RU2002215C1 - Optical loss meter - Google Patents

Description

combining the functions of measuring and reference. When a caustic matching the radiation beam with the caustic of a multi-pass system is used in the meter, the beam parameters incident on the focusing systems in the measuring and reference channels are identical, which reduces the accuracy requirements for the photodetectors to be installed at the corresponding conjugate points. The use of a stable open optical resonator with off-axis propagation of the radiation beam as a multi-path system makes it possible to reduce the optical path length of the reference channel and thereby reduce the size of the meter.

A positive effect is achieved due to the fact that the front and rear principal points of a stable open optical resonator are located on the reflective surface of the mirror with a radiation input / output hole. The combination of the beam splitter and the input / output window of the radiation of the multi-way system simplifies the optical design of the meter and, in addition, allows to reduce the accuracy requirements for the photodetectors to be installed at the corresponding conjugate points, since the radiation entering the measuring and reference channels is reflected from hard-coupled channels among themselves the elements of a multi-pass system: radiation of the reference channel from the radiation input-output window, and radiation of the measuring channel from the open optical resonator as a whole.

The drawing shows an optical circuit meter. The meter contains a radiation source 1, a system 2 for matching the caustics of radiation with the caustics of a multi-path system, a multi-path system 3 formed by spherical mirrors 4 and 5, one of which has a window b, as well as a modulator 7, a focusing system 8, a photodetector 9, and a recording circuit 10 Window 6 is also a beam splitter.

The meter operates as follows. The radiation from source 1 passes through matching optical system 2 and is directed to multi-pass system 3.

The radiation emerging from the multi-path system passes through the modulator 7 and is sent to the photodetector 9 by the focusing system 8. The radiation reflected by the beam splitter 6 is also directed to the photodetector 9 by the focusing system 8. In the recording circuit 10, the standard signal processing from the measurement signal (from the multi-path system is carried out) ) and reference (reflected from the beam splitter) channels, which allows one to determine the magnitude of the losses introduced by the object under study. In this way, for example, losses in an object placed inside a multi-pass system, a gas absorption coefficient or concentration, a reflection coefficient of a mirror that is set in place of one of the mirrors of a multi-way system can be determined.

Using the meter as an OTDR is most effective when using a multi-way system in the form of a stable open optical resonator with a concave mirror having an input-output window, since the mirror under investigation in this case can have different curvatures, including being convex. The studied grain is installed instead of the continuous mirror of the multi-pass system and is moved along the axis of the system until the light spots of the input and output rays coincide on the input-output window.

(56) 1. Tokhtuev E.G., Larchenko V, I., Geyko O.N., Zhelo N.S. Use of the laser absorption method for determination of microconcentrations of hydrocarbons in air ./ Modern instrumental methods and means of gas analysis: Sat. scientific works of VNIIAP. Kiev, VNIIAP, 1985, p. 52-62,

2. Geiko O.N., Sugloba A. I. .. Tohtueo E. G. Investigation of the influence of He-Ne laser parameters on the stability of laser gas analytic system readings. Status and prospects of development of systems and instruments for analyzing the composition of substances: Abstracts . Republican scientific and technical conf. Kiev, 1978, p. 73.

Claims (6)

1. OPTICAL LOSS MEASURER, comprising an optically coupled radiation source, a beam splitter, a modulator, a measuring channel including a multi-pass system having front and rear main planes, a first focusing system and a first photodetector, a reference channel including a second focusing system and a second photodetector as well as a registration circuit connected to photodetectors, characterized in that in the measuring channel the photodetector is optically coupled to the rear main plane of the multi-way system, in supports In the channel, the photodetector is optically coupled to a point whose reduced distance from the radiation source is equal to the reduced distance from the source to the front main plane of the multi-pass system, and the ratio of the linear magnifications of the focusing systems in the channels is equal to the ratio of the sizes of the receiving areas of the photodetectors. 2. The meter according to claim 1, characterized in that the photodetectors are identical or aligned, and the magnifications of the focusing systems are equal. 0 0 5 0 5 3. The meter according to claim 2. characterized in that the reduced distance from the radiation source to the second photodetector in the reference channel is equal to that in the measuring channel minus the reduced distance from the front to the rear main planes of the multi-path system, and the focusing systems are made identical or combined. A. The meter according to claim 2 or 3, characterized in that the reference and measuring channels further comprise optical systems for matching the study caustics with the own caustic of the multi-path system, and the distances from the radiation source to the optical systems are equal, the latter being identical or combined . 5. The meter according to claim 2, or claim 3, or claim 4, wherein the multi-way system is designed as a stable open. an optical resonator formed by two mirrors, one of which has a window for input and output of radiation. 6. The meter according to claim 5, characterized in that the beam splitter and the radiation input and output window are aligned. 8