Integrated multi-channel optical transceiver assembly control system based on FPGA (Field Programmable Gate Array)

Abstract

The invention discloses an integrated multi-channel optical transceiver assembly control system based on an FPGA, and relates to the technical field of microwave photons.The integrated multi-channel optical transceiver assembly control system comprises an electric control module and a plurality of optical integration modules, and the electric control module is electrically connected with the optical integration modules; the optical integration module adopts a micro-assembly mode, integrates a laser, a modulator, a photoelectric coupler and a photoelectric detector on a single carrier plate, and is used for radio frequency signal modulation and demodulation; the electric control module integrates an ATC module, an APC module and an MZM modulator bias point control module on a single carrier plate, and integrates an FPGA and a multi-channel AD / DA to complete analog domain and digital domain signal conversion and processing.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics technology, and more specifically to an integrated multi-channel optical transceiver control system based on FPGA. Background Technology

[0002] With the development of modern communication technology, future radar equipment will show a trend towards ultra-wideband, high-frequency, and integrated development. Radar based on microwave photonics technology has the advantages of ultra-wideband, low loss, lightweight, and strong anti-interference capabilities, and is one of the important development directions for future electronic equipment.

[0003] Microwave photonic radar requires the conversion between optical and electrical signals, with key components including lasers and modulators. Currently, the most widely used laser is the junction-type semiconductor laser, which features high power density and quantum efficiency. However, it has poor resistance to current surges; even small changes in bias current can lead to significant variations in output optical power and device parameters, affecting the reliability and stability of optical transmission. Simultaneously, semiconductor lasers possess excellent optical performance, with good beam collimation, coherence, and monochromaticity. Semiconductor lasers are temperature-sensitive; a 1°C temperature change results in approximately a 0.1nm wavelength change, which also affects the laser's output optical power, impacting the reliability of radar signal transmission. Therefore, designing a constant-current, stable, high-precision temperature and power feedback control module to ensure the stability of output wavelength and output optical power is crucial.

[0004] The most widely used modulator is the Mach-Zehnder modulator (MZM), which has advantages such as zero or adjustable chirp, high modulation rate, and good linearity. However, during its operation, changes in the external environment, such as temperature and mechanical vibration, can cause the bias point to drift, resulting in a decrease in the quality of the transmitted optical signal and affecting the stability of radar signal transmission. Therefore, research on automatic bias point control systems is very important.

[0005] Currently, there are two main methods for modulator bias point control. One is direct feedback control based on optical power monitoring, which is susceptible to insertion loss and input optical power. The other is a harmonic response feedback control scheme based on low-frequency disturbance signals, which also suffers from significant noise, low stability, excessive drift, and decreased control accuracy. In existing microwave photonic devices, lasers and modulators are treated as discrete components connected by optical cables, resulting in low integration, large size, high cost, and poor channel consistency, making it difficult to meet the engineering requirements of microwave photonic radar. Summary of the Invention

[0006] To address the aforementioned problems, the objective of this invention is to design a high-precision, miniaturized, integrated multi-channel optical transceiver component control system based on FPGA, employing a centralized drive control approach. This system enables automatic power control (APC) and automatic temperature control (ATC) of the laser (LD), and automatic bias point control (ABC) of the modulator. The optical path of the transceiver component integrates the laser and modulator, while the circuitry integrates power, temperature, and bias point control. The control module adopts a centralized control approach, utilizing multiple digital-to-analog converters / analog-to-digital converters (AD / DA) to integrate multiple optical transceiver components. This achieves a multi-channel, miniaturized, and highly reliable design for the optical transceiver component, meeting the engineering application requirements of microwave photonic radar.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: an FPGA-based integrated multi-channel optical transceiver component control system, comprising an electrical control module and multiple optical integrated modules, wherein the electrical control module and the optical integrated modules are electrically connected; the optical integrated modules adopt a micro-assembly method, integrating a laser, modulator, optocoupler and photodetector on a single carrier board for radio frequency signal modulation and demodulation; the electrical control module integrates an ATC module, an APC module and an MZM modulator bias point control module on a single carrier board, and integrates an FPGA and a multi-channel AD / DA to complete analog-domain and digital-domain signal conversion and processing.

[0008] As a preferred method of the present invention, the ATC module uses the thermistor R inside the laser. NTC The laser temperature is monitored and compared with the setpoint. Pulse Width Modulation (PWM) is then used to control the thermoelectric cooler (TEC) for heating or cooling, thereby maintaining a stable laser temperature. The ATC module simultaneously supports analog proportional-integral-derivative (PID) control and digital PID control, which can be switched via software configuration.

[0009] As a preferred method of the present invention, the APC module controls the output power through the laser drive current. The laser output optical signal is converted into a voltage signal by a photodetector PD after passing through a coupler, and the feedback control increases or decreases the drive current to achieve stable laser output optical power.

[0010] As a preferred method of the present invention, the MZM bias point control module uses a feedback control method of low-frequency disturbance signal to adjust the modulator bias point to achieve stability.

[0011] As a preferred method of the present invention, the FPGA module includes an ATC temperature control module, an APC power control module, an MZM bias point control module, and a system scheduling module. The ATC temperature control module configures analog PID and digital PID control parameters according to parameters. The analog PID control directly configures the output voltage through DA to achieve temperature control. The modulator's automatic bias point control injects jitter and bias signals through the DA converter. The output light is converted into a digital voltage signal through a coupler, photodetector (PD), and AD converter. After signal processing is completed in the FPGA, the spectral distribution is obtained. The DC output of the DA converter is controlled by feedback based on the magnitude of the second harmonic, thereby stabilizing the modulator bias point.

[0012] The digital PID control generates a control quantity based on the temperature information output by the AD converter and the bias point, and outputs it to the DA converter to achieve temperature point control. The APC power control module controls the potentiometer according to the configuration parameters to achieve laser power point control; The MZM bias point control module controls the DC level and jitter signal output by the DA, and collects the optical power signal output by the MZM through the AD. After digital PID processing, the DC level control quantity of the modulator is obtained and output to the DA to realize feedback control. The system scheduling module completes the parameter configuration of each module and feeds back the component status to the host computer.

[0013] As a preferred method of the present invention, the thermistor R inside the laser... NTC Connected to external resistors Rx and R of the ATC temperature control module, forming a voltage divider circuit; when the laser temperature changes, R... NTC The resistance value changes, thus affecting the signal V at the output of the first op-amp. O The signal changes; after passing through the analog PID network, it is sent to the feedback control module, which increases or decreases the TEC current in the direction of reducing deviation, thereby adjusting the laser temperature to maintain stability.

[0014] As a preferred method of the present invention, V O The signal can also be output to the AD sampling port of the FPGA. After digital PID control and PWM modulation in the FPGA, it drives the TEC to keep the laser temperature stable. Both control methods can be set by software.

[0015] Compared with the prior art, the technical solution adopted in this invention has the following beneficial effects: 1. Optical transceiver components are the core components of microwave photonic radar. This invention adopts a centralized control approach, integrating the laser, modulator optics, and control circuitry, as well as multiple optical transceiver components. This solves the complex coupling problem between various physical fields such as light, electricity, force, and heat that arises from integration. The control technology uses digital technology, which easily corrects inconsistencies between optical transceiver channel channels, enabling the engineering application of microwave photonic radar.

[0016] 2. The optical transceiver component control system uses FPGA as the signal processing and control center and integrates multi-channel AD and DA. The number of control channels is easy to expand and adjust, and the number of channels corresponds to the number of optical integrated modules.

[0017] 3. The control module converts analog domain signals to digital domain processing and combines FPGA high-efficiency parallel processing technology, which improves reliability, increases flexibility, greatly reduces the size of the control module, makes it easy to correct inconsistencies between optical transceiver components, and can be integrated into microwave photonic radar with a large number of channels. Attached Figure Description

[0018] Figure 1 This is a block diagram of an integrated multi-channel optical transceiver control system based on FPGA in this embodiment. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

[0020] like Figure 1 As shown in the figure, this embodiment is a block diagram of an integrated multi-channel optical transceiver control system based on FPGA. The negative temperature coefficient thermistor R is integrated inside the laser LD. NTC Together with external resistor Rx and resistor R, they form a voltage divider circuit. When the LD temperature changes, R... NTC The resistance value changes, thus affecting the signal V at the output of the first op-amp. O The signal changes. After passing through an analog PID network, it is fed into the feedback control module, which increases or decreases the TEC current in the direction of reducing deviation, thereby regulating the laser temperature to maintain stability.

[0021] V O The signal can also be output to the AD sampling port of the FPGA. After digital PID control and PWM modulation in the FPGA, it drives the TEC to keep the laser temperature stable. Both control methods can be set by software.

[0022] The APC power control module uses feedback current control to maintain stable laser power, primarily employing the ADN2830 chip. The ADN2830 has a maximum drive current of 200mA, and an operational amplifier (such as...) is added to the output. Figure 1 This extends the drive current to 400mA. The APC power control module adjusts the output bias current to maintain R. PSETThe terminal voltage remains at 1.23V, therefore the stable value of the drive current (corresponding to optical power) can be determined by setting R. PSET The value is set to achieve adjustable optical power. PSET It uses an adjustable potentiometer, with ADN2850, which can achieve 10-bit resolution, a maximum resistance of 25kΩ, a resolution of 24Ω, and an accuracy of ±8%.

[0023] The MZM bias point control module uses a low-frequency disturbance signal feedback control method to automatically control the modulator bias point. The circuit structure for injecting a jitter signal to achieve modulator bias control is as follows: Figure 1 As shown, the FPGA controls the DA to generate a control signal, which is output to the bias control terminal of the MZM. This signal includes a 1kHz jitter signal and a DC bias signal. The MZM optical signal output passes through an optocoupler, and part of the optical signal enters a low-frequency diode photodetector (PD). The low-frequency photodetector is only sensitive to DC signals and low-frequency signals; the radio frequency signal on the optical carrier is filtered out.

[0024] The demodulated signal, after filtering, conditioning, and amplification, is sampled by an analog-to-digital converter (ADC) and then input into the FPGA module. Within the FPGA module, digital filtering and FFT transformation are performed to determine the second harmonic amplitude. This amplitude is then processed by a digital PID control module to obtain the control input, which is converted to a digital-to-analog converter (DA converter) and output to control the bias voltage of the MZM, achieving feedback control of the modulator's bias operating point. This control method is less affected by changes in the external environment, exhibits a large feedback amplitude, and provides high control precision.

[0025] The FPGA module mainly includes an ATC temperature control module, an APC power control module, an MZM bias point control module, and a system scheduling module. The ATC temperature control module configures analog PID and digital PID control parameters according to the parameters. Analog PID control directly configures the output voltage via a DA converter to achieve temperature control. Digital PID control generates control quantities based on the temperature information output from the AD converter and the bias point, and outputs these quantities to the DA converter to achieve temperature point control. The APC power control module controls the potentiometer according to the configured parameters to achieve laser power point control. The MZM bias point control module controls the DC level and jitter signal output from the DA converter, and acquires the MZM output optical power signal through an AD converter. After digital PID processing, it obtains the modulator DC level control quantity and outputs it to the DA converter for feedback control. The system scheduling module completes the parameter configuration of each module and feeds back the component status to the host computer.

[0026] Although the present invention has been disclosed above with reference to preferred embodiments, the embodiments and accompanying drawings are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention, and these changes will also be within the protection scope of the invention. Therefore, the protection scope of the present invention should be defined by the scope of the claims of this application.

Claims

1. A control system for an integrated multi-channel optical transceiver component based on FPGA, characterized in that: It includes an electrical control module and multiple optical integrated modules, which are electrically connected. The optical integrated modules adopt a micro-assembly method, integrating a laser, modulator, optocoupler, and photodetector on a single carrier board for radio frequency signal modulation and demodulation. The electrical control module integrates an ATC module, an APC module, and an MZM modulator bias point control module on a single carrier board, and integrates an FPGA and a multi-channel AD / DA to complete analog-to-digital signal conversion and processing.

2. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The ATC module uses the thermistor R inside the laser. NTC The laser temperature is monitored and compared with the set temperature value. Then, pulse width modulation (PWM) is used to control the semiconductor cooler (TEC) to heat or cool, thereby maintaining the stability of the laser temperature.

3. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The APC module controls the output power through the laser drive current. The laser output optical signal is converted into a voltage signal by the photodetector PD after passing through the coupler. The feedback control increases or decreases the drive current to achieve stable laser output optical power.

4. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The FPGA module includes an ATC temperature control module, an APC power control module, an MZM bias point control module, and a system scheduling module. The ATC temperature control module configures analog PID and digital PID control parameters according to parameters. The analog PID control directly configures the output voltage through DA to achieve temperature control. The digital PID control generates a control quantity based on the temperature information output by the AD converter and the bias point, and outputs it to the DA converter to achieve temperature point control. The APC power control module controls the potentiometer according to the configuration parameters to achieve laser power point control; The MZM bias point control module controls the DC level and jitter signal output by the DA, and collects the optical power signal output by the MZM through the AD. After digital PID processing, the DC level control quantity of the modulator is obtained and output to the DA to realize feedback control. The system scheduling module completes the parameter configuration of each module and feeds back the component status to the host computer.

5. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The thermistor R inside the laser NTC Connected to external resistors Rx and R of the ATC temperature control module, forming a voltage divider circuit; when the laser temperature changes, R... NTC The resistance value changes, thus affecting the signal V at the output of the first op-amp. O The signal changes; after passing through the analog PID network, it is sent to the feedback control module, which increases or decreases the TEC current in the direction of reducing deviation, thereby adjusting the laser temperature to maintain stability.

6. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 5, characterized in that: V O The signal can also be output to the AD sampling port of the FPGA. After digital PID control and PWM modulation in the FPGA, it drives the TEC to keep the laser temperature stable. Both control methods can be set by software.

7. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The output of the APC power control module is equipped with an operational amplifier, which can extend the drive current from 200mA to 400mA; the stable value of the drive current can be achieved by setting R... PSET The value is used to set it.

8. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 7, characterized in that: The APC power control module uses the ADN2830 chip; the R PSET It uses an adjustable potentiometer, which can achieve 10-bit resolution and 25kΩ resistance, with a resolution of 24Ω and an accuracy of ±8%.

9. The FPGA-based integrated multi-channel optical transceiver component control system according to claim 1, characterized in that: The MZM bias point control module uses a low-frequency disturbance signal feedback control method to automatically control the modulator bias point, specifically: The FPGA controls the DA to generate a control signal output to the bias control terminal of the MZM modulator. This signal includes a 1kHz jitter signal and a DC bias signal. The optical signal output of the MZM modulator passes through an optocoupler, and part of the optical signal enters the low-frequency diode photodetector. The low-frequency photodetector is only sensitive to DC signals and low-frequency signals, and the radio frequency signal on the optical carrier is filtered out. The demodulated signal is filtered, conditioned and amplified, and then sampled by an AD converter and enters the FPGA. After digital filtering and FFT transformation in the FPGA, the second harmonic amplitude is analyzed and the control quantity is obtained through the digital PID control module. The control quantity is output after DA conversion, thereby controlling the bias voltage of the MZM modulator.

Images