JP5718032B2 - Optical fiber cut surface measurement method - Google Patents

Description

  The present invention relates to an optical fiber cut surface measuring method for measuring a characteristic value related to a dimension (coating dimension) of a coating layer of a cut surface of an optical fiber.

  The demand for optical fibers used for optical communications is increasing worldwide. In the optical fiber, a coating layer made of resin is formed on a core and a clad made of glass. The coating layer generally consists of two layers, a primary coating layer and a secondary coating layer. As one of methods for measuring the coating dimensions of an optical fiber, an optical fiber cut surface measuring method using a dedicated end face cutting device and an end view (cut surface projection) measuring device is known (for example, , See Patent Document 1).

  In the measurement method described in Patent Document 1, an optical fiber is cut by a cutting device, and the cut surface is heated by a heater (heat gun) to measure the coating size of the cut surface. Note that this heating repairs the recessed portion of the coating layer that is depressed by the cutting tool blade during cutting. According to this optical fiber cut surface measurement method, the entire cut surface is focused, the cut surface can be accurately dimensioned, no errors occur in the calculation processing of the end-view measuring instrument, and many coating dimensions can be measured per unit time. Is supposed to be possible.

Japanese Patent Laid-Open No. 7-71927

  However, when the optical fiber is cut, the coating layer made of resin is soft and thus crushed greatly. When the characteristic value related to the coating size of the cut surface in a state where the coating layer is crushed is measured, a problem that the measurement cannot be performed correctly occurs.

  The present invention has been made in view of the above, and provides a measurement method capable of obtaining a true value with extremely small variation in measurement of a characteristic value related to a covering dimension of a cut surface of an optical fiber. For the purpose.

In order to solve the above problems, an optical fiber cut surface measuring method according to the present invention includes:
A cutting step of cutting an optical fiber having a core, a clad, a primary coating layer, and a secondary coating layer with a cutting device;
A heating step of heating the cut surface of the cut optical fiber with a heater;
Measuring a characteristic value related to a covering dimension of a cut surface of the heated optical fiber with an end view measuring instrument,
In the heating step, heating to make the coating surface temperature of the cut surface of the optical fiber strand 47 [° C.] or higher is performed for a heating time of 7 [seconds] or longer.

  Preferably, in the heating step, heating is performed so that the coating surface temperature of the cut surface of the optical fiber is 47 [° C.] or higher and 70 [° C.] or lower for a heating time of 7 [seconds] or longer.

  Preferably, the characteristic value related to the coating size of the cut surface of the optical fiber is at least one of an outer diameter and a non-circularity of the secondary coating layer.

  According to the present invention, in the measurement of the characteristic value related to the coating size of the cut surface of the optical fiber, the influence of the collapse of the coating layer due to the cutting of the optical fiber can be completely eliminated, and the variation is extremely small. A more true value can be obtained.

It is sectional drawing of an optical fiber strand. It is a figure which shows a cutting device. It is a figure which shows the heater which heats an optical fiber strand. It is a figure which shows an end view measuring device. It is a figure which shows the secondary coating diameter and secondary coating non-circularity with respect to the frequency | count of repeated measurement. It is a figure which shows the secondary coating diameter with respect to the elapsed time after a heating for every coating | coated surface temperature. It is a figure which shows the secondary coating diameter with respect to the elapsed time after a heating for every heating time. (A) is a figure which shows the image of the cut surface of the optical fiber strand immediately after a cutting | disconnection. (B) is a figure which shows the edge data of the cut surface of the optical fiber strand immediately after a cutting | disconnection. (A) is a figure which shows the image of the cut surface of the optical fiber strand after a heating. (B) is a figure which shows the edge data of the cut surface of the optical fiber strand after a heating.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the illustrated examples.

  First, the configuration of an apparatus used in the present embodiment will be described with reference to FIGS. FIG. 1 shows a cut surface 10 a of the optical fiber 10. FIG. 2 shows the cutting device 20. FIG. 3 shows a heater 30 that heats the optical fiber 10. FIG. 4 shows an end view measuring instrument 40.

  In the present embodiment, an operator cuts the optical fiber strand 10 shown in FIG. 1 and heats the cut surface 10a of the optical fiber strand 10 to an appropriate temperature for an appropriate time. Then, the operator measures the secondary coating diameter and secondary coating non-circularity (the outer diameter and non-circularity of the secondary coating layer 12B) of the cut surface 10a of the optical fiber 10 by the end-view measurement method. .

  In the conventional optical fiber cut surface measuring method, the measured secondary coating diameter may be smaller than the true value, and the measured secondary coating non-circularity may be larger than the true value. In such a case, the cut surface may be crushed in some cases, and the crushed state is not uniform. For this reason, even if the cut surface is simply repaired by heating the cut surface with a heater, even if the overall focus is achieved by the projection of the cut surface, the measured value of the coating dimension is still highly variable. There was a risk that many things would be understood.

  Actually, the standard deviation of the measurement dimension of the core and the clad in the optical fiber manufactured in a certain period and the standard deviation of the measurement dimension of the coating layer are aggregated and compared. The deviation is larger. For this reason, it is estimated that the variation in the measured value is not caused by the manufactured optical fiber itself, but rather is caused by a problem of the measuring method. The present embodiment provides an optical fiber cut surface measuring method that improves measurement accuracy and performs more accurate secondary coating diameter and secondary coating non-circularity measurement.

  As shown in FIG. 1, the optical fiber strand 10 includes a core and clad 11 and a coating layer 12. The coating layer 12 includes a primary coating layer 12A and a secondary coating layer 12B. The cut surface 10 a of the optical fiber strand 10 is a surface that is perpendicular and smooth to the axial direction of the optical fiber strand 10. The optical fiber 10 is a general single mode optical fiber.

  The core and clad 11 are made of quartz (glass) and are arranged at the center of the axis of the optical fiber 10. In the core and the clad 11, the optical signal incident on the core is totally reflected at the boundary surface with the clad, so that the core becomes an optical waveguide.

The core and the clad 11 are covered with a primary coating layer 12A. The secondary coating layer 12B is coated on the primary coating layer 12A. The material of the primary coating layer 12A and the secondary coating layer 12B is an ultraviolet (UV) curable resin. The primary coating layer 12A is softer than the secondary coating layer 12B, and has a cushioning effect and high adhesion to the core and the clad 11. The secondary coating layer 12B is harder than the primary coating layer 12A, and protects the core and the cladding 11 from external pressure, friction, and the like.
The primary coating layer 12A has a Young's modulus of 0.3 to 1.5 [MPa], and the secondary coating layer 12B has a Young's modulus of 300 to 1000 [MPa].

  The refractive index of the primary coating layer 12A is 1.495. The refractive index of the secondary coating layer 12B is 1.510. The difference between these refractive indexes is 0.015, which is relatively small. The measurement of the coating diameter includes an end view measurement method and a side view measurement method. The side view measurement method does not require cutting of the optical fiber and has high measurement accuracy. However, when the side view measurement method has no or small difference in refractive index between the primary coating layer and the secondary coating layer of the optical fiber to be measured, the outer diameter of the primary coating layer and the secondary coating layer (coating diameter) ) Cannot be measured. Therefore, in the present embodiment, the secondary coating diameter and the secondary coating non-circularity (the outer diameter and non-circularity of the secondary coating layer 12B) of the optical fiber 10 are measured by the end view measurement method. Yes.

  For cutting the optical fiber 10, a cutting device 20 shown in FIG. 2 is used. The cutting device 20 includes a blade 21 and folders 22, 23, and 24. The blade 21 is a diamond blade that cuts into the optical fiber 10. The folders 22, 23 and 24 support the optical fiber 10. The blade 21 is movable in a direction perpendicular to the axial direction of the optical fiber 10 supported by the folders 22, 23, and 24. The folders 23 and 24 are movable in the axial direction of the optical fiber 10.

  At the time of cutting the optical fiber 10, the optical fiber 10 fixed by the folders 22, 23, 24 is pushed by the blade 21 from the direction perpendicular to the axial direction to make a cut, and the folders 23, 24 The optical fiber strands 10 are pulled in the outer axial direction. As a result, the cut grows at once, and the optical fiber 10 is cut smoothly and perpendicularly to the axial direction. This surface is a cut surface 10a.

For heating the optical fiber 10, a heater (heat gun) 30 shown in FIG. 3 is used. The heater 30 heats the object by outputting warm air. The heater 30 includes a temperature adjustment knob (not shown) as an operation unit, and by switching the temperature adjustment knob, set values corresponding to a plurality of heating temperatures can be switched. Table 1 shows the heating temperature (temperature of the warm air of the heater 30) for each set value.

  The end view measuring instrument 40 shown in FIG. 4 is used for measuring the cut surface of the optical fiber 10. The end view measuring device 40 is a measuring device using the end view method. As the measurement sample, an optical fiber 10 cut to a length of 2 to 3 [m] is used. The end view measuring instrument 40 includes a display unit 41 and connection units 42 and 43. The end view measuring instrument 40 includes a light source, an optical system (objective lens), an imaging unit, an image processing unit (all not shown), and the like.

  The display unit 41 displays information such as an image obtained by capturing the cut surface 10a of the optical fiber 10 and the measurement result of the secondary coating diameter and the secondary coating non-circularity. One end of the cut optical fiber 10 is connected to the connecting portion 42. Further, the other end having the cut surface 10 a of the cut optical fiber 10 is connected to the connection portion 43. The connection portion 42 and the connection portion 43 are optical connection portions with the optical fiber strand 10, and light emitted from the light source in the end view measuring instrument 40 enters the optical fiber strand 10 at the connection portion 42. Is done. Further, in the connection portion 43, the cut surface 10 a of the optical fiber 10 is imaged from the axial direction through the optical system by the imaging portion in the end view measuring instrument 40. The image processing unit in the end view measuring instrument 40 analyzes the image of the cut surface 10a imaged by the imaging unit, calculates the secondary coating diameter and the secondary coating non-circularity, and displays the measurement result on the display unit 41. indicate.

  Next, a method for measuring the secondary coating diameter and the secondary coating non-circularity of the cut surface 10a of the optical fiber 10 will be described. First, an operator sets the optical fiber strand 10 in the cutting device 20 shown in FIG. 2, and cuts both ends with a length of 2 to 3 m. After this cutting, the cut surface 10a of the optical fiber 10 is crushed. Then, the operator uses the heater 30 shown in FIG. 3 to apply hot air from the axial direction to heat the cut surface 10 a at one end of the cut optical fiber 10. More specifically, the cut surface 10a of the optical fiber 10 is heated to a surface temperature (covering surface temperature) of the coating layer 12 of 47 [° C.] or higher for a heating time of 7 [seconds] or longer. By making the coating surface temperature and heating time of the cut surface 10a during heating within these ranges, the influence of the crushing of the coating layer 12 of the optical fiber 10 on the measurement of the secondary coating diameter and secondary coating non-circularity can be achieved. It can be reduced and the extra heating time can be suppressed.

  And an operator connects the optical fiber strand 10 after a heating to the end view measuring device 40 shown in FIG. More specifically, the operator connects one end of the optical fiber 10 that has not been heated to the connection portion 42, and connects one end having the heated cut surface 10 a to the connection portion 43. Then, light is incident on the optical fiber strand 10 from the connection portion 42 by the end-view measuring instrument 40, and the heated cut surface 10a of the optical fiber strand 10 is imaged by the connection portion 43. Then, the image of the imaged cut surface 10a is processed by the end view measuring device 40 to calculate the secondary coating diameter and the secondary coating non-circularity, and the calculation result and the image of the imaged cut surface 10a are obtained. It is displayed on the display unit 41. At this time, in practice, the end view measuring instrument 40 also measures the outer diameter and non-circularity of the primary coating layer 12A of the cut surface 10a.

  Next, with reference to FIG. 5 to FIG. 9, experimental results regarding the measurement of the secondary coating diameter and the secondary coating non-circularity of the cut surface 10 a of the optical fiber 10 will be described. FIG. 5 shows the secondary coating diameter and secondary coating non-circularity with respect to the number of repeated measurements. FIG. 6 shows the secondary coating diameter with respect to the elapsed time after heating for each coating surface temperature. In FIG. 7, the secondary coating | coated diameter with respect to the elapsed time after a heating for every heating time is shown. FIG. 8A shows an image of the cut surface of the optical fiber immediately after cutting. FIG. 8B shows edge data (XY data) of the cut surface of the optical fiber immediately after cutting. FIG. 9A shows an image of the cut surface of the optical fiber after heating. FIG. 9B shows edge data (XY data) of the cut surface of the optical fiber after heating.

  As shown in FIG. 5, the secondary coating diameter [μm] and the secondary coating non-circularity [%] of the cut surface 10 a of the optical fiber 10 immediately after being cut by the cutting device 20 are repeatedly measured by the end view measuring device 40. did. At this time, the interval between repeated measurements (number of times) was set to 0.5 [seconds]. Further, FK11 made by Photon Kinetics was used as the cutting device 20.

  Looking at the measurement results over time, the secondary coating diameter gradually increased and became saturated at some point. Conversely, the secondary coating non-circularity gradually decreased. According to this measurement result, it can be estimated that the coating layer 12 is crushed by cutting, but is recovered over time.

  Next, an appropriate coating surface temperature of the coating layer 12 in the heating of the surface (cut surface 10a) of the coating layer 12 of the optical fiber 10 will be described with reference to FIG. The optical fiber 10 was cut, the cut surface 10a was heated with the heater 30, and the change over time in the secondary coating diameter after the heating was measured.

Specifically, the optical fiber 10 is cut by the cutting device 20, the set value of the heater 30 is switched, and the cut surface 10a of the optical fiber 10 is operated for the heater 30 (7 [seconds]). And the coating surface temperature of the coating layer 12 on the cut surface 10a was measured with a non-contact thermocouple thermometer. The relationship between the set value of the heater 30 and the coating surface temperature is shown in Table 2 below. The coating surface temperature when the heater 30 was not heated was 26 [° C.].

  Then, by switching the set value of the heater 30, the optical fiber strand 10 is cut immediately after cutting at each stage of the coating surface temperature (37 [° C.], 47 [° C.], 57 [° C.]) shown in Table 2. The surface 10a was heated for a predetermined heating time (operation time of the heater 30 (7 [seconds])). And the secondary coating diameter of the cut surface 10a was measured by the elapsed time (0 (immediately after heating), 3, 6, 9 [minutes]) immediately after cutting and after the end of heating. Then, the measurement result shown in FIG. 6 was obtained.

  From the measurement results of FIG. 6, when heated, if the coating surface temperature was 47 [° C.], the secondary coating diameter recovered immediately after heating, and the secondary coating diameter was almost saturated over time. Value. Since it was the same at the coating surface temperature of 57 [° C.], it was found that the crushing due to cutting (cutting) recovered immediately. However, at a coating surface temperature of 37 [° C.], the value immediately after heating is not a saturated value, but the value of the secondary coating diameter stabilizes after an elapsed time of 6 [minutes] after heating. It was found that crushing due to was not recovered.

  That is, in the heating after cutting the optical fiber 10, the coating surface temperature is preferably set to 47 [° C.] or higher. Moreover, the value where the coating surface temperature is higher than 70 [° C.] is a level at which the folders 23 and 24 holding the optical fiber 10 are very hot when handled by hand, and measures must be taken for safety. For this reason, it is necessary to suspend the work until the temperature of the folder is lowered to be able to be handled by hand (about 60 seconds), and in the heating after cutting the optical fiber 10, the coating surface temperature is set to 70 [° C.] or less. It is preferable to do. Therefore, in the heating after cutting the optical fiber 10, the appropriate range of the coating surface temperature is 47 [° C.] or more and 70 [° C.] or less.

  Furthermore, when the coating surface temperature exceeds 57 [° C.], the folders 23 and 24 holding the optical fiber 10 are hot when handled by hand, and it is preferably at a level where measures must be taken for safety. For this reason, it is more preferable that the coating surface temperature is 57 [° C.] or less because the operation does not need to be interrupted until the temperature is lowered to a temperature at which the folder can be handled by hand.

  Then, with reference to FIG. 7, the suitable heating time in the heating of the surface (cut surface 10a) of the coating layer 12 of the optical fiber strand 10 is demonstrated. The optical fiber 10 was cut, the cut surface 10a was heated with the heater 30, and the change in the secondary coating diameter with time was measured.

  Specifically, the optical fiber 10 is cut by the cutting device 20 and the set surface temperature of the heater 30 is changed to 47 [° C.] by switching the set value of the heater 30, and the cut surface 10 a of the optical fiber 10 immediately after cutting is cut. Was heated at each stage of the heating time (0 (no heating), 5, 7, 11 [seconds]). Then, the secondary coating diameter of the cut surface 10a was measured immediately after cutting and the elapsed time after heating (0 (immediately after heating), 3, 6, 9 [minutes]). Then, the measurement result shown in FIG. 7 was obtained.

  From the measurement results of FIG. 7, if the heating time is 7 [seconds] or 11 [seconds], the secondary coating diameter immediately after heating after cutting is already saturated even when viewed over time, and crushing has recovered. I can judge. However, when the heating time is changed with time of 5 [seconds] without heating, the value of the coating diameter continues to increase, so that crushing cannot be recovered immediately. That is, it is preferable that the heating time is 7 [seconds] or longer after the optical fiber 10 is cut.

  Furthermore, considering the time required for the inspection man-hour, the heating time should be short. For this reason, after the optical fiber strand 10 is cut, it is preferable that the heating time is 11 [seconds] or less, and it is more preferable that the heating time is 9 [seconds] or less.

  As shown to Fig.8 (a), the end view measuring device 40 actually imaged the cut surface 10a of the optical fiber strand 10 immediately after a cutting | disconnection (before a heating), and acquired the image. Further, as shown in FIG. 8B, the end view measuring device 40 captures edge data of the cut surface image of FIG. 8A (XY data of the outer diameter of the secondary coating layer 12B after image processing). The analysis was performed. Similarly, as shown in FIG. 9A, the end-view measuring instrument 40 actually images the cut surface 10a of the optical fiber 10 after heating in the above-mentioned range of the appropriate coating surface temperature and heating temperature. The image was acquired. Further, as shown in FIG. 9B, the end view measuring instrument 40 took in the edge data of the cut surface image of FIG.

  The difference between the image and the edge data before and after the heating was clear, and it was found that the crushing of the coating layer 12 was recovered by the heating. When viewed over time, the collapse of the coating layer 12 naturally recovers without heating, but the recovery time of the collapse of the coating layer 12 can be shortened by heating.

  As described above, according to the present embodiment, the operator cuts the optical fiber 10 with the cutting device 20, and sets the covering surface temperature to 47 [° C.] on the cut surface 10 a of the cut optical fiber 10. The above heating is performed by the heater 30 with a heating time of 7 [seconds] or more. Then, the operator measures the secondary coating diameter and the secondary coating non-circularity as characteristic values related to the coating size of the cut surface 10 a of the heated optical fiber 10 by the end view measuring instrument 40. For this reason, in the measurement of the secondary coating diameter and the secondary coating non-circularity of the cut surface 10a of the optical fiber 10, a true value with extremely small variation can be obtained.

  Further, the coating surface temperature in heating the cut surface 10a of the optical fiber 10 is set to 70 [° C.] or less. For this reason, it can prevent that the folders 23 and 24 which are suppressing the optical fiber strand 10 become hot, and can improve an operator's safety. Moreover, when the coating surface temperature in heating the cut surface 10a of the optical fiber strand 10 is set to 57 [° C.] or less, the folders 23 and 24 holding the optical fiber strand 10 are further prevented from becoming hot, and the operator's Safety can be further increased.

  Further, the heating time in heating the cut surface 10a of the optical fiber 10 is set to 11 [seconds] or less. For this reason, in the measurement of the secondary coating diameter and the secondary coating non-circularity of the cut surface 10a of the optical fiber 10, a true value can be obtained and the measurement time can be shortened. If the heating time for heating the cut surface 10a of the optical fiber 10 is set to 9 [seconds] or less, the measurement time for the secondary coating diameter and the secondary coating non-circularity of the cut surface 10a of the optical fiber 10 is reduced. It can be further shortened.

  In addition, the description in the said embodiment is an example of the optical fiber cut surface measuring method which concerns on this invention, and is not limited to this.

  For example, in the above embodiment, the secondary coating diameter and the secondary coating non-circularity of the optical fiber 10 having a small refractive index difference between the primary coating layer 12A and the secondary coating layer 12B are measured. It is not something. The secondary coating diameter and secondary coating non-circularity of an optical fiber having a large refractive index difference between the primary coating layer and the secondary coating layer can also be measured by the optical fiber coating dimension measuring method of the present embodiment.

  In addition, the detailed configuration and detailed operation of each component of the equipment used in the optical fiber coating dimension measuring method described in the above embodiment can be changed as appropriate without departing from the spirit of the present invention. Of course.

DESCRIPTION OF SYMBOLS 10 Optical fiber 10a Cut surface 11 Core and clad 12 Coating layer 12A Primary coating layer 12B Secondary coating layer 20 Cutting device 21 Blade 22, 23, 24 Folder 30 Heater 40 End view measuring device 41 Display part 42, 43 Connection Part

Claims (3)

A cutting step of cutting an optical fiber having a core, a clad, a primary coating layer, and a secondary coating layer with a cutting device;
A heating step of heating the cut surface of the cut optical fiber with a heater;
Measuring a characteristic value related to a covering dimension of a cut surface of the heated optical fiber with an end view measuring instrument,
A method for measuring an optical fiber cut surface, wherein in the heating step, heating is performed so that a coating surface temperature of the cut surface of the optical fiber is 47 [° C.] or higher in a heating time of 7 [seconds] or longer.   2. The optical fiber cut surface according to claim 1, wherein in the heating step, heating is performed so that the temperature of the cut surface of the optical fiber strand is 47 ° C. or higher and 70 ° C. or lower for a heating time of 7 seconds or longer. Measuring method.   3. The optical fiber cut surface measuring method according to claim 1, wherein the characteristic value related to the coating size of the cut surface of the optical fiber is at least one of an outer diameter and a non-circularity of the secondary coating layer.