Differential feedback photoelectric balance detection circuit
The photoelectric balance detection circuit with differential feedback solves the problems of sampling rate mismatch and inflexible signal processing in existing photoelectric balance detectors in femtosecond spectrum detection, and achieves high-quality detection of high-frequency signals and improvement of signal-to-noise ratio.
Patent Information
- Application Number
- CN202510890830.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-09-19
AI Technical Summary
The sampling rate of existing photoelectric balanced detectors in the field of femtosecond spectroscopy detection is not suitable for high-repetition-rate femtosecond lasers above 1 MHz. The high-frequency part is severely distorted, the gain setting of the signal processing module is not flexible, photocurrent saturation is prone to occur under high-flux detection, the integration frequency and gain settings cannot be flexibly adjusted, and it is not optimized for specific wavelengths.
A differential feedback photoelectric balance detection circuit was designed, which included an optical signal receiving module, a common-mode signal processing module, a differential-mode signal splitting module, a differential feedback module, and a differential-mode signal processing module. The optical signal was converted into an electrical signal through a photodiode and a transimpedance amplifier. The common-mode signal processing module performed subtraction, amplification, and noise reduction. The differential feedback module improved the quality of high-frequency signals. The differential-mode signal processing module further reduced noise and output resistance.
It achieves high-quality detection of high-repetition-rate femtosecond laser signals above 1 MHz, reduces high-frequency signal distortion, prevents photocurrent saturation, flexibly sets gain, optimizes specific wavelength detection, and improves signal-to-noise ratio.
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Figure CN120668256A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of weak signal detection, and in particular to a photoelectric balance detection circuit with differential feedback. Technical Background
[0002] Photoelectric balanced detectors offer superior sensitivity and performance to traditional photodetectors and are often used to measure weak optical signals. They have applications in a variety of fields, including biomedical imaging, optical communications, lidar, and quantum communications. They operate by using balanced circuits in the signal transmission path to reduce noise and drift, thereby improving the sensitivity and interference resistance of the photodetector.
[0003] Currently, photoelectric balanced detectors typically consist of two photodiodes and a differential amplifier. The basic principle is as follows: a light signal is first split into two paths by an optical beam splitter and then input into two photodiodes. These two photodiodes operate identically, but with opposite phases of the input light signals. When the two photodiodes receive light signals of equal intensity but opposite phases, their output currents are also opposite, resulting in a differential signal that can be subtracted from each other. This differential signal is amplified by the amplifier, and a feedback loop adjusts the operating points of the two photodiodes to ensure that their output signals are always equal. This eliminates any unevenness or variations in light source intensity and photodiode performance, improving the detector's sensitivity and anti-interference capabilities.
[0004] Currently, domestically produced photoelectric balanced detectors are primarily targeted at the larger industrial detection market. Photoelectric balanced detectors used in scientific research equipment, which require higher precision, are primarily dominated by a few foreign brands. None of these commercially available photoelectric balanced detectors, both domestically and internationally, have been optimized for the smaller femtosecond spectroscopy market.
[0005] Therefore, the commercial photoelectric balanced detectors commonly used in time-domain terahertz spectroscopy in ultrafast spectroscopy laboratories have many shortcomings. For example, due to the rise time of the selected photodiode and the gain-bandwidth product of the operational amplifier, the sampling rate of the commonly used photoelectric balanced detector is not suitable for high-repetition-rate femtosecond lasers above 1 MHz, and the high-frequency part is severely distorted. The gain setting of the signal processing module is not flexible, and photocurrent saturation is prone to occur under high-flux detection conditions. The settings of the integration frequency and gain cannot be flexibly adjusted and are not specifically optimized according to the detection wavelength.
[0006] Therefore, in order to improve the detection sensitivity and signal-to-noise ratio of time-domain terahertz spectroscopy, it is urgent to develop a photoelectric balanced detector optimized for femtosecond pulse lasers. Summary of the Invention
[0007] The main technical problem to be solved by the present invention is to provide a differential feedback photoelectric balance detection circuit, which outputs an electrical signal with a high signal-to-noise ratio and is applicable to high-frequency spectroscopy systems.
[0008] In order to solve the above technical problems, the present invention provides a differential feedback photoelectric balance detection circuit, comprising: an optical signal receiving module, a common mode signal processing module, a differential mode signal splitting module, a differential feedback module and a differential mode signal processing module;
[0009] The optical signal receiving module is used to receive the optical signal, convert the optical signal into an electrical signal, and transmit it to the common mode signal processing module;
[0010] The common-mode signal processing module is used to perform subtraction, amplification and noise reduction processing on the signal output by the optical signal receiving module;
[0011] The differential mode signal splitting module is used to split the differential mode signal output by the common mode signal processing module in proportion to obtain a feedback signal and an output signal, and input them into the differential feedback module and the differential mode signal processing module respectively;
[0012] The differential feedback module is used to differentiate the feedback signal and then input it back to the common mode signal processing module;
[0013] The differential mode signal processing module is used to perform noise reduction processing on the output signal and output the signal.
[0014] In a preferred embodiment, the optical signal receiving module includes a first photodiode, a second photodiode, a first transimpedance amplifier, and a second transimpedance amplifier;
[0015] The anode of the first photodiode is connected to the negative pole of the power supply or the ground, and the cathode is connected to the first transimpedance amplifier; the anode of the second photodiode is connected to the negative pole of the power supply or the ground, and the cathode is connected to the second transimpedance amplifier;
[0016] The common-mode signal processing module is connected to the outputs of the first transimpedance amplifier and the second transimpedance amplifier, subtracts, amplifies, and performs noise reduction processing on the signals output by the first transimpedance amplifier and the second transimpedance amplifier to obtain a differential-mode signal, and outputs the differential-mode signal to the differential signal splitting module.
[0017] In a preferred embodiment, the ratio of the feedback signal to the output signal is 1:5 or 1:10 or 1:20 or 1:50 or 1:100.
[0018] In a preferred embodiment, the optical signal is an optical signal introduced by an optical fiber or an optical signal in free space.
[0019] In a preferred embodiment, the common-mode signal processing module is used to subtract the signal output by the optical signal receiving module, specifically referring to: subtracting the signals output by two photodiodes in the optical signal receiving module, or subtracting the signal output by one photodiode in the optical signal receiving module from the dark noise.
[0020] In a preferred embodiment, the first photodiode and the second photodiode are in photovoltaic mode or photoconductive mode at the same time; and the first transimpedance amplifier and the second transimpedance amplifier have the same resistance value.
[0021] In a preferred embodiment, the differential feedback module includes a differential capacitor.
[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0023] The present invention provides a differential feedback optoelectronic balance detection circuit. This circuit effectively converts two optical signals into stable electrical signals through the photodiode and transimpedance amplifier in the optical signal receiving module. A common-mode signal processing module performs subtraction, amplification, and noise reduction on the output signal of the optical signal receiving module, improving the signal-to-noise ratio of the differential-mode signal. A differential feedback module is innovatively introduced to feed the differentiated signal back to the common-mode signal processing module, improving the processing quality of high-frequency signals and reducing distortion. The differential-mode signal processing module further performs noise reduction on the differential-mode signal and reduces the output resistance, improving the signal-to-noise ratio of the output electrical signal and minimizing the impact of subsequent signal acquisition devices on the output signal. The circuit optimizes the rise time of the photodiode in the optical signal receiving module and the gain-bandwidth product of the operational amplifier in the signal processing module. Flexible setting of the integration frequencies in the common-mode and differential-mode signal processing modules enables high-quality detection of high-repetition-rate femtosecond laser signals exceeding 1 MHz. Flexible setting of the gain of the common-mode signal processing module prevents photocurrent saturation under high-light-flux detection conditions. Optimization for specific wavelengths is also possible, improving the detection quality of optical signals of specific wavelengths. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.
[0025] Figure 1 This is one of the schematic diagrams of a balance detection circuit provided in an embodiment of the present application;
[0026] Figure 2A second schematic diagram of a balance detection circuit provided in an embodiment of the present application;
[0027] Figure 3 A third schematic diagram of a balance detection circuit provided in an embodiment of the present application;
[0028] Figure 4 A fourth schematic diagram of a balance detection circuit provided in an embodiment of the present application;
[0029] Figure 5 A schematic diagram of current flow in a common-mode signal processing module of a balanced detection circuit provided in an embodiment of the present application;
[0030] Figure 6 A schematic diagram of current flow in a differential-mode signal splitting module of a balanced detection circuit provided in an embodiment of the present application;
[0031] Figure 7 A circuit diagram of a differential feedback module of a balance detection circuit provided in an embodiment of the present application;
[0032] Figure 8 A performance comparison diagram of a balanced detection circuit provided in an embodiment of the present application and a circuit without a differential feedback module;
[0033] Figure 9 A schematic diagram of a balanced detection circuit according to an embodiment of the present application performing single-channel optical signal detection;
[0034] Figure 10 A schematic diagram of signal flow when a balanced detection circuit according to an embodiment of the present application performs single-channel optical signal detection;
[0035] Icon: 100-balanced detection circuit; 111-optical signal receiving module; 112-common-mode signal processing module; 113-differential-mode signal splitting module; 114-differential feedback module; 115-differential-mode signal output module; 11-first photodiode; 12-second photodiode; 13-first transimpedance amplifier; 14-second transimpedance amplifier; 15-feedback signal arm; 16-output signal arm; 17-differential capacitor. DETAILED DESCRIPTION
[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.
[0037] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.
[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.
[0039] In addition, the terms "first", "second", etc., if used, are merely used to distinguish and describe, and should not be understood as indicating or implying relative importance.
[0040] Photoelectric balanced detectors offer superior sensitivity and performance to traditional photodetectors and are often used to measure weak optical signals. They have applications in a variety of fields, including biomedical imaging, optical communications, lidar, and quantum communications. They operate by using balanced circuits in the signal transmission path to reduce noise and drift, thereby improving the sensitivity and interference resistance of the photodetector.
[0041] Currently, photoelectric balanced detectors typically consist of two photodiodes and a differential amplifier. The basic principle is as follows: a light signal is first split into two paths by an optical beam splitter and then input into two photodiodes. These two photodiodes operate identically, but with opposite phases of the input light signals. When the two photodiodes receive light signals of equal intensity but opposite phases, their output currents are also opposite, resulting in a differential signal that can be subtracted from each other. This differential signal is amplified by the amplifier, and a feedback loop adjusts the operating points of the two photodiodes to ensure that their output signals are always equal. This eliminates any unevenness or variations in light source intensity and photodiode performance, improving the detector's sensitivity and anti-interference capabilities.
[0042] Currently, domestically produced photoelectric balanced detectors are primarily targeted at the larger industrial detection market. Photoelectric balanced detectors used in scientific research equipment, which require higher precision, are primarily dominated by a few foreign brands. None of these commercially available photoelectric balanced detectors, both domestically and internationally, have been optimized for the smaller femtosecond spectroscopy market.
[0043] Therefore, the commercial photoelectric balanced detectors commonly used in time-domain terahertz spectroscopy in ultrafast spectroscopy laboratories have many shortcomings. For example, due to the rise time of the selected photodiode and the gain-bandwidth product of the operational amplifier, the sampling rate of the commonly used photoelectric balanced detector is not suitable for high-repetition-rate femtosecond lasers above 1 MHz, and the high-frequency part is severely distorted. The gain setting of the signal processing module is not flexible, and photocurrent saturation is prone to occur under high-flux detection conditions. The settings of the integration frequency and gain cannot be flexibly adjusted and are not specifically optimized according to the detection wavelength.
[0044] Therefore, in order to improve the detection sensitivity and signal-to-noise ratio of time-domain terahertz spectroscopy, it is urgent to develop a photoelectric balanced detector optimized for femtosecond pulse lasers.
[0045] In view of the discovery of the above problems, this embodiment provides a differential feedback photoelectric balance detection circuit, which effectively converts two optical signals into stable electrical signals through the photodiode and transimpedance amplifier in the optical signal receiving module; the common-mode signal processing module subtracts, amplifies and reduces noise on the output signal of the optical signal receiving module, thereby improving the signal-to-noise ratio of the differential-mode signal; the differential feedback module is innovatively introduced to feed back the differentiated signal to the common-mode signal processing module, thereby improving the processing quality of the high-frequency signal and reducing distortion; the differential-mode signal processing module further reduces noise on the differential-mode signal, reduces the output resistance, improves the signal-to-noise ratio of the output electrical signal, and reduces the impact of subsequent signal acquisition devices on the output signal.
[0046] Please refer to Figure 1 This embodiment provides a balanced detection circuit 100, including: an optical signal receiving module 111, a common-mode signal processing module 112, a differential-mode signal splitting module 113, a differential feedback module 114 and a differential-mode signal processing module 115.
[0047] The optical signal receiving module 111 is used to receive optical signals introduced by optical fibers or in free space, convert the optical signals into electrical signals, and transmit them to the common-mode signal processing module 112. In this embodiment, the optical signal receiving module 111 has two photodiodes 11 and 12, each of which is used to receive the optical signal introduced by the optical fiber. The common-mode signal processing module 112 is used to perform phase subtraction, amplification, and noise reduction on the signal output by the optical signal receiving module 111. The differential-mode signal splitting module 113 is used to split the differential-mode signal output by the common-mode signal processing module 112 into a certain proportion and input it to the differential feedback module 114 and the differential-mode signal processing module 115. The differential feedback module 114 is used to differentiate the differential-mode signal and then input it back to the common-mode signal processing module 112. The differential-mode signal processing module 115 is used to perform noise reduction on the differential-mode signal and output it.
[0048] Among them, such as Figure 2The two photodiodes 11 and 12 in the optical signal receiving module 111 can choose between photovoltaic and photoconductive modes. In photovoltaic mode, the anodes of the photodiodes 11 and 12 are grounded, which is the photovoltaic mode. In this mode, the response frequency is low but the signal-to-noise ratio is higher; when the anodes are connected to the negative pole of the power supply, it is the photoconductive mode, which has a high response frequency and is more suitable for high-frequency systems. The resistors in the two transimpedance amplifiers 13 and 14 can be adjusted. The resistance directly determines the gain and affects the common-mode signal size input to the common-mode processing module 112. It should be noted that the photodiodes 11 and 12 must be in photovoltaic mode or photoconductive mode at the same time; the resistance values of the first transimpedance amplifier 13 and the second transimpedance amplifier 14 in the optical signal receiving module 111 must be set to the same value.
[0049] The common mode signals output by the two optical signal receivers in the optical signal receiving module 111 are input to the common mode signal processing module 112 for a series of processing. Figure 5 The common-mode signal processing module 112 first subtracts the two common-mode signals to obtain the original differential-mode signal. Since the photocurrent is very small, the gain of the first transimpedance amplifier 13 and the second transimpedance amplifier 14 should not be too high. The useful differential-mode signal is often buried deep in the noise, so noise reduction processing is required. The common-mode signal processing module 112 will integrate the signal at a certain frequency, which is equivalent to low-pass filtering, which can effectively reduce noise. Finally, the common-mode processing module 112 will also amplify the noise-reduced differential-mode signal to facilitate subsequent output.
[0050] The differential mode signal output by the common mode signal processing module 112 is input to the differential mode signal splitting module 113. Figure 6 , splitting it into an output signal and a feedback signal. The splitting ratio is determined by the resistance values of the feedback signal arm 15 and the output signal arm 16, with a recommended setting of feedback:output = 1:10. The splitting ratio can also be flexibly adjusted by adjusting the resistance ratio of resistors 15 and 16, such as 1:100, 1:50, 1:20, 1:5, etc., but this embodiment of the present application does not impose any specific limitations on this.
[0051] The feedback signal will flow into the differential feedback module 114, which performs differential processing on the signal, which is equivalent to performing a high-pass filter. The differential feedback signal will be input back to the common mode signal processing module 112 to improve the quality of the high frequency part of the signal. Figure 4 The strength of the feedback signal can be flexibly set by adjusting the capacitance of the differential capacitor 17 in the differential feedback module 114, which can be 10pF, 22pF, 100pF, etc., and the embodiment of the present application does not impose any specific restrictions on this.
[0052] The output signal of the differential mode signal splitting module 113 is as follows: Figure 6, will enter the differential mode signal processing module 115. This module will further reduce noise and gain the output signal, further reducing noise and improving the signal-to-noise ratio. At the same time, this module reduces the output resistance, which can effectively reduce the impact of subsequent signal acquisition devices on it.
[0053] In this embodiment, the differential mode signal splitting module 113 and the differential feedback module 114 are innovatively introduced to feed back the high frequency part of the signal to the common mode signal processing module 112 according to a certain ratio, thereby achieving noise reduction processing of the high frequency part of the signal, reducing high frequency signal distortion, and improving signal quality. The specific effects are as follows: Figure 8 , the high-frequency terahertz small signal peak collected by differential feedback is clearer and smoother; the rise time of the photodiode in the optical signal receiving module 111 and the gain-bandwidth product of the operational amplifiers in the signal processing modules 112, 113, 114, and 115 are optimized, and the integration frequency in the common-mode signal processing module 112 and the differential-mode signal processing module 115 are flexibly set to achieve high-quality detection of high-repetition-rate femtosecond laser signals above 1 MHz; the gain of the common-mode signal processing module 112 can be flexibly set to prevent photocurrent saturation under high-light flux detection conditions, and can be optimized for specific wavelengths to improve the detection quality of optical signals of specific wavelengths. By comparing this embodiment with a balanced detection circuit that does not use a differential feedback module, it can be seen that the signal strength of this application at high frequencies has been significantly enhanced.
[0054] It should be noted that the balanced detection circuit provided in this application can be used not only to detect the differential mode signal of a dual-channel optical signal, but also to detect a single-channel optical signal. Figure 9 , the second photodiode 12 can be shielded. The signal diagram when in use is as follows Figure 10 After the common-mode signal processing module 112 performs subtraction and noise reduction on the photoelectric signal and dark noise, the output differential-mode signal is the high-quality optical signal received by the first photodiode 12. Compared to conventional single-channel photodetectors, this solution can effectively reduce signal output instability caused by environmental instability and significantly improve the signal-to-noise ratio.
[0055] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.
Claims
1. A differential feedback photoelectric balance detection circuit, characterized in that: include: Optical signal receiving module, common mode signal processing module, differential mode signal splitting module, differential feedback module and differential mode signal processing module; The optical signal receiving module is used to receive the optical signal, convert the optical signal into an electrical signal, and transmit it to the common mode signal processing module; The common-mode signal processing module is used to perform subtraction, amplification and noise reduction processing on the signal output by the optical signal receiving module; The differential mode signal splitting module is used to split the differential mode signal output by the common mode signal processing module in proportion to obtain a feedback signal and an output signal, and input them into the differential feedback module and the differential mode signal processing module respectively; The differential feedback module is used to differentiate the feedback signal and then input it back to the common mode signal processing module; The differential mode signal processing module is used to perform noise reduction processing on the output signal and output the signal.
2. The differential feedback photoelectric balance detection circuit according to claim 1, characterized in that: The optical signal receiving module includes a first photodiode, a second photodiode, a first transimpedance amplifier and a second transimpedance amplifier; The anode of the first photodiode is connected to the negative pole of the power supply or the ground, and the cathode is connected to the first transimpedance amplifier; the anode of the second photodiode is connected to the negative pole of the power supply or the ground, and the cathode is connected to the second transimpedance amplifier; The common-mode signal processing module is connected to the outputs of the first transimpedance amplifier and the second transimpedance amplifier, subtracts, amplifies, and performs noise reduction processing on the signals output by the first transimpedance amplifier and the second transimpedance amplifier to obtain a differential-mode signal, and outputs the differential-mode signal to the differential signal splitting module.
3. The differential feedback photoelectric balance detection circuit according to claim 1, characterized in that: The ratio of the feedback signal to the output signal is 1:5 or 1:10 or 1:20 or 1:50 or 1:
100.
4. The differential feedback photoelectric balance detection circuit according to claim 1, characterized in that: The optical signal is an optical signal introduced by an optical fiber or an optical signal in free space.
5. The differential feedback photoelectric balance detection circuit according to claim 1, characterized in that: The common-mode signal processing module is used to subtract the signal output by the optical signal receiving module, specifically referring to: subtracting the signals output by two photodiodes in the optical signal receiving module, or subtracting the signal output by one photodiode in the optical signal receiving module from dark noise.
6. The differential feedback photoelectric balance detection circuit according to claim 2, characterized in that: The first photodiode and the second photodiode are in a photovoltaic mode or a photoconductive mode at the same time; and the first transimpedance amplifier and the second transimpedance amplifier have the same resistance value.
7. The differential feedback photoelectric balance detection circuit according to claim 1, characterized in that: The differential feedback module includes a differential capacitor.