SU1637012A1 - Device for checking optical pulse duration - Google Patents

Abstract

The invention relates to a measurement technique, in particular to optical physical measurements, and can be used for the metrological circuits providing a pulsed laser ranging, in particular, as an apparatus for the on-line operational control of the signal duration of a transmitter. The purpose of the invention is to improve the accuracy of monitoring the duration of optical pulses. The device contains fiber-optic delay lines 2 and 3 and photodetector 5. Introduction of fiber-optic delay line 1, photo-receiver 4, peak detectors 6 and 7, scale amplifiers 8 and 9 and blocks 10 and 11 Comparison allows you to control whether the duration of the input optical pulse is within the specified limits and, when outside the interval of duration, gives an indication signal. 2 Il. about s

Description

Fiel

The invention relates to a measuring technique in the field of optical and physical measurements and can be used for the purpose of metrological assurance of pulsed laser distance measurement, in particular, as an instrument of built-in operational control of the signal duration of a transmitter,

. The purpose of the invention is to improve the accuracy of monitoring the duration of optical pulses.

Fig „1 shows the block diagram of the device; in fig. 2 is a plot of the relative amplitude of the total signal versus the relative delay of the summed pulses for cosine-square pulses.

The device contains fiber-optic delay lines 1-3 with the same transmission, with the length of the delay line 3 longer than the delay line 2 by a fixed value D1, two photodetectors 4 and 5, two peak detectors 6 and 7, two large-scale amplifiers 8 and 9 and two comparison units 10 and 11, the inputs of the delay lines 1-3, are combined and are the device input, the outputs of the delay lines 2 and 3 are optically coupled to the input of the photoreceiver 5, the output of which is connected to the input of the peak detector 7E whose output is connected to the second inputs blocks 10 and 11 as compared The output of the delayed line 1 is optically coupled to the input of the photodetector 4, the output of which is connected to the input of the peak detector 6, the output of which is connected to the inputs of the scale amplifiers 8 and 9, the outputs of which are connected to the first inputs of the comparison units 10 and 11, respectively, the outputs of which are the output of the device,

The device works as follows

The device controls the presence of the duration C of the input optical pulse within the specified limits from

- ЈС0 до 0 + when finding

B

out of this interval of duration gives an indication signal. The operation of the device is based on the dependence of the relative amplitude of the total pulse in the measuring channel (relative to the pulse amplitude in the reference channel) on the duration of the monitored pulse at a fixed

0

five

0

the difference in delay times in the lines of the measuring channel holder. A controlled optical pulse of duration about or part of its power in the form of a collimated light flux enters the device, where it is divided between three optical delay lines into three pulses of the same power. The pulse from the output of the delay line 1 is fed to the input of the photodetector 4, in which it is converted into electrical equivalent, ribbons with amplitude U, which is the reference signal. Optical pulses from the outputs of the lines 2 and 3 delays enter the input of the photodetector 5 ". Since the lengths of the lines are 2 and 3 delays differ by a fixed value A1, then the pulses delayed by them appear at the input of the photodetector 5 time-shifted by one relative to

other by value

-N

where v 5

0

five

0

the pulse propagation speed inside the delay line, and the condition 2/2 must be fulfilled. The photodetector 5 converts the total optical pulse into an electrical equivalent with amplitude U. which depends on the relative shift t / Ј of the summed optical signals and their amplitude U. U depends only on the value of t / Ј, and for a given value of t

Only the duration of the ff controlled input pulse.

FIG. Figure 2 shows this relationship for cosine-square pulses. Analytically, it is expressed by the formula Uj / U co8g (1m: / 2Ј), where 0 t / С 0.5 A fixed value of t and a certain pulse duration corresponds to a certain value 5 of the relative amplitude UЈ / U of the total pulse in the measuring channel, which can be found for a particular pulse shape from a graph or analytically

50

(| b,

where f is a function defined by the form

momentum.

If the duration Ј of the pulse being monitored lies within the specified limits from + 6Ј0, then the corresponding value of 1% / U is also in the range from (Ug / U) to (Ug / U) B, where

(U./U) (; -Ј-Ј-) (ig / i) in, or the values (ig / I) and and (ig / i) in are from a graph similar to that shown

in fig. 2, for values of -c and

tс ° te l

 respectively. If, however, V on t-o) is outside the range of values from

, -e.

to c +

e.

That and I correspond

its value is outside the specified limits.

From the outputs of photodetectors 4 and 5, electrical signals are fed to the inputs of peak detectors 6 and 7, respectively, which store the maximum values of the signals U and Uj. From the output of the peak detector 7, the signal of magnitude U2: is fed to the second inputs of comparison units 10 and 11, and from the output of the peak detector 6, the signal of magnitude U is fed to the inputs of scale amplifiers 8 and 9 with gain factors () e and (UgVU) H, respectively which form the signals of the magnitude of U-GJgVlOa and U- (Ug- / U), respectively. Further, the signal of the U value (from the output of the scale amplifier 8 is fed to the input of the comparison unit 10, in which it is compared with the signal Ug. Of the peak detector 7. If Ug; exceeds the upper limit set by the scale amplifier 8, the comparison unit 10 generates an indication signal.

Similarly, the comparator unit 11 compares the signal of the magnitude from the output of the peak detector 7 and the signal of the values of U (Ug; / U) from the output of the scale amplifier 9, and if Ug is less than the settable

five

0

five

five

0

large-scale amplifier 9 of the lower limit, then gives an indication signal. Thus, if the duration of the controlled pulse импуль is outside | given interval of values from ToЈ0 + ЈЈ, then this is indicated at the output of one of the blocks 10 or AND comparison

Claims (1)

Invention Formula An apparatus for monitoring the duration of optical pulses, comprising a measuring channel comprising two optical delay lines, the inputs of which are combined and the input of the device, and a photo-receiver optically coupled to them, in order to improve the accuracy of monitoring the duration of optical pulses. A reference channel is inserted, which includes a third optical delay line, the input of which is combined with the inputs of two delay lines of the measuring channel, an optically coupled photodetector and connected to its output has a peak detector, two large-scale amplifiers and two comparison units, a peak detector connected to the photoreceiver output is additionally inserted into the measuring channel, the inputs of the large-scale amplifiers are connected to the output peak detector of the reference channel, and the outputs to the first inputs of the reference blocks, the second inputs which are connected to the k output of the peak detector of the measuring channel. 0.5 Fi8.1 t / t