SU1281949A1 - Device for measuring chromatic dispersion of optical fibre - Google Patents

Abstract

The invention can be used to determine the dispersion characteristics of single mode optical fibers. The purpose of the invention is to increase the accuracy of measurements. The light pulse from the optical radiation source 2, after passing through the narrowband filter 3, is introduced into the fiber section under study, pass through it, enters the input of the photodetector 9, which forms an electrical pulse at the output, which enters the pulse counter B and is recorded there. The same pulse arrives at the input of the AND 5 circuit, and since the other input of this circuit, timer 6 has set logical 1, is applied to the output of the AND circuit, 5 and then to the input of the modulator 1 and the cycle repeats. To measure chromatic dispersion, pulse frequency is measured at various wavelengths. 1 il. (L

Description

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The invention relates to optical communication and can be used to determine the dispersion characteristics of single-mode optical fibers.

The aim of the invention is to improve the measurement accuracy.

Increasing the accuracy is achieved by determining the dispersion by the frequency difference of the pulse-digital generator, the feedback circuit of which includes (via interchangeable chromatic filters) the measured fiber.

The drawing shows the block diagram of the device.

The block diagram shows modulator 1, optical radiation source 2, replaceable filter unit 3, fiber 4 under test, logic AND 5, TaijMep 6, converter 7, counter 8, photodetector 9, trigger circuit 10. The AND logic circuit, timer, transducer, pulse counter, and trigger circuit constitute the meter (circled in dotted lines) 11.

The device works as follows.

The trigger circuit 10 generates a trigger pulse that goes to the control input of the pulse counter 8 and zeroes it, the same pulse goes to the control input of timer 6 and to the input of the modulator 1, Timer 6 at the control output going to circuit 5 , sets the logic level 1, which is fed to one of the inputs of the logic circuit AND, and also begins to form counting impulses, which from the counting output of the timer arrive at the time input of the converter 7. At the input of the modulator 1, a start pulse forms the output of the modulator A pulse that enters the source of optical radiation source 2 and excites it, while the source of optical radiation emits a short light pulse. A light pulse, passing through a narrow-band filter 3, is introduced into a segment of the fiber under study, passes through it and enters the input of a photodetector 9. At the output, a photodetector 9 generates an electrical pulse that enters the pulse counter 8 and registers in it. The same impulse goes to the second input of the AND 5 logic circuit and, since And the other input of the circuit AND, the timer 6 set the logic level 1, is fed to the output

And then to the input of the modulator 1, and the cycle repeats. The circuit will operate for the time T, which is set by timer 6. After this, timer 6 sets the logic O level at its control output and stops the circuit operation. During the operation of the circuit, the counter 8 of the pulses will register N pulses.

Ratio - determines the frequency F

I ..

following impulses in the device,

This division is performed by the transducer 7. The pulse frequency in the device depends on the wavelength of the light pulse in accordance with the output voltage.

F ()

J

 L

, + n ()

25

40 45 50

where bd is the time of conversion of the light pulse in the electrical part of the device; L is the length of the segment under study

fibers;

n (i) is the refractive index of the fiber core material, which characterizes the chromatic dispersion.

Chromatic dispersion measurements are made frequently for measurements. following pulses at different 35 wavelengths. Use block replaceable

filters. The wavelengths A and Aj correspond to the frequencies F and F, and

 Ni.

N,

TH

Where

TU measurement interval, N, and

NZ number registered by the pulse counter, respectively, for

A, and A. From here

p N - N2

 - pg

(1) CAN BE WRITTEN

(one)

CxFs - F,

yp n (,) - n (A2) (- rr-H.

Thus, in order to measure db, it is necessary to measure F and F,

Claims (1)

Invention Formula An apparatus for measuring chromatic dispersion of an optical fiber, comprising a modulator electrically coupled to an optical source 31281949 a radiation filter unit, located on the radiation path, a photodetector electrically connected to an electronic meter, the output of which is electrically connected to the modulator input, characterized in that, in order to improve the measurement accuracy, the meter contains a pulse counter, a timer, a logical The pulse of pulses is with the counting input of the converter, the temporal input of which is electrically connected to the counting output of the timer, the control output of which is connected to one of the inputs of the logic circuit I, the other input of which is connected to the input of the counter and the pulses, and the output of the circuit. start-up - with a control input of the pulse counter, an Ipscheme I, a converter, a starting circuit tO with the equalizing input of the timer and with an output ska, the pulse counter input is connected to the photodetector, the pulse counter output is connected to the counting input of the converter, the time input of which is electrically connected to the counting output of the timer, the control output of which is connected to one of the inputs of the logic circuit And the other input It is connected with the input of the counter of the pulses, and the output of the starting circuit is connected with the control input of the pulse counter, the preforming AND circuit, which is connected to the input of the modulator.