SU1649256A1 - Method of measuring diameter of fibres and single-core light conduits - Google Patents

Abstract

The invention relates to an instrumentation technique and is intended to measure the diameter of transparent optical fibers and single-core light guides. The purpose of the invention is to improve the accuracy of control by increasing the contrast of the interference pattern. The same maxima are separated in a differentiating beam and form two pairs of beams from them, one of these pairs of beams is illuminated by a controlled light guide, and the other is a reference one. The intensity distribution in the interference patterns behind the monitored and reference fibers and the difference of the photoelectric signals from these cards is recorded by inspecting the diameter of the monitored fiber 1 or less.

Description

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

The purpose of the invention is to improve the control accuracy by increasing the contrast of the interference fringes and eliminating the effect of fluctuations in the wavelength of light and improving performance by separating the maxima of the like diffraction orders.

The drawing shows a diagram of the device that implements the method of controlling the diameter of the fibers.

The device contains a laser 1, collimator 2. radial raster 3, first wedge 4, Dove prism 5, first 6, second 7 photodetectors, second wedge 8, second Dove S prism, third 10 and fourth 11 photodetectors.

The method is carried out as follows.

The beam from laser 1 is converted into a parallel beam by means of a collimator 2 and directed onto a rotating radial raster 3. The monopuc diffracts on the raster to form a series of diffraction maxima. The phase change of the light wave is proportional to the speed of rotation of the raster. From the radial raster, two families of diffracted beams are formed: in the forward and reflected directions. The first wedge 4 and the first Dove 5 lagsmus produce one-max maxima, for example, and correct them in space in direction so that they intersect with each other on the reference fiber of the OSE. In parallel with the correction of the Dove 5 prism, the wave front of the beam is 180 °, it is necessary to fully match it with the front of the beam that has passed the wedge 4. On the optical fiber, the OCEE beams interact to form interference bands whose spatial period is functionally connected with

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diameter of the fiber. In the plane of analysis, the first and second photodetectors b and 7 are installed, spaced apart by the period of the interference band. The diffracted beams in the forward direction are isolated and corrected by the second wedge 8 and the second prism of Dove 9, respectively. The function of the second prism of Dove 9 is the same as the first one. These elements allocate single-peak maxima with the same number as in the reflected direction. The corrected beams intersect at the controlled light OSK also with the formation of an interference pattern, which is read by the third 10 and fourth 11 photodetectors, which are also spaced apart by an amount equal to the period of the reference interference signal. With the rotation of the radial raster 3, absolute synchronism is achieved in the optical and electrical signals. Due to the phase change in the beams, the interference fringes in both patterns are moved with a frequency proportional to the frequency of the phase change, and recorded in the analysis plane. The period of the bands is functionally related to the diameter of the fiber, both monitored and reference. The diameter / reference fiber is constant; therefore, the period of interference fringes changes under the effect of fluctuations in the wavelength of light, atmospheric pressure and ambient temperature. The period of the interference signal from the monitored fiber varies, besides the factors listed above, also from the diameter fluctuations arising in the process of drawing the fiber out of molten glass.

At a known reference fiber diameter, a correction factor is calculated taking into account the effect on the measurement result of changes in wavelength.

light, ambient temperature, etc. Then the diameter of the controlled fiber is calculated taking into account the correction factor.

Thus, by eliminating measurement errors due to fluctuations in wavelength, atmospheric pressure, temperature, and also due to an increase in contrast with amplitude addition

similar diffraction orders increase measurement accuracy and performance.

Claims (1)

Invention Formula The method of controlling the diameter of fibers and single-core light guides, which consists in splitting a beam of coherent radiation into a number of diffraction peaks, illuminates a controlled light guide, continuously varying the phases of the diffracted waves, register the intensity distribution in the interference pattern, control the parameter of the photoelectric signals from the monitored light guide, characterized in that, in order to improve the control accuracy and performance, a couple of diffraction maxima of the same name are extracted in the beam before the light is illuminated two pairs of beams are formed from them, the fiber is illuminated by one of these pairs of beams, and simultaneously with the illumination of the controlled fiber, the reference pair is illuminated the fiber with a known diameter and register the distribution of the intensity of the interference pattern from the reference fiber, as a parameter for which the control is carried out, choose the relative phase difference of the photoelectric signals from the registered distributions of the intensity of the interference patterns. to eleven