RU1768962C - Device for checking diameter of light guides and optical fibers - Google Patents

Abstract

The invention relates to a control and measuring technique and is intended for measuring the diameter of transparent chemical fibers and single-core optical fibers. The aim of the invention is to increase the accuracy of control. Using a lighting system consisting of a laser 1, a beam splitter 2, a second mirror 7 and two focusing lenses 3 and 8, the raster 4 is illuminated in two diametrically opposite areas by converging beams. In raster 4, the incident beams are diffracted to form a series of orders. In both regions of the raster, the 0th and two first diffraction orders are used to form the IR-IR2 and IR3 interference patterns. All three 1 / IKs are driven by the rotation of the radial raster 4, so their speed of movement is the same. Initially, the condition that y must be satisfied. and the photodetectors are spaced apart in space by the step size (or several steps m Ne) of the reference IR, while the condition is met. A change in the radius rc of the controlled OSK will lead to a change in the pitch Hk of the interference band. Therefore, the condition is violated and the photodetectors 11, 12 and 15.16 will record the phase increment with respect to Ne, which makes it possible to determine the diameter of the fiber being monitored. 1 ill. J / 4 L

Description

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The invention relates to a control and measuring technique and is intended for measuring the diameter of transparent optical fibers and single-core optical fibers with single and double-clad structure

The closest technical solution is a device for monitoring optical fibers and optical fibers, comprising a laser and a collimator and a radial raster located along the radiation, an optical wedge mounted along the beam corresponding to the diffraction maximum of the same name, and a mirror mounted along the beam corresponding to the other of the same name diffraction maximum, a beam splitter with a beam splitting face, placed along the beam corresponding to the zero order of diffraction and oriented so that about the normal to its beam-splitting faces is 45 ° angle to the direction of radiation, a reference optical fiber arranged in the movable spot beams reflected from the beamsplitter and mirrors and two pairs of photodetectors installed on a course for controlled emission of the first light guide, the second - for the reference waveguide.

A disadvantage of the device is the influence on the result of the control of errors in the manufacture of the raster, in particular, the non-flatness of the surfaces of the glass disk (wedge), or, what is the same. uneven thickness of the glass of the disk on which the raster is applied. a. When illuminated with a collimated beam, the latter leads to spurious interference, similar to that in a thin wedge-shaped plate.

The aim of the invention is to increase the accuracy of control.

The goal is achieved in that the device containing the laser and located along the radial radial raster with a stroke line installed along the beam corresponding to one of the diffraction maxima of the radial raster, an optical wedge installed along the beam corresponding to the other diffraction maximum of the same name, mirrors, a reference fiber, a holder for a controlled fiber, a beam splitter, a first pair of photodetectors placed downstream of a holder for a controlled fiber, and W The first pair of photodetectors placed along the radiation behind the reference fiber is additionally equipped with the first and second focusing lenses mounted between the laser and the radial raster with the diameters of opposite sides relative to the groove path at the focal distance from the raster surface, the second and third mirrors, the second optical wedge, and a third pair of photodetectors, a beam splitter is installed between the laser and the first focusing lens, the second mirror is placed along the beam reflected from the beam splitter before Ora focusing lens, the third mirror and the second

0 an optical wedge is mounted along the optical axis of the second focusing lens behind the radial raster in the directions corresponding to the diffraction orders of the same name, the reference fiber is located in

At the intersection of the beams reflected from the first and third mirrors, the fiber holder is oriented so that its axis passes through the points of intersection of the beams from the first wedge and the zero order of diffraction and the beams from the second wedge and the zero order of diffraction, and a third pair of photodetectors is installed along the radiation behind the KOI holder of the trolled fiber at the intersection of the beams from the second wedge and

5 zero order diffraction.

The drawing shows a device for controlling the diameter of optical fibers and optical fibers.

The device comprises optically coupled laser 1, a beam splitter 2, a first focusing lens 3, a radial raster 4, in the same order of which the first mirror 5 and the first optical wedge are placed 6. In the beam 2 reflected from the beam splitter

The beam is sequentially placed in the beam: the second mirror 7 at an angle of 45 ° to the beam, the second focusing lens 8 is also at the focal distance from the radial raster 4, behind which, on the path of the same order, a third mirror 9 is placed, the second optical wedge Yu. First pair 11 and 12, the photodetector is located behind the OSK optical fiber in the plane of the image of the interference pattern of the ICT, the second pair 13 and 14

5 photodetectors - behind the reference optical fiber of the OSE in the image plane, and a third of the pair of 15 and 16 photodetectors - behind the controlled OSK in the second section in the image plane of the interference pattern I / 1K2,

The device operates as follows.

Using a lighting system consisting of a laser 1, a beam splitter 2, a second mirror 7 and two focusing lenses 3 and 8, the raster 4 is illuminated in two diametrically opposite areas by converging beams. In raster 4, incident beams are diffracted to form a series of orders. In both regions of the raster, the 0th and two first diffraction orders are used to form 1 / lKi, IR 2, and IR 3 interference patterns. The first control channel is formed by a pair of beams of the 01th and +11th diffraction orders. The + 11th order is corrected in the direction of the first optical wedge 6 and at an angle "coincides with the 01th order at the controlled object of the CCS with the formation of the interference pattern HKi. The latter is read by the first pair of photodetectors 11 and 12.

The second control channel is formed by another pair of beams of the 0th and +1th diffraction orders, the +1th order is corrected in the direction of the second optical wedge 10 and at an angle converges with the 0th order in the second section of the controlled OS object with the formation of the interference pattern of IR2, which is read by the third pair of photodetectors 15 and 16. The second section on the Osc is separated from the first by the distance L HKV2 / Vi, (1) where Hk is the step of the interference fringes from the Osc. V2 is the velocity of the object moving Osc; Vi is the velocity of movement of the interference fringes.

The 1st diffraction pattern in the first section falls on the first mirror 5 and is corrected in the direction of the reference OS object; the 1st diffraction pattern in the second section falls on the third mirror 9 and is also corrected B in the direction of the reference object of the OSE at an angle y to the beam is of the first order. These beams interfere with the formation of a reference interference pattern of the IKE. The latter is read by a second pair of photodetectors 13 and 14.

All three IRs are driven by the rotation of the radial raster 4, therefore their speed of movement is the same. Initially, the condition must be satisfied that a ft y, and the photodetectors are spaced apart in space by the step size (or several steps m He) of the reference IR, while the condition is met. A change in the radius R of the controlled USC will lead to a change in the step H of the interference band. Therefore, the photodetectors 11. 12 and 15,

16 will fix the phase increment with respect to Ne. which is assigned a value of 360 °.

Given that ± 360 ° (NE- -H,) / Hk, we finally obtain

().

360 °

For example, in the first section, Du + 1 ° and at Ge 500 μm,, 39 μm, and in the second

DN -1 ° and then, 61 microns in the prototype

the size would be averaged for these two sections, i.e. Gk.sr. (gk + g) microns.

In the proposed device due to the observance of condition (1), the duration of the photopulse (proportional to Hk)

determined by the beginning of the interference band in the first section and the end of the interference band in the second section.

To implement the device, we used a laser L GN-302, a radial raster with a diameter of 80 mm and a stroke pitch of 10 μm, a beam splitter 10X10X10 mm with approximately equal transmittance and reflection, optical

a wedge with a beam refraction angle equal to the first-order diffraction angle, mirrors with an external reflective coating, focusing lenses with a focal length fw of 80 mm, and FD-256 photodetectors.

The latter were connected to amplifiers made on K157UD2 series microcircuits with standard switching.

Thus, when focusing optical radiation on a raster of several

the contrast of spurious interference fringes, which are practically not perceived by photodetectors, decreases. In this case, the signal-to-noise ratio of the working interference signal is significantly increased, and the measurement errors are reduced by 7-8%. The organization of the second measuring channel in compliance with the above conditions ensured the reduction of the measurement base (section

object on which the measurement result is averaged) several times. which also increased the accuracy and reliability of control.

A device for controlling the diameter of optical fibers and optical fibers can be widely used in the production of fiber-optic elements, mainly in process control systems for their drawing.

Claims (1)

Formula invented and A device for controlling the diameter of optical fibers and optical fibers, comprising a laser and a radial raster located along the line of strokes, installed along the beam corresponding to one of the diffraction maxima of the radial raster, an optical wedge installed along the beam corresponding to another diffraction maximum of the same name, a mirror, reference fiber, holder of the controlled fiber, beam splitter, the first pair of photodetectors, placed along the radiation behind the holder of the controlled a fiber guide, and a second pair of photodetectors, placed along the radiation behind the reference fiber, characterized in that, in order to increase the accuracy of control, it is equipped with first and second focusing lenses mounted between the laser and the radial raster from diametrically opposite sides relative to the strokes on the focal distance from the raster surface, the second and third mirrors, the second optical wedge and the third pair of photodetectors, a beam splitter is installed between the laser and the first focusing lens, the second calorie taken along the reflected from the beam splitter in front of the second focusing lens, the third mirror and the second optical wedge are mounted on the optical axis of the second focusing lenses behind the radial raster in the directions of the corresponding diffraction patterns of the raster, the reference fiber is located at the intersection of the beams reflected from the first and third mirrors, the holder of the controlled fiber is oriented so that its axis passes through the points of intersection of the beams from the first wedge and zero order diffraction and beams from the second wedge and zero order diffraction, and a third of the pair of photodetectors is installed along the radiation behind the holder of the controlled fiber at the intersection of the beams from the second wedge and the zero diffraction order.