Compact automatic bias control board

Abstract

The utility model relates to a compact automatic bias control board which comprises a circuit board, a main control circuit, a power supply circuit, a scrambling signal generating circuit, a coherent circuit, a bias signal generating circuit, a feedback signal amplifying circuit and a signal mixing circuit are integrated on the circuit board, and a feedback signal interface and a bias signal interface are arranged on the circuit board. The feedback signal interface is connected with the feedback signal amplification circuit, the feedback signal amplification circuit is connected with the input end of the coherent circuit, the output end of the coherent circuit is connected with the main control circuit, and the input end of the scrambling signal generation circuit and the input end of the bias signal generation circuit are respectively connected with the main control circuit. The output end of the scrambling signal generation circuit and the output end of the bias signal generation circuit are respectively connected with the input end of the signal mixing circuit, and the output end of the signal mixing circuit is connected with the bias signal interface. The lithium niobate electro-optical modulator has the advantages that the case type design is abandoned, the integration level is high, the size is small, and the lithium niobate electro-optical modulator can be integrated into the lithium niobate electro-optical modulator.

Description

Technical Field

[0001] This utility model relates to the field of optical communication technology, and in particular to a compact automatic bias control board. Background Technology

[0002] Due to the drift characteristics of lithium niobate electro-optic modulators, they require long-term automatic biasing. However, existing automatic biasing devices are usually chassis-type designs, requiring users to connect links during use, making them difficult to integrate into their own systems or products. Summary of the Invention

[0003] This invention mainly solves the above-mentioned problems and provides a compact automatic bias control board.

[0004] The technical solution adopted by this utility model to solve its technical problem is a compact automatic bias control board for automatically biasing a feedback signal obtained from the output of a lithium niobate electro-optic intensity modulator. The board includes a circuit board on which a main control circuit, a power supply circuit, a scrambling signal generation circuit, a coherent circuit, a bias signal generation circuit, a feedback signal amplification circuit, and a signal mixing circuit are integrated. The circuit board is provided with a feedback signal interface and a bias signal interface. The feedback signal interface is connected to the feedback signal amplification circuit. The feedback signal amplification circuit is connected to the input terminal of the coherent circuit. The output terminal of the coherent circuit is connected to the main control circuit. The input terminals of the scrambling signal generation circuit and the bias signal generation circuit are respectively connected to the main control circuit. The output terminals of the scrambling signal generation circuit and the bias signal generation circuit are respectively connected to the input terminal of the signal mixing circuit. The output terminal of the signal mixing circuit is connected to the bias signal interface.

[0005] As a preferred embodiment of the above scheme, the coherent circuit includes operational amplifiers U1A, U1B, U15B, U3A, and U3B, multiplexers D1 and U27, and instrumentation amplifier U6. The amplified feedback signal output from the feedback signal amplification circuit is divided into two paths: the non-inverting input of operational amplifier U1A and the inverting input of operational amplifier U1B, respectively. The outputs of operational amplifiers U1A and U1B are respectively connected to multiplexer D1. The output of multiplexer D1 is amplified sequentially by operational amplifiers U15B, U3A, and U3B before being connected to multiplexer U27. The output of multiplexer U27 is connected to instrumentation amplifier U6, and the output of instrumentation amplifier U6 is connected to the main control circuit.

[0006] As a preferred embodiment of the above scheme, the scrambling signal generation circuit includes operational amplifiers U5A and U5B and an adjustable resistor R107. The 1KHz signal output by the main control circuit is connected to the inverting input terminal of operational amplifier U5B. The output of operational amplifier U5B is connected to the non-inverting input terminal of operational amplifier U5A after passing through the adjustable resistor R107. The output terminal of operational amplifier U5A is connected to the signal mixing circuit.

[0007] As a preferred embodiment of the above scheme, the bias signal generation circuit includes a digital-to-analog converter U23, an operational amplifier U13A, and an operational amplifier U13B. The input terminal of the digital-to-analog converter U23 is connected to the main control circuit, the output terminal of the digital-to-analog converter U23 is connected to the non-inverting input terminal of the operational amplifier U13A, the output terminal of the operational amplifier U13A is connected to the non-inverting input terminal of the operational amplifier U13B, and the output terminal of the operational amplifier U13B is connected to the signal mixing circuit.

[0008] As a preferred embodiment of the above scheme, the signal mixing circuit includes an operational amplifier U14A, the output terminals of the scrambling signal generation circuit and the bias signal generation circuit are both connected to the inverting input terminal of the operational amplifier U14A, and the output terminal of the operational amplifier U14A is connected to the bias signal interface.

[0009] As a preferred embodiment of the above scheme, the feedback signal amplification circuit includes operational amplifiers U15A, U17A, and U17B. The non-inverting input terminal of operational amplifier U17A is grounded, and the output terminal of operational amplifier U17A is connected to the non-inverting input terminal of operational amplifier U17B and the inverting input terminal of operational amplifier U17A, respectively. The output terminal of operational amplifier U17B is connected to the non-inverting input terminal of operational amplifier U15A, and the output terminal of operational amplifier U15A is connected to the feedback signal interface, the coherent circuit input terminal, and the inverting input terminal of operational amplifier U15A, respectively.

[0010] As a preferred embodiment of the above solution, the circuit board is a four-layer board, which includes a top layer, a ground layer, a power layer and a bottom layer from top to bottom, and the signal lines of the top layer and the bottom layer are arranged adjacent to the power layer and the ground layer.

[0011] As a preferred embodiment of the above scheme, the power layer and ground layer are provided with copper foil.

[0012] The advantages of this invention are: it abandons the chassis-style design, has high integration and small size, and can be integrated into a lithium niobate electro-optic modulator. Attached Figure Description

[0013] Figure 1 This is a circuit block diagram of a compact automatic bias control board.

[0014] Figure 2 This is the circuit schematic of the main control circuit.

[0015] Figure 3 This is the circuit schematic of a coherent circuit.

[0016] Figure 4 The circuit diagram for the scrambling signal generation circuit.

[0017] Figure 5 This is the circuit schematic for the bias signal generation circuit.

[0018] Figure 6 This is the circuit schematic of a signal mixing circuit.

[0019] Figure 7 This is the circuit schematic of the feedback signal amplification circuit.

[0020] Figure 8 This is the circuit schematic of the power supply circuit. Detailed Implementation

[0021] The technical solution of this utility model will be further described below through embodiments and in conjunction with the accompanying drawings.

[0022] Example:

[0023] This embodiment presents a compact automatic bias control board for automatically biasing a feedback signal obtained from the output of a lithium niobate electro-optic intensity modulator. The board includes a circuit board integrating a main control circuit, a power supply circuit, a scrambling signal generation circuit, a coherent circuit, a bias signal generation circuit, a feedback signal amplification circuit, and a signal mixing circuit. In this embodiment, to prevent the influence of ground bounce, the circuit board employs a four-layer design to improve the signal-to-noise ratio of the analog section. Considering that ground segmentation is too complex and lacks theoretical guidance, a complete ground plane is used instead of ground segmentation. The top and bottom signal lines are adjacent to the power / ground plane, forming a closed electromagnetic field loop, reducing crosstalk between signal lines and external radiation. The characteristic impedance of the microstrip / stripline is precisely controlled by adjusting the PP sheet thickness and linewidth. The complete power plane reduces power path impedance, reducing voltage drop and switching noise. The dielectric between the power layer and the ground layer forms a natural distributed capacitance, filtering out high-frequency noise and reducing dependence on external decoupling capacitors. The signal line return current returns through the nearest reference plane, reducing the loop area and lowering radiated energy. The intermediate ground plane serves as an electromagnetic shielding layer, isolating the signal lines of the top and bottom layers and preventing interlayer interference. The large copper foil area of ​​the power / ground plane improves heat dissipation efficiency, preventing signal drift caused by localized overheating. The low-impedance ground plane absorbs instantaneous large currents, stabilizing the reference ground potential. This effectively improves integration density and board layout. The circuit board also includes feedback signal interfaces and bias signal interfaces. In this embodiment, the circuit board is a four-layer board, consisting of a top layer, ground layer, power layer, and bottom layer from top to bottom. The signal lines of the top and bottom layers are positioned adjacent to the power and ground layers, respectively.

[0024] like Figure 1 As shown, the feedback signal interface 8 is connected to the feedback signal amplification circuit 6, the feedback signal amplification circuit 6 is connected to the input terminal of the coherent circuit 4, the output terminal of the coherent circuit 4 is connected to the main control circuit 1, the input terminal of the scrambling signal generation circuit 3 and the input terminal of the bias signal generation circuit 5 are respectively connected to the main control circuit 1, the output terminal of the scrambling signal generation circuit 3 and the output terminal of the bias signal generation circuit 5 are respectively connected to the input terminal of the signal mixing circuit 7, the output terminal of the signal mixing circuit 7 is connected to the bias signal interface 9, and the power supply circuit 2 supplies power to the main control circuit 1, the scrambling signal generation circuit 3, the coherent circuit 4, the bias signal generation circuit 5, the feedback signal amplification circuit 6 and the signal mixing circuit 9.

[0025] like Figure 2 As shown, the main control circuit uses STM8S207C8T6 as the control chip U12 to control the scrambling signal generation circuit 3, the coherent circuit 4, the bias signal generation circuit 5, and the feedback signal amplification circuit 6, respectively.

[0026] like Figure 3As shown, the coherent circuit includes operational amplifiers U1A, U1B, U15B, U3A, and U3B, multiplexers D1 and U27, and instrumentation amplifier U6. The amplified feedback signal output from the feedback signal amplifier circuit is divided into two paths, connected to the non-inverting input of operational amplifier U1A and the inverting input of operational amplifier U1B, respectively. The output of operational amplifier U1A is connected to the inverting input of operational amplifier U1A and the SA pin of multiplexer D1, respectively. The output of operational amplifier U1B is connected to the inverting input of operational amplifier U1B and the SB pin of multiplexer D1, respectively. The IN pin of multiplexer D1 is connected to the 43rd pin of control chip U12, and the D pin of multiplexer D1 is connected to the non-inverting input of operational amplifier U15B. The output terminals of the multiplexer U15B are connected to the inverting input terminal of operational amplifier U15B and the non-inverting input terminal of operational amplifier U3A, respectively. The output terminals of operational amplifier U3A are connected to the inverting input terminal of operational amplifier U3A and the non-inverting input terminal of operational amplifier U3B, respectively. The output terminal of operational amplifier U3B is grounded through resistors R22 and R34. The output terminal of operational amplifier U3B is directly connected to the SA pin of multiplexer U27. The SA pin of multiplexer U27 is connected between resistors R22 and R23. The SA pin of multiplexer U27 is connected to the +IN pin of instrumentation amplifier U6. The OUT terminal of instrumentation amplifier U6 is connected to the input terminal of ADC acquisition unit U18. The output terminal of ADC acquisition unit U18 is connected to control chip U12. In this embodiment, the multiplexer model is TMUX6219DGK, the instrumentation amplifier signal is AD8221, and the ADC acquisition unit model is MCP3421.

[0027] like Figure 4 As shown, the scrambling signal generation circuit includes operational amplifiers U5A and U5B and an adjustable resistor R107. The 1KHz signal output from pin 43 of the control chip U12 in the main control circuit is connected to the inverting input of operational amplifier U5B. The output of operational amplifier U5B is connected to the inverting input of operational amplifier U5B and the adjustable resistor R107. The adjustable resistor R107 is connected to the non-inverting input of operational amplifier U5A. The output of operational amplifier U5A is connected to the inverting input of operational amplifier U5A and the signal mixing circuit.

[0028] like Figure 5As shown, the bias signal generation circuit includes a digital-to-analog converter (DAC) U23, operational amplifiers U13A and U13B. The input terminal of DAC U23 is connected to the main control circuit, and the output terminal of DAC U23 is connected to the non-inverting input terminal of operational amplifier U13A. The output terminal of operational amplifier U13A is connected to the inverting input terminal of operational amplifier U13A, the fourth pin of DAC U23, and the non-inverting input terminal of operational amplifier U13B. The output terminal of operational amplifier U13B is connected to the signal mixing circuit and the inverting input terminal of operational amplifier U13B. In this embodiment, the DAC U23 is a DAC8311-Q1.

[0029] like Figure 6 As shown, the signal mixing circuit includes an operational amplifier U14A. The output terminals of the scrambling signal generation circuit and the bias signal generation circuit are both connected to the inverting input terminal of the operational amplifier U14A. The non-inverting input terminal of the operational amplifier U14A is grounded. The output terminal of the operational amplifier U14A is connected to the inverting input terminal of the operational amplifier U14A and the bias signal interface, respectively.

[0030] like Figure 7 As shown, the feedback signal amplification circuit includes operational amplifiers U15A, U17A, U17B, U19A, and U19B. The non-inverting input terminal of operational amplifier U17A is grounded. The output terminal of operational amplifier U17A is connected to the non-inverting input terminal of operational amplifier U17B and the inverting input terminal of operational amplifier U17A, respectively. The output terminal of operational amplifier U17B is connected to the inverting input terminal of operational amplifier U17B and the non-inverting input terminal of operational amplifier U15A, respectively. The output terminal of operational amplifier U15A is connected to the feedback signal interface, the coherent circuit input terminal, and the inverting input terminal of operational amplifier U15A, respectively. The inverting input of operational amplifier U17A is also connected to the cathode of diode PD1. The anode of diode PD1 is connected to the inverting input of operational amplifier U19A. The non-inverting input of operational amplifier U19A is grounded. The output of operational amplifier U19A is connected to the inverting inputs of operational amplifier U19B and operational amplifier U19B respectively. The output of operational amplifier U19B is connected to the inverting input of operational amplifier U19B and control chip U12 respectively.

[0031] like Figure 8 The power supply circuit converts the input 5V power supply into different voltages to power the main control circuit 1, scrambling signal generation circuit 3, coherent circuit 4, bias signal generation circuit 5, feedback signal amplification circuit 6, and signal mixing circuit 9.

[0032] In use, the optical link is connected in the following order: CW light source - lithium niobate electro-optical intensity modulator and splitter. One branch fiber of the splitter is connected to the feedback signal interface of the compact automatic bias control board. The bias signal interface of the compact automatic bias control board is connected to the bias interface of the lithium niobate electro-optical intensity modulator. Then, the light source and DC power supply are turned on. After waiting for 1-2 minutes, the automatic bias board will automatically control the point finding. The compact automatic bias control board in this embodiment uses the PI algorithm. It uses the coherent feedback signal as the feedback terminal and the DAC output as the control terminal to form a closed-loop control loop. Stable control is achieved using software PI. In addition, it abandons the chassis-style design and integrates the main control circuit, power supply circuit, scrambling signal generation circuit, coherent circuit, bias signal generation circuit, feedback signal amplification circuit and signal mixing circuit onto a four-layer PCB board. It has high integration and small size, and can be integrated into the lithium niobate electro-optical modulator.

[0033] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A compact automatic bias control board for automatically biasing a feedback signal obtained from the output of a lithium niobate electro-optic intensity modulator, characterized in that: The device includes a circuit board that integrates a main control circuit, a power supply circuit, a scrambling signal generation circuit, a coherent circuit, a bias signal generation circuit, a feedback signal amplification circuit, and a signal mixing circuit. The circuit board has a feedback signal interface and a bias signal interface. The feedback signal interface is connected to the input terminal of the feedback signal amplification circuit. The output terminal of the feedback signal amplification circuit is connected to the input terminal of the coherent circuit. The output terminal of the coherent circuit is connected to the main control circuit. The input terminals of the scrambling signal generation circuit and the bias signal generation circuit are respectively connected to the main control circuit. The output terminals of the scrambling signal generation circuit and the bias signal generation circuit are respectively connected to the input terminal of the signal mixing circuit. The output terminal of the signal mixing circuit is connected to the bias signal interface.

2. The compact automatic bias control board according to claim 1, characterized in that: The coherent circuit includes operational amplifiers U1A, U1B, U15B, U3A, and U3B, multiplexers D1 and U27, and instrumentation amplifier U6. The amplified feedback signal output from the feedback signal amplification circuit is divided into two paths: the non-inverting input of operational amplifier U1A and the inverting input of operational amplifier U1B. The outputs of operational amplifiers U1A and U1B are connected to multiplexer D1, and the output of multiplexer D1 is amplified sequentially by operational amplifiers U15B, U3A, and U3B before being connected to multiplexer U27. The output of multiplexer U27 is connected to instrumentation amplifier U6, and the output of instrumentation amplifier U6 is connected to the main control circuit.

3. The compact automatic bias control board according to claim 1, characterized in that: The scrambling signal generation circuit includes operational amplifiers U5A and U5B and an adjustable resistor R107. The 1KHz signal output by the main control circuit is connected to the inverting input terminal of operational amplifier U5B. The output of operational amplifier U5B is connected to the non-inverting input terminal of operational amplifier U5A after passing through the adjustable resistor R107. The output terminal of operational amplifier U5A is connected to the signal mixing circuit.

4. The compact automatic bias control board according to claim 1, characterized in that: The bias signal generation circuit includes a digital-to-analog converter U23, an operational amplifier U13A, and an operational amplifier U13B. The input terminal of the digital-to-analog converter U23 is connected to the main control circuit, the output terminal of the digital-to-analog converter U23 is connected to the non-inverting input terminal of the operational amplifier U13A, the output terminal of the operational amplifier U13A is connected to the non-inverting input terminal of the operational amplifier U13B, and the output terminal of the operational amplifier U13B is connected to the signal mixing circuit.

5. The compact automatic bias control board according to claim 1, characterized in that: The signal mixing circuit includes an operational amplifier U14A. The outputs of the scrambling signal generation circuit and the bias signal generation circuit are both connected to the inverting input of the operational amplifier U14A. The output of the operational amplifier U14A is connected to the bias signal interface.

6. The compact automatic bias control board according to claim 1, characterized in that: The feedback signal amplification circuit includes operational amplifiers U15A, U17A, and U17B. The non-inverting input terminal of operational amplifier U17A is grounded. The output terminal of operational amplifier U17A is connected to the non-inverting input terminal of operational amplifier U17B and the inverting input terminal of operational amplifier U17A, respectively. The output terminal of operational amplifier U17B is connected to the non-inverting input terminal of operational amplifier U15A. The output terminal of operational amplifier U15A is connected to the feedback signal interface, the coherent circuit input terminal, and the inverting input terminal of operational amplifier U15A, respectively.

7. The compact automatic bias control board according to claim 1, characterized in that: The circuit board is a four-layer board, consisting of a top layer, a ground layer, a power layer, and a bottom layer from top to bottom. The signal lines of the top and bottom layers are arranged adjacent to the power and ground layers.

8. The compact automatic bias control board according to claim 7, characterized in that: The power layer and ground layer are provided with copper foil.

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