SU1647920A1 - Digital optoelectronic transmitter - Google Patents

Abstract

The invention relates to an optoelectronic technique. The purpose of the invention is to increase the reliability of the device by increasing the service life. The transmitter contains 1.2 and 17 reference level sources, a gating pulse shaper 3, a signal presence analyzer 4, keys 5-8, a photo detector 9, level 10 and 11 detectors, subtractors 12-14, integrators 15 and 16, amplifiers 18 -20, a semiconductor emitter 21, adders 22-24 and a threshold el-25. The transmitter jointly controls the reference level and the signal component of the radiation power. This leads to the fact that increasing or decreasing the ambient temperature and the corresponding deformation of the energy x-ki is accompanied by an increase or decrease in the reference current generated by the amplifier 19 for the radiator 21, and the necessary change in the modulation current produced by the amplifier 20, so that the minimum and maximum radiation levels remain unchanged. In order to avoid ejection of the radiator 21 during its operation in the high temperature mode, the control circuit of the signal component contains the control circuit of the reference voltage. 1 il. fe

Description

The invention relates to optoelectronic technology and can be used in fiber optic transmission systems for digital electrical signals.

The purpose of the invention is to increase the reliability of the device by increasing the service life.

The drawing shows a structural diagram of a digital optoelectronic transmitter.

The transmitter contains the first and second sources 1 and 2 of the reference level, the driver 3 gating pulses, the analyzer 4 the presence of the signal, the first, second, third and fourth keys 5-8, photodetector 9, the first and second level detectors 10 and 11, the first, second and third subtraction elements 12-14, first and second integrators 15 and 16, third reference level source 17, first, second and third amplifiers 18-20, semiconductor emitter 21, first, second and third adders 22-24 and threshold element 25.

The device operates as follows.

The current of the photodetector 9, optically coupled to the emitter 21, is amplified by the first amplifier 18. As a result, a voltage with high and low levels is present at its output. This voltage is applied to the information input of the first 10 and second 11 level detectors. The first of them produces a constant voltage equal to the low voltage level. To achieve this, sample pulses are received at its control input from the first output of the shaper 3. The delay, determined mainly by the time of establishment of the transient response of the amplifier 18, is necessary to eliminate errors in the formation of the specified level of the detector.

At the control input of the analyzer 4 there is a high level voltage, at the information - a converted digital signal. Under these conditions, the analyzer 4 generates a voltage of a high level as well. It, arriving at the control input of the second key 6, maintains it in the open state, and the reference level generated by the source 1, passes to the second input of the subtraction element 12, at the first input of which there is a constant voltage of a low level. The subtraction element 12 forms a control signal, which is supplied through the first integrator 15 to the input of the amplifier 19. The amplifier 19 at the output generates a bias current of the emitter 21.

The signal from the output of amplifier 18 also enters the information input of the second level detector 11, which generates a constant voltage equal to the voltage of a high level of the input signal. To achieve this, sample pulses are applied to the control input of the detector from the second output of the shaper 3.

At the control input of the third switch 7 there is a high level voltage. It maintains the key in the open state, and the reference voltage generated by the source 2 passes to the first input of the third adder 24. At the initial stages of the degradation of the semiconductor emitter 21, when the instantaneous values of the pump current are less than the maximum permissible, the fourth key 8 is in the closed state, and the first input of the adder 24 is no voltage. With this in mind, the output of the adder 24, i.e. at the second input of the subtraction element 13 there is a reference voltage of the source 2. The subtraction element 13 forms a control signal, which is fed through the second integrator 16 to the input of the amplifier 20. The amplifier 20 generates a modulation current at the output.

The combined action of the control circuits of the reference level and the signal component of the radiation power leads to the fact that an increase or decrease in the ambient temperature and the corresponding deformation of the energy characteristic is accompanied by an increase or decrease in the reference current generated by the amplifier 19 and the necessary change in the modulation current generated by the amplifier 20, so that the minimum and maximum radiation levels remain unchanged. Operation at high temperature and observing the condition of constant radiation levels requires (due to degradation) the total current (reference and modulation) of the pump exceeding the maximum permissible value, which disables (possibly instantly) the laser. To avoid this, the signal component control circuit contains a voltage reference control circuit. It is formed by a third reference voltage source 17, a second 23 and a third 24 adders, a third subtraction element 14 and a threshold element 25. At the initial stages of the degradation of the semiconductor emitter 21, the total current of the amplifiers 19 and 25 is less than the maximum permissible and, accordingly, the voltage at the output of the adder is less than the level generated by the source

17. In this case, the threshold element 25 generates a low level voltage at the output. It maintains the key 8 in the closed state and the signal from the output of the subtraction element 14 does not pass to the first input of the adder circuit 24.

With increasing temperature or the degree of degradation of the emitter 21, the total current increases and can become equal to the maximum permissible. The output of the adder 23 appears corresponding to the total voltage greater than the level of the source 17, the Subtraction Element 14 forms a negative control signal, which, passing through the public key 8, is fed to the first input of the adder 24 and reduces the input voltage of the amplifier 20. The modulation current at the output of the amplifier decreases until the total current is again equal (with some error) to the maximum allowable. Thus, the total current is fixed (limited from above) at the maximum permissible level.

In the case of continued operation of the transmitter, the energy characteristic of the laser shifts even more and the control circuit of the signal component of the radiation power further reduces the amplitude of the modulating current and, accordingly, the amplitude of the signal component of optical power.

With decreasing ambient temperature, the control circuit of the reference level of radiation power decreases the reference current, which leads to a decrease in the total current and, as a consequence, to a decrease in the absolute value of the negative control signal generated by the control circuit of the reference voltage and supplied to the first input of the adder 24. In this case the control circuit of the signal component of the radiation power increases the amplitude of the modulating current. The process continues until then. while the maximum level of radiation power corresponding to symbol 1 of the digital electric signal does not reach the maximum permissible radiation power, the voltage at the output of the adder 23, decreasing in value, does not equal the level of the source 17, and the control signal · is equal to zero. In this case, the threshold element 25 returns to its initial state corresponding to the formation of a low level voltage at the output, which puts the key 8 in the closed state and turns off the control circuit of the reference voltage. With a further decrease in temperature, the control circuit of the signal component no longer increases, but decreases the amplitude of the modulating current. If there is no digital signal at the input of the device, analyzer 4 generates a low voltage level. It supports keys 6 and 7 in the closed state, and the voltage at the second inputs of the subtraction elements 12 and 13 is zero, i.e. in the absence of a convertible digital signal at the input of the proposed transmitting module, the pump current of the semiconductor emitter is zero.

When a digital signal appears at the input of the device at the output of the analyzer 4, a high level voltage appears, which switches the keys 6 and 7 to the open state. As a result, a voltage jump equal to the reference level of the source 1 appears at the output of the subtraction element 12. The current of the amplifiers 19 and 20 begins to increase exponentially and by the same law the output voltage of the subtraction elements 12 and 13 decreases. Similarly, the transmitter operates when the input digital signal is lost (turned off).

Claims (1)

Claim A digital optoelectronic transmitter comprising first and second reference level sources, a gate pulse generator, a first level detector and a first subtraction element connected in series, a second level detector and a second subtraction element connected in series, a photodetector and a first amplifier connected in series, a second amplifier connected in series, a first adder and a semiconductor emitter and a third amplifier and a first key connected in series, the output of the first key is connected to the second input of the first adder, the input of the gate pulse generator is connected to the control input of the first key and is the information input of the device, the emitter output is optically connected to the photodetector input and is the output of the device, the first and second outputs of the gate pulse generator are connected to the control inputs of the first and second level detectors, respectively , the output of the first amplifier is connected to the information inputs of the first and second level detectors, characterized in that, in order to increase the reliability of the device by increasing the service life, the second, third and fourth keys, the signal availability analyzer, the first and second integrators, the third reference level source, the second and third adders, the third subtraction element and the threshold element, the control input of the signal availability analyzer are the control input devices, the input of the signal availability analyzer is connected to the information input of the device, the output of the signal availability analyzer is connected to the control inputs of the second and third keys, the outputs of the first the second sources of the reference level are connected to the inputs of the second and third keys, respectively, the output of the second key is connected to the second input of the first subtraction element, the output of the first and second subtraction elements are connected to the inputs of the first and second integrators, the outputs of which are connected to the inputs of the second and third amplifiers, the outputs of which are connected respectively to the first and second inputs of the second adder, the output of which is connected to the first input of the third 5 subtraction element and to the threshold input about the element whose output is connected to the control input of the fourth key, the output of the third source of the reference level is connected to the second input of the third subtraction element 10, the output of which is connected to the input of the fourth key, the output of which is connected to the first input of the third adder, the output of which is connected to the second input of the second subtraction element, the output 15 of the third key is connected to the second input of the third adder. Compiled by A. Alexandrov Editor N. Yatsola Tehred M. Morgenthal Corrector O. Kundrick Order 1415 Circulation 394 Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.