SU1278645A1 - Method for determining losses in multimode light guide - Google Patents

Abstract

The invention relates to the metric of multimode light guides and allows to increase the efficiency and simplify the measurement process. When determining losses in multimode fibers, the light from the collimated radiation source linearly polarizes Polarizer 2, passes through a half-shot, an cancer mirror 3 and is focused with the help of micro-optics 4 at the input end 5 of the optical fiber 6. Then the flow of linearly polarized light reflected from the input end 5, and the depolarized light reflected from the output end 8, after reflection from the mirror 3, passes through the analyzer 9, the lens 10, the aperture 11 and is focused on the photodiode 13. With the analyzer 9 parallel and polarizer 2 through the analyzer 9 passes the light reflected from the input end 5, and half the light reflected from the output end 8. In the case of a crossed analyzer and polarizer, only half of the depolarized light reflected from the output end 8 comes to the photodiode 13, and linearly polished light is completely quenched. From the values of the light fluxes measured in both cases, the magnitude of the losses in multimode fibers is calculated. I il, H (L

Description

This invention relates to metrIlSn fibers.

The purpose of the invention is to increase the efficiency and simplify the measurement process.

The method uses the property of multimode fibers with their DOS-distance (2 m) to completely depolarize the linearly polarized radiation introduced into the fiber.

According to the method, collimated linearly polarized radiation of intensity P is fed to the input end. Then, the intensity Φ of the back reflected light flux of the same polarization is measured. The value of Ф includes the flux reflected by the end-face input and the flux reflected by the output end, taking into account the K-fold attenuation in the fiber

9, -f-i K (l-p) VPa, (O

R

- reflection coefficient from

Where

the end of the fiber.

Thereafter, the intensity Φ of back-reflected radiation with orthogonal polarization is measured. The value includes only the luminous flux reflected by the output end

F - | - K (i-pfp9. (2)

On the basis of expressions (1) and (2), the magnitude of losses (z decibels) is determined.

TO

- Ig (1-p)

2Fz

The proposed method makes it possible to determine the value of K by simple means and operatively (it is not necessary to have access to the output end of the fiber).

The drawing shows a device that implements the proposed method.

Behind the source of collimated radiation perpendicular to its optical axis, there is a polarizer 2, the crystallographic axis of which is oriented in an arbitrary manner. Behind the floor is installed a translucent mirror 3 at an angle of 45

to the optical axes of the radiation source 1 and the radiation input / output system into the multi-mode light guide 6 with a length of at least 2 meters. Input system

m

to

20

m

25

12786452

yes contains a micro-lens 4 (20x, 0.4) located at the focal length from the input end 5 of the multi-mode fiber 6. The input end 5 is equipped with an alignment system 7. The output end 8 can be located in any, even inaccessible place. A recording system is oriented relative to a semitransparent mirror, the optical axis of which is perpendicular to the optical axis of the radiation input-output system. An analyzer 9 is located along the optical axis of the recording system behind the translucent mirror, which during the process of determining losses is either aligned in parallel or shortened with the polarization plane of the polarizer. Behind the analyzer 9, the focusing lens 10, the aperture 11, the focusing lens 12, and the photodiode 13 are successively placed along the optical axis of the recording system.

The device works as follows.

Light from source 1 through the polarizer 2, the translucent mirror 3 hits the microscope lens 4 and focuses on the input end 5 of the multimode fiber 6 under investigation. The reflected light from the input end 5 and the high end 8 passes after reflection from the semi-transparent mirror 3 passes

“Through the analyzer 9, lens, 10, form an enlarged image of the ends. By means of the diaphragm 11, a part of the light reflected from the end part of the light-insulating sheath is cut out. Lens 12 focuses the radiation on the photodiode 13. With a parallel polarizer and an analyzer, linearly polarized light passes through the analyzer 9, reflected from the input end.

45 of the light guide 5, and half of the radiation reflected from the output end 8. When the polarizer and analyzer are crossed, the linearly polarized light from the input end is completely extinguished, only half of the radiation reflected from the output end comes to the photodiode 13. From the flux values, the loss in the optical fiber is calculated by expression (3).

Claims (1)

This invention relates to metrIlSn fibers. The purpose of the invention is to increase operability and simplify the measurement process. The method uses the property of multimode fibers with their longitudinal distance (2 m) to completely depolarize the linearly polarized radiation introduced into the fiber. According to the method, collimated linearly polarized radiation of intensity P is fed to the input torus. Then, the intensity Φ of the back reflected light flux of the same polarization is measured. The value of Φ includes the flux reflected by the input end and the flux reflected by the output end, taking into account the K-fold attenuation in the optical fiber 9, -f - i K (lp) VPa, (O is the reflection coefficient from the fiber end. After that, the intensity F of back-reflected radiation with orthogonal polarization is measured. The value includes only the luminous flux, the reflected output end face of F - | - K (i-pfp9. (2 Based on expressions (1) and (2), the value loss (in decibels) - Ig (1-p) The proposed method makes it possible to determine the value of K by simple means and clearly (no access to the output end of the fiber is required. The drawing shows a device that implements the proposed method. A polarizer 2 is installed perpendicular to its optical axis perpendicular to its optical axis, the crystallographic axis of which is oriented in an arbitrary manner. A semi-transparent mirror is installed behind the polarizer 3 at an angle of 45 to the optical axes of the source 1 of the radiation and the input / output system of the radiation in the multi-mode fiber 6 with a length of at least 2 meters. The input system is 452 and contains a micro-lens 4 (20x, 0.4) located at the focal distance from the input end 5 of the multimode light guide 6. The input end 5 is equipped with an alignment system 7. The output end 8 can be located at any, even inaccessible place. A recording system is oriented relative to a semitransparent mirror, the optical axis of which is perpendicular to the optical axis of the radiation input-output system. the polarization plane of the polarizer. Behind the analyzer 9, the focusing lens 10, the diaphragm 11, the focusing lens 12, and the photodiode 13 are sequentially placed along the optical axis of the recording system. The device operates as follows. The light from source 1 through the polarizer 2, the semitransparent mirror 3 hits the microscope lens 4 and is focused on the input end 5 of the multimode fiber 6 under investigation. The reflected light from the input end 5 and the upper end 8 after reflection from the semi-transparent mirror 3 passes through the analyzer 9, lens 10, to form an enlarged image of the ends. By means of the diaphragm 11, a part of the light reflected from the end part of the light-insulating sheath is cut out. Lens 12 focuses the radiation on the photodiode 13. With a parallel polarizer and an analyzer, linearly polarized light reflected from the input end of the light guide 5 and half the radiation reflected from the output end 8 passes through the analyzer. When the polarizer and analyzer are crossed, the linearly polarized light From the input end, completely quenched, only half of the radiation reflected from the output end comes to the photodiode 13. From the flux values, the loss in the optical fiber is calculated by expression (3). Claims of Invention A method for determining losses in a multi-mode light guide, according to which 31278645 the input end of the fiber serves a count of its intensity, reflected reflected radiation and measures the current polarized in the same plane, in the intensity of the reflected light which polarizes the applied flux, which is different, and the loss coefficient K in that, in order to increase the efficiency, the light guide calculates from the ratio and simplification of the measurement process, the i-7 radiation supplied to the input end face is polarized, the reflected light current is polarized in an orthogonal plane-i the bones and for the second time measure its 1-d-10 where the p is the reflection coefficient of sv, and for the first measurement of the optical fiber.