Dither signal filtering and sampling method based on TFLN laser

Abstract

The invention discloses a dither signal filtering and sampling method based on a TFLN laser. The method comprises the following steps: step 1, loading a fundamental wave / second harmonic of a low-frequency dither signal into a photo-generated current of an optical module; 2, the photo-generated current signal loaded with the fundamental wave / second harmonic of the dither signal is amplified through an operational amplifier circuit and then is divided into two paths to be output; 3, after the first path of output in the two paths of output passes through a low-pass RC filter circuit, optical power sampling is carried out to monitor optical power, and the second path of output in the two paths of output is divided into a fundamental wave branch and a second harmonic wave branch; 4, enabling the fundamental wave branch and the second harmonic wave branch to pass through a corresponding frequency-selecting filtering and amplifying circuit and a rear-end amplifying and biasing circuit respectively to obtain a fundamental wave signal and a second harmonic wave signal, and outputting the fundamental wave signal and the second harmonic wave signal to an ADC sampling module for sampling. According to the invention, effective sampling of the fundamental wave and the second harmonic wave of the dither is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical modules, and in particular to a dither signal filtering and sampling method based on a TFLN laser. Background Art

[0002] Since 2020, with the advent of 800G / 1.6T single-mode high-end optical modules, the single-channel modulation rate of optical modules has also increased from single-wave 100G to 200G. Traditional DML lasers (Directly Modulated Laser) have been difficult to meet new application requirements, and TFLN MZ modulators (thin-film lithium niobate MZ) have become the best choice for single-wave 200G and above rate applications. However, the Quad locking of the TFLN modulator has become a technical difficulty in the application of the TFLN modulator. The premise for achieving Quad locking is to effectively detect the Quad point. Summary of the invention

[0003] In view of the technical defects and disadvantages in the prior art, the embodiments of the present invention provide a dither signal filtering and sampling method based on a TFLN laser to overcome the above problems or at least partially solve the above problems, and solve the problem of amplifying and detecting dither signals. The specific scheme is as follows:

[0004] A dither signal filtering and sampling method based on a TFLN laser, the method comprising:

[0005] Step 1, loading the fundamental wave / second harmonic of the low-frequency dither signal into the photocurrent of the optical module;

[0006] Step 2, amplifying the fundamental wave / second harmonic photocurrent signal loaded with the dither signal through an operational amplifier circuit and then dividing it into two output paths;

[0007] Step 3, performing optical power sampling on the first output of the two outputs after passing through a low-pass RC filter circuit to monitor the output optical power, and further dividing the second output of the two outputs into a fundamental wave branch and a second harmonic branch;

[0008] Step 4: After the fundamental wave branch and the second harmonic branch are respectively passed through the corresponding frequency selection filtering and amplification circuit and the back-end amplification and biasing circuit, a fundamental wave signal and a second harmonic signal are obtained, and output to the ADC sampling module for sampling.

[0009] Furthermore, in step 1, a low-frequency dither signal is coupled to the input end of the heater modulator of the optical module, so that the fundamental wave / second harmonic of the dither signal is carried in the photogenerated current of the MPD.

[0010] Furthermore, in step 2, the operational amplifier circuit is a front-end photoelectric signal amplifier circuit, and the front-end photoelectric signal amplifier circuit includes a first integrated operational amplifier MAX4233ABC+T and its peripheral circuits.

[0011] Further, the peripheral circuit includes a resistor R3, a resistor R9, a resistor R10, a resistor R11, a resistor R14, a resistor R15, a resistor R16, a capacitor C4, a capacitor C9, a capacitor C8 and a capacitor C13, a capacitor C13, and a light-emitting diode PD1; the positive input terminal of the first integrated operational amplifier MAX4233ABC+T is grounded through a resistor R16, and is also connected to a power supply VCC_2V5 through a resistor R14; one end of the resistor R3 is connected to the cathode of the light-emitting diode PD1, and the other end is connected to the power supply VCC_2V5, the anode of the light-emitting diode PD1 is connected to the ground GND_POWER, and the common point of the light-emitting diode PD1 and the resistor R3 is connected to the negative input terminal of the first integrated operational amplifier MAX4233ABC+T through a resistor R9; the capacitor C4 and the resistor R10 are connected in parallel to form a feedback circuit, and one end of the feedback circuit is connected to the first integrated operational amplifier MAX4233AB The negative input end of C+T, and the other end is connected to the output end of the first integrated operational amplifier MAX4233ABC+T; the resistor R11 and the capacitor C8 form a low-pass RC filter circuit, the output of the first integrated operational amplifier MAX4233ABC+T is divided into two paths, the first output is subjected to optical power sampling to monitor the optical power after passing through the low-pass RC filter circuit, and the other output is output to the frequency selection filtering and amplification circuit; the control end of the first integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R15; the positive power supply end and the negative power supply end of the first integrated operational amplifier MAX4233ABC+T are respectively connected to the power supplies VCC_2V5 and VCC_-2V5; the positive power supply end of the first integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C13, and the negative power supply end is connected to the ground GND_POWER through the capacitor C13.

[0012] Furthermore, let the voltage of the common point signal MPD_IN between the light emitting diode PD1 and the resistor R3 be U MPD_IN , the voltage of the negative input signal U1A_IN1- of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1- , the voltage of the positive input signal U1A_IN1+ of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1+ ; The voltage of the second output signal U1A_OUT is U U1A_OUT ;;The voltage of the signal PD1_MON output through the low-pass RC filter circuit is U PD1_MON, the current on the optical module MPD is i, which satisfies:

[0013]

[0014] Eliminate the intermediate quantity and get U U1A_OUT The relationship between and i is:

[0015]

[0016] Where R9 = R14, R10 = R16, we get:

[0017]

[0018] Furthermore, the frequency selective filtering and amplifying circuit includes a first frequency selective filtering and amplifying circuit and a second frequency selective filtering and amplifying circuit, the first frequency selective filtering and amplifying circuit is used to perform frequency selective filtering and amplifying on the fundamental branch to select the fundamental component in the dither signal, and the second frequency selective filtering and amplifying circuit is used to perform frequency selective filtering and amplifying on the second harmonic branch to select the second harmonic component in the dither signal.

[0019] Further, the first frequency selection filtering and amplification circuit includes a second integrated operational amplifier MAX4233ABC+T, a resistor R4, a resistor R6, a resistor R7, a resistor R12, a capacitor C2 and a capacitor C6; the fundamental wave branch is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T through R6 and capacitor C6 in sequence; the positive input terminal of the second integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R7; one end of the resistor R12 is grounded, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the capacitor C2 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the resistor R4 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T; the output terminal of the second integrated operational amplifier MAX4233ABC+T is connected to the back-end amplification and biasing circuit;

[0020] The second frequency-selective filtering and amplifying circuit comprises a third integrated operational amplifier MAX4233ABC+T, a resistor R19, a resistor R21, a resistor R23, a resistor R24, a capacitor C12 and a capacitor C15; the second harmonic branch is connected to the negative input terminal of the third integrated operational amplifier MAX4233ABC+T through R21 and capacitor C15 in sequence; the positive input terminal of the third integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R24; the resistor One end of R23 is grounded, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the capacitor C12 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the resistor 19 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input end of the third integrated operational amplifier MAX4233ABC+T; the output end of the third integrated operational amplifier MAX4233ABC+T is connected to the back-end amplification and biasing circuit.

[0021] Furthermore, in step 4, the fundamental wave branch is connected to the corresponding frequency selective filtering and amplifying circuit via the first DC blocking AC capacitor C5, and the second harmonic branch is connected to the corresponding frequency selective filtering and amplifying circuit via the second DC blocking AC capacitor C14.

[0022] Furthermore, the back-end amplification and biasing circuit includes a first back-end amplification and biasing circuit and a second back-end amplification and biasing circuit, the first back-end amplification and biasing circuit is used to amplify and bias the fundamental branch after frequency selection filtering and amplification, and the second back-end amplification and biasing circuit is used to amplify and bias the second harmonic branch after frequency selection filtering and amplification.

[0023] Further, the first back-end amplification and biasing circuit includes a fourth integrated operational amplifier MAX4233ABC+T, a resistor R1, a resistor R2, a resistor R5, a resistor R8, a resistor R13, a capacitor C1, a capacitor C3, a capacitor C7 and a capacitor C10; the positive input terminal of the fourth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input terminal is grounded GND_POWER through the resistor R1; the resistor R2 and the capacitor C1 are connected in parallel to form a feedback circuit, one end of the corresponding feedback circuit is connected to the negative input terminal of the fourth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output terminal of the fourth integrated operational amplifier MAX4233ABC+T; the resistor R5 and the resistor R13 are connected in series to form a bias circuit, corresponding One end of the bias circuit is connected to the power supply VCC_2V5, and the other end is connected to the ground GND_POWER; the common end of the resistor R5 and the resistor R13 is connected to the output end of the fourth integrated operational amplifier MAX4233ABC+T through C17; the control end of the fourth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R8; the positive power supply end and the negative power supply end of the fourth integrated operational amplifier MAX4233ABC+T are respectively connected to the power supplies VCC_2V5 and VCC_-2V5; the positive power supply end of the fourth integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C3, and the negative power supply end is connected to the ground GND_POWER through the capacitor C10;

[0024] The second back-end amplification and biasing circuit includes a fifth integrated operational amplifier MAX4233ABC+T, a resistor R17, a resistor R18, a resistor R20, a resistor R22, a resistor R25, a capacitor C11 and a capacitor C16; the positive input end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input end is grounded to GND_POWER through the resistor R17; the resistor R18 and the capacitor C11 are connected in parallel to form a feedback circuit, and one end of the corresponding feedback circuit is connected to the fifth integrated operational amplifier MAX4233ABC+T The negative input terminal of the resistor R20 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T; the resistor R20 and the resistor R25 are connected in series to form a bias circuit, one end of the corresponding bias circuit is connected to the power supply VCC_2V5, and the other end is grounded GND_POWER; the common end of the resistor R20 and the resistor R25 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T through C16; the control end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R22.

[0025] The present invention has the following beneficial effects:

[0026] The present invention couples a low-frequency dither signal at the heater (heating of a TFLN modulator) input end, and the fundamental wave / second harmonic of the signal will appear in the photogenerated current of the output MPD. The photogenerated current is then amplified and debiased, and then passes through a capacitor to isolate the DC current and a dither fundamental wave / second harmonic frequency-selective filter amplifier circuit, and finally through operational amplification and adding a DC bias, thereby achieving effective sampling of the dither's fundamental wave and second harmonic. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart of a dither signal filtering and sampling method based on a TFLN laser provided in an embodiment of the present invention;

[0028] Figure 2 A circuit schematic diagram of a dither signal filtering and sampling circuit based on a TFLN laser provided in an embodiment of the present invention;

[0029] Figure 3 The fundamental wave 1KHz frequency selective amplifier gain-frequency curve (including normalization) provided in the embodiment of the present invention;

[0030] Figure 4 The second harmonic 2KHz frequency selective amplifier gain-frequency curve (including normalization) provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Unless otherwise defined, the technical or scientific terms used in the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "an" or "the" do not indicate a quantity limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described target changes, the relative positional relationship may also change accordingly; R in the formula of the present invention i Expressed as resistance Ri, C i Expressed as capacitance Ci.

[0033] In each of the accompanying drawings, identical elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not all drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0034] Many specific details of the present disclosure are described below to provide a clearer understanding of the present disclosure. However, as those skilled in the art will appreciate, the present disclosure may be implemented without following these specific details.

[0035] Figure 1 A flowchart of a dither signal filtering and sampling method based on a TFLN laser provided in an embodiment of the present invention is shown in FIG. Figure 1 As shown, an embodiment of the present invention provides a dither signal filtering and sampling method based on a TFLN laser, comprising:

[0036] Step 1, loading the fundamental wave / second harmonic of the low-frequency dither signal into the photocurrent of the optical module;

[0037] Step 2, amplifying the fundamental wave / second harmonic photocurrent signal loaded with the dither signal through an operational amplifier circuit and then dividing it into two output paths;

[0038] Step 3, performing optical power sampling on the first output of the two outputs after passing through a low-pass RC filter circuit to monitor the output optical power, and further dividing the second output of the two outputs into a fundamental wave branch and a second harmonic branch;

[0039] Step 4: After the fundamental wave branch and the second harmonic branch are respectively passed through the corresponding frequency selection filtering and amplification circuit and the back-end amplification and biasing circuit, a fundamental wave signal and a second harmonic signal are obtained, and output to the ADC sampling module for sampling.

[0040] Specifically, the fundamental wave branch passes through a first frequency selection filter and amplification circuit, selects the fundamental wave signal in the dither signal and amplifies it, and the amplified fundamental wave signal passes through a first back-end amplification and biasing circuit to obtain a 1KHz fundamental wave; the second harmonic branch passes through a second frequency selection filter and amplification circuit, selects the second harmonic signal in the dither signal and amplifies it, and the amplified second harmonic signal passes through a second back-end amplification and biasing circuit to obtain a 1KHz fundamental wave.

[0041] In step 1, a low-frequency dither signal is coupled to the input end of the heater modulator of the optical module, so that the fundamental wave / second harmonic of the dither signal is carried in the photogenerated current of the MPD.

[0042] The present invention starts with the backlight MPD (monitor diode) at the light output end of the module detecting the weak light signal containing dither, amplifies the front-end photocurrent and removes the DC bias, then passes through the capacitor DC isolation and dither fundamental / second harmonic frequency selection filter amplifier circuit, and then undergoes operational amplification and adds DC bias to achieve effective separate sampling of the dither fundamental and second harmonic signals.

[0043] In some embodiments, the operational amplifier circuit is a front-end photoelectric signal amplifier circuit, and the front-end photoelectric signal amplifier circuit includes a first integrated operational amplifier MAX4233ABC+T and its peripheral circuits, referring to Figure 2 shown.

[0044] Specifically, the peripheral circuit includes a resistor R3, a resistor R9, a resistor R10, a resistor R11, a resistor R14, a resistor R15, a resistor R16, a capacitor C4, a capacitor C9, a capacitor C8 and a capacitor C13, a capacitor C13, and a light-emitting diode PD1; the positive input terminal of the first integrated operational amplifier MAX4233ABC+T is grounded through a resistor R16, and is also connected to a power supply VCC_2V5 through a resistor R14; one end of the resistor R3 is connected to the cathode of the light-emitting diode PD1, and the other end is connected to the power supply VCC_2V5, the anode of the light-emitting diode PD1 is connected to the ground GND_POWER, and the common point of the light-emitting diode PD1 and the resistor R3 is connected to the negative input terminal of the first integrated operational amplifier MAX4233ABC+T through a resistor R9; the capacitor C4 and the resistor R10 are connected in parallel to form a feedback circuit, and one end of the feedback circuit is connected to the first integrated operational amplifier MAX4233AB The negative input end of C+T, and the other end is connected to the output end of the first integrated operational amplifier MAX4233ABC+T; the resistor R11 and the capacitor C8 form a low-pass RC filter circuit, and the output of the first integrated operational amplifier MAX4233ABC+T is divided into two paths, the first output is sampled after passing through the low-pass RC filter circuit to monitor the optical power, and the other output is output to the frequency selection filter and amplification circuit; the control end of the first integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R15; the positive power supply end and the negative power supply end of the first integrated operational amplifier MAX4233ABC+T are connected to the power supply VCC_2V5 and VCC_-2V5 respectively; the positive power supply end of the first integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C13, and the negative power supply end is connected to the ground GND_POWER through the capacitor C13.

[0045] In some embodiments, the voltage of the common point signal MPD_IN between the light emitting diode PD1 and the resistor R3 is U MPD_IN , the voltage of the negative input signal U1A_IN1- of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1- , the voltage of the positive input signal U1A_IN1+ of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1+ ; The voltage of the second output signal U1A_OUT is U U1A_OUT ;;The voltage of the signal PD1_MON output through the low-pass RC filter circuit is U PD1_MON , the current on the optical module MPD is i, which satisfies:

[0046]

[0047] Among them, Uref is the reference voltage of the integrated operational amplifier. After eliminating the intermediate quantity, we get U U1A_OUT The relationship between and i is:

[0048]

[0049] Where R9 = R14, R10 = R16, we get:

[0050]

[0051] In this embodiment, U ref =2.5V, R3=120Ω, R9=R14=24.9KΩ, R10=R16=100KΩ, U U1A_OUT The first item in the square bracket can be ignored due to the resistance relationship, that is:

[0052]

[0053] so:

[0054]

[0055] From the results, we can see that the output voltage of the front-end photoelectric signal amplifier circuit is proportional to the MPD photocurrent. When the photocurrent is 1mA, U U1A_OUT The voltage output is about 0.48V. If the photocurrent generated by the dither disturbance is about 50uA, the dither AC voltage amplitude generated is about 24mV.

[0056] After the front-end photoelectric signal is amplified, it is divided into two paths. One path is sampled by a low-pass RC filter circuit, where the low-pass filter cutoff frequency is:

[0057]

[0058] The other path is further divided into two branches, and is named as the fundamental branch and the second harmonic branch. The fundamental branch and the second harmonic branch are respectively input to the frequency selection filtering and amplifying circuit through the DC blocking capacitor to obtain two branches of 1KHz and 2KHz. Specifically, the first frequency selection filtering and amplifying circuit is used to perform frequency selection filtering and amplification on the fundamental branch to select the fundamental signal in the dither signal, that is, the 1KHz signal, and the second frequency selection filtering and amplifying circuit is used to perform frequency selection filtering and amplification on the second harmonic branch to select the second harmonic signal in the dither signal, that is, the 2KHz signal.

[0059] Wherein, the first frequency selection filtering and amplification circuit comprises a second integrated operational amplifier MAX4233ABC+T, a resistor R4, a resistor R6, a resistor R7, a resistor R12, a capacitor C2 and a capacitor C6; the fundamental wave branch is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T through R6 and capacitor C6 in sequence; the positive input terminal of the second integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R7; one end of the resistor R12 is grounded, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the capacitor C2 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the resistor R4 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T; the output terminal of the second integrated operational amplifier MAX4233ABC+T is connected to the back-end amplification and biasing circuit;

[0060] The second frequency-selective filtering and amplifying circuit comprises a third integrated operational amplifier MAX4233ABC+T, a resistor R19, a resistor R21, a resistor R23, a resistor R24, a capacitor C12 and a capacitor C15; the second harmonic branch is connected to the negative input terminal of the third integrated operational amplifier MAX4233ABC+T through R21 and capacitor C15 in sequence; the positive input terminal of the third integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R24; the resistor One end of R23 is grounded, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the capacitor C12 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the resistor 19 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input end of the third integrated operational amplifier MAX4233ABC+T; the output end of the third integrated operational amplifier MAX4233ABC+T is connected to the back-end amplification and biasing circuit.

[0061] refer to Figure 2 As shown, the 1KHz frequency selection filter and amplifier circuit (i.e., the first frequency selection filter and amplifier circuit) is the upper part, and the input signal is U in1 , the output signal is U out1 , the common point voltage of C6 / R6 / C2 / R12 is U x , the negative input voltage of op amp U1B is U U1B_IN2- , the voltage at the positive input terminal of the op amp U1B is U U1B_IN2+, using the vector method to express the voltage, the KCL and KVL laws give:

[0062]

[0063] Eliminate U x , the transfer function of output to input is:

[0064]

[0065] The transfer function is written in standard bandpass filter form:

[0066]

[0067] The standard form of a bandpass filter is as follows;

[0068]

[0069] The transfer function is compared with the standard form:

[0070]

[0071] This design of bandpass filter and amplifier requires narrow bandwidth, and the bandwidth is designed to be 12.5Hz, and the resonant gain is designed to be |H 0BP |=20, because Q=W0 / BW, W0=2πf 0， f0 = 1KHz, so Q = 80. If C2 and C6 are designed to be 10nF, we can theoretically calculate: R4 = 2547.7KΩ, R6 = 63.694KΩ, R12 = 0.099KΩ, and use the actual 1% precision resistors: R4 = 2.55MΩ, R6 = 63.4KΩ, R12 = 100Ω.

[0072] Similarly, for the second harmonic bandpass filter design, the bandwidth is also set to 12.5 Hz, and the resonant gain is designed to |H 0BP |=20, because Q=W0 / BW, W0=2πf 0， f0=2KHz, so Q=160. If C12 and C15 are designed to be 10nF, we can theoretically calculate: R19=2547.7KΩ, R21=63.694KΩ, R23=0.02489KΩ. Using actual 1% precision resistors: R19=2.55MΩ, R21=63.4KΩ, R23=24.9Ω.

[0073] In some embodiments, the rear-end amplification and biasing circuit includes a first rear-end amplification and biasing circuit and a second rear-end amplification and biasing circuit, the first rear-end amplification and biasing circuit is used to amplify and bias the fundamental wave branch after frequency selection filtering and amplification, and the second rear-end amplification and biasing circuit is used to amplify and bias the second harmonic branch after frequency selection filtering and amplification;

[0074] Among them, the first back-end amplification and biasing circuit includes a fourth integrated operational amplifier MAX4233ABC+T, a resistor R1, a resistor R2, a resistor R5, a resistor R8, a resistor R13, a capacitor C1, a capacitor C3, a capacitor C7 and a capacitor C10; the positive input end of the fourth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input end is grounded GND_POWER through the resistor R1; the resistor R2 and the capacitor C1 are connected in parallel to form a feedback circuit, one end of the corresponding feedback circuit is connected to the negative input end of the fourth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output end of the fourth integrated operational amplifier MAX4233ABC+T; the resistor R5 and the resistor R13 are connected in series to form a bias circuit, and the corresponding bias One end of the circuit is connected to the power supply VCC_2V5, and the other end is connected to the ground GND_POWER; the common end of the resistor R5 and the resistor R13 is connected to the output end of the fourth integrated operational amplifier MAX4233ABC+T through C17; the control end of the fourth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R8; the positive power supply end and the negative power supply end of the fourth integrated operational amplifier MAX4233ABC+T are respectively connected to the power supplies VCC_2V5 and VCC_-2V5; the positive power supply end of the fourth integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C3, and the negative power supply end is connected to the ground GND_POWER through the capacitor C10;

[0075] The second back-end amplification and biasing circuit includes a fifth integrated operational amplifier MAX4233ABC+T, a resistor R17, a resistor R18, a resistor R20, a resistor R22, a resistor R25, a capacitor C11 and a capacitor C16; the positive input end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input end is grounded to GND_POWER through the resistor R17; the resistor R18 and the capacitor C11 are connected in parallel to form a feedback circuit, and one end of the corresponding feedback circuit is connected to the fifth integrated operational amplifier MAX4233ABC+T The negative input terminal of the resistor R20 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T; the resistor R20 and the resistor R25 are connected in series to form a bias circuit, one end of the corresponding bias circuit is connected to the power supply VCC_2V5, and the other end is grounded GND_POWER; the common end of the resistor R20 and the resistor R25 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T through C16; the control end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R22.

[0076] Considering the frequency selection filtering and amplification of 20 times (26dB), the input fundamental wave and second harmonic amplitude of the back-end circuit are about 0.5V, so it needs to be amplified again to facilitate ADC sampling. It is reasonable to set it to 2 times. A 5pF capacitor is connected in parallel to the feedback resistor to solve the stability problem of the operational amplifier. Then, it is coupled to the 1.25V bias through the capacitor 2.2uF, and the back-end amplification and biasing are realized. Since this part of the circuit is relatively simple to implement, it will not be described in detail here.

[0077] refer to Figure 3 and Figure 4 As shown, a fundamental wave 1KHz frequency selective amplifier gain-frequency curve (including normalization) and a second harmonic 2KHz frequency selective amplifier gain-frequency curve (including normalization) provided in an embodiment of the present invention.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dither signal filtering and sampling method based on TFLN laser, characterized in that: The method comprises: Step 1, loading the fundamental wave / second harmonic of the low-frequency dither signal into the photocurrent of the optical module; Step 2, amplifying the fundamental wave / second harmonic photocurrent signal loaded with the dither signal through an operational amplifier circuit and then dividing it into two output paths; Step 3, performing optical power sampling on the first output of the two outputs after passing through a low-pass RC filter circuit to monitor the output optical power, and further dividing the second output of the two outputs into a fundamental wave branch and a second harmonic branch; Step 4: After the fundamental wave branch and the second harmonic branch are respectively passed through the corresponding frequency selection filtering and amplification circuit and the back-end amplification and biasing circuit, a fundamental wave signal and a second harmonic signal are obtained, and output to the ADC sampling module for sampling.

2. The dither signal filtering and sampling method based on TFLN laser according to claim 1, characterized in that: In step 1, a low-frequency dither signal is coupled to the input end of the heater modulator of the optical module, so that the fundamental wave / second harmonic of the dither signal is carried in the photogenerated current of the MPD.

3. The dither signal filtering and sampling method based on TFLN laser according to claim 1, characterized in that: In step 2, the operational amplifier circuit is a front-end photoelectric signal amplifier circuit, and the front-end photoelectric signal amplifier circuit includes a first integrated operational amplifier MAX4233ABC+T and its peripheral circuits.

4. The dither signal filtering and sampling method based on TFLN laser according to claim 3 is characterized in that: The peripheral circuit includes a resistor R3, a resistor R9, a resistor R10, a resistor R11, a resistor R14, a resistor R15, a resistor R16, a capacitor C4, a capacitor C9, a capacitor C8 and a capacitor C13, a capacitor C13, and a light emitting diode PD1; the positive input terminal of the first integrated operational amplifier MAX4233ABC+T is grounded through a resistor R16, and is also connected to a power supply VCC_2V5 through a resistor R14; one end of the resistor R3 is connected to the cathode of the light emitting diode PD1, and the other end is connected to the power supply VCC_2V5, the anode of the light emitting diode PD1 is connected to the ground GND_POWER, and the common point of the light emitting diode PD1 and the resistor R3 is connected to the negative input terminal of the first integrated operational amplifier MAX4233ABC+T through a resistor R9; the capacitor C4 and the resistor R10 are connected in parallel to form a feedback circuit, and one end of the feedback circuit is connected to the first integrated operational amplifier MAX4233ABC+ T, and the other end is connected to the output end of the first integrated operational amplifier MAX4233ABC+T; the resistor R11 and the capacitor C8 form a low-pass RC filter circuit, and the output of the first integrated operational amplifier MAX4233ABC+T is divided into two paths, the first output is subjected to optical power sampling to monitor the optical power after passing through the low-pass RC filter circuit, and the other output is output to the frequency selection filtering and amplification circuit; the control end of the first integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R15; the positive power supply end and the negative power supply end of the first integrated operational amplifier MAX4233ABC+T are respectively connected to the power supplies VCC_2V5 and VCC_-2V5; the positive power supply end of the first integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C13, and the negative power supply end is connected to the ground GND_POWER through the capacitor C13.

5. The dither signal filtering and sampling method based on TFLN laser according to claim 4, characterized in that: Let the voltage of the common point signal MPD_IN of the light emitting diode PD1 and the resistor R3 be U MPD_IN , the voltage of the negative input signal U1A_IN1- of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1- , the voltage of the positive input signal U1A_IN1+ of the first integrated operational amplifier MAX4233ABC+T is U U1A_IN1+ ; The voltage of the second output signal U1A_OUT is U U1A_OUT ;;The voltage of the signal PD1_MON output through the low-pass RC filter circuit is U PD1_MON , the current on the optical module MPD is i, which satisfies: Among them, U ref is the reference voltage of the integrated operational amplifier. After eliminating the intermediate quantity, we get U U1A_OUT The relationship between and i is: Where R9 = R14, R10 = R16, we get:

6. The dither signal filtering and sampling method based on TFLN laser according to claim 1, characterized in that: The frequency selective filtering and amplifying circuit includes a first frequency selective filtering and amplifying circuit and a second frequency selective filtering and amplifying circuit. The first frequency selective filtering and amplifying circuit is used to perform frequency selective filtering and amplifying on the fundamental branch to select the fundamental signal in the dither signal. The second frequency selective filtering and amplifying circuit is used to perform frequency selective filtering and amplifying on the second harmonic branch to select the second harmonic signal in the dither signal.

7. The dither signal filtering and sampling method based on TFLN laser according to claim 6, characterized in that: The first frequency selection filtering and amplification circuit comprises a second integrated operational amplifier MAX4233ABC+T, a resistor R4, a resistor R6, a resistor R7, a resistor R12, a capacitor C2 and a capacitor C6; the fundamental wave branch is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T through R6 and capacitor C6 in sequence; the positive input terminal of the second integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R7; one end of the resistor R12 is grounded, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the capacitor C2 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R6 and the capacitor C6; one end of the resistor R4 is connected to the output terminal of the second integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input terminal of the second integrated operational amplifier MAX4233ABC+T; the output terminal of the second integrated operational amplifier MAX4233ABC+T is connected to the rear-end amplification and biasing circuit; The second frequency-selective filtering and amplifying circuit comprises a third integrated operational amplifier MAX4233ABC+T, a resistor R19, a resistor R21, a resistor R23, a resistor R24, a capacitor C12 and a capacitor C15; the second harmonic branch is connected to the negative input terminal of the third integrated operational amplifier MAX4233ABC+T through R21 and capacitor C15 in sequence; the positive input terminal of the third integrated operational amplifier MAX4233ABC+T is grounded GND_POWER, and the control terminal is connected to the power supply VCC_2V5 through the resistor R24; the resistor One end of R23 is grounded, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the capacitor C12 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the common end of the resistor R21 and the capacitor C15; one end of the resistor 19 is connected to the output end of the third integrated operational amplifier MAX4233ABC+T, and the other end is connected to the negative input end of the third integrated operational amplifier MAX4233ABC+T; the output end of the third integrated operational amplifier MAX4233ABC+T is connected to the back-end amplification and biasing circuit.

8. The dither signal filtering and sampling method based on TFLN laser according to claim 1, characterized in that: In step 4, the fundamental wave branch is connected to the corresponding frequency selective filtering and amplifying circuit through the first DC blocking AC capacitor C5, and the second harmonic branch is connected to the corresponding frequency selective filtering and amplifying circuit through the second DC blocking AC capacitor C14.

9. The dither signal filtering and sampling method based on TFLN laser according to claim 1, characterized in that: The back-end amplification and biasing circuit includes a first back-end amplification and biasing circuit and a second back-end amplification and biasing circuit. The first back-end amplification and biasing circuit is used to amplify and bias the fundamental branch after frequency selection filtering and amplification, and the second back-end amplification and biasing circuit is used to amplify and bias the second harmonic branch after frequency selection filtering and amplification.

10. The dither signal filtering and sampling method based on TFLN laser according to claim 9, characterized in that: The first back-end amplification and biasing circuit includes a fourth integrated operational amplifier MAX4233ABC+T, a resistor R1, a resistor R2, a resistor R5, a resistor R8, a resistor R13, a capacitor C1, a capacitor C3, a capacitor C7 and a capacitor C10; the positive input terminal of the fourth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input terminal is grounded GND_POWER through the resistor R1; the resistor R2 and the capacitor C1 are connected in parallel to form a feedback circuit, one end of the corresponding feedback circuit is connected to the negative input terminal of the fourth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output terminal of the fourth integrated operational amplifier MAX4233ABC+T; the resistor R5 and the resistor R13 are connected in series to form a bias circuit, and the corresponding bias One end of the circuit is connected to the power supply VCC_2V5, and the other end is connected to the ground GND_POWER; the common end of the resistor R5 and the resistor R13 is connected to the output end of the fourth integrated operational amplifier MAX4233ABC+T through C17; the control end of the fourth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R8; the positive power supply end and the negative power supply end of the fourth integrated operational amplifier MAX4233ABC+T are respectively connected to the power supplies VCC_2V5 and VCC_-2V5; the positive power supply end of the fourth integrated operational amplifier MAX4233ABC+T is also connected to the ground GND_POWER through the capacitor C3, and the negative power supply end is connected to the ground GND_POWER through the capacitor C10; The second back-end amplification and biasing circuit includes a fifth integrated operational amplifier MAX4233ABC+T, a resistor R17, a resistor R18, a resistor R20, a resistor R22, a resistor R25, a capacitor C11 and a capacitor C16; the positive input end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the fundamental branch, and the negative input end is grounded to GND_POWER through the resistor R17; the resistor R18 and the capacitor C11 are connected in parallel to form a feedback circuit, and one end of the corresponding feedback circuit is connected to the fifth integrated operational amplifier MAX4233ABC+T The negative input terminal of the resistor R20 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T, and the other end is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T; the resistor R20 and the resistor R25 are connected in series to form a bias circuit, one end of the corresponding bias circuit is connected to the power supply VCC_2V5, and the other end is grounded GND_POWER; the common end of the resistor R20 and the resistor R25 is connected to the output terminal of the fifth integrated operational amplifier MAX4233ABC+T through C16; the control end of the fifth integrated operational amplifier MAX4233ABC+T is connected to the power supply VCC_2V5 through the resistor R22.

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