Optical module, alignment system, and optical measurement method

Abstract

Provided is an optical module suitable for accurately observing the overall intensity of visible light of a relatively short wavelength propagating through an optical fiber, and downsizing an optical device. An optical module provided in an optical fiber connected to an optical component to or from which light can be input or output comprises: a case body 10 that forms a closed space C in which a portion of an optical fiber 21, 22 is housed; a fiber securing part 120 that secures the optical fiber 21, 22 in predetermined position and shape within the case body 10; and a photodiode 33 that is mounted in a position where radiated light radiated from the optical fiber 21, 22 secured by the fiber securing part can be received within the case body 10.

Description

[Technical field]

[0001] The present invention relates to an optical module using an optical fiber, a core alignment system for this optical module, and an optical measurement method for an optical fiber. [Background technology]

[0002] Small optical modules combining multiple optical components are being developed. Such optical modules are described in, for example, Non-Patent Document 1, and the 3D measurement system described in Non-Patent Document 1 is configured by connecting a laser light source and a planar light wave circuit (hereinafter referred to as "PLC") via an optical fiber. The 3D measurement system described in Non-Patent Document 1 describes that a laser beam emitted from a laser light source is split into two equal lights by a 3 dB fiber coupler, and the split lights interfere with each other to project a fringe pattern on an object. In addition, Non-Patent Document 2 describes the development of a small RGB fiber coupler with low loss for each color. Such optical modules can realize small optical devices that require less alignment work and are less likely to cause optical axis deviation due to vibration, compared to optical systems configured with bulk components.

[0003] In order to operate the above 3D measurement system stably and continuously, it is necessary to monitor the intensity of light propagating through the PLC of the optical module and the optical fiber, and perform maintenance such as axial alignment (centering) and replacement of the optical fiber as necessary. Conventional maintenance of optical systems using optical modules has been performed by calculating the overall light intensity propagating through the optical fiber using the intensity of light divided by the above fiber coupler. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] S. Katayose et al, "Fabrication and demonstration of ultra-compact 3D measurement module using silica-based planar lightwave circuit", Jpn. J. Appl. Phys., Vol. 59, No. SOOD01, 2020. [Non-Patent Document 2] Sakamoto, et al., "Compact and low-loss RGB coupler using mode-conversion waveguides", Opt. Commun., Vol. 420, pp. 46-51, 2018. Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is known that commercially available fiber couplers are not reliable enough for visible light with a relatively short wavelength. This is thought to be due to the fact that the optical fiber of the fiber coupler experiences a fluctuation in transmittance and refractive index, called photodarning, for visible light, especially for light with a short wavelength. This tendency is prominent for visible light with a wavelength of 500 nm or less and an optical intensity of about several tens of mW, and when short-wavelength visible light is input to a fiber coupler, the branching ratio to the optical fiber fluctuates over time.

[0006] To avoid the above problems, it is possible to use bulk components such as beam splitters instead of fiber couplers. However, the use of beam splitters increases the size of optical devices including optical modules, which may limit the applications of the optical devices. In addition, beam splitters cause optical connection loss when recombining light with the optical fiber following the beam splitter. The connection loss causes an error when calculating the overall light intensity propagating through the optical fiber from the light split by the beam splitter.

[0007] The present invention has been made in consideration of the above points, and relates to an observation module, an alignment system, and an optical measurement method that are optical modules that accurately observe the overall intensity of relatively short-wavelength visible light propagating through an optical fiber and are suitable for miniaturizing optical devices. [Means for solving the problem]

[0008] An optical module according to one aspect of the present invention is an optical module provided on an optical fiber connected to an optical component capable of inputting or outputting light, the optical module comprising: a case body forming a closed space in which a part of the optical fiber is housed; At least two connected to each other a fiber fixing portion for fixing the optical fiber; and the optical fiber fixed to the fiber fixing portion inside the case body. Connection and a scattering member covering a radiating portion of the optical fiber from which the radiated light is radiated and having a larger light scattering coefficient than the radiating portion, wherein the fiber fixing portion comprises a groove-shaped first recess having a first width for fixing the optical fiber covered with the scattering member, and a groove-shaped second recess having a second width narrower than the first width for fixing the optical fiber not covered with the scattering member, the scattering member being fitted into the first recess and the optical fiber being fitted into the second recess, and a third recess for fixing the light receiving element is provided inside the case body, and a light receiving element fixing portion into which the light receiving element is fitted.

[0009] The alignment system according to one embodiment of the present invention is 1 to the optical module described above; a light source that injects light from one end of the optical fiber into at least a portion of the optical fiber that is contained inside the case body; and a centering mechanism that adjusts the position of at least one of the light source and the end based on the emitted light received by the light receiving element. Effect of the Invention

[0011] According to the above aspects, it is possible to provide an optical module, an alignment system, and an optical measurement method that are capable of accurately observing the overall intensity of visible light with a relatively short wavelength propagating through an optical fiber and that are suitable for miniaturizing optical devices. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram for explaining an experiment showing the basis of the present invention. [Diagram 2] FIG. 2(a) is a diagram showing the relationship between propagated light and emitted light obtained by the experiment described with reference to FIG. 1, and FIG. 2(b) is a diagram showing the change over time in the difference between propagated light and emitted light. [Diagram 3] 1 is a perspective view showing an external appearance of an optical module according to a first embodiment; [Figure 4] FIG. 4 is a vertical sectional view of the optical module shown in FIG. [Diagram 5] 5 is a schematic top view of the optical module shown in FIG. 3 and FIG. 4 as viewed from above. [Figure 6] 6A is a cross-sectional view taken along the cross-sectional line VIa shown in FIG. 5, FIG. 6B is a cross-sectional view taken along the cross-sectional line VIb, FIG. 6C is a cross-sectional view taken along the cross-sectional line VIc, and FIG. 6D is a diagram showing the positional relationship between the cross-section shown in FIG. 6C and the optical fiber and photodiode. [Figure 7] FIG. 2 is a schematic diagram for explaining the alignment system according to the first embodiment of the present invention. [Figure 8] FIG. 11 is a diagram for explaining the concept of a second embodiment of the present invention. [Figure 9] 9 is a schematic top view of the optical module described in FIG. 8 as viewed from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [overview] Prior to describing the embodiments of the present invention, an overview of the present invention will be described below.

[0014] Fig. 1 is a schematic diagram for explaining an experiment showing the basis of the present invention. The configuration shown in Fig. 1 includes an optical module 1 having a closed space C in which a photodiode (denoted as "PD" in the figure) 33 is provided, optical fibers 21 and 22 inserted into the closed space C, and a control unit 3 that inputs a radiation signal Ss indicating the intensity of light received by the photodiode 33 and a propagation signal St indicating the intensity of light received by the photodiode 34.

[0015] The optical fiber 21 and the optical fiber 22 are connected in a closed space C. In the experiment, the optical fibers 21 and 22 were connected by thermal fusion using arc discharge. The fusion portion of the optical fibers 21 and 22 is shown in FIG. 1 as fusion portion M. Of the optical fibers 21 and 22 fused to each other, light is incident from a light source (not shown) from the optical fiber 21 toward the optical fiber 22. In the experiment, a laser device was used as the light source, and laser light was incident on the optical fibers 21 and 22. The laser light incident on the optical fiber 21 is referred to as incident light Lin, and the laser light emitted from the optical fiber 22 is referred to as output light Lout. The wavelength of the laser light is 405 nm, and the propagation light intensity propagating through the optical fibers 21 and 22 is approximately 12 dbm to 18 dbm. The optical fibers 21 and 22 used in the experiment are both non-doped core fibers.

[0016] It is known that laser light passing through optical fibers leaks out from the connection and bent parts of the optical fibers. In the following description, the light emitted to the outside of the optical fibers 21 and 22 of the laser light is referred to as "emitted light," and the light that passes through the optical fibers 21 and 22 without scattering and is emitted from the end of the optical fiber 22 is referred to as "propagated light." In this experiment, the emitted light Lout corresponds to the propagated light.

[0017] The photodiode 33 is provided at a position relative to the optical fibers 21, 22 where it can receive the radiated light Ls, and receives the radiated light Ls. The intensity of the received radiated light Ls is converted into a radiation signal Ss and output from the photodiode 33. The photodiode 34 is provided at a position where it can receive the propagating light emitted from the optical fiber 22, and receives the propagating light. The intensity of the received propagating light is converted into a propagation signal St and output from the photodiode 34.

[0018] In this experiment, a heat shrink tube 25 is provided on the surface of the fused portion M as a scattering member having a scattering coefficient larger than that of the surfaces of the optical fibers 21 and 22. The heat shrink tube 25 is transparent to the laser light, but has a scattering coefficient larger than that of the optical fibers 21 and 22 due to its material, surface roughness, and the shape of the unevenness of the surface. The fused portion M is located inside the heat shrink tube 25, but the heat shrink tube 25 is shown by a dashed line in FIG. 1 to clearly show the fused portion M in FIG. The radiated light Ls emitted from the optical fibers 21 and 22 is scattered on the surface of the heat shrink tube 25, and is easily received by the photodiode 33.

[0019] The control unit 3 receives the radiation signal Ss and the propagation signal St. Then, the control unit 3 compares the radiation signal Ss with the propagation signal St that is input at the same timing as the input timing of the radiation signal Ss.

[0020] 2(a) and 2(b) are graphs for explaining the results of comparing the emitted signal Ss and the propagating signal St, which have the same input timing to the control unit 3. In Fig. 2(a), the horizontal axis shows the propagating light intensity, and the vertical axis shows the radiated light intensity. The propagating light intensity is a value determined by the signal strength (dbm) of the propagating signal St, and the radiated light intensity is a value determined by the signal strength (dbm) of the radiating signal Ss. In Fig. 2(b), the horizontal axis shows time (hours), and the vertical axis shows the difference (db) between the propagating light intensity and the radiated light intensity.

[0021] As shown in FIG. 2(a), the radiated light intensity and the propagated light intensity are in a directly proportional relationship, and both show good linearity. Also, as shown in FIG. 2(b), the difference between the radiated light intensity and the propagated light intensity is approximately constant for more than 1000 hours (more than 42 days). Such experimental results show that there is a strong correlation between the propagated light and the radiated light, and that the correlation is stable over a long period of time. The inventors of the present invention have previously obtained the relationship between the propagated light intensity and the radiated light intensity for one optical system, and have come up with the idea of ​​observing the intensity of the propagated light based on the intensity of the radiated light of the optical fiber. Observation of the propagated light using the radiated light can reduce the error of the observed value compared to observation using light split by a fiber coupler, regardless of photodarning that occurs when visible light with a relatively short wavelength is input to the optical fiber. Also, the optical module 1 can be made smaller than bulk parts such as a beam splitter, and is therefore suitable for miniaturizing optical devices.

[0022] Next, a first embodiment and a second embodiment of the present invention will be described. The drawings of the first embodiment and the second embodiment described later are intended to explain the technical concept, configuration, function, effect, etc. of the present invention, and do not limit the specific configuration of the embodiment. In addition, the drawings of the first embodiment and the second embodiment are schematic diagrams, and do not necessarily accurately show the aspect ratio or thickness. Furthermore, in the first embodiment and the second embodiment, the same members among the members shown in the drawings are given the same reference numerals. In addition, for the configurations given the same reference numerals, the description of the configurations shown later may be partially omitted.

[0023] [First embodiment] (Optical module) Fig. 3 is a perspective view showing the appearance of the optical module 1 of the first embodiment. Fig. 4 is a schematic cross-sectional view of the optical module 1 shown in Fig. 3 cut on the zx plane of the coordinate system shown in Fig. 3. Fig. 4 is a vertical cross-sectional view of the optical module 1 cut at a position that divides the length of the optical module 1 in the y direction in half. In the first embodiment, the up-down direction is determined along the z axis of the coordinate system, and the side with a relatively large z coordinate is defined as the top, and the side with a relatively small z coordinate is defined as the bottom.

[0024] The optical module 1 is a module provided on an optical fiber connected to an optical component capable of inputting or outputting light. Here, the optical component refers to one that can input or output light, and may be a component having an optical waveguide or a light source that outputs light. Furthermore, the shape of the optical component having an optical waveguide is not limited, and may be, for example, an optical fiber or a sheet-like or plate-like PLC. Furthermore, the optical component may be an optical waveguide, or may be one that incorporates a structure or electric element that branches or couples optical waveguides, or may be a bulk optical system component such as a lens or a prism.

[0025] 3 and 4, the optical module 1 includes a case body 10 forming a closed space C in which a portion of the optical fibers 21 and 22 are housed, a fiber fixing portion 120 (121, 122) that fixes the optical fiber in a predetermined position and shape inside the case body 10, and a photodiode 33 that is a light receiving element attached in a position inside the case body 10 where it can receive radiation light emitted from the optical fiber fixed to the fiber fixing portion 120. The optical fibers 21 and 22 may be non-doped core fibers, or may be optical fibers doped with rare earth elements.

[0026] Also in the first embodiment, the optical fibers 21 and 22 are connected to each other by fusion. In the first embodiment, the photodiode 33 observes the radiated light emitted from the fused portion M of the optical fibers 21 and 22. However, fusion is a widely used method for connecting optical fibers, and the connection loss at the fused portion M is small. In the first embodiment, the light leaking from the fused portion M is efficiently received, and the intensity of the light propagating through the optical fiber is monitored with a simpler configuration and lower loss than the case of using a fiber coupler or a beam splitter. Note that, although FIG. 4 illustrates a configuration in which the photodiode 33 receives the radiated light Ls from above the fused portion M, the photodiode 33 is not limited to being provided above the fused portion M, and may be provided at any position as long as it is a position where the radiated light Ls of sufficient intensity for observation can be received.

[0027] The heat shrink tube 25 covers at least the radiating portion of the optical fibers 21, 22 from which the radiated light is emitted, and functions as a scattering member having a larger light scattering coefficient than the radiating portion. In the example shown in FIG. 4, the heat shrink tube 25 covers the portion including the fused portion M to protect the fused portion. The radiating portion of the radiated light is the surface of the fused portion M, and the scattering coefficient of the heat shrink tube 25 is larger than that of the fused portion surface due to the material composition, surface roughness, and the shape of the unevenness of the surface. By providing the heat shrink tube 25, the degree of scattering of the radiated light from the optical fibers 21, 22 increases, making it easier for the photodiode 33 to receive the light. With this configuration, the signal strength of the radiation signal Ss output from the photodiode 33 can be increased, thereby improving the measurement accuracy of the radiated light.

[0028] The case body 10 has an upper case part 11 and a lower case part 12, and is configured by overlapping the upper case part 11 and the lower case part 12 and screwing them together with a screw 111. The lower case part 12 is provided with packing parts 112a and 112b made of, for example, a rubber material, sandwiching the optical fibers 21 and 22, and the packing parts 112a and 112b are respectively formed with semicircular cutout parts 113a and 113b for passing the optical fibers 21 and 22 through. The upper case part 11 has a base part 11b having a short length in the z-axis direction (hereinafter referred to as "height") and a convex base part 11a having a higher height than the base part 11b, and the base part 11b is in contact with the packing part 112a. The material of the case body 10 is preferably a material that does not transmit light from the outside, and is preferably, for example, a metal or an opaque resin. When the case body 10 is made of metal, the degree of scattering of light within the closed space C can be increased, and the light intensity of the emitted light received by the photodiode 33 can be increased.

[0029] FIG. 5 is a schematic top view of the optical module 1 shown in FIG. 3 and FIG. 4 as viewed from above. In FIG. 5, the upper case part 11 is shown by a two-dot chain imaginary line outside the lower case part 12 to avoid overlapping with the lower case part 12. FIG. 6(a), FIG. 6(b), and FIG. 6(c) are cross-sectional views showing the cross sections of the lower case part 12 cut along the cross-sectional lines VIa, VIb, and VIc in FIG. 5, respectively. FIG. 6(a) is a view of the cross section along the cross-sectional line VIa as seen in the direction of the arrow, FIG. 6(b) is a view of the cross section along the cross-sectional line VIb as seen in the direction of the arrow, and FIG. 6(c) is a view of the cross section along the cross-sectional line VIc as seen in the direction of the arrow. FIG. 6(d) is a view showing the positional relationship between the cross section shown in FIG. 6(c) and the optical fiber 21 and the photodiode 33.

[0030] 5, 6(a) and 6(b), the fiber fixing part 120 formed on the upper surface 12a of the lower case part 12 has a fused part fixing part 121 having a shape that conforms to the heat shrink tube 25 that covers the fused parts M of the optical fibers 21 and 22, and a non-fused part fixing part 122 having a shape that conforms to the parts of the optical fibers 21 and 22 that are not covered by the heat shrink tube 25. The fused part fixing part 121 and the non-fused part fixing part 122 are both groove-shaped recesses formed on the upper surface 12a, and the heat shrink tube 25 fits into the fused part fixing part 121, and the optical fibers 21 and 22 fit into the non-fused part fixing part 122. The non-fused part fixing part 122 shown in Fig. 6(a) has the shortest length (width) in the y-axis direction shown in Fig. 3 among the fiber fixing parts 120, and the fused part fixing part 121 shown in Fig. 6(b) has a width larger than the optical fibers 21, 22 by the thickness of the heat shrink tube 25. The lengths (depths) in the -z-axis direction based on the top surface 12a of the fused part fixing part 121 and the non-fused part fixing part 122 are constant. The fused part fixing part 121 and the non-fused part fixing part 122 fix the optical fibers 21, 22 in constant positions and shapes, and in a state where they are connected to each other.

[0031] In order to reliably fix the heat shrink tube 25 to the fusion part fixing part 121, for example, an adhesive may be applied to the bottom surface of the fusion part fixing part 121 in advance, and the optical fibers 21, 22 covered with the heat shrink tube 25 may be inserted into the fusion part fixing part 121 from above the adhesive. In addition, for example, the wall surface along the length direction of the fusion part fixing part 121, which is a recess, may be inclined so as to approach each other from the bottom surface toward the upper side. In this way, the heat shrink tube 25 fitted to the fusion part fixing part 121 is less likely to come off toward the upper side, and the reliability of the measurement of the radiation light of the optical fibers 21, 22 can be improved. The non-fusion part fixing part 122 is formed to have a width approximately equal to the diameter of the optical fibers 21, 22 in order to prevent the upper surface 12a of the optical fibers 21, 22 from bending or curving. Furthermore, the optical fibers 21, 22 are sandwiched between the packing parts 112a, 112b below the base part 11b. For example, the packing portions 112a and 112b made of a rubber material generate a relatively large frictional force between them, which can further increase the reliability of fixing the optical fibers 21 and 22. With the above-mentioned configuration, the optical fibers 21 and 22 are fixed inside the case body 10 without being bent.

[0032] The lower case 12 also includes an element fixing portion 123 above the fusion portion fixing portion 121 formed on the upper surface 12a. The element fixing portion 123 is a recess that conforms to the shape of the photodiode 33. As shown in FIG. 6(d), a portion of the photodiode 33 fits into the element fixing portion 123 and is fixed when radiated light is received. With this configuration, both the photodiode 33 and the heat shrink tube 25 can be fixed when radiated light is received, so that radiated light emitted from a certain portion of the optical fibers 21 and 22 can always be received at a certain position. In addition, the photodiode 33 can be brought close to the optical fibers 21 and 22 and the heat shrink tube 25, so that the intensity of the radiated light received by the photodiode 33 can be further increased.

[0033] [Optical measurement method] The optical measurement method performed using the optical module 1 of the first embodiment described above is an optical measurement method used to observe light propagating through the optical fibers 21, 22 connected to optical components. The optical measurement method of the first embodiment includes a step of receiving radiated light emitted from the optical fibers 21, 22 fixed at a predetermined position and shape inside the case body 10 forming the closed space C, and a step of determining the intensity of the light propagating through the optical fibers 21, 22 based on the intensity of the received radiated light Ls. Such an optical measurement method observes the propagated light using radiated light reflecting the propagated light, so that it is not affected by photodarning even when observing visible light with a relatively short wavelength, and can obtain highly reliable observation results.

[0034] [Alignment system] Next, a core alignment system using the optical module 1 described above will be described.

[0035] FIG. 7 is a schematic diagram for explaining the alignment system 100. The alignment system 100 is an alignment system for aligning the optical fibers 21, 22 connected to the optical components. The alignment system 100 includes the optical module 1 described above, a light source 5 that inputs light from one end (hereinafter also referred to as the "incident end") 27 of the optical fiber 21 to at least a portion of the optical fiber 21 that is accommodated inside the case body, and an alignment mechanism 8 that adjusts the position of at least one of the light source 5 and the incident end 27 based on the emitted light received by the photodiode 33. The light source 5 is, for example, a laser light source, and a condenser lens 6 is provided between the light source 5 and the incident end 27. The laser light Lo emitted from the light source 5 is condensed by the condenser lens 6 and enters the incident end 27. The incident end 27 is formed, for example, by end cap processing on the end of the optical fiber 21 facing the light source 5.

[0036] 7 adjusts the optical axis of an apparatus including, for example, a light source 5, a condenser lens 6, an optical module 1, and optical components (not shown) connected to an optical fiber 22 extending from the optical module 1. As an example of such an apparatus, a measurement apparatus that measures an object three-dimensionally can be considered.

[0037] The alignment system 100 includes an optical module 1, an alignment mechanism 8, and a control unit 3 connected to the light source. The control unit 3 controls the fixed position of the light source 5 and the fixed position of the incident end 27. For example, the light source 5 is attached to a drive shaft (not shown), and the control unit 3 outputs a control signal Sc1 to the drive shaft to drive the drive shaft, thereby changing the fixed position of the light source 5. For example, the control unit 3 outputs a control signal Sc2 to the alignment mechanism 8 to drive a fixing table (not shown) to which the incident end 27 is fixed, thereby changing the fixed position of the incident end 27. At this time, the control unit 3 inputs a radiation signal Ss from the optical module 1, and specifies the positions of the light source 5 and the incident end 27 at which the light intensity indicated by the radiation signal Ss is the strongest. Then, the control unit 3 outputs a control signal Sc1 to fix the light source 5 to the specified position, and outputs a control signal Sc2 to the alignment mechanism 8 to fix the incident end 27.

[0038] The alignment system 100 is not limited to a configuration in which the positions of both the light source 5 and the incident end 27 are adjusted as described above, and one may be fixed while the position of the other is adjusted. The control unit 3 may be a dedicated device for performing the above control, or a general-purpose computer may be made to execute a program for the above control. The control unit 3 includes a known CPU (Central Processing Unit), a memory device, an interface used for inputting and outputting information, and the like, in order to control the light source 5 and the alignment mechanism 8, and further to determine the intensity of the radiation signal Ss.

[0039] The above-described alignment system 100 can compensate for axial misalignment caused by expansion and contraction of members due to fluctuations in environmental temperature and vibration, and can stabilize the ratio (optical coupling rate) of the laser light emitted from the light source 5 that is captured by the optical fiber 21 over a long period of time. Furthermore, the alignment system 100 can maintain a constant optical coupling rate even when a relatively short-wavelength visible light is used, so that the light source 5 and the optical fiber 21 do not need to be fixed with an adhesive, and the optical fiber 21 can be easily replaced. It is known that the end face of an optical fiber deteriorates when used with visible light of a particularly short wavelength. For this reason, the alignment system of the first embodiment, which allows easy replacement of the optical fiber 21, is particularly suitable for alignment of a device that uses a short-wavelength visible light.

[0040] [Second embodiment] FIG. 8 is a diagram for explaining the concept of the second embodiment of the present invention. In the optical module 9 of the second embodiment, the optical fiber 28 is inserted into the case body 90 in a state where at least a part of the optical fiber 28 is bent, and the incident light Lin is incident from one end extending to the outside of the case body 90, and the outgoing light Lout is emitted from the other end. Then, the photodiode 33 receives the radiated light Ls emitted from the bent part of the optical fiber 28. Such a configuration can increase the light intensity of the radiated light Ls and improve the measurement accuracy of the radiated light Ls. That is, it is known that the amount of light leaking (lost) from the core of an optical fiber changes when the optical fiber is bent, and the amount of loss increases with a larger bending radius. In the second embodiment, utilizing this point, the optical fiber 28 is bent to an extent that the amount of light leaking from the core of the optical fiber 28 increases and the amount of loss does not become a problem, and the radiated light Ls is observed.

[0041] Fig. 9 is a diagram for explaining a configuration for realizing the above configuration, and is a schematic top view of the optical module 9 as viewed from above. A case body 90 of the optical module 9 is formed by combining an upper case part 91 and a lower case part 92. In Fig. 9, the upper case part 91 is shown by a two-dot chain imaginary line outside the lower case part 92 to avoid overlapping with the lower case part 92.

[0042] The lower case part 92 has a fiber fixing part 281 on the upper surface 92a. The fiber fixing part 281 is configured with a groove that fixes the optical fiber 28 in a bent state. The groove width of the fiber fixing part 281 is designed to be approximately the same length as the diameter of the optical fiber 28 to prevent the optical fiber 28 from bending or coming off. The optical fiber 28 is fitted into the groove of the fiber fixing part 281 and fixed in a curved state following the shape of the fiber fixing part 281. At this time, the optical fiber 28 may be fitted into the fiber fixing part 281 and temporarily fixed, and after confirming that the photodiode 33 can receive radiated light of sufficient light intensity, the optical fiber 28 may be securely fixed with a thermosetting resin or the like.

[0043] It is known that the optical loss of the optical fiber 28 varies depending on the degree of bending of the optical fiber, i.e., the bending radius. In the second embodiment, the optical fiber 28 is bent and fixed within a range where the optical loss is larger than that in an unbent state, where there is no hindrance to the propagation of light, and where no mechanical damage occurs. For example, such a range may be determined based on the short term bend radius listed in the optical fiber specification table. In this case, the bending radius of the optical fiber 28 may be set to 2 cm or less. The fiber fixing portion 281 is formed on the upper surface 92a as a groove having a curve that matches the bending radius thus set.

[0044] As described above, in the second embodiment, the amount of radiant light leaking from the optical fiber 28 is increased by bending the optical fiber 28, and the measurement accuracy of the radiant light can be improved. In addition, in the second embodiment, the fiber fixing portion 281 is formed on the upper surface 92a of the lower case portion 92, and the optical fiber is fixed at a constant bending radius. Therefore, the amount of radiant light emitted from the optical fiber and the radiating position are fixed, and the radiant light can be stably received by the photodiode 33. Furthermore, in the second embodiment, as in the first embodiment, a recess into which a part of the photodiode 33 is fitted may be provided together with the fiber fixing portion 281, and the photodiode 33 may also be fixed. In this way, the second embodiment can further stabilize the emission and reception of the radiant light. [Explanation of symbols]

[0045] 1,9 Optical Module 3. Control Unit 5 light source 6 Condenser lens 8 Alignment mechanism 10,90 Case body 11,91 Upper case part 12,92 Lower case part 12a,92a top surface 21, 22, 28 Optical fiber 25 Heat shrink tubing 27 Incidence end 33,34 Photodiode 100 Alignment System 120 Fiber fixing part 121 Fusion part fixing part 122 Non-fused part fixed part 123 Element fixing part Lout output light Ls synchrotron radiation M Welded part

Claims

1. An optical module provided on an optical fiber connected to an optical component capable of inputting or outputting light, a case body that forms a closed space in which a portion of the optical fiber is accommodated; a fiber fixing portion that fixes at least two of the optical fibers connected to each other inside the case body; a light receiving element attached inside the case body at a position capable of receiving light emitted from a connection portion of the optical fiber fixed to the fiber fixing portion; a scattering member that covers a radiation portion of the optical fiber from which the radiation light is emitted and has a light scattering coefficient larger than that of the radiation portion, the fiber fixing portion includes a groove-shaped first recess having a first width for fixing the optical fiber covered with the scattering member, and a groove-shaped second recess having a second width narrower than the first width for fixing the optical fiber not covered with the scattering member, the scattering member being fitted into the first recess, and the optical fiber being fitted into the second recess; a light receiving element fixing portion including a third recess for fixing the light receiving element inside the case body, the light receiving element being fitted into the third recess; An optical module comprising:

2. The optical module according to claim 1 ; a light source that inputs light from one end of the optical fiber to at least a portion of the optical fiber that is accommodated inside the case body; an alignment mechanism for adjusting a position of at least one of the light source and the end portion based on the emitted light received by the light receiving element; An alignment system comprising:

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