A miniaturized optoelectronic external modulation module

Abstract

This scheme belongs to the field of optoelectronic communication technology, and specifically relates to a miniaturized optoelectronic external modulation module. It includes a Mach-Zehnder external modulator; it also includes a laser, an analog backlight signal processing module, a digital processing module and a bias signal output module; the optical signal and bias signal output by the laser enter the Mach-Zehnder external modulator as an optical carrier, and the Mach-Zehnder external modulator is used to control the bias point of the external modulator and modulate the pilot signal onto the optical carrier; this scheme overcomes the respective defects of power method control and pilot method control, combines the advantages of the two control methods, and proposes an external modulation control scheme that combines power method and pilot method control, which not only has the advantages of higher control accuracy and environmental adaptability, does not deteriorate the quality of the transmission signal, but also greatly simplifies the hardware circuit, reduces the size of the drive control circuit, and can be integrated and packaged inside the external modulator.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic communication technology, and specifically relates to a miniaturized optoelectronic external modulation module. Background Art

[0002] In the field of optical communications, there are two main modulation technologies for microwave signals, one is direct intensity modulation and the other is external modulation. With the development of modern microwave photonic technology, microwave signal external modulation technology is the main modulation technology for microwave photonic signals due to its advantages such as high frequency bandwidth and low noise coefficient. Mach-Zehnder external modulator, as a key component of microwave photonic external modulation technology, is widely used in various optical external modulation transmission links.

[0003] The purpose of bias point control of Mach-Zehnder external modulator is to perform stable bias control on the Mach-Zehnder external modulator, so as to achieve stable operation of the modulator bias control point under the influence of external temperature, vibration, electric field and other conditions, so that the external modulation of microwave signals has stable transmission characteristics and ensures the communication quality of signals and communication systems.

[0004] There are two main Mach-Zehnder external modulation bias control methods currently used at home and abroad: one is power control and the other is pilot control. The core idea of ​​power control is to monitor the output optical power of the external modulator to feedback control the bias control point of the modulator. Its control method mainly includes three parts: obtaining the output optical power fluctuation value, processing the output optical power fluctuation value and compensating the bias point; setting a control balance point of the external modulator, inputting the continuous light source into the external modulator, and then converting part of the output optical power into an electrical signal through the built-in photodiode of the external modulator (or an external optical splitter and photodetector), and finally sampling and detecting the electrical signal to give the compensation value of the bias point. The core idea of ​​pilot control is to control the bias point by loading, receiving and detecting the perturbation signal to the modulator. Its control method mainly includes three parts: generating the perturbation signal, receiving and processing the perturbation signal and compensating the bias voltage; generating a perturbation signal, loading it on the modulator, converting it into an electrical signal through the built-in PD of the modulator, sampling the electrical signal, extracting and monitoring the perturbation signal, and finally giving the compensation value of the bias point.

[0005] However, the two control methods mentioned above have their own obvious disadvantages. The power control method requires that the optical power input to the modulator is absolutely stable, and the gain of the entire control loop is absolutely stable. Therefore, it is easily affected by the light source, optical connector, optical fiber, etc. It is also easily affected by environmental conditions and has low control accuracy over a wide temperature range. The pilot control method loads a perturbation signal on the modulator, which introduces spurious signals to the communication system. Therefore, the pilot control method will deteriorate the quality of the transmission signal and is not applicable in some optical communication systems with high phase noise requirements.

[0006] The patent with application number CN202010278341.0 discloses a Mach-Zehnder modulator and an optical modulation device. The Mach-Zehnder modulator comprises: a first branch waveguide; a second branch waveguide; a conductive region connecting the first branch waveguide and the second branch waveguide to each other; a differential transmission path, including a third metal body for a reference potential and a first metal body and a second metal body respectively connected to the first branch waveguide and the second branch waveguide; and a capacitor connected between the conductive region and the third metal body.

[0007] Although this solution can reduce the common mode, the control circuit is relatively complex and large in size, and is not suitable for use in environments with volume requirements. Summary of the invention

[0008] This solution provides a miniaturized optoelectronic external modulation module that combines power method and pilot method control.

[0009] In order to achieve the above-mentioned purpose, the present invention provides a miniaturized photoelectric external modulation module, including a Mach-Zehnder external modulator; and also including a laser, a photodetector, an analog backlight signal processing module, a digital processing module and a bias signal output module;

[0010] The optical signal and bias signal output by the laser enter the Mach-Zehnder external modulator as an optical carrier, and the Mach-Zehnder external modulator is used to control the bias point of the external modulator and modulate the pilot signal onto the optical carrier respectively;

[0011] The scattered light of the optical signal output by the Mach-Zehnder external modulator is received by the photodetector, which converts the modulated optical signal loaded with the pilot signal into a PD back-photoelectric signal containing the pilot signal, thus realizing the conversion of the optical signal into the electrical signal.

[0012] The PD backlight photoelectric signal enters the analog backlight signal processing module, which outputs an electrical signal containing the pilot fundamental wave and harmonic components after processing; the electrical signal enters the digital processing module for signal processing, and the digital processing module simultaneously outputs the DC bias signal and pilot signal of the next moment. The DC bias signal and pilot signal enter the bias signal output module and are finally output to the bias control signal of the Mach-Zehnder external modulator.

[0013] The effect of this solution: The external modulation control scheme combining power method and pilot method control is adopted, which overcomes the respective defects of power method control and pilot method control, and combines the advantages of the two control methods. It not only has the advantages of higher control accuracy and environmental adaptability, and does not deteriorate the quality of transmission signals, but also greatly simplifies the hardware circuit and reduces the size of the drive control circuit, so that it can be integrated and packaged inside the external modulator.

[0014] Further, the analog backlight signal processing module includes a gain-capable transimpedance amplifier, a DC isolation circuit and a preamplifier; the digital processing module includes a digital bandpass filter, a digital processing unit, a digital-to-analog converter, a pilot generator, a first analog-to-digital converter and a second analog-to-digital converter;

[0015] The gain-capable transimpedance amplifier is respectively connected to the photodetector and the DC isolation circuit signal;

[0016] The gain-capable transimpedance amplifier is sequentially connected to the first analog-to-digital converter, the digital processing unit, the digital-to-analog converter and the bias signal output module for signal connection; the DC isolation circuit is sequentially connected to the preamplifier, the second analog-to-digital converter, the digital bandpass filter, the digital processing unit, the pilot generator and the bias signal output module for signal connection.

[0017] The gain transimpedance amplifier receives the signal transmitted by the photodetector, and the gain transimpedance amplifier transmits the signal to the first analog-to-digital converter and the DC isolation circuit respectively; the DC isolation circuit transmits the signal to the preamplifier; the preamplifier transmits the signal to the second analog-to-digital converter; the second analog-to-digital converter transmits the signal to the digital bandpass filter, the digital bandpass filter transmits the signal to the digital processing unit, and the digital processing unit transmits the signal to the pilot generator; the pilot generator transmits the signal to the bias signal output module; the first analog-to-digital converter transmits the signal to the digital processing unit, and the digital processing unit transmits the signal to the digital-to-analog converter.

[0018] Furthermore, the bias signal includes a DC bias voltage and a pilot signal.

[0019] Furthermore, the pilot fundamental wave contained in the PD backlight signal is processed by current-to-voltage conversion, voltage amplification, and low-pass filtering, and the processed electrical signal enters the digital processing module. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the control principle block diagram of the Mach-Zehnder external modulator.

[0021] Figure 2 This is the main functional block diagram of the Mach-Zehnder external modulator control data processing module.

[0022] Figure 3 This is a flow chart of the Mach-Zehnder external modulator control method. DETAILED DESCRIPTION

[0023] The following is further described in detail through specific implementation methods:

[0024] The marks in the drawings of the specification include: light source 1, Mach-Zehnder external modulator 2, photodetector 21, analog backlight signal processing module 3, gain-capable transimpedance amplifier 31, DC isolation circuit 32, preamplifier 33, digital processing module 4, first analog-to-digital converter 41, second analog-to-digital converter 42, digital bandpass filter 43, digital processing unit 44, digital-to-analog converter 45, pilot generator 46, bias signal output module 5.

[0025] Embodiment 1 is basically as attached Figure 1 and 3 As shown:

[0026] A miniaturized photoelectric external modulation module comprises a Mach-Zehnder external modulator 2, a laser, an analog backlight signal processing module 3, a digital processing module 4 and a bias signal output module 5.

[0027] The light source 1 and bias signal output by the laser enter the Mach-Zehnder external modulator 2 as an optical carrier. The Mach-Zehnder external modulator 2 is used to control the bias point of the external modulator and modulate the pilot signal onto the optical carrier.

[0028] The scattered light of the optical signal output by the Mach-Zehnder external modulator 2 is received by the photodetector 21, and the photodetector 21 converts the modulated optical signal loaded with the pilot signal into a PD back-photoelectric signal containing the pilot signal, thereby realizing the conversion of the optical signal into the electrical signal.

[0029] The PD backlight photoelectric signal enters the analog backlight signal processing module 3, and the analog backlight signal processing module 3 outputs an electrical signal containing the pilot fundamental wave and harmonic components after processing; the electrical signal enters the digital processing module 4 for signal processing, and the digital processing module 4 simultaneously outputs the DC bias signal and the pilot signal at the next moment, and the DC bias signal and the pilot signal enter the bias signal output module 5, and finally output to the bias control signal of the Mach-Zehnder external modulator 2; the bias signal includes a DC bias voltage and a pilot signal.

[0030] The analog backlight signal processing module 3 includes a gain-capable transimpedance amplifier 31, a DC isolation circuit 32, and a preamplifier 33; the digital processing module 4 includes a digital bandpass filter 43, a digital processing unit 44, a digital-to-analog converter 45, a pilot generator 46, a first analog-to-digital converter 41, and a second analog-to-digital converter 42. The gain-capable transimpedance amplifier 31 is signal-connected to the photodetector 21 and the DC isolation circuit 32, respectively. The gain-capable transimpedance amplifier 31 is signal-connected to the first analog-to-digital converter 41, the digital processing unit 44, the digital-to-analog converter 45, and the bias signal output module 5 in sequence; the DC isolation circuit 32 is signal-connected to the preamplifier 33, the second analog-to-digital converter 42, the digital bandpass filter 43, the digital processing unit 44, the pilot generator 46, and the bias signal output module 5 in sequence.

[0031] The gain transimpedance amplifier 31 receives the signal transmitted by the photodetector 21, and the gain transimpedance amplifier transmits the signal to the first analog-to-digital converter 41 and the DC isolation circuit 32 respectively; the DC isolation circuit 32 transmits the signal to the preamplifier 33; the preamplifier 33 transmits the signal to the second analog-to-digital converter 42; the second analog-to-digital converter 42 transmits the signal to the digital bandpass filter 43, the digital bandpass filter 43 transmits the signal to the digital processing unit 44, the digital processing unit 44 transmits the signal to the pilot generator 46; the pilot generator 46 transmits the signal to the bias signal output module 5; the first analog-to-digital converter 41 transmits the signal to the digital processing unit 44, and the digital processing unit 44 transmits the signal to the digital-to-analog converter 45.

[0032] As attached Figure 2 As shown:

[0033] The pilot fundamental wave contained in the PD backlight signal is processed by current-to-voltage conversion, voltage amplification, and low-pass filtering, and the processed electrical signal enters the digital processing module 4.

[0034] Embodiment 2,

[0035] The difference between the second embodiment and the first embodiment is that it also includes an adaptive compensation method for suppressing the bias point drift of the Mach-Zehnder external modulator 2.

[0036] Step 1: Use a thermistor to detect the ambient temperature t at the waveguide of the Mach-Zehnder external modulator 2. The resistance value of the thermistor changes with the ambient temperature at the waveguide of the Mach-Zehnder external modulator 2.

[0037] Step 2: Input the resistance value of the thermistor as the monitoring quantity into the bias point control circuit of the Mach-Zehnder external modulator 2, then the ambient temperature t at the waveguide of the Mach-Zehnder external modulator 2 is the input quantity of the bias point control circuit of the Mach-Zehnder external modulator 2, and the output quantity of the bias point control circuit of the Mach-Zehnder external modulator 2 at the next moment is the bias voltage V of the Mach-Zehnder external modulator 2bias ,

[0038] Step 3: Establish the corresponding relationship between the output and input of the bias point control circuit of Mach-Zehnder external modulator 2.

[0039] This corresponding relationship is an expression of the bias voltage with respect to the ambient temperature at the waveguide of the Mach-Zehnder external modulator 2.

[0040] Among them, V 0 represents the bias voltage of the waveguide of Mach-Zehnder external modulator 2 when the ambient temperature is 25 degrees, V π represents the half-wave voltage of the Mach-Zehnder external modulator 2, k is the drift coefficient of the bias point of the Mach-Zehnder external modulator 2 with respect to the ambient temperature variable t, ((t+&I)-25) represents the change in ambient temperature at the waveguide, and by using the known half-wave voltage Vπ of the Mach-Zehnder external modulator 2, the bias voltage Vπ of the Mach-Zehnder external modulator 2 under different ambient temperatures t is tested. bias , after linear fitting, we get V 0 and drift coefficient k; where & represents the current coefficient, I represents the current of the laser; according to the actual ambient temperature t at the waveguide of the current Mach-Zehnder external modulator 2, using Get the bias voltage V of Mach-Zehnder external modulator 2 at the next moment bias , thereby realizing adaptive compensation of the bias point drift of the Mach-Zehnder external modulator 2 as the ambient temperature changes.

[0041] Because there is a time delay from the temperature rise at the waveguide of the Mach-Zehnder external modulator 2 to the ambient temperature t detected by the thermistor at the waveguide of the Mach-Zehnder external modulator 2, the current detector is used to detect the current of the laser as I, so that ((t+&I)-25) represents the change in the ambient temperature at the waveguide, thereby making the adaptive compensation of the voltage at the next moment when the bias point of the Mach-Zehnder external modulator 2 drifts with the change of the ambient temperature more accurate, and the drift coefficient and the current of the laser are input into the control circuit of the Mach-Zehnder external modulator 2, so that the bias voltage output by the control circuit changes with the change of the ambient temperature.

[0042] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A miniaturized optoelectronic external modulation module, comprising a Mach-Zehnder external modulator (2); characterized in that: It also includes a laser, an analog backlight signal processing module (3), a digital processing module (4) and a bias signal output module (5); The optical signal and bias signal output by the laser enter the Mach-Zehnder external modulator (2) as an optical carrier, and the Mach-Zehnder external modulator (2) is used to control the bias point of the external modulator and modulate the pilot signal onto the optical carrier respectively; The scattered light of the optical signal part output by the Mach-Zehnder external modulator (2) is received by the photodetector (21), and the photodetector (21) converts the modulated optical signal loaded with the pilot signal into a PD back-photoelectric signal containing the pilot signal, thereby realizing the conversion of the optical signal into the electrical signal; The PD backlight photoelectric signal enters the analog backlight signal processing module (3), and the analog backlight signal processing module (3) outputs an electrical signal containing a pilot fundamental wave and harmonic components after processing; the electrical signal enters the digital processing module (4) for signal processing, and the digital processing module (4) simultaneously outputs a DC bias signal and a pilot signal at the next moment, and the DC bias signal and the pilot signal enter the bias signal output module (5), and finally output a bias control signal to the Mach-Zehnder external modulator (2); Also included is an adaptive compensation method for suppressing bias point drift of a Mach-Zehnder external modulator (2). Step 1: using a thermistor to detect the ambient temperature t at the waveguide of the Mach-Zehnder external modulator (2), wherein the resistance value of the thermistor changes with the ambient temperature at the waveguide of the Mach-Zehnder external modulator (2); Step 2: The resistance value of the thermistor is input as a monitoring quantity into the bias point control circuit of the Mach-Zehnder external modulator (2). Then, the ambient temperature t at the waveguide of the Mach-Zehnder external modulator (2) is the input quantity of the bias point control circuit of the Mach-Zehnder external modulator (2). The output quantity of the bias point control circuit of the Mach-Zehnder external modulator (2) at the next moment is the bias voltage V of the Mach-Zehnder external modulator (2). bias ; Step 3: Establish the corresponding relationship between the output and input of the bias point control circuit of the Mach-Zehnder external modulator (2). Among them, V bias is the bias voltage of the Mach-Zehnder external modulator (2); V0 is the bias voltage of the waveguide of the Mach-Zehnder external modulator (2) when the ambient temperature is 25 degrees; (t+&I)-25) represents the change in ambient temperature at the waveguide; I is the current of the laser; & is the current coefficient; t is the actual ambient temperature at the current Mach-Zehnder external modulator waveguide; k is the drift coefficient of the bias point of the Mach-Zehnder external modulator (2) with respect to the ambient temperature variable t; Vπ represents the half-wave voltage of the Mach-Zehnder external modulator (2).

2. The miniaturized optoelectronic external modulation module according to claim 1, characterized in that: The analog backlight signal processing module (3) comprises a gain-capable transimpedance amplifier, a DC isolation circuit (32) and a preamplifier (33); the digital processing module (4) comprises a digital bandpass filter (43), a digital processing unit (44), a digital-to-analog converter (45), a pilot generator (46), a first analog-to-digital converter (41) and a second analog-to-digital converter (42); The gain-capable transimpedance amplifier is signal-connected to the photodetector (21) and the DC isolation circuit (32) respectively; The gain-adjustable transimpedance amplifier is sequentially connected to a first analog-to-digital converter (41), a digital processing unit (44), a digital-to-analog converter (45), and a bias signal output module (5); the DC isolation circuit (32) is sequentially connected to a preamplifier (33), a second analog-to-digital converter (42), a digital bandpass filter (43), a digital processing unit (44), a pilot generator (46), and a bias signal output module (5).

3. The miniaturized optoelectronic external modulation module according to claim 1, characterized in that: The bias signal includes a DC bias voltage and a pilot signal.

4. The miniaturized optoelectronic external modulation module according to claim 1, characterized in that: The pilot fundamental wave contained in the PD backlight signal is subjected to current-to-voltage conversion, voltage amplification, and low-pass filtering, and the processed electrical signal enters the digital processing module (4).

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