JPH0581678U - Optical fiber base material eccentricity measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] To measure the eccentricity between the center of the core and the center of the clad in the optical fiber preform in a single measurement in a short time. The light beam generators 2 and 4 and the photodetectors 3 and 5 that receive the light beam and detect its incident position are
Group, the light beams are arranged so as to be substantially perpendicular to each other, and the optical fiber preform 1 is moved in the direction of approximately 45 degrees with respect to both the light beams in the vicinity of the intersection of the light beams, 1 with respect to the incident position from each photodetector
Obtain dimensional distribution data.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an apparatus for measuring a positional deviation amount (eccentricity amount) between a center of a core part of an optical fiber preform and a center of a clad part.

[0002]

[Prior Art]

 The optical fiber preform is for making an optical fiber by melting it and drawing and spinning it. The optical fiber preform is usually made of quartz glass or the like, and has a core part in the center and a clad part in the periphery. In the optical fiber made by drawing and spinning, the positional relationship of the base material is maintained as it is, so if the core part is eccentric in the base material, the eccentricity will remain in the manufactured optical fiber. As a result, the optical characteristics of the device are affected. Therefore, the amount of eccentricity is measured at the base metal stage.

Conventionally, an eccentricity measuring device for an optical fiber preform uses a photodetection system that combines a laser generator that generates a light beam and a photodetector that receives the light. It is configured by moving the measured optical fiber preform. That is, the light beam is applied to the side surface of the optical fiber preform to be measured, and the light beam transmitted through the optical fiber preform is incident on the photodetector to detect the incident position. The optical fiber preform is moved in one direction while the incident position is detected in this way. Then, since the refraction angle of the light beam varies depending on the refractive index in the optical fiber preform, the incident position changes with the movement. Since this change in the incident position corresponds to the change in the refractive index, the refractive index distribution in the moved one direction is obtained. After that, the optical fiber preform is rotated by 90 degrees and measured while moving in the same manner to obtain the refractive index distributions in other directions (different by 90 degrees). Then, the amount of eccentricity is calculated from the refractive index distribution in these two directions.

[0004]

[Problems to be solved by the device]

 However, since the conventional optical fiber preform eccentricity measuring device needs to measure the refractive index distribution in two directions, the measurement is repeated twice in order to measure the eccentricity of one optical fiber preform. However, there is a problem in that measurement time is required.

In view of the above, the present invention makes it possible to measure the refractive index distribution in two directions by moving the optical fiber preform to be measured once, and thus it is possible to measure the amount of eccentricity in one measurement. However, it is an object of the present invention to provide an eccentricity measuring device for an optical fiber preform, which can shorten the measuring time.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the optical fiber preform eccentricity measuring device according to the present invention uses two sets of a light beam generator and a photodetector. The light beams from the respective light beam generators are arranged to face each other so that they are incident on the photodetector, and two sets of light beam generators and photodetectors are arranged so that the light beams are substantially orthogonal to each other. Adjust the position. Then, the optical fiber preform to be measured is placed in the vicinity of the intersection of the light beams, and is moved in one direction in which both the light beams cross each other (for example, a direction of about 45 degrees with respect to both the light beams). Then, the refractive index distributions in the two directions can be obtained by the two photodetectors with one movement, and the eccentricity can be calculated from them.

[0007]

【Example】

 An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. As shown in this figure, a laser light source 2 and a line sensor 3 are arranged to face each other to form one photodetection system, and another laser light source 4 and a line are arranged. The sensor 5 is disposed so as to face the other photodetection system. These two light detection systems are arranged so that the light beams 6 and 7 from the laser light sources 2 and 4 form an angle of approximately 90 degrees with each other. The laser light sources 2 and 4 generate narrow light beams 6 and 7, and the line sensors 3 and 5 are one-dimensional photodetectors in which semiconductor photodetection elements such as CCDs are arranged in a line. is there. In the two light detection systems, the laser light sources 2 and 4 and the line sensors 3 and 5 are arranged so as to face each other, and the light beams 6 and 7 from the laser light sources 2 and 4 respectively enter the line sensors 3 and 5. It is supposed to do.

Then, the optical fiber preform 1 to be measured is placed near the intersection of the two light beams 6 and 7 so as to be approximately 90 degrees with respect to each of the two light beams 6 and 7. That is, for example, in this figure, the optical fiber preform 1 is placed at a right angle to the plane (paper surface) formed by the two light beams 6 and 7. As a result, the two optical beams 6 and 7 which are orthogonal to each other are transmitted through the side surface of the optical fiber preform 1. The optical fiber preform 1 is held by a holding device (not shown) and is moved in an angular direction that forms 45 degrees with respect to both light beams 6 and 7, as shown by an arrow 8.

The two transmitted light beams 6 and 7 are incident on the line sensors 3 and 5, respectively, and their incident positions are detected. Since the core portion and the cladding portion have different refractive indices in the optical fiber preform 1, the refraction angles when the light beams 6 and 7 pass therethrough are different. When moved to, the incident position changes. The data on the incident position detected by each of the line sensors 3 and 5 changes with time as shown by A and B in FIG.

In FIGS. 2A and 2B, the left and right axes are time axes, and the upper and lower axes represent the incident position, that is, the refractive index. Therefore, A in FIG. 2 represents the refractive index distribution in the horizontal direction of the optical fiber preform 1 to be measured, and B in FIG. 2 represents the refractive index distribution in the vertical direction. The corrugated portion corresponds to the clad portion, the center of which is represented by P, and the large portion corresponds to the core portion and the center of which is represented by Q. When the deviation between the clad center P and the core center Q in the left-right direction is a, and the deviation between the clad center P and the core center Q in the up-down direction is b, the eccentricity is the sum of the square of a and the square of b. Expressed as the square root of. Therefore, it is possible to obtain the amount of eccentricity by obtaining the deviation between the cladding center P and the core center Q from the output waveforms such as A and B in FIG.

[0011]

As described above, according to the eccentricity amount measuring apparatus for the optical fiber preform of the present invention, the eccentricity amount can be obtained by the measurement in which the measured optical fiber preform is moved only once. Therefore, the eccentricity amount can be easily measured in a very short time.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a waveform diagram showing an output waveform from the line sensor in the embodiment.

[Explanation of symbols]

1 optical fiber base material to be measured 2, 4 laser light source 3, 5 line sensor 6, 7 light beam 8 arrow indicating the moving direction of the optical fiber base material to be measured

Claims (1)

[Scope of utility model registration request] 1. A first light beam generator for generating a light beam, a first light detection system comprising a first light detector for detecting an incident position of the light beam, and the first light beam. Second light detection including a second light beam generator that generates a light beam in a direction substantially orthogonal to the light beam from the generator, and a second photodetector that detects the incident position of the light beam An optical system comprising: a system; and a holding device for the optical fiber preform to be measured, which moves the optical fiber preform to be measured in one direction in the vicinity of the intersection of the two light beams. Eccentricity measuring device for fiber preform.