Multi-core fiber light intensity distribution measuring device and multi-core fiber light intensity distribution measuring method

Abstract

To provide a light intensity distribution measuring device of a multi-core fiber and a light intensity distribution measuring method of the multi-core fiber, which can more accurately measure light intensity distribution.SOLUTION: A light intensity distribution measuring device 1 includes: an incident section 20 that changes an amount of light and causes the light to enter a core 11 a plurality of times; an image data generation section 30 that images light emitted from the core 11 with a camera 31; an extracted image data generation section 42 that extracts a pixel obtained by imaging light between a lower limit value and an upper limit value of a dynamic range of the camera 31 from image data; a converted image data generation section 43 that converts the intensity of the light of the extracted pixel into the intensity of the light incident to the core 11 per unit amount; and a composite image data generation section 44 that generates composite image data indicating intensity distribution of the light emitted from the core 11 by combining a plurality of pieces of converted image data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus for measuring a light intensity distribution of a multicore fiber and a method for measuring a light intensity distribution of a multicore fiber. [Background technology]

[0002] Multicore fibers having multiple cores arranged in a cladding are known, and a known characteristic measuring device for such a multicore fiber is described in the following Patent Document 1. In this characteristic measuring device for a multicore fiber, light is incident on each core from one end of the multicore fiber, and the light exiting from the other end of the multicore fiber is imaged by an imaging device, and the characteristics of the multicore fiber are determined based on the image thus captured. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-138910 A Summary of the Invention [Problem to be solved by the invention]

[0004] The light image captured by the imaging device of the above-mentioned Patent Document 1 is nothing but the light intensity distribution. Therefore, it can be understood that the light intensity distribution is measured by this imaging device. However, imaging devices have a dynamic range of light that can be captured, and light that exceeds this dynamic range tends to white out, while light that falls below this dynamic range tends to be unable to be captured or the S / N ratio tends to deteriorate beyond the allowable range.

[0005] The characteristics of each core of a multi-core fiber tend not to be uniform, and even when light is incident on each core under the same conditions, there is a tendency for the intensity of light emitted from each core to vary. Therefore, in a core that emits light with a high intensity, the light near the center of the core may exceed the dynamic range of the imaging device, and in a core that emits light with a low intensity, the light near the periphery of the core may fall below the dynamic range of the imaging device. In these cases, even if the characteristics of the core are calculated based on the captured data, there is a concern that the characteristics may be inaccurate. For this reason, there is a demand for more accurate measurement of the intensity distribution of light emitted from each core.

[0006] Therefore, an object of the present invention is to provide a light intensity distribution measuring device for a multicore fiber and a light intensity distribution measuring method for a multicore fiber, which are capable of more accurately measuring the intensity distribution of light emitted from each core. [Means for solving the problem]

[0007] In order to achieve the above object, the light intensity distribution measuring device for a multi-core fiber of the present invention includes an input unit that inputs light of the same intensity simultaneously into one end of each core of a multi-core fiber; an image data generation unit that captures the light exiting the other end of each of the cores with a camera and generates image data indicating the light exiting each of the cores with a plurality of pixels; an extracted image data generation unit that extracts from the image data the pixels at which light of an intensity between a lower limit value and an upper limit value of a dynamic range that can be captured by the camera is captured, and generates extracted image data; a converted image data generation unit that converts the light intensity of each of the pixels extracted by the extracted image data generation unit into an intensity per unit amount of light entering the core, and generates converted image data; and a synthetic image data generation unit that combines a plurality of the converted image data to generate synthetic image data indicating the intensity distribution of light exiting each of the cores. The incident unit incidents light into each of the cores multiple times by changing the amount of light incident on the cores so that the intensity of at least a portion of the light emitted from each of the cores falls within the range between the lower limit value and the upper limit value more than twice, the image data generation unit generates the image data each time light is incident on each of the cores, the extracted image data generation unit generates the extracted image data for each of the image data, the converted image data generation unit generates the converted image data for each of the extracted image data, and the synthetic image data generation unit combines two or more of the converted image data for each of the cores to generate the synthetic image data.

[0008] Furthermore, in order to achieve the above object, the light intensity distribution measuring method of the present invention includes an input step of inputting light of the same intensity simultaneously into one end of each core of a multicore fiber; an image data generating step of capturing an image of the light exiting from the other end of each of the cores with a camera and generating image data indicating the light exiting from each of the cores with a plurality of pixels; an extracted image data generating step of extracting from the image data the pixels at which the image of light of an intensity between a lower limit value and an upper limit value of a dynamic range that can be captured by the camera is captured, and generating extracted image data; a converted image data generating step of converting the light intensity of each of the pixels extracted in the extracted image data generating step into an intensity per unit amount of light incident on the core, and a synthetic image data generating step of synthesizing a plurality of the converted image data to generate synthetic image data indicating the intensity distribution of the light exiting each of the cores. In the incidence step, light is incident on each of the cores multiple times by changing the amount of light incident on the cores so that the intensity of at least a portion of the light emitted from each of the cores falls within the range between the lower limit value and the upper limit value at least twice; in the image data generation step, the image data is generated each time light is incident on each of the cores; in the extracted image data generation step, the extracted image data is generated for each of the image data; in the converted image data generation step, the converted image data is generated for each of the extracted image data; and in the composite image data generation step, two or more of the converted image data are combined for each of the cores to generate the composite image data.

[0009] When a certain amount of light is incident on each core and the light emitted from each core is captured by a camera, there is a possibility that the light emitted from a certain core that is incident on pixels in a certain range falls within the dynamic range of the camera, and the light that is incident on other pixels falls outside the dynamic range. Furthermore, when an amount of light different from this amount of light is incident on each core, the light emitted from this specific core that is incident on pixels in a range different from the pixels in the certain range tends to fall within the dynamic range of the camera. Therefore, in the above-mentioned multi-core fiber light intensity distribution measurement device and light intensity distribution measurement method, the amount of light incident on the core is changed and light is incident on each core multiple times so that the intensity of at least a part of the light emitted from each core falls within the dynamic range two or more times. Therefore, the range of pixels extracted from the image data to become the extracted image data tends to be different each time light is incident on the core. By combining pixels in different ranges in this way, a wider range of pixels than one extracted image data falls within the dynamic range of the camera. However, when the amount of light incident on the core is changed, different image data will show different light intensities even for the same pixel. Therefore, normalization is performed to convert the light intensity of each pixel extracted in the extracted image data into the intensity per unit amount of light incident on the core, so that the same pixel in each converted image data shows approximately the same light intensity. In this way, by synthesizing two or more converted image data obtained by normalizing the extracted image data for each core, the range of light captured within the dynamic range of the camera can be made larger than when image data showing the light intensity distribution is generated by capturing the light emitted from each core only once. Therefore, the light intensity distribution measuring device and the light intensity distribution measuring method for a multi-core fiber can more accurately measure the intensity distribution of light emitted from each core.

[0010] The incident section can change the amount of light incident on the core by changing the power of the light incident on the core or the period of time during which the light is incident on the core.

[0011] In addition, when light of the same intensity is incident on each of the cores, the core from which light with the lowest intensity is output is defined as a dark core, and the core from which light with the highest intensity is output is defined as a bright core, and the amount of light incident on the dark core when the peak intensity of the light output from the dark core becomes the lower limit value is defined as a lower limit amount of the amount of light incident on each of the cores, and 1 / e of the peak intensity of the light output from the bright core is defined as a lower limit amount of the amount of light incident on the dark core when the peak intensity of the light output from the bright core becomes the lower limit amount of the amount of light incident on the dark core. 2 Assume that the amount of light incident on the bright core when the intensity of the bright core reaches the upper limit is set to the upper limit of the amount of light incident on each of the cores. In this case, it is preferable that the incidence unit causes light to be incident on each of the cores multiple times so that the amount of light incident on the cores varies within a range between the lower limit and the upper limit. Also, it is preferable that in the incidence step, light is incident on each of the cores multiple times so that the amount of light incident on the cores varies within a range between the lower limit and the upper limit.

[0012] In a general multi-core fiber, each core tends to exhibit roughly the same optical properties, so that in a general multi-core fiber, light is incident on each core multiple times so that the amount of light incident on the core varies within a range between a lower limit value and an upper limit value as described above, and multiple extracted image data can be generated based on the light emitted multiple times from each core.

[0013] Moreover, the light intensity distribution measuring device for a multicore fiber preferably includes a bright and dark core predicting unit that predicts the bright cores and the dark cores, and the light intensity distribution measuring method for a multicore fiber preferably includes a bright and dark core predicting step that predicts the bright cores and the dark cores. In this case, the bright and dark core predicting unit and the bright and dark core predicting step perform the following processing. That is, when light of the same intensity is incident on each of the three cores arranged in a non-linear manner, one end of a straight line having a length proportional to the intensity of the light emitted from the three cores is arranged on the same plane so as to be arranged in the same arrangement as the three cores, and a slope passing through the other end of each of the straight lines is defined, the core of each of the cores of the multicore fiber whose slope is located on the side farthest from the plane is defined as the bright core, and the core whose slope is located on the side closest to the plane is defined as the dark core.

[0014] In a multicore fiber, due to its manufacturing method, a bright core is located at one end side in a specific diameter direction of the cladding, and the intensity of light emitted from the core gradually decreases from the one end side to the other end side in the diameter direction, and a dark core tends to be located at the other end side in the diameter direction. Therefore, as described above, the one end side and the other end side in the diameter direction can be known based on the intensity of light emitted from three cores positioned in a non-linear manner. Therefore, the bright cores and dark cores can be easily predicted without measuring the light emitted from all the cores.

[0015] In addition, in the synthetic image data generating unit in the above-mentioned multicore fiber light intensity distribution measuring device and the synthetic image data generating step in the multicore fiber light intensity distribution measuring method, it is preferable that the average of the light intensities at the same pixel of each of the converted image data is set to the light intensity at that pixel of the synthetic image data.

[0016] When a pixel is extracted multiple times to generate multiple extracted images as described above, the pixels extracted in each extracted image may be the same. In this case, by averaging the light intensity of the same pixel as described above and combining the images, the measurement error can be reduced compared to when one of the same pixels extracted multiple times is selected.

[0017] In the extracted image data generating unit in the light intensity distribution measuring device for a multicore fiber and the extracted image data generating step in the light intensity distribution measuring method for a multicore fiber, 2 It is preferable to not extract pixels in which light with an intensity lower than the intensity of the pixel is captured.

[0018] The characteristics of the mode field diameter of light propagating through an optical fiber are generally 1 / e 2 Therefore, even if the peak intensity of the light emitted from the core is 1 / e 2 Even if an intensity lower than the intensity is within the dynamic range, by not extracting light of that intensity, it is possible to remove light components that are not necessary for the general process of determining light characteristics, thereby facilitating the process. Effect of the Invention

[0019] As described above, according to the present invention, it is possible to provide a multicore fiber light intensity distribution measuring device and a multicore fiber light intensity distribution measuring method that can more accurately measure the intensity distribution of light output from each core. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram showing an outline of a multicore fiber light intensity distribution measuring device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of a flowchart of steps of a method for measuring a light intensity distribution of a multicore fiber according to an embodiment of the present invention. [Diagram 3] FIG. 13 is a diagram illustrating a bright / dark core prediction step. [Figure 4] FIG. 1 shows image data with an exposure time of 3 ms. [Diagram 5] FIG. 1 shows image data with an exposure time of 10 ms. [Figure 6] FIG. 1 shows image data with an exposure time of 20 ms. [Figure 7] FIG. 7 is a diagram showing the light intensity distribution in FIGS. 4 to 6. [Figure 8] FIG. [Figure 9] FIG. 13 is a diagram illustrating that composite image data can measure light intensity distribution more accurately than a single image data. [Figure 10] 13A to 13C are diagrams illustrating a modified example of the extracted image data generating step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments for carrying out the multicore fiber light intensity distribution measuring device and the multicore fiber light intensity distribution measuring method according to the present invention will be illustrated with the accompanying drawings. The embodiments exemplified below are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified and improved from the following embodiments without departing from the gist of the present invention. In addition, in this specification, the dimensions of each member may be exaggerated in some cases to facilitate understanding.

[0022] 1 is a diagram showing an outline of a multicore fiber light intensity distribution measuring device according to an embodiment. A multicore fiber 10 whose light intensity distribution is measured in this embodiment has a plurality of cores 11 and a cladding 12 surrounding the outer circumferential surface of each of the cores 11. Note that this embodiment will be described taking as an example a multicore fiber having four cores.

[0023] As shown in FIG. 1, the multi-core fiber light intensity distribution measuring device 1 of this embodiment includes an input unit 20, an image data generating unit 30, a processor CP, a memory ME, and an intensity measuring unit 50.

[0024] The input unit 20 inputs light of the same intensity simultaneously to one end of each of the cores 11 of the multicore fiber 10. The wavelengths of the light input to each of the cores 11 are preferably the same. The means for inputting light to each of the cores 11 is not particularly limited. For example, a core of a single-core fiber is connected to each of the cores 11, and the input unit 20 inputs light to each of the cores 11 via the core of each of the single-core fibers. The input unit 20 can change the amount of light input to each of the cores 11 by changing the power of the light input to each of the cores 11 or the input period of the light input to each of the cores 11.

[0025] The intensity measuring unit 50 includes a light receiving device such as a plurality of photodiodes, receives the light emitted from the other end of each of the cores 11, and outputs a signal indicating the intensity of the light emitted from the other end of each of the cores 11. The signal output from the intensity measuring unit 50 is input to the processor CP. The intensity measuring unit 50 is also configured to be movable between the optical path of the light emitted from the other end of each of the cores 11 and a position other than the optical path. Therefore, when measuring the intensity of the light emitted from at least one of the cores 11, the intensity measuring unit 50 is disposed on the optical path, but otherwise moves to a position other than the optical path.

[0026] The image data generating unit 30 includes a camera 31 and a conversion unit 32. The camera 31 captures the light emitted from the other end of each core 11, and generates image data of the light emitted from each core 11. At this time, the intensity measuring unit 50 moves to a location other than the optical path. The camera 31 is, for example, a CCD camera or the like, and has a plurality of light receiving elements arranged in a matrix, and each light emitted from the core 11 is received by each of the plurality of light receiving elements. Each light received by each light receiving element is output from the camera 31 as a pixel signal constituting an image. Therefore, each light emitted from the core 11 is represented by a plurality of pixels. The conversion unit 32 converts the signal of each pixel output from the camera 31 into a state that can be processed by the processor CP. For example, if the signal output from the camera 31 is an analog signal, the conversion unit 32 converts the signal into a digital signal, or assigns the address of the pixel to the signal of each pixel output from the camera 31. The signal including the image data generated by the image data generating unit 30 is input to the processor CP. The signal of each pixel contains information related to the intensity of light received by the light receiving element of the camera 31 that corresponds to that pixel.

[0027] The processor CP may be, for example, an integrated circuit such as a microcontroller, an integrated circuit (IC), a large-scale integrated circuit (LSI), or an application specific integrated circuit (ASIC), or a numerical control (NC) device. When an NC device is used, the processor CP may be one that uses a machine learning device, or one that does not use a machine learning device. The processor CP includes a light / dark core prediction unit 41, an extracted image data generation unit 42, a converted image data generation unit 43, and a composite image data generation unit 44.

[0028] The processor CP is electrically connected to the memory ME, and the processor CP stores information in the memory ME and reads out information stored in the memory ME. The memory ME is, for example, a non-transitory recording medium, and is preferably a semiconductor recording medium such as a random access memory (RAM) or a read only memory (ROM), but may include any known type of recording medium, such as an optical recording medium or a magnetic recording medium. Note that a "non-transitory" recording medium includes all computer-readable recording media except for transient, propagating signals, and does not exclude volatile recording media.

[0029] When light of the same intensity is input to each core 11 of the multi-core fiber 10, the bright and dark core prediction unit 41 predicts the dark and bright cores when the core from which the light with the lowest intensity is output is the dark core and the core from which the light with the highest intensity is output is the bright core. Specifically, the bright and dark core prediction unit 41 inputs light of the same intensity from the input unit 20 to each of the three cores 11 arranged in a non-linear manner among the cores 11 of the multi-core fiber 10. Then, using a signal input from the intensity measurement unit 50 to the processor CP, the bright and dark core prediction unit 41 arranges one end of a straight line having a length proportional to the intensity of each of the lights output from the three cores 11 on the same plane so as to be arranged in the same manner as the arrangement of the three cores 11, and defines a slope passing through the other end of each straight line. The bright and dark core prediction unit 41 determines the core 11 of the multi-core fiber 10 whose inclined surface is located on the side farthest from the plane as a bright core, and determines the core 11 of the core 11 of the multi-core fiber 10 whose inclined surface is located on the side closest to the plane as a dark core. The bright and dark core prediction unit 41 performs calculations to predict the bright and dark cores. Therefore, the straight line, plane, and inclined surface are imaginary and do not actually exist. The specific content of the bright and dark core prediction will be described later.

[0030] The extracted image data generating unit 42 extracts pixels in which light with an intensity between the lower limit and the upper limit of the dynamic range that the camera 31 can capture is captured from the image data, and generates extracted image data. The extracted image data generating unit 42 uses information related to the light intensity of the signal of each pixel in the image data output by the image data generating unit 30 to compare the light intensity of each pixel with the range of the dynamic range of the camera 31 stored in the memory ME. Then, the extracted image data generating unit 42 extracts pixels whose light intensity is between the lower limit and the upper limit of the dynamic range. The extracted image data generating unit 42 leaves the information of the extracted pixels as is, and replaces information related to the light intensity of pixels whose light intensity is not between the lower limit and the upper limit of the dynamic range with zero, and converts the image data into extracted image data. Note that information related to the light intensity of pixels whose light intensity is not between the lower limit and the upper limit of the dynamic range may be replaced with no information.

[0031] The converted image data generating unit 43 performs normalization to convert the light intensity of each pixel extracted by the extracted image data generating unit 42 into the intensity per unit amount of light incident on the core 11, and generates converted image data. For example, assume that light of a predetermined intensity is incident on each core 11 for 10 ms, and the image data generating unit 30 generates image data using that light. In the case where the unit amount is the amount of light incident on the core 11 for 1 ms, if there is a linear relationship between the amount of light incident on the core 11 and the light intensity indicated by each pixel of the image data generated by the image data generating unit 30, the converted image data generating unit 43 converts information related to the light intensity of each pixel extracted by the extracted image data generating unit 42 into information indicating 1 / 10 of the light intensity. However, in general, there is no linear relationship between the amount of light incident on the core 11 and the light intensity indicated by each pixel of the image data generated by the image data generating unit 30. Therefore, the converted image data generating unit 43 calculates the light intensity of each extracted pixel using a predetermined formula so that it becomes the intensity per unit amount of light incident on the core 11. In this way, by normalizing each extracted pixel, even if different amounts of light are incident on each core 11 from the incident section 20, the converted image data generated by the converted image data generation section 43 shows approximately the same light intensity for the same pixel.

[0032] The composite image data generating unit 44 synthesizes the multiple converted image data generated by the converted image data generating unit 43 to generate composite image data showing the intensity distribution of light emitted from each core 11. When two or more converted image data are generated for each core 11 by multiple incidence of different amounts of light from the incident unit 20 to each core 11, the ranges of pixels extracted by the extracted image data generating unit 42 and converted by the converted image data generating unit 43 are different in the two or more converted image data. Therefore, the composite image data generating unit 44 combines pixels of different ranges to generate composite image data. Note that when two or more converted image data have data of the same pixel, it is preferable to set the average of the light intensity indicated by the same pixel in each converted image data as the light intensity of the pixel in the composite image data. By averaging and synthesizing the light intensity of the same pixel in this way, the measurement error can be reduced compared to the case of selecting one of the same pixels extracted multiple times.

[0033] Next, a method for measuring the light intensity distribution of the multi-core fiber 10 using the multi-core fiber light intensity distribution measuring device 1 will be described.

[0034] Fig. 2 is a diagram showing an example of a flowchart of steps of the method for measuring light intensity distribution of the multi-core fiber 10 according to this embodiment. As shown in Fig. 2, the method for measuring light intensity distribution of this embodiment includes a bright and dark core prediction step S1 including a first incidence step S11, an intensity measurement step S12, and a calculation step S13, a second incidence step S2, an image data generation step S3, an extracted image data generation step S4, a converted image data generation step S5, and a composite image data generation step S6.

[0035] (First injection step S11) In this step, three cores 11 arranged in a non-linear manner are selected from the cores 11 of the multicore fiber 10. Then, the bright / dark core prediction unit 41 of the processor CP controls the incidence unit 20 to cause light of the same intensity to be incident on one end of these three cores 11.

[0036] (Strength measurement step S12) In this step, the intensity measuring unit 50 measures the intensity of light emitted from the other end of each of the three cores 11 into which light was incident in the first incident step S11. Therefore, the intensity measuring unit 50 is placed on the optical path of the light emitted from the other end of the three cores 11 so that the intensity of the light emitted from the other end of these cores 11 can be measured at least before this step. The intensity measuring unit 50 outputs a signal including information on each measured intensity to the processor CP. After that, the intensity measuring unit 50 moves to a location other than the optical path.

[0037] (Calculation step S13) In this step, the bright and dark core prediction unit 41 predicts, by calculation, a dark core from which the light with the lowest intensity is output and a bright core from which the light with the highest intensity is output when light with the same intensity is input to each core 11 of the multi-core fiber 10 based on information input from the intensity measurement unit 50. FIG. 3 is a diagram for explaining this step. In FIG. 3, the multiple cores 11 of the multi-core fiber 10 are respectively designated as cores 11a to 11d. As exemplified in the explanation of the bright and dark core prediction unit 41, in this step, the bright and dark core prediction unit 41 assumes three straight lines STa to STc having lengths proportional to the intensities of the lights output from the three cores 11a to 11c, using a signal input from the intensity measurement unit 50 to the processor CP. These straight lines STa to STc are virtual lines. Then, the bright and dark core prediction unit 41 arranges the straight lines STa to STc on one plane PL so that they are parallel to each other and one end of each of the straight lines STa to STc is arranged in the same arrangement as the three cores 11a to 11c. This plane PL is an imaginary plane. Next, the bright and dark core prediction unit 41 defines a slope SL passing through the other end of each of the straight lines STa to STc. This slope SL is a planar imaginary plane. The bright and dark core prediction unit 41 determines the core 11 of the multi-core fiber 10 whose slope SL is located closest to the plane PL as the dark core, and determines the core 11 of the multi-core fiber 10 whose slope SL is located farthest from the plane PL as the bright core. Note that in this step, it is sufficient to obtain the dark core and the bright core as a result, and when obtaining the dark core and the bright core, the slope SL may not be defined, but the gradient vector GR of the slope SL may be defined. In this case, the core 11 located closest to the gradient vector GR among the cores 11 is defined as a dark core, and the core 11 located closest to the gradient vector GR among the cores 11 is defined as a light core. Even when the gradient vector is used to find the dark core and the light core in this way, the dark core is ultimately the core located on the side of the core 11 whose slope SL is closest to the plane PL, and the light core is the core located on the side of the core 11 whose slope SL is furthest from the plane PL.

[0038] 3 shows an example in which light of the same intensity is incident on each of the cores 11a to 11c, the intensity of the light emitted from the core 11a is higher than the intensity of the light emitted from the cores 11b and 11c, and the intensity of the light emitted from the cores 11b and 11c is the same. In this example, the core 11a is a bright core, and the core 11d is a dark core. In this way, the dark cores and the bright cores are predicted.

[0039] The reason why the dark core and the bright core can be predicted in this way is as follows. That is, in a multi-core fiber, not limited to the multi-core fiber 10 shown in this embodiment, due to its manufacturing method, a bright core is located at one end side in a specific diameter direction of the cladding, and the intensity of the light emitted from the core gradually decreases from the one end side to the other end side in the diameter direction, and a dark core tends to be located at the other end side in the diameter direction. Therefore, as described above, based on the intensity of the light emitted from the three cores 11a to 11c positioned in a non-linear manner, the one end side and the other end side in the diameter direction can be known, and the core 11 located at the one end side can be determined as a bright core, and the core 11 located at the other end side can be determined as a dark core. Therefore, the bright core and the dark core can be easily predicted without measuring the light emitted from all the cores 11.

[0040] In the bright and dark core prediction step S1 of this embodiment, the dark core and the bright core are obtained based on the intensity of the light emitted from the three cores 11a to 11c as described above, so that the dark core and the bright core can be obtained more easily than when light is incident on all the cores 11 to obtain the dark core and the bright core. However, instead of the bright and dark core prediction step S1 of this embodiment, the dark core and the bright core may be obtained by other methods. For example, light of the same intensity may be incident on all the cores 11, the intensity of the light emitted from each core 11 may be measured by the intensity measurement unit 50, and the processor CP may obtain the dark core and the bright core based on the information on the intensity of the light emitted from each core 11 output from the intensity measurement unit 50. In this case, the dark core and the bright core can be obtained more accurately than when the dark core and the bright core are obtained by the example shown in FIG. 3.

[0041] (Second injection step S2) In this step, the processor CP controls the incident unit 20 to cause the incident unit 20 to simultaneously incident light of the same intensity on one end of each of the cores 11 of the multicore fiber 10. It is preferable that the wavelength of the light incident from the incident unit 20 to each of the cores 11 is the same. The incident unit 20 changes the amount of light incident on the cores so that the intensity of at least a part of the light emitted from each of the cores 11 falls within the range between the lower limit value and the upper limit value of the dynamic range of the camera 31 two or more times, and causes the light to be incident on each of the cores 11 multiple times.

[0042] In this way, as long as light is incident on each core 11 multiple times so that the intensity of at least a portion of the light emitted from each core 11 falls within the range between the above lower limit and upper limit two or more times, there is no particular limit to the range in which the amount of light incident on the core is changed. However, if the amount of light incident on the dark core when the peak intensity of the light emitted from the dark core is the lower limit of the dynamic range is set as the lower limit of the amount of light incident on each core, and the amount of light incident on the dark core when the peak intensity of the light emitted from the bright core is set as 1 / e 2 When the amount of light incident on the bright core when the intensity of the bright core is the upper limit value of the dynamic range is set as the upper limit amount of the amount of light incident on each core, in this step, it is preferable to make light incident on each core multiple times so that the amount of light incident on each core 11 changes in a range between the lower limit amount and the upper limit amount. Generally, each core of a multicore fiber has roughly the same characteristics. Therefore, when light of the same intensity is incident on each core 11, the light emitted from each core 11 has an intensity distribution close to each other. Therefore, by making light incident on each core 11 multiple times while changing the amount of light within such a range, in the case of a general optical fiber, two or more extracted image data described below can be generated for each core 11 based on the light emitted multiple times from each core 11.

[0043] (Image data generation step S3) In this step, the image data generating unit 30 captures the light emitted from the other end of each core 11 with the camera 31, and generates image data showing the light emitted from each core 11 with multiple pixels. The camera 31 receives each light emitted from each core 11 with multiple light receiving elements, and a signal for each pixel is formed from the signal output from each light receiving element. Therefore, the image data captured by the camera 31 and output from the image data generating unit 30 via the conversion unit 32 includes data in which each light emitted from each core 11 is shown with multiple pixels.

[0044] In this step, the incident unit 20 changes the amount of light incident on the core 11, and generates image data each time the light is incident on each core 11 multiple times. Each of the generated image data is input to the processor CP and stored in the memory ME. In the following description, the description will be focused on the light emitted from one core 11. FIG. 4 is a diagram showing image data with an exposure time of 3 ms, FIG. 5 is a diagram showing image data with an exposure time of 10 ms, and FIG. 6 is a diagram showing image data with an exposure time of 20 ms. These image data are image data of light emitted from a specific core 11. The exposure time can be considered as the period of incidence of light incident on the core 11, and the intensity of the light emitted from the incident unit 20 when capturing each image data is constant. Therefore, in this case, the exposure time is proportional to the amount of light incident on the core 11. As shown in FIGS. 4 to 6, it can be seen that as the amount of light incident on the core 11 increases, the apparent diameter of the light reflected in the image increases. This does not mean that the diameter of the light exiting core 11 increases as the amount of light entering core 11 increases; rather, because near the outer edge of the light, the intensity of the light becomes smaller than the lower limit of the dynamic range of camera 31, the smaller the amount of light entering core 11, the narrower the range of pixels that are exposed and appear as a light image.

[0045] (Extracted image data generation step S4) In this step, the extracted image data generating unit 42 extracts pixels in which light with an intensity between the lower limit and upper limit of the dynamic range that the camera 31 can capture is captured from the image data, and generates extracted image data. In this step, the extracted image data generating unit 42 reads out each image data from the memory ME, and generates extracted image data for each image data. Thus, the extracted image data generating unit 42 generates extracted image data each time the incident unit 20 causes light to be incident on each core 11 multiple times. Each generated extracted image data is stored in the memory ME.

[0046] FIG. 7 is a diagram showing the light intensity distributions of FIGS. 4 to 6. In this figure, data relating to FIG. 4, in which the exposure time is 3 ms, is shown by a dotted line, data relating to FIG. 5, in which the exposure time is 10 ms, is shown by a dashed line, and data relating to FIG. 6, in which the exposure time is 20 ms, is shown by a dashed line. FIG. 7(A) is a diagram showing a schematic diagram of the image data in FIGS. 4, 5, and 6. In FIG. 7(A), the solid line indicates 1 / e of the peak light intensity. 2 7 shows the periphery of light with a predetermined intensity below 1000 Hz. FIG. 7(B) shows the relationship between the light intensity distribution and the dynamic range of the camera 31. As shown in FIG. 7(A) and FIG. 7(B), when the exposure time is 3 ms, the light intensity of the pixels near the center of the light falls within the dynamic range of the camera 31, and the light intensity of the pixels other than the center of the light falls below the lower limit of the dynamic range. When the exposure time is 10 ms, the light intensity of the pixels near the center of the light exceeds the upper limit of the dynamic range, and the light intensity of the pixels near the periphery of the light falls below the lower limit of the dynamic range. When the exposure time is 20 ms, the area where the light intensity falls within the dynamic range is closer to the periphery of the light than when the exposure time is 10 ms.

[0047] In this embodiment, pixels whose light intensity is between the lower limit and upper limit of the dynamic range of the camera 31, i.e., pixels in the circular area surrounded by the dotted line in Fig. 7(A), the annular area surrounded by two dashed lines, and the annular area surrounded by two dashed and dotted lines, are extracted, and the light intensity of pixels whose light intensity is not between the lower limit and upper limit of the dynamic range is set to zero. Therefore, the extracted image data generated by the extracted image data generating unit 42 for each exposure time has the light intensity distribution shown in Fig. 7(C). In order to avoid the figure becoming complicated, the manner in which the light intensity is set to zero is not shown in Fig. 7(C).

[0048] (Converted image data generation step S5) In this step, the converted image data generation unit 43 converts the light intensity of each pixel extracted in the extracted image data generation step S4 into the intensity per unit amount of light incident on the core 11 to generate converted image data. The converted image data generation unit 43 reads each piece of extracted image data from the memory ME and generates converted image data for each piece of extracted image data. Therefore, the converted image data generation unit 43 generates converted image data every time the incidence unit 20 causes light to be incident on each core 11 multiple times. Each piece of generated converted image data is stored in the memory ME.

[0049] As described above, generally, the amount of light incident on the core 11 and the light intensity indicated by each pixel of the image data generated by the image data generating unit 30 are not linearly related. Therefore, the converted image data generating unit 43 uses a predetermined formula to calculate the light intensity of each extracted pixel so that it becomes the intensity per unit amount of light incident on the core 11, and generates the converted image data. The converted image data in which each pixel is converted in this manner has a light intensity distribution in which the light intensity distribution shown in FIG. 7(C) is compressed in the light intensity direction, as shown in FIG. 7(D). Note that, in order to avoid complicating the diagram, the scale of the light intensity direction is made different between FIG. 7(C) and FIG. 7(D). In this way, by performing normalization to convert the light intensity of each pixel extracted in the extracted image data into the intensity per unit amount of light incident on the core 11, the same pixel in each converted image data shows approximately the same intensity of light. In FIG. 7(D), in order to distinguish between each line, the curve showing the converted image data with an exposure time of 3 ms, the curve showing the converted image data with an exposure time of 10 ms, and the curve showing the converted image data with an exposure time of 20 ms are drawn slightly shifted from each other.

[0050] (Synthetic image data generation step S6) In this step, the composite image data generating unit 44 generates composite image data by combining two or more converted image data for each core 11. In this step, each converted image data is read from the memory ME, and the same pixels of each converted image data are combined. The converted image data of 3 ms shown by the dotted line, the converted image data of 10 ms shown by the dashed line, and the converted image data of 20 ms shown by the dashed line in FIG. 7(D) are combined. In this example, some pixels of the converted image data with an exposure time of 3 ms overlap with pixels of the converted image data with an exposure time of 10 ms, and other pixels indicating the area near the center of the light do not overlap with pixels of any of the converted image data. In addition, some pixels of the converted image data with an exposure time of 20 ms overlap with pixels of the converted image data with an exposure time of 10 ms, and other pixels indicating the area near the periphery of the light do not overlap with pixels of any of the converted image data. In this example, if there is only one data indicating the intensity of light for the same pixel of multiple converted image data, the data is used as the data indicating the intensity of light of the pixel in the composite image data. On the other hand, when the data indicating the light intensity for the same pixel in the multiple converted image data is 2 or more, as described above, the average of the light intensities indicated by the pixel in each converted image data is used as the data indicating the light intensity of the pixel in the composite image data. However, when the data indicating the light intensity for the same pixel in the multiple converted image data is 2 or more, the pixel in any of the converted image data may be used as the pixel in the composite image data. In this way, the composite image data having the light intensity distribution shown in Figure 7(D) is generated.

[0051] 8 is a diagram showing a composite image obtained by applying light of the same intensity to each core 11 from the entrance portion 20 multiple times with exposure times of 3 ms, 5 ms, 8 ms, 10 ms, 15 ms, 20 ms, 30 ms, 50 ms, 100 ms, 300 ms, and 500 ms. In this example, the composite image was visually almost identical to the image obtained with an exposure time of 5 ms.

[0052] As described above, the multi-core fiber light intensity distribution measuring device 1 of the present embodiment includes the incident unit 20 that simultaneously incidents light of the same intensity into one end of each of the cores 11 of the multi-core fiber 10, the image data generating unit 30 that captures light exiting the other end of each of the cores 11 with the camera 31 and generates image data indicating the light exiting each of the cores 11 with a plurality of pixels, the extracted image data generating unit 42 that extracts from the image data pixels at which light of an intensity between a lower limit value and an upper limit value of the dynamic range that can be captured by the camera 31 is captured, and generates extracted image data, the converted image data generating unit 43 that converts the light intensity of each pixel extracted by the extracted image data generating unit 42 into the intensity per unit amount of light incident on the core 11, and generates converted image data, and the composite image data generating unit 44 that combines the plurality of converted image data to generate composite image data indicating the intensity distribution of light exiting each of the cores. The incident unit 20 changes the amount of light incident on the core 11 so that the intensity of at least a portion of the light emitted from each core 11 falls within the range between the lower and upper limits of the dynamic range at least twice, and causes light to be incident on each core 11 multiple times, the image data generation unit 30 generates image data each time light is incident on each core 11, the extracted image data generation unit 42 generates extracted image data for each image data, the converted image data generation unit 43 generates converted image data for each extracted image data, and the composite image data generation unit 44 combines two or more converted image data for each core 11 to generate composite image data.

[0053] Moreover, the light intensity distribution measuring method of the multi-core fiber of the present embodiment includes a second incidence step S2 which is an incidence step of simultaneously injecting light of the same intensity into one end of each of the cores 11 of the multi-core fiber 10; an image data generating step S3 of capturing an image of light exiting from the other end of each of the cores 11 with the camera 31 and generating image data showing the light exiting from each of the cores 11 in a plurality of pixels; an extracted image data generating step S4 of extracting from the image data pixels where light of an intensity between a lower limit value and an upper limit value of the dynamic range that can be captured by the camera 31 is captured, and generating extracted image data; a converted image data generating step S5 of converting the light intensity of each pixel extracted in the extracted image data generating step S4 into an intensity per unit amount of light incident on the core 11, and generating converted image data; and a synthetic image data generating step S6 of combining the plurality of converted image data to generate synthetic image data showing the intensity distribution of light exiting from each of the cores 11. In a second incidence step S2, light is incident on each core 11 multiple times by changing the amount of light incident on the core 11 so that the intensity of at least a portion of the light emitted from each core 11 falls within the range between the lower and upper limits of the dynamic range at least twice; in an image data generation step S3, image data is generated each time light is incident on each core 11; in an extracted image data generation step S4, extracted image data is generated for each image data; in a converted image data generation step S5, converted image data is generated for each extracted image data; and in a composite image data generation step S6, two or more converted image data are combined for each core 11 to generate composite image data.

[0054] When a certain amount of light is made incident on each core 11 and the light emitted from each core 11 is imaged by the camera 31, there is a possibility that, of the light emitted from a certain core 11, the light incident on a certain range of pixels falls within the dynamic range of the camera 31, and the light incident on the other certain pixels falls outside the dynamic range. Furthermore, when an amount of light different from this amount of light is made incident on each core 11, of the light emitted from this specific core 11, the light incident on a range of pixels different from the certain range of pixels tends to fall within the dynamic range of the camera 31. Therefore, in the above-mentioned light intensity distribution measuring device 1 and light intensity distribution measuring method for a multi-core fiber, the amount of light incident on the core 11 is changed and the light is made to enter each core 11 multiple times so that the intensity of at least a part of the light emitted from each core 11 falls within the dynamic range two or more times. For this reason, the range of pixels extracted from the image data to become the extracted image data tends to be a different range each time light is incident on the core 11. By combining pixels with different ranges in this way, a wider range of pixels than one extracted image data is dynamically captured by the camera 31. However, when the amount of light incident on the core 11 is changed, the same pixel will show a different amount of light. Therefore, by performing normalization to convert the light intensity of each pixel extracted in the extracted image data into the intensity per unit amount of light incident on the core 11, the same pixel in each converted image data will show light of approximately the same intensity. In this way, by synthesizing two or more converted image data obtained by normalizing the extracted image data for each core 11, the range of light captured within the dynamic range of the camera can be made larger than when the light emitted from each core 11 is captured only once to generate image data showing the light intensity distribution. Therefore, according to the light intensity distribution measuring device 1 and the light intensity distribution measuring method for the multi-core fiber 10, the intensity distribution of light emitted from each core 11 can be measured more accurately.

[0055] FIG. 9 is a diagram showing that the composite image data can measure the light intensity distribution more accurately than one image data. In FIG. 9, the solid line shows the light intensity distribution when the exposure time is 5 ms, and the dashed line shows the light intensity distribution by the composite image shown in FIG. 11. As described above, the composite image shown in FIG. 8 was almost the same in appearance as the image when the exposure time is 5 ms. However, it was found that the light intensity distribution when the exposure time is 5 ms had a curve distorted outside about 9 μm from the center of the light, and could not be evaluated correctly due to poor S / N. In contrast, the light intensity distribution of the composite image had a curve with less distortion at least from the center of the light to about 12 μm, resulting in a good S / N. Therefore, as described above, according to the light intensity distribution measuring device 1 and the light intensity distribution measuring method of the multi-core fiber 10 of the present embodiment, the intensity distribution of the light emitted from each core 11 can be measured more accurately.

[0056] Although the present invention has been described above by taking the above-mentioned embodiment as an example, the present invention is not limited to the above-mentioned embodiment.

[0057] In the above embodiment, a multi-core fiber having four cores is exemplified, but the number of cores is not limited to four as long as it is plural.

[0058] In the above embodiment, the bright core and the dark core are predicted. However, if the amount of light incident on the core 11 is changed so that the intensity of at least a part of the light emitted from the core 11 falls within the range between the lower limit and the upper limit of the dynamic range at least twice, and light is incident on each core multiple times, the bright core and the dark core do not need to be predicted. In this case, the intensity measurement unit 50 and the bright and dark core prediction unit 41 are not necessary. In this case, the amount of light may be changed in multiple stages, for example, from a sufficiently small amount of light that causes the light emitted from all cores to be lower than the lower limit of the dynamic range to a sufficiently large amount of light that causes the light emitted from all cores to be higher than the upper limit of the dynamic range.

[0059] Moreover, the extracted image data generating step S4 may be modified as follows. Fig. 10 is a diagram for explaining this modified example. This diagram shows a state in which the peak intensity of light is lower than the upper limit of the dynamic range of the camera 31. The curve consisting of the solid line and the dashed line in Fig. 10 shows the light intensity distribution in the image data. In this modified example, even for pixels having a light intensity within the dynamic range of the camera 31, the light intensity distribution is 1 / e of the peak intensity of the light emitted from each core 11. 2 10 is not extracted, and the light intensity of the pixels in the region indicated by the dotted line in the above embodiment is set to zero, and extracted image data having the light intensity indicated by the solid line is generated.

[0060] The characteristics of the mode field diameter of light propagating through an optical fiber are generally 1 / e 2 Therefore, even if the peak intensity of the light emitted from the core is 1 / e 2 Even if an intensity lower than the intensity is within the dynamic range, by not extracting light of that intensity, it is possible to remove light components that are not necessary for the general process of determining light characteristics, thereby facilitating the process.

[0061] In the multi-core fiber 10, crosstalk may occur between the cores 11. However, if the light intensity of this crosstalk is less than 1 / e 2 If the intensity is equal to or less than this, the effect of crosstalk can also be eliminated by implementing the above modification. [Industrial Applicability]

[0062] According to the present invention, it is possible to provide a light intensity distribution measurement device for a multi-core fiber and a light intensity distribution measurement method for a multi-core fiber, which are capable of more accurately measuring the intensity distribution of light emitted from each core, and which can be used in fields such as optical communications, for example. [Explanation of symbols]

[0063] 1...Light intensity distribution measuring device 10. Multicore fiber 11. Core 20...Incidence section 30...Image data generating unit 41...Bright / dark core prediction section 42 Extracted image data generating unit 43... Transformed image data generating unit 44...Synthetic image data generation unit 50 Strength measurement section CP···Processor ME···Memory S1 · · · Bright and dark core prediction step S2: Second entrance step (entrance step) S3: Image data generation step S4: Extracted image data generation step S5: Converted image data generation step S6: Composite image data generation step

Claims

1. an input section for simultaneously inputting light of the same intensity into one end of each of the cores of the multi-core fiber; an image data generating unit that captures an image of the light emitted from the other end of each of the cores with a camera and generates image data that shows the light emitted from each of the cores using a plurality of pixels; an extracted image data generating unit that generates extracted image data by extracting from the image data the pixels at which light with an intensity between a lower limit value and an upper limit value of a dynamic range that can be captured by the camera is captured; a converted image data generating unit that converts the light intensity of each of the pixels extracted by the extracted image data generating unit into an intensity per unit amount of light incident on the core, to generate converted image data; a composite image data generating unit that combines a plurality of the converted image data to generate composite image data indicating an intensity distribution of light emitted from each of the cores; Equipped with the incidence unit changes the amount of light incident on the cores so that an intensity of at least a portion of the light emitted from each of the cores falls within a range between the lower limit value and the upper limit value two or more times, thereby causing light to be incident on each of the cores a plurality of times; the image data generation unit generates the image data each time light is incident on each of the cores, the extracted image data generating unit generates the extracted image data for each of the image data; the converted image data generating unit generates the converted image data for each of the extracted image data; The composite image data generating unit generates the composite image data by combining two or more of the converted image data for each of the cores.

1. A multicore fiber light intensity distribution measuring device comprising:

2. When light of the same intensity is incident on each of the cores, the core from which light with the lowest intensity is output is defined as a dark core, and the core from which light with the highest intensity is output is defined as a bright core. The amount of light incident on the dark core when the peak intensity of the light output from the dark core is the lower limit is defined as a lower limit amount of the amount of light incident on each of the cores, and 1 / e of the peak intensity of the light output from the bright core is defined as a lower limit amount of the amount of light incident on the dark core when the peak intensity of the light output from the bright core is the lower limit amount of the amount of light incident on the dark core. ２ the amount of light incident on the bright core when the intensity of the bright core reaches the upper limit is set to an upper limit of the amount of light incident on each of the cores, the incident unit causes light to be incident on each of the cores multiple times such that the amount of light incident on the cores varies within a range between the lower limit and the upper limit.

2. The optical intensity distribution measuring device for a multi-core fiber according to claim 1 .

3. a bright and dark core prediction unit that predicts the bright cores and the dark cores, The bright and dark core prediction unit causes light of the same intensity to be incident on each of the three cores arranged in a non-linear manner, arranges one end of a straight line having a length proportional to the intensity of the light emitted from the three cores on the same plane so as to be arranged in the same manner as the arrangement of the three cores, and defines a slope passing through the other end of each of the straight lines. When this is done, the core of each of the cores of the multicore fiber whose slope is located on the side farthest from the plane is determined as the bright core, and the core whose slope is located on the side closest to the plane is determined as the dark core.

3. The multi-core fiber light intensity distribution measuring device according to claim 2 .

4. The composite image data generating unit sets an average of light intensities at the same pixel of each of the converted image data as the light intensity at that pixel of the composite image data.

4. The device for measuring light intensity distribution of a multicore fiber according to claim 1 .

5. The extracted image data generating unit calculates 1 / e ２ The pixel in which light having an intensity lower than the intensity of the light is captured is not extracted.

5. The device for measuring light intensity distribution of a multicore fiber according to claim 1 .

6. an input step of simultaneously inputting light of the same intensity into one end of each core of the multicore fiber; an image data generating step of capturing an image of light emitted from the other end of each of the cores with a camera and generating image data showing the light emitted from each of the cores with a plurality of pixels; an extracted image data generating step of generating extracted image data by extracting from the image data the pixels at which light with an intensity between a lower limit value and an upper limit value of a dynamic range that can be captured by the camera is captured; a converted image data generating step of converting the light intensity of each of the pixels extracted in the extracted image data generating step into an intensity per unit amount of light incident on the core to generate converted image data; a composite image data generating step of generating composite image data indicating an intensity distribution of light emitted from each of the cores by combining a plurality of the converted image data; Equipped with In the incidence step, the amount of light incident on each of the cores is changed so that the intensity of at least a portion of the light emitted from each of the cores falls within the range between the lower limit value and the upper limit value two or more times, and light is incident on each of the cores a plurality of times; In the image data generating step, the image data is generated every time light is incident on each of the cores, In the extraction image data generating step, the extraction image data is generated for each of the image data; In the converted image data generating step, the converted image data is generated for each of the extracted image data; In the composite image data generating step, two or more of the converted image data are combined for each of the cores to generate the composite image data.

13. A method for measuring a light intensity distribution of a multicore fiber.

7. When light of the same intensity is incident on each of the cores, the core from which light with the lowest intensity is output is defined as a dark core, and the core from which light with the highest intensity is output is defined as a bright core. The amount of light incident on the dark core when the peak intensity of the light output from the dark core is the lower limit is defined as a lower limit amount of the amount of light incident on each of the cores, and 1 / e of the peak intensity of the light output from the bright core is defined as a lower limit amount of the amount of light incident on the dark core when the peak intensity of the light output from the bright core is the lower limit amount of the amount of light incident on the dark core. ２ When the amount of light incident on the bright core when the intensity of the bright core reaches the upper limit is set to an upper limit of the amount of light incident on each of the cores, in the incident step, light is incident on each of the cores multiple times such that the amount of light incident on the cores varies within a range between the lower limit and the upper limit. The method for measuring a light intensity distribution of a multi-core fiber according to claim 6 .

8. A bright and dark core prediction step of predicting the bright core and the dark core, In the bright and dark core prediction step, light of the same intensity is incident on each of the three cores arranged in a non-linear manner, and one end of a straight line having a length proportional to the intensity of the light emitted from the three cores is arranged on the same plane so as to be arranged in the same manner as the arrangement of the three cores. When a slope passing through the other end of each of the straight lines is defined, the core of each of the cores of the multicore fiber whose slope is located on the side farthest from the plane is defined as the bright core, and the core whose slope is located on the side closest to the plane is defined as the dark core. The method for measuring a light intensity distribution of a multi-core fiber according to claim 7 .

9. In the synthetic image data generating step, an average of light intensities at the same pixel of each of the converted image data is set as the light intensity at that pixel of the synthetic image data. The method for measuring a light intensity distribution of a multi-core fiber according to any one of claims 6 to 8.

10. In the extraction image data generation step, 1 / e ２ The pixel in which light having an intensity lower than the intensity of the light is captured is not extracted. The method for measuring a light intensity distribution of a multi-core fiber according to any one of claims 6 to 9.

Images