CN118316535A

CN118316535A - Optical link with stable gain bias and method for maintaining stable gain bias of optical link

Info

Publication number: CN118316535A
Application number: CN202410521384.5A
Authority: CN
Inventors: 吕宗璟; 盛亮; 李海涛; 李阳; 张美�; 罗通顶; 田耕; 王晶; 李玉婷
Original assignee: Northwest Institute of Nuclear Technology
Current assignee: Northwest Institute of Nuclear Technology
Filing date: 2024-04-28
Publication date: 2024-07-09

Abstract

The invention relates to an optical link and a method for maintaining stable gain bias of the optical link, in particular to an optical link with stable gain bias and a method for maintaining stable gain bias of the optical link, which solve the technical problems of poor stability, system gain and bias along with temperature change of the existing optical link. According to the backlight monitoring PD current value detected by the backlight monitoring PD current detection circuit and the system output voltage sampling signal acquired by the control unit, the attenuation multiple of the electrically adjustable attenuator and the output of the direct current bias circuit are regulated, so that the gain and bias of the optical link are controlled, the gain and bias of the optical link are kept stable, the influence of factors such as temperature change, optical fiber bending and the like on the gain of the optical link and the influence of factors such as temperature drift and optical power change of the photoelectric device and the electronic device on the output bias of the optical link can be effectively eliminated.

Description

Optical link with stable gain bias and method for maintaining stable gain bias of optical link

Technical Field

The invention relates to an optical link and a method for maintaining gain offset stability of the optical link, in particular to an optical link with stable gain offset and a method for maintaining gain offset stability of the optical link.

Background

The optical link has the advantages of low noise, low loss, high broadband and the like, and is widely applied to the fields of civil communication, radar, electronic countermeasure, radio astronomy, aerospace and the like at present; the principle is that an electro-optical conversion device is used for modulating an input signal onto laser, and then an optical signal is restored into an electric signal at a receiving end, so that the remote transmission of the signal is realized.

However, the existing optical link is affected by factors such as light source stability, optical fiber loss, semiconductor device temperature drift, and the like, and has the problems of poor stability, system gain and bias changing along with temperature, and the like, so that the performance of the optical link is poor, and the quality of a transmission signal is affected.

Disclosure of Invention

The invention aims to solve the technical problems of poor stability and system gain and bias variation along with temperature of the existing optical link, and provides an optical link with stable gain bias and a method for maintaining the stable gain bias of the optical link.

In order to achieve the above purpose, the invention adopts the following technical scheme:

An optical link with stable gain bias is characterized in that: the device comprises a light emitting circuit, a laser light source, a photoelectric detector, a light receiving circuit, an electrically adjustable attenuator, an isolation buffer circuit, a gating controller, a standard square wave source, a direct current bias circuit, a backlight monitoring PD current detection circuit and a control unit which are sequentially connected;

The two input ends of the gating controller are respectively connected with the output end of the standard square wave source and the input signal, the output end of the gating controller is connected with the input end of the light emitting circuit, the control end of the gating controller is connected with the first output end of the control unit, and the gating controller is used for selecting the input signal or the standard square wave signal output by the standard square wave source as the input electric signal of the light emitting circuit;

one output end of the isolation buffer circuit is used for outputting a system output signal, and the other output end of the isolation buffer circuit is connected with the first input end of the control unit and used for outputting a system output voltage sampling signal;

The input end of the backlight monitoring PD current detection circuit is connected with the backlight monitoring PD current output end of the laser light source, the output end of the backlight monitoring PD current detection circuit is connected with the second input end of the control unit, and the backlight monitoring PD current detection circuit is used for detecting the backlight monitoring PD current and outputting a detection current value to the control unit;

The two control ends of the direct current bias circuit are respectively connected with the second output end and the third output end of the control unit, the two output ends are respectively connected with the direct current bias ends of the light emitting circuit and the light receiving circuit, and the direct current bias circuit is used for generating a first direct current bias signal required by the laser light source and a second direct current bias signal required by the isolation buffer circuit

The fourth output end of the control unit is connected with the control end of the electrically adjustable attenuator;

The control unit is used for adjusting the attenuation multiple of the electrically adjustable attenuator, controlling the output of the gating controller, adjusting a first direct current bias signal output by the direct current bias circuit according to the detection current value output by the backlight monitoring PD current detection circuit, and adjusting a second direct current bias signal output by the direct current bias circuit according to the system output voltage sampling signal output by the isolation buffer circuit.

Further, the laser light source comprises a DFB laser diode and a backlight monitoring PD arranged in the illumination range of the DFB laser diode;

The input end of the DFB laser diode is connected with the output end of the light emitting circuit, and the output end of the DFB laser diode is connected with the photoelectric detector through an optical fiber;

And the output end of the backlight monitoring PD is connected with the input end of the backlight monitoring PD current detection circuit.

Further, the light emitting circuit includes an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, and a resistor R5;

The non-inverting input end of the operational amplifier A1 is connected with the output end of the gating controller, and the inverting input end of the operational amplifier A1 is connected with the output end of the gating controller and one end of the resistor R1;

the non-inverting input end of the operational amplifier A2 is connected with the first output end of the direct current bias circuit, and the inverting input end of the operational amplifier A2 is connected with the output end of the direct current bias circuit and one end of the resistor R2;

The non-inverting input end of the operational amplifier A3 is connected with the other end of the resistor R1 and the other end of the resistor R2, the inverting input end of the operational amplifier A3 is connected with one end of the resistor R4 and one end of the resistor R3, and the output end of the operational amplifier A3 is connected with the other end of the resistor R3 and one end of the resistor R5;

The other end of the resistor R4 is grounded, and the other end of the resistor R5 is connected with the input end of the DFB laser diode.

Further, the light receiving circuit includes an operational amplifier A5, an operational amplifier A6, an operational amplifier A7, a resistor R8, a resistor R9, a resistor R10, and a resistor R11;

The inverting input end of the operational amplifier A5 is connected with the output end of the photoelectric detector and one end of the resistor R7, the output end is connected with the other end of the resistor R7 and one end of the resistor R8, and the non-inverting input end is grounded;

the non-inverting input end of the operational amplifier A6 is connected with the second output end of the direct current bias circuit, and the inverting input end of the operational amplifier A6 is connected with the output end of the direct current bias circuit and one end of the resistor R9;

The non-inverting input end of the operational amplifier A7 is connected with the other end of the resistor R8 and the other end of the resistor R9, the inverting input end of the operational amplifier A is connected with one end of the resistor R10 and one end of the resistor R11, and the output end of the operational amplifier A is connected with the other end of the resistor R10 and the input end of the electrically adjustable attenuator;

The other end of the resistor R11 is grounded.

Further, the isolation buffer circuit comprises an operational amplifier A8, a resistor R12, a resistor R13, a resistor R14 and a resistor R15;

One end of the resistor R12 and one end of the resistor R13 are connected with the output end of the electrically adjustable attenuator, and the other end of the resistor R12 is used for outputting a system output signal;

The other end of the resistor R13 is connected with the non-inverting input end of the operational amplifier A8;

The inverting input end of the operational amplifier A8 is connected with one end of the resistor R14 and one end of the resistor R15, the output end of the operational amplifier A8 is connected with the other end of the resistor R14, and the output end of the operational amplifier A8 is used for generating a system output voltage sampling signal and is connected with the first input end of the control unit;

The other end of the resistor R15 is grounded.

Further, the backlight monitoring PD current detection circuit comprises an operational amplifier A4 and a resistor R6;

The inverting input end of the operational amplifier A4 is connected with the output end of the backlight monitoring PD42 and one end of the resistor R6, the output end is connected with the other end of the resistor R6 and the second input end of the control unit, and the non-inverting input end is grounded.

Further, the control unit comprises a first control unit and a second control unit;

the direct current bias circuit comprises a first direct current bias circuit and a second direct current bias circuit;

the output end of the first direct current bias circuit is used as a first output end of the direct current bias circuit, is connected with the direct current bias end of the light emitting circuit and is used for outputting a first direct current bias signal;

the output end of the second direct current bias circuit is used as a second output end of the direct current bias circuit, is connected with the direct current bias end of the light receiving circuit and is used for outputting a second direct current bias signal;

The input end of the first control unit is used as a second input end of the control unit, is connected with the output end of the backlight monitoring PD current detection circuit, the two output ends of the first control unit are respectively used as a first output end and a second output end of the control unit, are respectively connected with the control end of the gating controller and the control end of the first direct current bias circuit, and the first control unit is used for controlling the output of the gating controller and adjusting the direct current bias signal output by the first direct current bias circuit according to the detection current value output by the backlight monitoring PD current detection circuit;

The input end of the second control unit is used as a first input end of the control unit and is connected with the other output end of the isolation buffer circuit, the two output ends of the second control unit are respectively used as a fourth output end and a third output end of the control unit and are respectively connected with the control end of the electrically adjustable attenuator and the control end of the second direct current bias circuit, and the second control unit is used for adjusting the attenuation multiple of the electrically adjustable attenuator and adjusting the direct current bias signal output by the second direct current bias circuit according to the system output voltage sampling signal output by the isolation buffer circuit.

Further, the gating controller adopts a relay;

The photoelectric detector adopts a PIN photoelectric detector;

the first direct current bias circuit and the second direct current bias circuit both adopt digital-to-analog converters;

the first control unit and the second control unit both adopt a singlechip.

The invention also provides a method for maintaining the stable gain bias of the optical link, which is based on the optical link with the stable gain bias, and is characterized by comprising the following steps:

Step 1, a control unit controls a gating controller to communicate a standard square wave source with an optical emission circuit, so that a standard square wave signal generated by the standard square wave source is sent to the optical emission circuit, and controls a direct current bias circuit to output a first direct current bias signal to the optical emission circuit and output a second direct current bias signal to an optical receiving circuit;

Step 2, the light emitting circuit modulates the standard square wave signal according to the first direct current bias signal to obtain a modulated signal, and then sends the modulated signal to the laser light source to be converted into an optical signal to be output; the backlight monitoring PD current detection circuit 5 detects the backlight monitoring PD current of the laser light source and sends the detected current value to the control unit; the photodetector 6 receives the optical signal and converts the optical signal into an electrical signal to output to the optical receiving circuit 7;

Step 3, the optical receiving circuit modulates the electric signal according to the second direct current bias signal, and then outputs a system output signal from one output end of the isolation buffer circuit through the electrically adjustable attenuator;

Step 4, the control unit reads a system output voltage sampling signal from the other output end of the isolation buffer circuit (9), then sets a critical value DC _bias of a first direct current bias signal, so that when the first direct current bias signal is smaller than DC _bias, the amplitude of the system output voltage sampling signal becomes smaller, and when the first direct current bias signal is larger than DC _bias, the amplitude of the system output voltage sampling signal remains unchanged;

Step 5, the control unit adjusts the first direct current bias signal to make the first direct current bias signal be DC _bias, marks the detection current value of the backlight monitoring PD at the moment as I _bias, then closes the gating controller to make the light emitting circuit have no input electric signal, adjusts the first direct current bias signal to make the detection current value of the backlight monitoring PD equal to I _bias, and marks the first direct current bias signal at the moment as DC ₁;

Step 6, the control unit processes the system output voltage sampling signal to obtain system output voltage and a direct current bias V _bias thereof, then adjusts a second direct current bias signal until V _bias is zero level, and records the second direct current bias signal as DC ₂;

step 7, the control unit controls the gating controller to communicate the standard square wave source with the light emitting circuit, the control unit adjusts the output of the direct current bias circuit to enable the first direct current bias signal to be DC ₁ and the second direct current bias signal to be DC ₂, then adjusts the attenuation multiple of the electrically adjustable attenuator until the output voltage of the system is equal to T times of the standard square wave source output standard square wave signal, and records the attenuation multiple of the electrically adjustable attenuator as K at the moment; wherein T is the system gain, given by the design requirement;

Step 8, the control unit controls the direct current bias circuit to enable the first direct current bias signal to be DC ₁, the second direct current bias signal to be DC ₂, the attenuation multiple of the electrically adjustable attenuator is set to be K, and then the gating controller is controlled to communicate the input signal with the light emitting circuit, and the light link starts to work normally;

Step 9, the control unit detects a detection current value I _bias2 of the backlight monitoring PD in real time, and if the difference value between I _bias2 and I _bias is smaller than I _bias/300, the DC ₁ is updated to the value of the first direct current bias signal at the moment; otherwise, the first direct current bias signal is adjusted until the difference between I _bias2 and I _bias is smaller than I _bias/300, and then DC ₁ is updated to the value of the first direct current bias signal at the moment;

The control unit reads the system output voltage sampling signal values according to a preset fixed frequency, and judges whether the direct current bias V _bias of the system output voltage is zero level or not every time M system output voltage sampling signal values are acquired, wherein M and the preset fixed frequency are given by design requirements; if the direct current bias V _bias of the system output voltage is zero level, the optical link continues to work; otherwise, returning to the step 1, calibrating the attenuation multiples of the first direct current bias signal, the second direct current bias signal and the electrically adjustable attenuator again, so that the gain bias of the optical link is kept stable.

Further, in step 5, the detection current value of the backlight monitoring PD being equal to I _bias means that the difference between the detection current value and I _bias is less than ±0.1%;

In steps 6 and 9, the V _bias being equal to zero level means-5 mV < V _bias <5mV.

Compared with the prior art, the invention has the following beneficial technical effects:

1. In the optical link with stable gain and bias, the attenuation multiple of the electrically adjustable attenuator and the output of the direct current bias circuit are regulated by monitoring the backlight monitoring PD current value detected by the backlight monitoring PD current detection circuit and the system output voltage sampling signal acquired by the control unit, so that the gain and bias of the optical link are controlled, and the gain and bias of the optical link are kept stable;

2. In the method for maintaining the stable gain bias of the optical link, the control unit controls the direct current bias circuit to provide the direct current bias required by normal operation for the laser light source, so that manual adjustment is not needed, and the working efficiency is greatly improved;

3. In the method for maintaining stable gain bias of the optical link, the real-time detection of the PD current detection circuit is monitored by the light source backlight, and the output light power of the laser light source can be maintained stable in the range of-40-85 ℃ at high and low temperatures;

4. In the method for maintaining the stable bias of the optical link gain, the attenuation multiple of the electrically adjustable attenuator is adjusted by monitoring the output signal in real time, so that the optical link gain can be kept stable, and the influence of factors such as temperature change, optical fiber bending and the like on the optical link gain can be effectively eliminated;

5. In the method for maintaining the stable gain bias of the optical link, the voltage sampling signal is output by the real-time monitoring system, the direct current bias of the optical receiving circuit is regulated, the bias of the optical link can be kept stable, and the influence of factors such as temperature drift, optical power change and the like of the photoelectric device and the electronic device on the output bias of the optical link can be effectively eliminated.

Drawings

FIG. 1 is a system block diagram of an optical link with gain bias stabilization in an embodiment of the present invention;

Fig. 2 is a schematic circuit diagram of an optical link with stabilized gain bias in an embodiment of the present invention.

The reference numerals are explained as follows:

The device comprises a 1-standard square wave source, an 11-DDS chip, a 12-crystal oscillator, a 21-first direct current bias circuit, a 22-second direct current bias circuit, a 3-light emitting circuit, a 4-laser light source, a 41-DFB laser diode, a 42-backlight monitoring PD, a 5-backlight monitoring PD current detection circuit, a 6-photoelectric detector, a 7-light receiving circuit, an 8-electrically adjustable attenuator, a 9-isolation buffer circuit, a 10-gating controller, a 111-first control unit and a 112-second control unit.

Detailed Description

The gain offset stabilized optical link and the method for maintaining gain offset stabilization of the optical link according to the present invention are described in further detail below with reference to the accompanying drawings and detailed description. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.

An optical link with stable gain bias, as shown in fig. 1, comprises an optical transmitting circuit 3, a laser light source 4, a photoelectric detector 6, an optical receiving circuit 7, an electrically adjustable attenuator 8, an isolation buffer circuit 9, a gating controller 10, a standard square wave source 1, a direct current bias circuit, a backlight monitoring PD current detection circuit 5 and a control unit which are sequentially connected. The dc bias circuit includes a first dc bias circuit 21 and a second dc bias circuit 22, and the control unit includes a first control unit 111 and a second control unit 112.

The two input ends of the gating controller 10 are respectively connected with the output end of the standard square wave source 1 and the input signal, the output end is connected with the input end of the light emitting circuit 3, and the control end is connected with the output end of the first control unit 111. The standard square wave source is used for generating a standard square wave signal with determined amplitude, and the gating controller 10 is used for selecting an input signal or the standard square wave signal output by the standard square wave source 1 as an input electric signal of the light emitting circuit 3. In this embodiment, the gate controller 10 employs a relay.

The control terminal of the first dc bias circuit 21 is connected to the output terminal of the first control unit 111, and the output terminal is connected to the dc bias terminal of the light emitting circuit 3, for generating a first dc bias signal required by the laser light source 4. The control end of the second dc bias circuit 22 is connected to the output end of the second control unit 112, and the output end is connected to the dc bias end of the light emitting circuit 3, for generating the second dc bias signal required by the isolation buffer circuit 9.

The light emitting circuit 3 is configured to receive the input electrical signal and the first dc bias signal output from the first dc bias circuit 21, and then modulate the input electrical signal according to the dc bias signal and output it to the laser light source 4.

The laser light source 4 is configured to convert the modulated signal output from the light emitting circuit into an optical signal output, and includes a DFB laser diode 41, and a backlight monitor PD42 disposed within the illumination range of the DFB laser diode 41. The DFB laser diode 41 has an input connected to the output of the light emitting circuit 3 and an output connected to the photodetector 6 via a single mode fiber.

An input terminal of the backlight monitor PD current detection circuit 5 is connected to an output terminal of the backlight monitor PD42, and an output terminal is connected to an input terminal of the first control unit 111. The backlight monitor PD current detection circuit 5 is configured to detect an output current of the light source backlight monitor PD42 and transmit the current value to the first control unit 111.

The photodetector 6 is used to restore the optical signal output by the laser light source 4 to an electrical signal, and in this embodiment, a PIN photodetector is used as the photodetector 6. The light receiving circuit 7 is configured to receive the electrical signal output from the photodetector 6, and modulate the electrical signal according to the second dc bias signal output from the second dc bias circuit 22. Electrically adjustable attenuators are used to adjust the system gain. One output end of the isolation buffer circuit 9 is used for outputting a system output signal, and the other output end is connected with the input end of the second control unit 112 and is used for outputting a system output voltage sampling signal. The isolation buffer circuit 9 is used to increase the load capacity of the system and send out a system output voltage sampling signal to the second control unit 112.

The first control unit 111 is configured to control the output of the gate controller 10, and adjust the dc bias signal output by the first dc bias circuit 21 according to the detected current value output by the backlight monitor PD current detection circuit 5. The output end of the second control unit 112 is further connected to the control end of the electrically adjustable attenuator 8, and the second control unit 112 is configured to adjust the attenuation multiple of the electrically adjustable attenuator 8, and adjust the dc bias signal output by the second dc bias circuit 22 according to the system output voltage sampling signal output by the isolation buffer circuit 9.

In this embodiment, the first dc bias circuit 21 and the second dc bias circuit 22 both use digital-to-analog converters, and the first control unit 111 and the second control unit 112 both use a single-chip microcomputer.

Specifically, as shown in fig. 2, the optical transmission circuit 3 includes an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, and a resistor R5. The non-inverting input terminal of the operational amplifier A1 is connected to the output terminal of the gate controller 10, and the inverting input terminal is connected to the output terminal thereof and to one end of the resistor R1. The non-inverting input terminal of the operational amplifier A2 is connected to the output terminal of the first dc bias circuit 21, and the inverting input terminal is connected to the output terminal and one end of the resistor R2. The non-inverting input end of the operational amplifier A3 is connected with the other end of the resistor R1 and the other end of the resistor R2, the inverting input end is connected with one end of the resistor R4 and one end of the resistor R3, and the output end is connected with the other end of the resistor R3 and one end of the resistor R5. The other end of the resistor R4 is grounded, and the other end of the resistor R5 is connected to the input end of the DFB laser diode 41.

The backlight monitor PD current detection circuit 5 includes an operational amplifier A4 and a resistor R6. The inverting input terminal of the operational amplifier A4 is connected to the output terminal of the backlight monitor PD42 and one end of the resistor R6, the output terminal is connected to the other end of the resistor R6 and the input terminal of the first control unit 111, and the non-inverting input terminal is grounded.

The light receiving circuit 7 includes an operational amplifier A5, an operational amplifier A6, an operational amplifier A7, a resistor R8, a resistor R9, a resistor R10, and a resistor R11. The inverting input end of the operational amplifier A5 is connected with the output end of the photoelectric detector 6 and one end of the resistor R7, the output end is connected with the other end of the resistor R7 and one end of the resistor R8, and the non-inverting input end is grounded. The non-inverting input terminal of the operational amplifier A6 is connected to the output terminal of the second dc bias circuit 22, and the inverting input terminal is connected to the output terminal thereof and to one end of the resistor R9. The non-inverting input end of the operational amplifier A7 is connected with the other end of the resistor R8 and the other end of the resistor R9, the inverting input end is connected with one end of the resistor R10 and one end of the resistor R11, and the output end is connected with the other end of the resistor R10 and the input end of the electrically adjustable attenuator 8; the other end of the resistor R11 is grounded.

The isolation buffer circuit 9 includes an operational amplifier A8, a resistor R12, a resistor R13, a resistor R14, and a resistor R15. One end of a resistor R12 and one end of a resistor R13 are connected with the output end of the electrically adjustable attenuator 8, and the other end of the resistor R12 is used for outputting a system output signal. The other end of the resistor R13 is connected with the non-inverting input end of the operational amplifier A8, the inverting input end of the operational amplifier A8 is connected with one end of the resistor R14 and one end of the resistor R15, the output end of the operational amplifier A8 is connected with the other end of the resistor R14, the output end of the operational amplifier A8 is used for generating a system output voltage sampling signal, the output end of the operational amplifier A8 is connected with the input end of the second control unit 112, and the other end of the resistor R15 is grounded.

The embodiment also provides a method for maintaining stable gain bias of an optical link, which adopts the optical link with stable gain bias, and comprises the following steps:

Step 1, a first control unit 111 controls a gating controller 10 to communicate a standard square wave source 1 with a light emitting circuit 3, so that a standard square wave signal generated by the standard square wave source 1 is sent to the light emitting circuit 3, and controls a first direct current bias circuit 21 to output a first direct current bias signal to the light emitting circuit 3; the second control unit 112 controls the second dc bias circuit 22 to output the second dc bias signal to the light receiving circuit 7.

Step 2, the light emitting circuit 3 modulates the standard square wave signal according to the first direct current bias signal to obtain a modulated signal, and then sends the modulated signal to the laser light source 4 to be converted into an optical signal to be output; the backlight monitoring PD current detection circuit 5 detects the backlight monitoring PD current of the laser light source and sends the detected current value to the control unit; the photodetector 6 receives the optical signal, converts the optical signal into an electrical signal, and outputs the electrical signal to the light receiving circuit 7.

And 3, modulating the electric signal by the light receiving circuit 7 according to the second direct current bias signal, and outputting a system output signal from one output end of the isolation buffer circuit 9 through the electrically adjustable attenuator 8.

Step 4, the second control unit 112 reads the system output voltage sampling signal from the other output end of the isolation buffer circuit 9, and then sets the critical value DC _bias of the first DC bias signal, so that when the first DC bias signal is smaller than DC _bias, the amplitude of the system output voltage sampling signal becomes smaller, and when the first DC bias signal is larger than DC _bias, the amplitude of the system output voltage sampling signal remains unchanged.

In step 5, the first control unit 111 adjusts the first DC bias signal to make the first DC bias signal DC _bias, marks the detected current value of the backlight monitor PD at this time as I _bias, then turns off the gate controller 10, makes the light emitting circuit 3 have no input electrical signal, adjusts the first DC bias signal output by the first DC bias circuit 21 to make the detected current value of the backlight monitor PD equal to I _bias, and marks the first DC bias signal at this time as DC ₁. When the difference between the detected current value and I _bias is less than ±0.1%, the detected current value is considered to be equal to I _bias.

Step 6, the second control unit 112 processes the system output voltage sampling signal to obtain a system output voltage and a DC bias V _bias thereof, and then adjusts the second DC bias signal until V _bias is at zero level, and considers V _bias as zero level when the second DC bias signal is recorded as DC ₂.-5mV<V_bias <5 mV.

Step 7, the first control unit 111 controls the gating controller 10 to communicate the standard square wave source 1 with the light emitting circuit 3, and adjusts the output of the first direct current bias circuit 21 to make the first direct current bias signal DC ₁; the second control unit 112 adjusts the output of the second DC bias circuit 21 to make the second DC bias signal DC ₂, and adjusts the attenuation multiple of the electrically adjustable attenuator 8 until the system output voltage is equal to T times of the standard square wave source 1 output standard square wave signal, and records the attenuation multiple of the electrically adjustable attenuator 8 at this time as K. Where T is the system gain, given by the design requirements.

Step 8, the first control unit 111 adjusts the output of the first DC bias circuit 21 to make the first DC bias signal DC ₁; the second control unit 112 adjusts the output of the second DC bias circuit 21 so that the second DC bias signal is DC ₂ and the attenuation multiple of the electrically adjustable attenuator 8 is set to K, and then the first control unit 111 controls the gate controller 10 to communicate the input signal with the light emitting circuit 3, and the optical link starts to operate normally.

Step 9, the control unit detects a detection current value I _bias2 of the backlight monitoring PD in real time, and if the difference value between I _bias2 and I _bias is smaller than I _bias/300, the DC ₁ is updated to the value of the first direct current bias signal at the moment; otherwise, the first DC bias signal is adjusted until the difference between I _bias2 and I _bias is less than I _bias/300, and then DC ₁ is updated to the value of the first DC bias signal at that time. The control unit reads the system output voltage sampling signal values according to a preset fixed frequency, and judges whether the direct current bias V _bias of the system output voltage is zero level or not every time M system output voltage sampling signal values are acquired, wherein M and the preset fixed frequency are given by design requirements; if the direct current bias V _bias of the system output voltage is zero level, the optical link continues to work; otherwise, returning to the step 1, calibrating the attenuation multiples of the first direct current bias signal, the second direct current bias signal and the electrically adjustable attenuator 8 again, so that the gain bias of the optical link is kept stable. In this example, V _bias is considered to be equal to zero level when m=1000, -5mV < V _bias <5 mV.

Specifically, after the optical link works normally, the second control unit 112 reads the system output voltage sampling signal value from the other output end of the isolation buffer circuit 9 once every ten milliseconds, and if the continuously read system output voltage sampling signal values are all zero level, the first control unit 111 reads the detection current value I _bias1 of the backlight monitoring PD once. If I _bias1 at this time is equal to I _bias, the first dc bias signal is maintained unchanged, otherwise, the first dc bias signal output by the first dc bias circuit 21 is adjusted until I _bias1 is equal to I _bias.

In normal operation of the system, the probability of the same value being acquired by the signal is smaller for the analog signal, and in long-time sampling, the probability of the same signal being continuously acquired is smaller, and only the base line can be sampled for a plurality of times. The sampling position may correspond to the actual signal and is not necessarily the baseline, so that multiple samplings are required when judging the dc offset of the system output voltage.

Claims

1. An optical link with stable gain bias, characterized by: the device comprises a light emitting circuit (3), a laser light source (4), a photoelectric detector (6), a light receiving circuit (7), an electrically adjustable attenuator (8) and an isolation buffer circuit (9), a gating controller (10), a standard square wave source (1), a direct current bias circuit, a backlight monitoring PD current detection circuit (5) and a control unit which are connected in sequence;

Two input ends of the gating controller (10) are respectively connected with the output end and the input signal of the standard square wave source (1), the output end is connected with the input end of the light emitting circuit (3), the control end is connected with the first output end of the control unit, and the gating controller (10) is used for selecting the input signal or the standard square wave signal output by the standard square wave source (1) as the input electric signal of the light emitting circuit (3);

one output end of the isolation buffer circuit (9) is used for outputting a system output signal, and the other output end of the isolation buffer circuit is connected with the first input end of the control unit and used for outputting a system output voltage sampling signal;

the input end of the backlight monitoring PD current detection circuit (5) is connected with the backlight monitoring PD current output end of the laser light source (4), the output end of the backlight monitoring PD current detection circuit is connected with the second input end of the control unit, and the backlight monitoring PD current detection circuit (5) is used for detecting the backlight monitoring PD current and outputting a detection current value to the control unit;

The two control ends of the direct current bias circuit are respectively connected with the second output end and the third output end of the control unit, the two output ends are respectively connected with the direct current bias ends of the light emitting circuit (3) and the light receiving circuit (7), and the direct current bias circuit is used for generating a first direct current bias signal required by the laser light source (4) and a second direct current bias signal required by the isolation buffer circuit (9);

The fourth output end of the control unit is connected with the control end of the electrically adjustable attenuator (8);

the control unit is used for adjusting the attenuation multiple of the electrically adjustable attenuator (8), controlling the output of the gating controller (10), adjusting the first direct current bias signal according to the detected current value and adjusting the second direct current bias signal according to the system output voltage sampling signal.

2. The gain-biased stable optical link of claim 1, wherein: the laser light source (4) comprises a DFB laser diode (41) and a backlight monitoring PD (42) arranged in the illumination range of the DFB laser diode (41);

the input end of the DFB laser diode (41) is connected with the output end of the light emitting circuit (3), and the output end is connected with the photoelectric detector (6) through an optical fiber;

the output end of the backlight monitoring PD (42) is connected with the input end of the backlight monitoring PD current detection circuit (5).

3. The gain-biased stable optical link of claim 2, wherein: the light emitting circuit (3) comprises an operational amplifier A1, an operational amplifier A2, an operational amplifier A3, a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a resistor R5;

The non-inverting input end of the operational amplifier A1 is connected with the output end of the gating controller (10), and the inverting input end is connected with the output end of the gating controller and one end of the resistor R1;

The other end of the resistor R4 is grounded, and the other end of the resistor R5 is connected with the input end of the DFB laser diode (41).

4. A gain-biased stable optical link as claimed in claim 3, wherein: the light receiving circuit (7) includes an operational amplifier A5, an operational amplifier A6, an operational amplifier A7, a resistor R8, a resistor R9, a resistor R10, and a resistor R11;

The inverting input end of the operational amplifier A5 is connected with the output end of the photoelectric detector (6) and one end of the resistor R7, the output end is connected with the other end of the resistor R7 and one end of the resistor R8, and the non-inverting input end is grounded;

The non-inverting input end of the operational amplifier A7 is connected with the other end of the resistor R8 and the other end of the resistor R9, the inverting input end of the operational amplifier A7 is connected with one end of the resistor R10 and one end of the resistor R11, and the output end of the operational amplifier A7 is connected with the other end of the resistor R10 and the input end of the electrically adjustable attenuator (8);

The other end of the resistor R11 is grounded.

5. The gain-biased stable optical link of claim 4, wherein: the isolation buffer circuit (9) comprises an operational amplifier A8, a resistor R12, a resistor R13, a resistor R14 and a resistor R15;

One end of the resistor R12 and one end of the resistor R13 are connected with the output end of the electrically adjustable attenuator (8), and the other end of the resistor R12 is used for outputting a system output signal;

The other end of the resistor R15 is grounded.

6. The gain-biased stable optical link of claim 5, wherein: the backlight monitoring PD current detection circuit (5) comprises an operational amplifier A4 and a resistor R6;

the inverting input end of the operational amplifier A4 is connected with the output end of the backlight monitoring PD (42) and one end of the resistor R6, the output end is connected with the other end of the resistor R6 and the second input end of the control unit, and the non-inverting input end is grounded.

7. A gain-biased stable optical link as claimed in any one of claims 1-6, wherein: the control unit comprises a first control unit (111) and a second control unit (112);

The direct current bias circuit comprises a first direct current bias circuit (21) and a second direct current bias circuit (22);

the output end of the first direct current bias circuit (21) is used as a first output end of the direct current bias circuit, is connected with the direct current bias end of the light emitting circuit (3) and is used for outputting a first direct current bias signal;

The output end of the second direct current bias circuit (22) is used as a second output end of the direct current bias circuit, is connected with the direct current bias end of the light receiving circuit (7) and is used for outputting a second direct current bias signal;

The input end of the first control unit (111) is used as a second input end of the control unit, is connected with the output end of the backlight monitoring PD current detection circuit (5), the two output ends of the first control unit are respectively used as a first output end and a second output end of the control unit, are respectively connected with the control end of the gating controller (10) and the control end of the first direct current bias circuit (21), the first control unit (111) is used for controlling the output of the gating controller (10), and adjusts a first direct current bias signal output by the first direct current bias circuit (21) according to a detection current value output by the backlight monitoring PD current detection circuit (5);

the input end of the second control unit (112) is used as a first input end of the control unit, is connected with the other output end of the isolation buffer circuit (9), the two output ends of the second control unit are respectively used as a fourth output end and a third output end of the control unit, and are respectively connected with the control end of the electric adjustable attenuator (8) and the control end of the second direct current bias circuit (22), and the second control unit (112) is used for adjusting the attenuation multiple of the electric adjustable attenuator (8) and adjusting the second direct current bias signal output by the second direct current bias circuit (22) according to the system output voltage sampling signal output by the isolation buffer circuit (9).

8. The gain-biased stable optical link of claim 7, wherein: the gating controller (10) adopts a relay;

the photoelectric detector (6) adopts a PIN photoelectric detector;

the first direct current bias circuit (21) and the second direct current bias circuit (22) adopt digital-to-analog converters;

the first control unit (111) and the second control unit (112) are both single-chip computers.

9. A method of maintaining gain bias stability for an optical link based on the gain bias stable optical link of any of claims 1-8, comprising the steps of:

Step1, a control unit controls a gating controller (10) to communicate a standard square wave source (1) with a light emitting circuit (3), so that a standard square wave signal generated by the standard square wave source (1) is sent to the light emitting circuit (3), and controls a direct current bias circuit to output a first direct current bias signal to the light emitting circuit (3) and a second direct current bias signal to a light receiving circuit (7);

Step 2, the light emitting circuit (3) modulates the standard square wave signal according to the first direct current bias signal to obtain a modulation signal, and then sends the modulation signal to the laser light source (4) to be converted into an optical signal to be output; a backlight monitoring PD current detection circuit (5) detects the backlight monitoring PD current of the laser light source (4) and sends the detected current value to the control unit; the photoelectric detector (6) receives the optical signal and converts the optical signal into an electric signal to be output to the optical receiving circuit (7);

Step 3, the light receiving circuit (7) modulates the electric signal according to the second direct current bias signal, and then outputs a system output signal from one output end of the isolation buffer circuit (9) through the electrically adjustable attenuator (8);

Step 5, the control unit adjusts the first direct current bias signal to make the first direct current bias signal be DC _bias, marks the detection current value of the backlight monitoring PD at the moment as I _bias, then closes the gating controller (10), makes the light emitting circuit (3) have no input electric signal, adjusts the first direct current bias signal to make the detection current value of the backlight monitoring PD equal to I _bias, and marks the first direct current bias signal at the moment as DC ₁;

Step 7, a control unit controls a gating controller (10) to communicate a standard square wave source (1) with a light emitting circuit (3), adjusts the output of a direct current bias circuit to enable a first direct current bias signal to be DC ₁ and a second direct current bias signal to be DC ₂, then adjusts the attenuation multiple of an electrically adjustable attenuator (8) until the output voltage of the system is equal to T times of the standard square wave source (1) outputting the standard square wave signal, and records the attenuation multiple of the electrically adjustable attenuator (8) as K at the moment; wherein T is the system gain, given by the design requirement;

Step 8, the control unit controls the direct current bias circuit to enable the first direct current bias signal to be DC ₁, the second direct current bias signal to be DC ₂, the attenuation multiple of the electrically adjustable attenuator (8) is set to be K, and then the gating controller (10) is controlled to communicate the input signal with the light emitting circuit (3), and the optical link starts to work normally;

The control unit reads the system output voltage sampling signal values according to a preset fixed frequency, and judges whether the direct current bias V _bias of the system output voltage is zero level or not every time M system output voltage sampling signal values are acquired, wherein M and the preset fixed frequency are given by design requirements; if the direct current bias V _bias of the system output voltage is zero level, the optical link continues to work; otherwise, returning to the step 1, calibrating the attenuation multiples of the first direct current bias signal, the second direct current bias signal and the electrically adjustable attenuator (8) again, so that the gain bias of the optical link is kept stable.

10. A method of maintaining optical link gain bias stability as claimed in claim 9, wherein: in step 5, the detection current value of the backlight monitoring PD being equal to I _bias means that the difference between the detection current value and I _bias is less than ±0.1%;