SU1725154A1 - Optical spectrum analyzer - Google Patents

Abstract

This invention relates to optical information processing and is intended to analyze an ensemble of signals in real time. The purpose of the invention is to improve the accuracy of the analysis. The device comprises a radiation source 3, a control unit 2, a collimator 4, a modulator 7, a generator of basic functions 8, a cylindrical 6 and a first spherical 10 lens, a photoreceiver 14, a block 1 time division channels and a synchronization unit 15. The goal is achieved by the introduction of a polarizer 5, an analyzer 9, a second spherical lens 13, a deflector 11 and a generator 12. 1 Il.

Description

WITH

WITH

The invention relates to optical information processing and can be used in tasks related to spectral analysis of an ensemble of signals in real time.

The aim of the invention is to increase the analysis accuracy by inputting signal samples by temporal separation of channels and a single radiation source with simultaneous deflection of the light beam during the analysis process, into certain rows of a two-dimensional time integrating photodetector.

The drawing shows a functional diagram of the optical spectrum analyzer.

The spectrum analyzer comprises a time division multiplexing unit 1 electrically connected to the control unit 2, which, in turn, is electrically connected to the radiation source 3. The latter is optically connected to the collimator 4, the polarizer 5, the cylindrical lens 6, the modulator 7, which is electrically connected to the generator 8 basic functions, the analyzer 9, the first spherical lens 10, the deflector 11, which is electrically connected to the generator 12, the second a spherical lens 13 and a photodetector 14. The synchronization unit 15 is connected with the corresponding inputs of the unit 1 for time division of the channel, control unit 2, GBF 8, generator 12.

The spectrum analyzer works as follows.

Analyzed signals Um (t), m

1.2M, arrive at block 1 temporary

channel separation.

At the input of block 1, a sequence of amplitude-modulated pulses is formed, which is fed to the control block 2 and the source of radiation 3. The intensity of the radiation last

,,, t- n At-m T0 h G (t) rect ()

(nAt) + Uo,

where is at

1 2TЈ

FB - upper frequency of the analyzed signals;

n is the reference number;

m is the signal number;

DT is the pulse duration of the radiation source;

That is the period of their following;

U0 is the reference level chosen from the condition V0 b-max Um (n A t).

five

0

five

0 5 0

five

0

five

0

five

The light beam is converted by the collimator 4, the polarizer 5 and the cylindrical lens 6 in such a way that a polarization plane falls in one direction and converges in the other direction to the modulator 7, and a signal is sent from the GBF 8. As a result, the light distribution is subject to modulation by law

R (x.t) rect ()) rect (At) x x 1 + cos (nk).

where K is the frequency channel number;

x, x0 is the size and spacing of the frequency channels (determined by the parameters of the modulator used);

r is the duration of the impulses of the basic function MTo and t At (it is possible to repeat M times the repetition of one basic function, then the last inequality changes its form);

n is the number of samples processed signals

in this case, the cosine component of the Fourier transform is represented.

The modulated light field falls on analyzer 9, which eliminates the non-information components of the light field. A second spherical lens 10 converts the light field in such a way that a beam, flat in one coordinate and converging in another, is incident on the deflector 11. On the deflector 11, which can be used as an acousto-optic modulator, a signal is sent from generator 12

S (t) Cos (coo t + // y),

where Sho is the central frequency of the AOM;

p is a parameter characterizing frequency deviation.

Value / i. it is chosen in such a way that a change in frequency over time To provides a shift in the output distribution in the focal plane of the spherical lens 13 by a distance equal to the distance between adjacent lines of the photodetector. The generator 12 is synchronized with the operation of other blocks, so after time At, the frequency of its signal becomes Sho and the scan begins again from the first row of the photodetector. After N cycles on the m-th row of the photodetector is formed by the distribution

N-1

x - to XQ

Fm (x) ()

n-o

In

x Um (n At) + Do 1 + Cos p n k.

The non-informational components of this distribution can be eliminated during post-detector processing. The information component is a discrete Fourier transform of the signal being analyzed. Thus, on each of the M lines of the photodetector, using the same radiation source, the spectrum of one signal is formed.

Claims (1)

Claims of the invention Optical spectrum analyzer comprising an optically coupled radiation source located on one optical axis, a collimator, a modulator, a cylindrical and first spherical lenses and a photodetector, and a time division unit whose output is connected to the input of the control unit with its output connected to the radiation source, and 0 50 a synchronization unit, the first and second outputs of which are connected to the synchronization inputs of the time division block, the control unit, the photodetector, and the basic function generator, the output of which is connected to the modulator input, so that In order to increase the accuracy of the analysis, a polarizer, a second spherical lens, a deflector and a generator electrically connected to the input of the deflector are introduced, with a cylindrical lens positioned in front of the modulator at the focal distance and its forming parallel In parallel to the modulator axis, the third output of the synchronization unit is connected to the generator synchronization input, the polarizer is installed after the collimator, the analyzer is installed after the modulator, the second spherical lens is installed at the focal distance from the modulator, and the deflector is located between the spherical lenses at the focal distance from each of them.