present invention, the scatterer is preferably made of crystallized glass.

  According to the above configuration, it is possible to specify the power of light propagating through the optical fiber with higher accuracy even when there is a positional shift in the relative position between the fusion point and the light receiving element. Become.

In order to solve the above problems, an optical power monitoring method according to the present invention is applied to a resin in which a section of an optical fiber including a fusion point is embedded and whose refractive index is equal to or higher than the refractive index of the cladding of the optical fiber. A detection step of detecting light leaking from the optical fiber at the fusion point using a light receiving element having a negative temperature characteristic, and the temperature of the resin when performing the detection step is Taking the z axis parallel to the optical axis of the optical fiber, the z coordinate of the fusion point is 0, the z coordinate of the center point of the light receiving surface of the light receiving element is z1 (z1> 0), and the light receiving surface of the light receiving element is The z coordinate of the point where the peak of the intensity distribution of the light leakage is formed on a straight line passing through the center point and parallel to the z axis is z _T (z _T > 0), and within a temperature range satisfying the condition z1> z _T. It is characterized by that.

  According to said structure, there exists an effect similar to said optical power monitoring method.

  ADVANTAGE OF THE INVENTION According to this invention, even if the temperature of a light receiving element changes, the optical power monitor apparatus which can pinpoint the power of the light which propagates an optical fiber accurately is implement | achieved.

1 is a side sectional view (upper left in the figure) and a transverse sectional view (upper right in the figure) of an optical power monitoring device according to a first embodiment of the present invention, together with a graph of intensity distribution of light leakage (lower left in the figure). is there. The graph of the intensity distribution obtained when the refractive index n2 (T) of the resin in the optical power monitoring apparatus according to the first embodiment of the present invention is n2 (T) = n1, and the temperature T of the resin is Tmin ≦ T A graph of intensity distribution obtained when ≦ Tmax is shown together with a cross-sectional view of the optical power monitor device. In the optical power monitoring apparatus according to the first embodiment of the present invention, a graph of an intensity distribution obtained when the resin temperature T is T = T1, and an intensity obtained when the resin temperature T is T = T2. The graph of distribution is shown with sectional drawing of an optical power monitor apparatus. The side sectional view (upper left of the figure) and the transverse sectional view (upper right of the figure) of the optical power monitoring device according to the second embodiment of the present invention are shown together with the graph of the intensity distribution of the leaked light (lower left of the figure). is there. It is a graph which shows the temperature dependence (dotted line) of the light reception power of a single light reception element, and the temperature dependence (solid line) of the light reception power of the light reception element mounted in the optical power monitor apparatus which concerns on a present Example.

  Several embodiments of the optical power monitoring apparatus according to the present invention will be described below with reference to the drawings. Note that an optical power monitoring device described below is inserted into an optical fiber constituting a fiber laser device, for example, and is used for specifying the output of the fiber laser. However, the use of the optical power monitoring apparatus according to the present invention is not limited to this.

[First Embodiment]
(Configuration of optical power monitor device)
The configuration of the optical power monitoring apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a side cross-sectional view (upper left of the figure) and a horizontal cross-sectional view (upper right of the figure) of an optical power monitoring apparatus 1 according to the present embodiment, and a graph of the intensity distribution I _Tmax (z) of light leakage described later. It is shown together with (lower left).

  The optical power monitor device 1 is a device for monitoring the intensity (power) of light propagating through the optical fiber F. As shown in FIG. 1, a section of the optical fiber F including the fusion point A is embedded. And a light receiving element 12 for detecting the intensity of light leaking from the optical fiber F to the resin 11.

  The optical fiber F is obtained by fusion-connecting at least two optical fibers, and includes at least one fusion point A. The optical fiber F is arranged so that the optical axis L is parallel to the z axis and the z coordinate of the fusion point A is 0. The propagation direction of light in the optical fiber F is assumed to coincide with the positive z-axis direction.

  In the optical power monitor device 1, the resin 11 is formed in a rectangular parallelepiped shape, and the light receiving element 12 is disposed so that the light receiving surface thereof is in contact with the side surface of the resin 11. The light leaked from the core of the optical fiber F passes through the clad having the thickness r1 and the resin 11 having the thickness r2, and then enters the light receiving surface of the light receiving element 12.

  As the resin 11, a resin whose refractive index n2 satisfies the following conditions A1 and A2 is used. In the following conditions A1 and A2, n1 represents the refractive index of the clad of the optical fiber F (substantially constant in the temperature region [Tmin, Tmax]). When the refractive index n2 has chromatic dispersion, the refractive index n2 with respect to the wavelength of the light propagating through the optical fiber F satisfies the following conditions A1 and A2.

  Condition A1: The refractive index of the clad of the optical fiber F is not less than n1 in a predetermined temperature region [Tmin, Tmax]. That is, n1 ≦ n2 (T) holds for an arbitrary temperature T that satisfies Tmin ≦ T ≦ Tmax. Here, n2 (T) is the refractive index of the resin 11 at the temperature T.

  Condition A2: It has a negative temperature characteristic in the temperature region [Tmin, Tmax]. That is, n2 (T1)> n2 (T2) holds for any temperature T1, T2 that satisfies Tmin ≦ T1 <T2 ≦ Tmax.

  The temperature region [Tmin, Tmax] is described in the spec sheet or the like, for example, as a temperature region in which the resin 11 is guaranteed to exhibit predetermined physical / optical properties (sometimes referred to as operation temperature). This is the temperature range. Further, the temperature dependence of the refractive index n2 of the resin 11 satisfying the condition A2 can be linearly approximated by, for example, n2 (T) = n2 (0) −α × T. Here, n2 (0) is the refractive index of the resin 11 at T = 0K, and α is a positive constant.

  As the light receiving element 12, a PD (Photo Diode) whose refractive index n3 is substantially constant in the temperature region [Tmin, Tmax] and whose sensitivity S satisfies the following condition B1 is used. When the sensitivity S has chromatic dispersion, the sensitivity S with respect to the wavelength of light propagating through the optical fiber F satisfies the following condition B1.

  Condition B1: It has a negative temperature characteristic in the temperature region [Tmin, Tmax]. That is, S (T1)> S (T2) holds for any temperature T1, T2 that satisfies Tmin ≦ T1 <T2 ≦ Tmax. Here, S (T) represents the sensitivity of the light receiving element 12 at the temperature T.

  The optical power monitor device 1 operates as follows. First, a part of the light propagating through the core of the optical fiber F leaks from the core to the cladding at the fusion point A. Next, a part of the leakage light leaked from the core to the clad at the fusion point A leaks from the optical fiber F (cladding) to the resin 11. A part of the light leaked from the optical fiber F to the resin 11 enters the light receiving element 12. The light receiving element 12 outputs a photocurrent having a magnitude proportional to the intensity of incident light. The intensity of light propagating through the core of the optical fiber F is calculated from the magnitude of the photocurrent output from the light receiving element 12.

The light leaked from the core of the optical fiber F at the fusion point A passes through the center point B of the light receiving surface of the light receiving element 12 and has a single peak on the straight line M parallel to the optical axis L of the optical fiber F. The intensity distribution I _T (z) is shown. The intensity distribution I _T (z) of the light leakage depends on the temperature T of the resin 11, but its unimodality (the property of having a single peak) is maintained regardless of the temperature T of the resin 11.

The optical power monitor device 1 is characterized in that the arrangement of the light receiving elements 12 is determined based on the intensity distribution I _Tmax (z) obtained when the temperature T of the resin 11 is T = Tmax. More specifically, the arrangement of the light receiving elements 12 is determined so as to satisfy the following condition B2.

Condition B2: When the z coordinate of the point C _Tmax where the peak of the intensity distribution I _Tmax (z) is formed is z0 and the z coordinate of the center point B of the light receiving surface of the light receiving element 12 is z1, z1> z0 is established. .

  The effect of determining the arrangement of the light receiving elements 12 so as to satisfy the condition B2 will be described later with reference to another drawing.

(Point where peak of intensity distribution I _T (z) is formed)
The point C _T at which the peak of the intensity distribution I _T (z) is formed will be supplemented with reference to FIG. FIG. 2 shows a graph of the intensity distribution I ′ (z) obtained when the refractive index n2 (T) of the resin 11 is n2 (T) = n1, and the temperature T of the resin 11 is Tmin ≦ T ≦ Tmax. The graph of intensity distribution I _T (z) obtained in this case is shown together with the cross-sectional view of the optical power monitor device 1.

  When the refractive index n2 (T) of the resin 11 matches the refractive index n1 of the clad of the optical fiber F, the leakage light leaked from the core of the optical fiber F at the fusion point A is the center point of the light receiving surface of the light receiving element 12 An intensity distribution I ′ (z) given by the following formula (1) is shown on a straight line M passing through B and parallel to the z-axis. The z coordinate z ′ of the point C ′ at which the peak of the intensity distribution I ′ (z) is formed can be derived using the following equation (1).

  Here, P is the total power of leakage light leaking from the core of the optical fiber F at the fusion point A, and NA is the numerical aperture of the optical fiber F. T12 is the transmittance between the clad and the resin, and the value can be determined by Fresnel's formula from the refractive index n1 of the clad of the optical fiber F and the refractive index n2 (T) of the resin 11. T23 is the transmittance between the resin and the light receiving element, and the value can be determined from the refractive index n2 (T) of the resin 11 and the refractive index n3 of the light receiving element 12 by the Fresnel equation.

When the temperature T is Tmin ≦ T ≦ Tmax, the refractive index n2 (T) of the resin 11 is higher than the refractive index n1 of the clad of the optical fiber F (condition A1). Therefore, the leakage light leaked from the core of the optical fiber F at the fusion point A is refracted at the interface between the cladding and the resin. For this reason, the z coordinate z _T of the point C _T at which the peak of the intensity distribution I _T (z) is formed is smaller than the z coordinate z ′ of the point C ′ at which the peak of the intensity distribution I ′ (z) is formed. Become. Z-coordinate _{z T} of the point _{C T} peak of the intensity distribution _I T (z) is formed, it can be derived using equation (2) to (4) below. See FIG. 2 for definitions of θ and φ.

(Effect by determining the arrangement of the light receiving elements so as to satisfy the condition B2)
Next, the effect obtained by determining the arrangement of the light receiving elements 12 so as to satisfy the above-described condition B2 will be described with reference to FIG. FIG. 3 shows a graph of the intensity distribution I _T1 (z) obtained when the temperature T of the resin 11 is T = T1, and the intensity distribution I _T2 (when the temperature T of the resin 11 is T = T2. The graph of z) is shown together with a cross-sectional view of the optical power monitor device 1. T1 and T2 are arbitrary temperatures that satisfy Tmin ≦ T1 <T2 ≦ Tmax.

And z-coordinate _{z T1} of the intensity distribution _I T1 point _{C T1} peaks are formed of (z), it is compared with the z-coordinate _{z T2} of the intensity distribution _I T2 point _{C T2} which peak is formed (z), z A magnitude relationship of _T1 <z _T2 is established. That is, when the temperature of the resin 11 is increased, C _T that peaks are formed of the intensity distribution I _{T (z)} is away from the fused point A, the temperature of the resin 11 is reduced, the intensity distribution I _T of _(z) C _T that peak is formed approaches the splice point a. This is because n2 (T1)> n2 (T2) is satisfied with respect to the refractive index n2 (T) of the resin 11 (condition A2), so that φ (T1) <φ with respect to the refraction angle φ (T) of light leakage incident on the resin 11. This is because (T2) holds. In addition, the peak height of the intensity distribution I _T2 (z) at the high temperature is higher than the peak height of the intensity distribution I _T1 (z) at the low temperature. This is because n2 (T1)> n2 (T2) is satisfied with respect to the refractive index n2 (T) of the resin 11 (condition A2), so that the refractive index difference n2 (T2) −n1 at high temperature is the refractive index difference n2 at low temperature. This is because the transmittance T12 (T2) at a high temperature is larger than the transmittance T12 (T1) at a low temperature.

Therefore, when defining the arrangement of the light receiving element 12 so as to satisfy the condition B2 described above, when the temperature of the resin 11 is increased, C _T that peaks are formed of the intensity distribution I _{T (z)} is the light receiving element 12 And the intensity of light leakage incident on the light receiving element 12 increases. This compensates for a decrease in sensitivity of the light receiving element 12 due to a temperature rise. Further, when defining the arrangement of the light receiving element 12 so as to satisfy the condition B2 described above, when the temperature of the resin 11 is reduced, C _T that peaks are formed of the intensity distribution I _{T (z)} is from the light receiving element 12 The intensity of light leakage incident on the light receiving element 12 is reduced. Thereby, an increase in sensitivity of the light receiving element 12 due to a temperature decrease is compensated.

  Instead of the configuration in which the arrangement of the light receiving elements 12 is determined so as to satisfy the above-described condition B2, a configuration in which the arrangement of the light receiving elements 12 is determined so as to satisfy the following condition B2 'may be employed.

  Condition B2 ′: z ′ is the z coordinate of the point C ′ at which the peak of the intensity distribution I ′ (z) obtained when the refractive index n2 (T) of the resin 11 is n2 (T) = n1 is received. When the z coordinate of the center point B of the light receiving surface of the element 12 is z1, z1 ≧ z ′ is established.

Since the above condition B2 ′ is a stricter condition than the above condition B2, even when the latter configuration is adopted, the same effect as that obtained when the former configuration is adopted can be obtained. Further, when the latter configuration is adopted, the design is facilitated because it is not necessary to specify the z coordinate of the point C _max where the peak of the intensity distribution I _Tmax (z) is formed.

  If the optical power monitor device 1 is used in a state where the temperature T of the resin 11 satisfies the following condition B2 ″, the above-described effects can be obtained regardless of the arrangement of the light receiving elements 12.

Condition B2 ": when the z-coordinate of the center point B of the light receiving surface of the light receiving element 12 was set to z1, z coordinate _{z T} of _{C T} point peak of the intensity distribution _I T (z) is formed, the condition _{z T} <Z1 is satisfied.

[Second Embodiment]
(Configuration of optical power monitor device)
The configuration of the optical power monitoring apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a side sectional view (upper left in the figure) and a lateral sectional view (upper right in the figure) of the optical power monitoring apparatus 1 according to the present embodiment, and a graph of the intensity distribution I _Tmax (z) of the leaked light (lower left in the figure). It is shown with.

  The optical power monitoring device 1 according to the present embodiment is obtained by adding a scatterer 13 to the optical power monitoring device 1 according to the first embodiment.

  In the present embodiment, a structure in which a groove extending in a direction parallel to the optical axis L of the optical fiber F is used as the scatterer 13 and the groove is filled with the resin 11 is employed. The present invention is not limited to this. For example, a structure in which a through hole extending in a direction parallel to the optical axis L of the optical fiber F is used as the scatterer 13 and the through hole is filled with the resin 11 may be employed.

  In this embodiment, the scatterer 13 is formed in a rectangular parallelepiped shape, and the above-described groove is formed on any of the four side surfaces. The light receiving element 12 is disposed such that its light receiving surface is in contact with a side surface of the four side surfaces of the scatterer 13 that faces the side surface on which the groove is formed. The light leaked from the core of the optical fiber F passes through the clad having the thickness r1, the resin 11 having the thickness r2, and the scatterer 13 having the thickness r3, and then enters the light receiving surface of the light receiving element 12.

  As the resin 11, a resin whose refractive index n2 satisfies the above conditions A1 and A2 is used as in the first embodiment. Further, as the light receiving element 12, as in the first embodiment, an element whose refractive index n3 is substantially constant in the temperature region [Tmin, Tmax] and whose sensitivity S satisfies the above condition B1 is used.

  The optical power monitor device 1 according to the present embodiment operates in the same manner as the optical power monitor device 1 according to the first embodiment. However, the light leaked from the optical fiber F to the resin 11 is incident on the light receiving element 12 after the propagation direction is randomized by the scatterer 13 interposed between the resin 11 and the light receiving element 12.

  When a configuration in which the scatterer 13 is not interposed between the resin 11 and the light receiving element 12 is used, if the positional deviation occurs between the fusion point A and the light receiving element 12, the power of the measured light leakage varies greatly. May end up. This is because, since the light propagating through the optical fiber F has high coherence, interference occurs between the leaked lights leaking out from the optical fiber F, and spatial spots ( That is, interference fringes) are generated.

  On the other hand, when a configuration in which the scatterer 13 is interposed between the resin 11 and the light receiving element 12 is adopted, the propagation direction of the leaked light leaking from the side surface of the optical fiber F is randomized by the scatterer 13. Even if interference fringes occur around the light receiving element 12, the period is significantly smaller than the size of the light receiving surface of the light receiving element 12. Therefore, even if a positional shift occurs in the relative position between the fusion point A and the light receiving element 12, the intensity of light measured by the light receiving element 12 does not vary greatly.

  The scatterer 13 can be made of crystallized glass, for example. Crystallized glass is a kind of heat-resistant glass obtained by incorporating microcrystals having a negative coefficient of thermal expansion into glass having a positive coefficient of thermal expansion. The reason why the crystallized glass has the above-described scattering action is that the microcrystal reflects light propagating in the glass in a random direction.

  As is clear from the above description, the crystallized glass is only an example of the material of the scatterer 13 and can be replaced with an arbitrary material having a function of emitting light with random propagation direction of incident light. For example, a transparent material containing a structure having a size comparable to the wavelength of light to be monitored, such as a resin kneaded with glass powder, can be used as the material of the scatterer 13. The transparent material here refers to a material whose light loss is only scattering and reflection for light having the same wavelength as the light to be monitored, that is, a material whose absorption is not a substantial loss factor. Refers to that.

The light leaked from the core of the optical fiber F at the fusion point A passes through the center point B of the light receiving surface of the light receiving element 12 and has a single peak on the straight line M parallel to the optical axis L of the optical fiber F. The intensity distribution I _T (z) is shown. This point is not different from the first embodiment. However, the intensity distribution I _T (z) is broader than that of the first embodiment due to the action of the scatterer 13.

Also in the present embodiment, the arrangement of the light receiving elements 12 is determined based on the intensity distribution I _Tmax (z) obtained when the temperature T of the resin 11 is T = Tmax. More specifically, the arrangement of the light receiving elements 12 is determined so as to satisfy the condition B2. Thereby, the sensitivity change of the light receiving element 12 due to the temperature change is compensated as in the first embodiment.

(Example)
OE-6520 manufactured by Toray Dow Corning Co. is used as the resin 11, KPDE086S, an InGaAs photodiode manufactured by Kyosemi Co., is used as the light receiving element 12, and white neoceram (registered trademark) manufactured by this Electric Glass Co., Ltd. is used as the scatterer 13. ) Will be described with reference to FIG.

In this example, the thickness r1 of the clad of the optical fiber F was 0.2 mm, the thickness r2 of the resin 11 was 0.2 mm, and the thickness r3 of the scatterer 13 was 1.2 mm. At this time, the z coordinate z0 of the point C _Tmax at which the peak of the intensity distribution I _Tmax (z) is formed becomes z0 = 6.8 mm, so the z coordinate z1 of the center point B of the light receiving surface is z1 = 11.5 mm. The arrangement of the light receiving elements 12 was determined so that

  FIG. 5 shows the temperature dependence (dotted line) of the light receiving power of the single light receiving element 12 and the temperature dependence (solid line) of the light receiving power of the light receiving element 12 mounted on the optical power monitoring device 1 according to this embodiment. It is a graph to show. Note that the “light reception power change rate” in FIG. 5 is a numerical value in which {(light reception power) − (reference power)} / (reference power) is expressed as a percentage, with the light reception power at 25 ° C. being the reference power. Point to.

  When the environmental temperature (particularly the temperature of the light receiving element 12) rose from 25 ° C. to 40 ° C., the rate of change in received light power of the single light receiving element 12 was about −3%. On the other hand, when the environmental temperature (particularly the temperature of the resin 11 and the light receiving element 12) is increased from 25 ° C. to 40 ° C., the light receiving power of the light receiving element 12 mounted on the optical power monitoring device 1 according to the present embodiment. The rate of change was about + 1.5%. That is, by mounting the light receiving element 12 in the optical power monitoring apparatus 1 according to the present embodiment, the absolute value of the light receiving power change rate can be suppressed to about half or less.

  When the environmental temperature (particularly the temperature of the light receiving element 12) decreased from 25 ° C. to 10 ° C., the rate of change in received light power of the single light receiving element 12 was about + 4%. On the other hand, when the environmental temperature (particularly the temperature of the resin 11 and the light receiving element 12) is lowered from 25 ° C. to 10 ° C., the light receiving power of the light receiving element 12 mounted on the optical power monitor device 1 according to the present embodiment. The rate of change was about -1.5%. That is, by mounting the light receiving element 12 in the optical power monitoring apparatus 1 according to the present embodiment, the absolute value of the light receiving power change rate can be suppressed to about half or less.

  Instead of OE-6520 made by Toray Dow Corning, OE-6635, OE-6550, or OE-6450 made by the same company, ASP-1010, ASP-1020, or SCR-made by Shin-Etsu Silicone 1011 can also be used as the resin 11. Even in this case, there is no change in the effect of keeping the absolute value of the received light power change rate small.

  In the present embodiment, the sensitivity of the entire optical power monitor device 1 shows a positive temperature characteristic. This is because the intensity change of the light leakage incident on the light receiving element 12 caused by the temperature change of the resin 11 exceeds the sensitivity change of the light receiving element 12 caused by the temperature change of the light receiving element 12. Therefore, for example, by reducing the thickness r2 of the resin 11 to reduce the intensity change of the light leakage incident on the light receiving element 12, the temperature dependence of the sensitivity of the entire optical power monitor device 1 can be further reduced. is there.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can be suitably used as, for example, an optical power monitor device used for specifying the output of a fiber laser.

DESCRIPTION OF SYMBOLS 1 Optical power monitor apparatus 11 Resin 12 Light receiving element 13 Scattering body F Optical fiber A Fusion point

Claims (6)

A resin in which a section of the optical fiber including the fusion point is embedded, a resin having a refractive index having a negative temperature characteristic, and a refractive index equal to or higher than the refractive index of the cladding of the optical fiber;
A light receiving element for detecting leakage light leaked from the optical fiber to the resin at the fusion point, the light receiving element having a negative temperature characteristic,
The light receiving element has a z axis parallel to the optical axis of the optical fiber, the z coordinate of the fusion point is 0, the z coordinate of the center point of the light receiving surface of the light receiving element is z1 (z1> 0), The peak of the intensity distribution of the light leakage is formed on a straight line passing through the center point of the light receiving surface of the light receiving element and parallel to the z axis when the temperature of the resin matches the upper limit value of a predetermined temperature range. The optical power monitoring device is characterized by being arranged so as to satisfy the condition z1> z0, where z is the coordinate z0 (z0> 0). The light receiving element has a z coordinate of a point at which a peak of the intensity distribution of the light leakage is formed on the straight line when the refractive index of the resin coincides with the refractive index of the cladding of the optical fiber. z0) are arranged so as to satisfy the condition z1> z ′.
The optical power monitor apparatus according to claim 1. The optical power according to claim 1, further comprising a scatterer interposed between the resin and the light receiving element, the scatterer randomizing a propagation direction of the light leakage. Monitor device. The scatterer is made of crystallized glass,
The optical power monitor device according to claim 3. A resin in which a section of the optical fiber including the fusion point is embedded, the resin having a negative refractive index and a refractive index equal to or higher than the refractive index of the cladding of the optical fiber, In a manufacturing method of an optical power monitor device for detecting light leaking from the optical fiber at a fusion point using a light receiving element having negative temperature characteristics,
The z-axis is taken in parallel with the optical axis of the optical fiber, the z-coordinate of the fusion point is 0, the z-coordinate of the center point of the light receiving surface of the light receiving element is z1 (z1> 0), and the resin temperature is The z-coordinate of the point at which the peak of the intensity distribution of the light leakage is formed on a straight line passing through the center point of the light receiving surface of the light receiving element and parallel to the z axis when the upper limit value of the predetermined temperature range is matched. z0 (z0> 0) includes an arrangement step of arranging the light receiving elements so as to satisfy the condition z1> z0.
The manufacturing method characterized by the above-mentioned. A resin in which a section of the optical fiber including the fusion point is embedded, the resin having a negative refractive index and a refractive index equal to or higher than the refractive index of the cladding of the optical fiber, A detection step of detecting light leakage from the optical fiber at the fusion point using a light receiving element having a negative temperature characteristic;
The temperature of the resin when performing the detection step is such that the z axis is parallel to the optical axis of the optical fiber, the z coordinate of the fusion point is 0, and the z coordinate of the center point of the light receiving surface of the light receiving element. Z1 (z1> 0), the z coordinate of the point where the peak of the intensity distribution of the light leakage is formed on a straight line passing through the center point of the light receiving surface of the light receiving element and parallel to the z axis is expressed as z _T (z _T > 0), it is within the temperature range satisfying the condition z1> _{z T,}
An optical power monitoring method.

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