Narrow linewidth laser driving circuit and phase-sensitive optical time domain reflectometer

Abstract

This utility model relates to the field of laser driving technology, and provides a narrow-linewidth laser driving circuit and a phase-sensitive optical time-domain reflectometer. The narrow-linewidth laser driving circuit includes a laser, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a current control module, and a temperature control module. The output terminal of the current control module is electrically connected to the negative terminal of the laser. The first and second output terminals of the DAC are electrically connected to the input terminals of the current control module and the temperature control module, respectively. The first and second input terminals of the ADC are electrically connected to the output terminals of the current control module and the temperature control module, respectively. By driving the laser current through the current control module, the operating current of the laser can be stabilized; by adjusting the operating temperature of the laser through the temperature control module, the operating temperature of the laser can be prevented from becoming too cold or too hot, thus enhancing the operating stability of the laser.

Description

Technical Field

[0001] This utility model relates to the field of laser driving technology, and more specifically, to a narrow linewidth laser driving circuit and a phase-sensitive optical time-domain reflectometer. Background Technology

[0002] Lasers play a crucial role in Distributed Acoustic Sensing (DAS) systems, emitting continuous or pulsed laser signals to detect acoustic disturbances in optical fibers. The performance of the laser directly affects the overall performance of the DAS system. If the laser is unstable, such as experiencing output power fluctuations or changes in spectral characteristics, the quality of the signal received by the DAS system will degrade, affecting the accurate detection of the acoustic signal. This can even lead to problems such as mode hopping, sidelobes in the spectrum, linewidth broadening, and output power fluctuations. These issues can severely impact the measurement accuracy and stability of the DAS system, and may even cause the system to malfunction. Utility Model Content

[0003] The present invention aims to overcome at least one defect (deficiency) of the prior art and provides a narrow linewidth laser driving circuit and a phase-sensitive optical time-domain reflectometer, which can stably drive the laser to work and effectively control the laser's operating temperature, thereby enhancing the stability of the laser's operation.

[0004] The technical solution adopted by this utility model is, according to the first aspect of this application, to provide a narrow linewidth laser driving circuit, the narrow linewidth laser driving circuit including a laser, a digital-to-analog converter circuit, an analog-to-digital converter circuit, a current control module and a temperature control module; The current control module includes a current drive circuit; the current drive circuit includes a first operational amplifier, a third resistor, a sampling resistor, and an NMOS transistor; The first output terminal of the digital-to-analog converter circuit is electrically connected to the non-inverting input terminal of the first operational amplifier; The first end of the sampling resistor is electrically connected to the inverting input terminal of the first operational amplifier, and the second end of the sampling resistor is grounded; the first end of the third resistor is electrically connected to the output terminal of the first operational amplifier, and the second end of the third resistor is electrically connected to the gate of the NMOS transistor; the source of the NMOS transistor is electrically connected to the first end of the sampling resistor; the drain of the NMOS transistor is electrically connected to the negative terminal of the laser; the positive terminal of the laser is connected to a voltage source, and the source of the NMOS transistor is electrically connected to the first input terminal of the analog-to-digital converter circuit. The second output terminal of the digital-to-analog converter circuit is electrically connected to the input terminal of the temperature control module, which is used to adjust the temperature of the laser. The second input terminal of the analog-to-digital converter circuit is electrically connected to the output terminal of the temperature control module.

[0005] The narrow-linewidth laser driving circuit provided by this invention drives the laser current through a current driving circuit, enabling the laser to operate under a stable current and effectively avoiding output power instability caused by current fluctuations. A temperature control module monitors and adjusts the laser's operating temperature in real time, preventing performance degradation or malfunctions caused by excessive cooling or heating, thus enhancing the laser's operational stability. By connecting the sampling resistor, the NMOS transistor, and the laser in series, the voltage across the sampling resistor increases as the current flowing through the laser increases. This voltage is captured by the inverting input of the first operational amplifier and compared with the voltage at the non-inverting input. Due to the action of the first operational amplifier, it adjusts the voltage at its output, reducing the voltage at its inverting input. This reduces the gate voltage of the NMOS transistor, decreasing its conduction level and consequently reducing the current flowing through the laser, making the laser's operating circuit more stable.

[0006] Optionally, the current control module further includes a voltage divider filter circuit and a non-inverting amplifier circuit; the input terminal of the voltage divider filter circuit is electrically connected to the first output terminal of the digital-to-analog converter circuit, the output terminal of the voltage divider filter circuit is electrically connected to the non-inverting input terminal of the first operational amplifier, the output terminal of the current drive circuit is electrically connected to the input terminal of the non-inverting amplifier circuit, and the output terminal of the non-inverting amplifier circuit is electrically connected to the source of the NMOS transistor.

[0007] By filtering out high-frequency noise and spurious waves in the input current signal through a voltage divider filter circuit, a smooth DC signal is provided for the subsequent current drive circuit, which helps to reduce the problem of laser performance instability caused by current fluctuations.

[0008] Optionally, the voltage divider filter circuit includes a first resistor, a second resistor, and a first capacitor. The first end of the first resistor is connected to the first output terminal of the digital-to-analog converter circuit. The second end of the first resistor is electrically connected to the first end of the second resistor, the first end of the first capacitor, and the non-inverting input terminal of the first operational amplifier. The second end of the second resistor is connected to the second end of the first capacitor and then grounded.

[0009] A voltage divider circuit is formed by connecting the first resistor, the second resistor, and the first capacitor. The voltage divider circuit can effectively reduce the voltage value of the input signal and bypass high-frequency noise through the first capacitor, thereby obtaining a smooth and stable DC signal and improving the anti-interference capability of the current control module.

[0010] Optionally, the non-inverting amplifier circuit includes a second operational amplifier, a fourth resistor, and a fifth resistor. The inverting input terminal of the second operational amplifier is electrically connected to the first terminal of the fourth resistor and the first terminal of the fifth resistor, and the second terminal of the fourth resistor is grounded. The second terminal of the fifth resistor is electrically connected to the output terminal of the second operational amplifier. The non-inverting input of the second operational amplifier is electrically connected to the source of the NMOS transistor; the first input of the analog-to-digital converter is electrically connected to the output of the second operational amplifier.

[0011] By amplifying the voltage signal from the sampling resistor using a second operational amplifier before inputting it into the analog-to-digital converter circuit, the resolution degradation caused by the small signal amplitude input to the analog-to-digital converter circuit can be effectively avoided.

[0012] Optionally, the narrow linewidth laser driving circuit further includes a second capacitor, which is connected in parallel with the laser.

[0013] By absorbing and storing transient voltage fluctuations generated during laser operation using a second capacitor, DC voltage can be smoothed and voltage ripple reduced, enabling the laser to operate in a more stable voltage environment, thereby improving the stability and consistency of the laser's output optical signal.

[0014] Optionally, the temperature control module includes a temperature detection circuit, a signal output circuit, and a temperature adjustment circuit; the temperature detection circuit is electrically connected to the input terminal of the signal output circuit, and the temperature detection circuit is used to detect the temperature of the laser. The first terminal of the temperature regulation circuit is electrically connected to the temperature detection circuit, and the temperature regulation circuit is used to regulate the temperature of the laser. The output terminal of the signal output circuit is electrically connected to the second input terminal of the analog-to-digital converter circuit, and the second terminal of the temperature regulation circuit is electrically connected to the second output terminal of the digital-to-analog converter circuit.

[0015] Optionally, the temperature regulation circuit further includes a differential integral circuit and a thermoelectric cooler; the thermoelectric cooler is used to regulate the temperature of the laser. The differential integration circuit includes a fourth operational amplifier, a fifth operational amplifier, a seventh resistor, an eighth resistor, a fourth capacitor, and a fifth capacitor; The non-inverting input terminal of the fourth operational amplifier is electrically connected to the temperature detection circuit, and the inverting input terminal of the fourth operational amplifier is electrically connected to the output terminal; the output terminal of the fourth operational amplifier is electrically connected to the first terminal of the seventh resistor. The inverting input terminal of the fifth operational amplifier is electrically connected to the second terminal of the seventh resistor, the non-inverting input terminal of the fifth operational amplifier is connected to the first terminal of the eighth resistor, and the output terminal of the fifth operational amplifier is electrically connected to the second terminal of the seventh resistor through the fourth capacitor. The second terminal of the eighth resistor is electrically connected to the output terminal of the digital-to-analog converter circuit, and the first terminal of the eighth resistor is also connected to the first terminal of the fifth capacitor. The second terminal of the fifth capacitor is grounded. The negative and positive terminals of the thermoelectric cooler are electrically connected to the output terminals of the fourth operational amplifier and the fifth operational amplifier, respectively.

[0016] The operating temperature of the thermoelectric cooler (TEC) is adjusted by calculating the control signal through a differential integral circuit, allowing the thermoelectric cooler to exchange heat with the laser, thereby enabling more precise adjustment of the laser's operating temperature.

[0017] Optionally, the temperature detection circuit includes a thermistor, a sixth resistor, and a third capacitor; the thermoelectric cooler is used to regulate the temperature of the laser. The first end of the sixth resistor is connected to a voltage source, the second end of the sixth resistor is electrically connected to the first end of the thermistor, and the second end of the thermistor is grounded. The third capacitor is connected in parallel with the thermistor; the first end of the thermistor is also electrically connected to the input end of the signal output circuit and the non-inverting input end of the fourth operational amplifier.

[0018] By connecting the thermistor and the sixth resistor in series to form a voltage divider circuit, the operating temperature of the laser can be indirectly obtained by measuring the output voltage of the voltage divider circuit, which is beneficial for subsequent adjustment of the laser's operating temperature.

[0019] Optionally, the signal output circuit includes a third operational amplifier, the non-inverting input terminal of the third operational amplifier is connected to the first terminal of the thermistor, the inverting input terminal of the third operational amplifier is connected to the output terminal, and the output terminal of the third operational amplifier is also electrically connected to the second input terminal of the analog-to-digital converter circuit.

[0020] According to a second aspect of this application, a phase-sensitive optical time-domain reflectometer is provided, the phase-sensitive optical time-domain reflectometer including the narrow linewidth laser driving circuit described in the first aspect above.

[0021] Based on any of the above aspects, the narrow linewidth laser driving circuit and phase-sensitive optical time-domain reflectometer provided by this utility model have the following effective effects: 1. The laser is driven by the current control module, which enables the laser to operate under a stable current, effectively avoiding the problem of unstable output power caused by current fluctuations. The laser's operating temperature is monitored and adjusted in real time by the temperature control module, which can prevent the laser from experiencing performance degradation or failure due to excessive cooling or heating, thereby enhancing the stability of the laser's operation.

[0022] 2. The voltage divider filter circuit can filter out high-frequency noise and spurious waves in the current signal, providing a smooth DC signal for the current drive circuit and reducing the instability of laser performance caused by current fluctuations; the in-phase amplifier circuit enhances the stability and anti-interference capability of the current signal, enabling the laser to operate under a stable operating current; the temperature control module monitors the laser's operating temperature in real time through a thermistor, calculates the control signal using a differential integral circuit, and exchanges heat with the laser through a thermoelectric cooler, thereby enhancing the stability of laser operation. Attached Figure Description

[0023] Figure 1 A schematic diagram of the narrow linewidth laser driving circuit provided by this utility model.

[0024] Figure 2 A schematic diagram of the overall structure of the current control module for the narrow linewidth laser driving circuit provided by this utility model.

[0025] Figure 3 The circuit diagram of the current control module of the narrow linewidth laser driving circuit provided by this utility model.

[0026] Figure 4 A schematic diagram of the overall structure of the temperature control module for the narrow linewidth laser driver circuit provided by this utility model.

[0027] Figure 5 The circuit diagram of the temperature control module of the narrow linewidth laser driver circuit provided by this utility model.

[0028] Figure 6 This is a schematic diagram of the phase-sensitive optical time-domain reflectometer provided by this utility model. Detailed Implementation

[0029] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0030] Example 1 like Figure 1As shown, this embodiment provides a narrow linewidth laser driving circuit, including a laser 13, a digital-to-analog converter 11, an analog-to-digital converter 14, a current control module 12, and a temperature control module 15.

[0031] In this embodiment, laser 13 is a narrow linewidth laser. The digital-to-analog converter circuit 11 can use a digital-to-analog converter or similar method to convert digital signals into analog signals. Similarly, the analog-to-digital converter circuit 14 can also use an analog-to-digital converter or similar method to convert analog signals into digital signals.

[0032] The output terminal of the current control module 12 is electrically connected to the negative terminal of the laser 13, and the current control module 12 is used to control the operating current of the laser 13.

[0033] The first output terminal of the digital-to-analog converter circuit 11 is electrically connected to the input terminal of the current control module 12, and the second output terminal of the digital-to-analog converter circuit 11 is electrically connected to the input terminal of the temperature control module 15. The first input terminal of the analog-to-digital converter circuit 14 is electrically connected to the output terminal of the current control module 12, and the second input terminal of the analog-to-digital converter circuit 14 is electrically connected to the output terminal of the temperature control module.

[0034] In practical applications, the output of analog-to-digital converter 14 and the input of digital-to-analog converter 11 can be connected to signal processors, etc. Laser 13 can be connected to other optical components; for example, laser 13 can be connected to an optical fiber via a fiber optic connector for fiber optic detection. It is understood that analog-to-digital converter 14, digital-to-analog converter 11, and laser 13 can be externally connected to other components as needed; this is merely illustrative and not intended to be limiting.

[0035] The narrow-linewidth laser driving circuit provided in this embodiment drives the current of the laser 13 through the current control module 12, enabling the laser 13 to operate under a stable operating current and effectively avoiding the problem of unstable output power caused by current fluctuations. The temperature control module 15 monitors and adjusts the operating temperature of the laser 13 in real time, preventing performance degradation or malfunctions caused by excessive cooling or heating, thereby enhancing the operating stability of the laser 13.

[0036] Specifically, such as Figure 2 As shown, the current control module 12 includes a current drive circuit 122.

[0037] like Figure 3 As shown, the current drive circuit 122 includes a first operational amplifier U1, a third resistor R3, a sampling resistor R0, and an NMOS transistor Q1.

[0038] The first output terminal of the digital-to-analog converter circuit 11 is electrically connected to the non-inverting input terminal of the first operational amplifier U1. The first terminal of the sampling resistor R0 is electrically connected to the inverting input terminal of the first operational amplifier U1, and the second terminal of the sampling resistor R0 is grounded. The first terminal of the third resistor R3 is electrically connected to the output terminal of the first operational amplifier U1, and the second terminal of the third resistor R3 is electrically connected to the gate of the NMOS transistor Q1. The source of the NMOS transistor Q1 is electrically connected to the first terminal of the sampling resistor R0. The drain of the NMOS transistor Q1 is electrically connected to the negative terminal of the laser 13. The positive terminal of the laser 13 is connected to a voltage source, and the source of the NMOS transistor Q1 is electrically connected to the first input terminal of the analog-to-digital converter circuit 14.

[0039] The second output terminal of the digital-to-analog converter circuit 11 is electrically connected to the input terminal of the temperature control module 15, which is used to adjust the temperature of the laser 13. The second input terminal of the analog-to-digital converter circuit 14 is electrically connected to the output terminal of the temperature control module 15.

[0040] By connecting the sampling resistor R0, the NMOS transistor Q1, and the laser 13 in series, the voltage across the sampling resistor R0 increases as the current flowing through the laser 13 increases. This voltage is captured by the inverting input of the first operational amplifier U1 and compared with the voltage at its non-inverting input. Due to the action of the first operational amplifier U1, its output voltage is adjusted, causing a decrease in the voltage at its inverting input. This reduces the gate voltage of the NMOS transistor Q1, decreasing its conduction level and consequently reducing the current flowing through the laser 13. Therefore, the current driving circuit 122 can adjust the output voltage of the first operational amplifier U1 in real time to control the current flowing through the laser 13.

[0041] like Figure 2 As shown, the current control module 12 may further include a voltage divider filter circuit 120 and a non-inverting amplifier circuit 124. The input terminal of the voltage divider filter circuit 120 is electrically connected to the first output terminal of the digital-to-analog converter circuit 11, and the output terminal of the voltage divider filter circuit 120 is electrically connected to the non-inverting input terminal of the first operational amplifier U1. The output terminal of the current drive circuit 122 is electrically connected to the input terminal of the non-inverting amplifier circuit 124 and the negative terminal of the laser 13. The output terminal of the non-inverting amplifier circuit 124 is electrically connected to the first input terminal of the analog-to-digital converter circuit 14.

[0042] In this embodiment, the voltage divider filter circuit 120 filters out high-frequency noise and spurious signals in the input current signal, providing a smooth DC signal for the subsequent current drive circuit. This helps reduce the instability of the laser 13's performance caused by current fluctuations. By adjusting the operating current of the laser 13 through the current drive circuit 122, the laser 13 can operate under a stable current, thereby improving the stability of the laser 13's operation.

[0043] like Figure 3 As shown, the voltage divider filter circuit 120 includes a first resistor R1, a second resistor R2, and a first capacitor C1. The first end of the first resistor R1 is connected to the first output terminal DAC_OUT1 of the digital-to-analog converter circuit 11; the second end of the first resistor R1 is electrically connected to the first end of the second resistor R2, the first end of the first capacitor C1, and the non-inverting input terminal of the first operational amplifier U1; the second end of the second resistor R2 is connected to the second end of the first capacitor C1 and then grounded.

[0044] According to Ohm's law, the current is the same everywhere in a series circuit, and the voltage distribution is directly proportional to the resistance. Therefore, a voltage divider can be formed by connecting the first resistor R1 and the second resistor R2 in series, thereby adjusting the voltage in the circuit. An RC filter is formed by connecting the first capacitor C1 in parallel with the second resistor R2. The RC filter smooths the output voltage and reduces noise and fluctuations caused by the output of the digital-to-analog converter circuit 11 or other components in the circuit. Since the output voltage range of the digital-to-analog converter circuit 11 is limited, and the operating current of the laser 13 needs to be precisely adjusted within a small range, the voltage divider filter circuit 120 can more effectively utilize the effective output voltage range of the digital-to-analog converter circuit 11 without increasing the number of bits, thereby improving the adjustment accuracy of the laser 13's operating current.

[0045] In specific implementation, the output voltage of the digital-to-analog converter circuit 11 can be selected and determined according to the number of bits in the digital-to-analog converter circuit 11 and the operating current value required by the laser 13. In some optional embodiments, the output voltage of the digital-to-analog converter circuit 11 can be selected as 2.5V, 3.3V, 4.096V or 5V, etc.

[0046] The narrow-linewidth laser driving circuit also includes a second capacitor C1, which is connected in parallel with the laser 13. In specific implementations, one or more second capacitors can be used, preferably two. The second capacitor C1 is used to smooth voltage fluctuations across the laser 13, reduce current ripple, and make the output of the laser 13 more stable. By absorbing and storing transient voltage fluctuations generated by the laser 13 during operation, the second capacitor C1 can smooth the DC voltage and reduce voltage ripple, enabling the laser 13 to operate in a more stable voltage environment, thereby improving the stability and consistency of the output optical signal of the laser 13.

[0047] The non-inverting amplifier circuit 124 includes a second operational amplifier U2, a fourth resistor R4, and a fifth resistor R5. The inverting input terminal of the second operational amplifier U2 is electrically connected to the first terminal of the fourth resistor R4 and the first terminal of the fifth resistor R5. The second terminal of the fourth resistor R4 is grounded. The second terminal of the fifth resistor R5 is electrically connected to the output terminal of the second operational amplifier U2.

[0048] The non-inverting input terminal of the second operational amplifier U2 is electrically connected to the source of the NMOS transistor Q1; the first input terminal ADC_IN1 of the analog-to-digital converter circuit 14 is electrically connected to the output terminal of the second operational amplifier U2.

[0049] By amplifying the voltage signal of the sampling resistor R0 through the second operational amplifier U3 before inputting it into the analog-to-digital converter circuit 14, the resolution degradation caused by the small signal amplitude input to the analog-to-digital converter circuit 14 can be effectively avoided.

[0050] like Figure 4 As shown, the temperature control module 15 includes a temperature detection circuit 150, a signal output circuit 152, and a temperature adjustment circuit 154. The temperature detection circuit 150 is electrically connected to the input terminal of the signal output circuit 152, and the first terminal of the temperature adjustment circuit 154 is electrically connected to the temperature detection circuit 150. The output terminal of the signal output circuit 152 is electrically connected to the second input terminal of the analog-to-digital converter circuit 14, and the second terminal of the temperature adjustment circuit 154 is electrically connected to the second output terminal of the digital-to-analog converter circuit 11.

[0051] like Figure 5 As shown, the temperature detection circuit 150 includes a thermistor NTC, a sixth resistor R6, and a third capacitor C3.

[0052] In this embodiment, a thermistor NTC is used to detect the operating temperature of the laser 13. The thermistor NTC has a negative temperature coefficient; its resistance decreases as the temperature increases and increases as the temperature decreases.

[0053] The first end of the sixth resistor R6 is connected to a voltage source, the second end of the sixth resistor R6 is electrically connected to the first end of the thermistor NTC, and the second end of the thermistor NTC is grounded.

[0054] By connecting the thermistor NTC in series with the sixth resistor R6 to form a voltage divider circuit, the operating temperature of the laser 13 can be indirectly obtained by measuring the output voltage of the voltage divider circuit.

[0055] In this embodiment, a constant current drive can be used to provide operating current to the thermistor NTC. Using a constant current drive allows the thermistor NTC to maintain a relatively stable current value under different temperature conditions, thereby improving the accuracy and stability of temperature detection.

[0056] like Figure 5 As shown, the third capacitor C3 is connected in parallel with the thermistor NTC. The first terminal of the thermistor NTC is also electrically connected to the input terminal of the signal output circuit 152 and the first terminal of the temperature regulation circuit 154. In one specific implementation, the third capacitor C3 can be a filter capacitor. The filter capacitor removes high-frequency noise and interference signals from the circuit, making the output voltage signal of the temperature detection circuit more stable and reliable.

[0057] The signal output circuit 152 includes a third operational amplifier U3. The non-inverting input terminal of the third operational amplifier U3 is electrically connected to the first terminal of the thermistor NTC. The inverting input terminal of the third operational amplifier U3 is electrically connected to the output terminal. The output terminal of the third operational amplifier U3 is also electrically connected to the second input terminal of the analog-to-digital converter circuit 14.

[0058] In this embodiment, the third operational amplifier U3 is used as a follower to output the voltage model measured by the thermistor NTC to the analog-to-digital converter circuit 14.

[0059] The temperature regulation circuit 154 includes a differential integral circuit and a thermoelectric cooler 16. The thermoelectric cooler 16 is used to regulate the temperature of the laser 13; like Figure 5 As shown, the differential integrator circuit includes a fourth operational amplifier U4, a fifth operational amplifier U5, a seventh resistor R7, an eighth resistor R8, a fourth capacitor C4, and a fifth capacitor C5. The non-inverting input of the fourth operational amplifier U4 is electrically connected to the first terminal of the thermistor NTC, and the inverting input of the fourth operational amplifier U4 is electrically connected to its output. The output of the fourth operational amplifier U4 is electrically connected to the first terminal of the seventh resistor R7.

[0060] The inverting input terminal of the fifth operational amplifier U5 is electrically connected to the second terminal of the seventh resistor R7, and the non-inverting input terminal of the fifth operational amplifier U5 is connected to the first terminal of the eighth resistor R8. The output terminal of the fifth operational amplifier U5 is electrically connected to the second terminal of the seventh resistor R7 through the fourth capacitor C4. The second terminal of the eighth resistor R8 is electrically connected to the output terminal DAC_OUT2 of the digital-to-analog converter circuit 11, and the first terminal of the eighth resistor R8 is also connected to the first terminal of the fifth capacitor C5. The second terminal of the fifth capacitor C5 is grounded. The negative terminal of the thermoelectric cooler 16 is electrically connected to the output terminal of the fourth operational amplifier U4, and the positive terminal of the thermoelectric cooler 16 is electrically connected to the output terminal of the fifth operational amplifier U5.

[0061] In this embodiment, the fourth operational amplifier U4 acts as a follower to receive the real-time temperature signal from the laser 13.

[0062] It is understood that the thermoelectric cooler 16 and the thermistor NTC can be in mechanical or physical contact with the laser 13. By having the thermistor NTC in contact with the laser 13, the temperature of the laser 13 can be detected more accurately; by having the thermoelectric cooler 16 in close contact with the laser 13, the thermoelectric cooler 16 can utilize the thermoelectric effect to cool or heat, thereby exchanging heat with the laser 13 and regulating its temperature. Exemplarily, the thermoelectric cooler 16 can be in direct contact with the laser 13, or it can be indirect contact with the laser 13 through a medium; the thermistor NTC can be in direct contact with the laser 13, or it can be indirect contact with the laser 13 through a medium.

[0063] During operation, the thermistor NTC converts the detected operating temperature of the laser 13 into an electrical signal and transmits it to the fourth operational amplifier U4. The fourth operational amplifier U4 acts as a follower and outputs a signal corresponding to the real-time temperature of the laser 13. The fifth operational amplifier U5 calculates the control signal through a differential integration circuit based on the differential voltage between the signal output by the fourth operational amplifier U4 and the signal corresponding to the set temperature output by the digital-to-analog converter circuit 11, thereby adjusting the operating temperature of the thermoelectric cooler 16. This allows the thermoelectric cooler 16 to exchange heat with the laser, thus regulating the operating temperature of the laser 13.

[0064] like Figure 6 As shown in the embodiments of this application, a phase-sensitive optical time-domain reflectometer is also provided, which may include the narrow linewidth laser driving circuit described in any of the above embodiments.

[0065] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the technical solution of this utility model, and are not intended to limit the specific implementation of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A narrow linewidth laser driver circuit, comprising: The narrow linewidth laser driving circuit includes a laser, a digital-to-analog converter circuit, an analog-to-digital converter circuit, a current control module, and a temperature control module. The current control module includes a current drive circuit; the current drive circuit includes a first operational amplifier, a third resistor, a sampling resistor, and an NMOS transistor; The first output terminal of the digital-to-analog converter circuit is electrically connected to the non-inverting input terminal of the first operational amplifier; The first end of the sampling resistor is electrically connected to the inverting input terminal of the first operational amplifier, and the second end of the sampling resistor is grounded; the first end of the third resistor is electrically connected to the output terminal of the first operational amplifier, and the second end of the third resistor is electrically connected to the gate of the NMOS transistor; the source of the NMOS transistor is electrically connected to the first end of the sampling resistor; the drain of the NMOS transistor is electrically connected to the negative terminal of the laser; the positive terminal of the laser is connected to a voltage source, and the source of the NMOS transistor is electrically connected to the first input terminal of the analog-to-digital converter circuit. The second output terminal of the digital-to-analog converter circuit is electrically connected to the input terminal of the temperature control module, which is used to adjust the temperature of the laser. The second input terminal of the analog-to-digital converter circuit is electrically connected to the output terminal of the temperature control module.

2. The narrow linewidth laser driver circuit of claim 1, wherein, The current control module further includes a voltage divider filter circuit and a non-inverting amplifier circuit; the input terminal of the voltage divider filter circuit is electrically connected to the first output terminal of the digital-to-analog converter circuit, the output terminal of the voltage divider filter circuit is electrically connected to the non-inverting input terminal of the first operational amplifier, the output terminal of the current drive circuit is electrically connected to the input terminal of the non-inverting amplifier circuit, and the output terminal of the non-inverting amplifier circuit is electrically connected to the source of the NMOS transistor.

3. The narrow linewidth laser driver circuit of claim 2, wherein, The voltage divider filter circuit includes a first resistor, a second resistor, and a first capacitor. The first end of the first resistor is connected to the first output terminal of the digital-to-analog converter circuit. The second end of the first resistor is electrically connected to the first end of the second resistor, the first end of the first capacitor, and the non-inverting input terminal of the first operational amplifier. The second end of the second resistor is connected to the second end of the first capacitor and then grounded.

4. The narrow linewidth laser driver circuit of claim 3, wherein, The non-inverting amplifier circuit includes a second operational amplifier, a fourth resistor, and a fifth resistor. The inverting input terminal of the second operational amplifier is electrically connected to the first terminal of the fourth resistor and the first terminal of the fifth resistor. The second terminal of the fourth resistor is grounded. The second terminal of the fifth resistor is electrically connected to the output terminal of the second operational amplifier. The non-inverting input of the second operational amplifier is electrically connected to the source of the NMOS transistor; the first input of the analog-to-digital converter is electrically connected to the output of the second operational amplifier.

5. The narrow linewidth laser driver circuit of claim 1, wherein, The narrow linewidth laser driving circuit also includes a second capacitor, which is connected in parallel with the laser.

6. A narrow linewidth laser driver circuit according to any one of claims 1 to 5, wherein, The temperature control module includes a temperature detection circuit, a signal output circuit, and a temperature adjustment circuit; The temperature detection circuit is electrically connected to the input terminal of the signal output circuit, and the temperature detection circuit is used to detect the temperature of the laser. The first terminal of the temperature regulation circuit is electrically connected to the temperature detection circuit, and the temperature regulation circuit is used to regulate the temperature of the laser. The output terminal of the signal output circuit is electrically connected to the second input terminal of the analog-to-digital converter circuit, and the second terminal of the temperature regulation circuit is electrically connected to the second output terminal of the digital-to-analog converter circuit.

7. The narrow-linewidth laser driving circuit according to claim 6, wherein The temperature regulation circuit further includes a differential integral circuit and a thermoelectric cooler; the thermoelectric cooler is used to regulate the temperature of the laser. The differential integration circuit includes a fourth operational amplifier, a fifth operational amplifier, a seventh resistor, an eighth resistor, a fourth capacitor, and a fifth capacitor; The non-inverting input terminal of the fourth operational amplifier is electrically connected to the temperature detection circuit, and the inverting input terminal of the fourth operational amplifier is electrically connected to the output terminal; the output terminal of the fourth operational amplifier is electrically connected to the first terminal of the seventh resistor. The inverting input terminal of the fifth operational amplifier is electrically connected to the second terminal of the seventh resistor, the non-inverting input terminal of the fifth operational amplifier is connected to the first terminal of the eighth resistor, and the output terminal of the fifth operational amplifier is electrically connected to the second terminal of the seventh resistor through the fourth capacitor. The second terminal of the eighth resistor is electrically connected to the output terminal of the digital-to-analog converter circuit, and the first terminal of the eighth resistor is also connected to the first terminal of the fifth capacitor. The second terminal of the fifth capacitor is grounded. The negative terminal of the thermoelectric cooler is electrically connected to the output terminal of the fourth operational amplifier, and the positive terminal of the thermoelectric cooler is electrically connected to the output terminal of the fifth operational amplifier.

8. The narrow-linewidth laser driving circuit according to claim 7, wherein The temperature detection circuit includes a thermistor, a sixth resistor, and a third capacitor; the thermistor is used to detect the temperature of the laser. The first end of the sixth resistor is connected to a voltage source, the second end of the sixth resistor is electrically connected to the first end of the thermistor, and the second end of the thermistor is grounded. The third capacitor is connected in parallel with the thermistor; the first end of the thermistor is also electrically connected to the input end of the signal output circuit and the non-inverting input end of the fourth operational amplifier.

9. The narrow-linewidth laser driving circuit according to claim 8, wherein The signal output circuit includes a third operational amplifier. The non-inverting input terminal of the third operational amplifier is connected to the first terminal of the thermistor, the inverting input terminal of the third operational amplifier is connected to the output terminal, and the output terminal of the third operational amplifier is also electrically connected to the second input terminal of the analog-to-digital converter circuit.

10. A phase sensitive optical time domain reflectometer, characterized in that, The phase-sensitive optical time-domain reflectometer includes a narrow linewidth laser driving circuit as described in any one of claims 1-9.

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