RU2297102C1 - Transceiving device for limited-access protected fiber-optic data transfer system - Google Patents

Abstract

FIELD: components of protected fiber-optic data transfer lines; uncontrolled-area limited digital-data transceiving devices.

SUBSTANCE: in order to make it possible to use proposed device in protected fiber-optic transmission systems, it is provided with newly introduced series-connected digital-to-analog converter, matching device, and regulator, radiator control device monitoring input is connected to first output port of controller whose second output port is connected to input of digital-to-analog converter, matching device output is connected to control input of regulator whose output is connected to input of amplifier; output of the latter is connected to input of detector whose output is connected to input of analog-to-digital converter; regulator input is connected to optical receiving module output.

EFFECT: ability of dispensing with controller output signal regulation when switching-on the device.

1 cl, 4 dwg

Description

The invention relates to components of secure fiber-optic information transmission systems and can be used as a limited-access digital information transceiver device over an uncontrolled territory.

The well-known "Transceiver unit of a fiber-optic information transmission system" (see RF Patent No. 2239286 of March 14, 2003, published in BI No. 27.10.2004). The device in its functionality and composition is closest to the claimed device and therefore is taken as a prototype.

The transmitter-receiver unit consists of the following components: a radiator control device, an adder, an emitter, a control photodetector, an integrator, an adder-regulator, a bandpass filter, a detector, a control unit, a digital-to-analog converter, a digital generator, output and input fiber-optic transmission lines (FOCL), receiving optical module (PROM), information signal amplifier, solution device, low-pass filter, pilot signal amplifier, high-pass filter, level detector, filter ra control band, digital to analog converter (DAC), the digital control unit (MCU), a light indicator control sound emitter.

The above device operates as follows. Input information signals are fed to the input of the emitter control device, where the modulator current of the emitter is generated by information signals. The magnitude of the current can be adjusted at the control input. The output signal of the device is summed with a constant bias current and a control signal. The resulting amount goes to the emitter, which emits an optical signal in the FOCL.

Part of the optical signal is fed to a control photodetector, which converts the input optical signal into an electrical signal. From the photodetector output, the signal enters in two chains: stabilization of the average optical power of the emitter and stabilization of the amplitude of the information and control signals.

The average power stabilization circuit contains an integrator and an adder controller. The integrator generates a mismatch signal of the average radiated power from a given value. The output signal is fed to the input of the device, which regulates the current through the emitter, trying to reduce the mismatch to a minimum. At the same time, the device modulates direct current with alternating current of the control signal, which is generated by a digital generator and converted into an analog form of the DAC.

The amplitude stabilization circuit of the information and control signals consists of a band-pass filter, detector, and control unit. The band-pass filter extracts a control signal from the signal of the control photodetector, which is converted by the detector into a constant signal, the value of which is proportional to the amplitude of the control signal at the input. At this input level, the control unit generates constant control levels of the DAC reference voltage and the emitter control device. The modulation currents of the emitter are changed in such a way as to minimize the mismatch of the input constant signal with a given voltage. In addition, the unit has a control input, through which a constant transmission enable signal from the monitoring device is received. In the absence of this signal, the unit does not supply constant levels to the DAC and emitter control device, thereby blocking the transmission of information and control signals.

After passing through the fiber optic link, the optical signal enters the PROM, which includes a photodetector and a photocurrent amplifier. An analog signal proportional to the input optical signal is generated at the PROM output. The received signal is fed to an information signal amplifier and a low-pass filter. The frequency band of the strip amplifier corresponds to the frequency band of information signals. At the output of the device, information signals amplified to the required amplitude are formed. The solution device generates digital information signals in the required format at the output. The amplifier may include automatic gain control (AGC).

The signal supplied to the low-pass filter is filtered in such a way as to separate the control signal from the information signal. Further, after amplification of the control signal by the amplifier and filtering by a high-pass filter, the selected control signal is fed to the level detector. The detector converts the amplitude of the control signal into a constant level signal. After that, using the filter, the required control band is selected. From the output of the filter, a constant-level signal is fed to the ADC, which generates a digital signal that is sent for analysis to a digital control unit (microcontroller). The control unit analyzes the changes in the input digital signal in such a way that a dangerous signal is generated corresponding to an attempt to extract information from the fiber-optic transmission line.

In this case, an alarm is generated, which is transmitted to the sound emitter and light indicator. At the output of the block, a constant enable signal is taken. In the absence of a dangerous signal at the output of the unit, a constant resolution level is maintained. The indicator light reflects the current deviation of the input signal from the set value.

The transceiver unit has the following disadvantages:

1. The lack of automatic adjustment of the input signal of a digital control unit when connected to a fiber optic link with various transmission ratios.

2. The lack of adjustment of the amplitude of the input signal of the control unit during operation.

3. The complexity of the implementation of technical means of protecting information from leakage through the optical channel.

The technical problem to be solved is the creation of a transceiver device with automatic tuning when connected to a fiber optic link with various transmission coefficients and with periodic automatic adjustment during operation, as well as the simplification of technical means of protecting information from leaks through the optical channel.

The technical result is the elimination of the need to adjust the level of the input signal of the controller when connecting and in operation of the device as part of protected FOTS.

This technical result is achieved by the fact that the transceiver of the protected fiber-optic system for transmitting information of limited access contains an optical transmitter including a control device and an emitter, the optical output pole of which is connected via an optical fiber transmission line to the input optical pole of the optical receiver, including a receiving optical module, a limiting amplifier and a solution device whose output is an electric the output of the transceiver device, a control unit including an amplifier, a level detector and serially connected ADCs, a controller and a sound emitter, while the input of the emitter control device is the input of the transceiver device. New is that the optical receiver additionally contains series-connected DACs, a matching device and a regulator, the control input of the emitter control device is connected to the first output port of the controller, the second output port of which is connected to the DAC input, the output of the matching device is connected to the controller control input, output which is connected to the input of the amplifier, the output of which is connected to the input of the detector, the output of which is connected to the input of the ADC, the input of the controller is connected to the output of the receiving optical module.

The set of essential features of the claimed device allows to exclude the adjustment of the input signal level of the controller. Figure 1 presents a functional diagram of a transceiver device.

1 - electrical input of the device;

2 - radiator control device (driver);

3 - emitter (LED, semiconductor laser);

4 - output optical pole (detachable optical connector);

5 - FOCL;

6 - input optical pole (detachable optical connector);

7 - receiving optical module (PROM);

8 - amplifier limiter;

9 - solution device;

10 - electrical output of the device;

11 - amplitude regulator;

12 - amplifier;

13 - level detector;

14 - analog-to-digital Converter (ADC);

15 - controller;

16 - sound emitter;

17 - digital-to-analog converter (DAC);

18 - control device;

19 - an optical transmitter;

20 - optical receiver;

21 - control unit.

Figure 2 shows the timing diagrams of the automatic adjustment of the input signal level of the controller.

The inventive device operates as follows. Input digital information signals are fed to the electrical input of the device 1 (figa). The control device of the emitter 2 generates a modulation current of the emitter 3. The information optical signal is fed to the output optical pole 4 and then to the FOCL 5.

After passing through the FOCL 5, the optical signal enters the input pole of the device 6 and then to the receiving optical module (PROM) 7. The PROM incorporates a photodetector and a photocurrent amplifier. An analog signal is generated at the output of the PROM, which then goes to the inputs of two devices: an amplifier-limiter 8 and an amplitude regulator 11. From the output of an amplifier-limiter 8, information signals are fed to the input of a solution 9, which restores the amplitude of the digital signals in the required format (Fig. 2A).

From the output of the amplitude controller 11, information signals are fed to an amplifier 12, which increases the amplitude of the signals to the desired value. From the output of amplifier 12, the signals are fed to the input of a level 13 detector, which generates a constant voltage level at the output, the value of which is proportional to the amplitude of the input signal.

The obtained constant level is fed to the input of the ADC 14, where it is converted to digital form, and fed to the input of the controller 15. The controller uses a special algorithm to process the input signal and extracts an unauthorized access signal from it. In this case, the controller 15 generates an ALARM signal to the sound emitter 18 and removes the transmission enable signal from the control input of the emitter control device 2.

Automatic configuration when you turn on the device is as follows (figb). The digital input signal U ₁ after transmission via the fiber optic link, reception and conversion of PROM 7 at the output of the regulator 11 has the approximate form, which is shown in the drawing (U ₁₁ ). The amplitude of this signal, depending on the transmission coefficient of the fiber optic link, can have a different value. Accordingly, a constant voltage level at the output of the detector 13 (U ₁₃ ) can also take different values.

When turned on, the controller 15 generates a digital signal at the output that corresponds to the minimum transfer coefficient of the regulator 11. The digital signal is converted into analog form using the DAC 17 and the matching device 18 and is fed to the control input of the regulator 11. After a delay exceeding the transient time in the regulator 11 , amplifier 12, level detector 13 and ADC 14, the controller compares the signal received at the input with the lower value of the range of nominal values U _min . If the signal is greater than this value, the controller generates the corresponding control signal of the sound emitter 16, warning about the need to reduce the modulation depth of the information signal at the transmitting pole of the FOCL. If the signal received at the input does not exceed U _min , the controller generates a digital signal at the output that corresponds to the maximum transfer coefficient of the regulator 11. After a corresponding delay, the controller compares the signal received at the input with the upper value of the range of nominal values U _max . If the signal is less than this value, the controller generates the corresponding control signal of the sound emitter 16, warning about the need to increase the modulation depth of the information signal at the transmitting pole of the FOCL. If the signal received at the input exceeds U _max , the controller changes the control signal of the transfer coefficient of the controller 11 according to the fastest descent method until the signal at the input of the controller is as close as possible to the average value of the range of nominal values U _n . After that, the device automatically switches to transmission mode with FOL control.

During operation, the controller input signal is periodically compared with the nominal value of U _n (figv). If the value of the input signal is outside the tolerance ΔU, then the nominal value of the signal is set by the method of successive approximation with a uniform increase or decrease in the transfer coefficient of the controller 11.

The ability to connect to the FOCL while changing the gear ratio of the controller 11 is excluded as follows. Before starting to change the transfer coefficient of the controller 11, the value of the signal at the input of the controller U ₀ and the corresponding value of the digital gain control signal U _{y0 are} stored in separate controller registers. After setting the nominal value of the signal at the controller input, the new value of the input signal U ₁ and the corresponding value of the digital control signal U _{y1 are} recorded in other registers. Next, the controller generates a digital signal U _y0 and compares the value of the input signal with the previously stored value U ₀ . If the signal difference exceeds the permissible value, the controller generates an ALARM signal and prohibits the transmission of information. In the case of an acceptable signal difference, the controller again generates a digital signal U _y1 and compares the value of the input signal with U ₁ . With an acceptable signal difference, the controller puts the device into transmission mode with FOL control. Otherwise, the controller generates an ALARM signal and prohibits the transmission of information.

To confirm the operability of the claimed device and experimental determination of the parameters, a mock transceiver unit was assembled. The emitter control device was made on 2T643A-2 microwave transistors and a current source on an operational amplifier (OU) 1053UD2A and a 2T3102E transistor. The transmitting optical module HFBR-1312T was used as an emitter. As the receiving optical module, the HFBR-2316T was used. The limiting amplifier and amplifier are made on a 500LP116 microcircuit, and the solution device is on a 597CA1A comparator.

The amplitude regulator is a common source cascade on a 2P327A two-gate field effect transistor. The level detector is made on a pulse diode bridge 2D523B. The ADC and controller are based on the PIC16C717 microcontroller with specially developed software. Sound emitter - piezoelectric bell with control.

The device model provided the transmission of digital information at a speed of 125 Mbit / s according to the 100Base-FX standard and control of changes in the magnitude of the introduced losses in the FOCL at the level of 0.05 dB, a high probability of detecting attempts to access the FOCL and a low probability of false positives.

Claims (1)

A transmitting device of a protected fiber-optic system for transmitting information of limited access, comprising an optical transmitter including a control device for an emitter and an emitter, the optical output pole of which is connected via an optical fiber transmission line to the input optical pole of an optical receiver, including a receiving optical receiver connected in series a module, an amplifier-limiter and a solution device, the output of which is an electrical output transceiver o device, a control unit including an amplifier, a level detector, and an analog-to-digital converter, a controller, and a sound emitter in series, the input of the emitter control device being an input to a transceiver device, characterized in that the digital-to-analog converter is additionally introduced into the optical receiver , the coordination device and the regulator, the control input of the radiator control device is connected to the first output port of the controller, the second the output port of which is connected to the input of the digital-analog converter, the output of the matching device is connected to the control input of the controller, the output of which is connected to the input of the amplifier, the output of which is connected to the input of the detector, the output of which is connected to the input of the analog-to-digital converter, the input of the controller is connected to the output of the receiving optical module .

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