A Calibration Method for the Control Voltage of an Optical Switch in an Optical Switching Delay Line

Abstract

The present invention discloses a method for calibrating the control voltage of an optical switch in an optical switch switching delay line. The control voltages of (n + 1) optical switches (S1 to S n+1 ) are calibrated by a voltage source array, a wavelength tunable laser, a spectrum analyzer, and a delay test system. When a broadband light source is input from the In port on the left side of the optical switch switching delay line, the voltage source array outputs a scanning step voltage to control the splitting ratio of the optical switches (S1 to S n+1 ). The interference degree of the interference spectrum output from the Out1 port on the right side of the optical switch switching delay line will change accordingly. According to the change of the interference degree of the interference spectrum, the control voltage of the optical switch in the delay line can be calibrated. The present invention utilizes the interference spectrum characteristics output by the optical switch switching delay line to calibrate the control voltage of each stage of the optical switch in the optical switch switching delay line without introducing an additional special structure.

Description

Technical Field

[0001] The present invention belongs to the technical fields of optical communication and microwave photonics, and particularly relates to a method for calibrating the control voltage of an optical switch in an optical switch switching delay line. Background Art

[0002] The optical switch switching delay line is one of the key modules in microwave photon signal processing and is currently mainly used for multi-channel true delay in microwave photon beamforming systems. In phased array radar systems and radio-over-fiber communication systems, the configuration of traditional electrical domain phase shifters is related to the microwave signal frequency, which results in a very narrow instantaneous bandwidth. To achieve a large instantaneous bandwidth, optical true delay technology should be used to replace electrical domain phase shifters, modulate microwave signals onto the optical domain, and use optical waveguides as the delay transmission path. The delay line designed based on optical true delay technology has the advantages of large instantaneous bandwidth and anti-electromagnetic radiation interference. After on-chip integration, the device volume and weight can be further reduced. The optical switch switching delay line, especially the on-chip integrated optical switch switching delay line, is an important research field in optical communication and microwave photonics.

[0003] For a typical on-chip integrated 2×2 optical switch switching delay line, due to the inevitable manufacturing errors of the delay line, the through / cross state voltages of each optical switch in the delay line need to be calibrated separately. The 2×2 optical switches in the delay line are cascaded through optical waveguides of different lengths, so the "through" and "cross" voltages of each optical switch cannot be directly measured. The currently commonly used calibration method is to add an optical coupler after each optical switch to extract part of the light as the optical switch output optical power monitoring port or insert a variable optical attenuator between cascaded optical switches to block the optical signal transmission of the specified path. However, the existing solutions bring difficulties to chip design, increase the chip insertion loss and production cost. There is an urgent need for a simple and lossless optical switch state calibration scheme. Summary of the Invention

[0004] Object of the Invention: Aiming at the above problems or improvement requirements of the existing calibration methods, the present invention provides a scheme for calibrating the control voltage of an optical switch in an optical switch switching delay line by using the output interference spectrum characteristics of the optical switch switching delay line, processing the spectral data, and without introducing additional special structures, realizing the switching of different delay transmission paths of the optical switch switching optical delay line.

[0005] Technical Solution: The method for calibrating the control voltage of an optical switch in an optical switch switching delay line according to the present invention includes the following steps:

[0006] (1) Arrange a voltage source array, a wavelength tunable laser, and a spectrum analyzer on the optical switch switching delay line to form an optical switch drive voltage-spectrum monitoring system;

[0007] (2) Change the driving voltage of the optical switch through the voltage source array, synchronously calculate the standard deviation of the interference spectrum output by the delay line, and calculate the through or cross state voltages of each level of optical switch according to the change data of the spectral standard deviation.

[0008] (3) Connect the output port Out1 of the optical switch switching delay line to the delay test system.

[0009] (4) Distinguish the through or cross state voltages of each level of optical switch according to the delay test results of the optical switch switching delay line.

[0010] Further, in step (1), the connection mode of the optical switch driving voltage - spectrum monitoring system is as follows: The wavelength - tunable laser is connected to the In input port of the optical switch switching delay line, and the control ports C1 - C n+1 of the voltage source array are connected to the optical switches S1 - S n+1 in the optical switch switching delay line one - to - one. The output port Out1 of the optical switch switching delay line is connected to the spectrum analyzer, where n≥1.

[0011] Further, in step (2), the method for calculating the through or cross state voltages of each level of optical switch according to the change data of the spectral standard deviation is as follows:

[0012] (2.1) Output a scanning step voltage from the control port C1 of the voltage source array to the optical phase shifter in the optical switch S1. The spectrum analyzer tests the interference spectrum output by the Out1 port of the delay line at different voltages; calculate the standard deviation of each spectrum; test the resistance value of the optical phase shifter in the optical switch S1, and calculate the power applied to the optical phase shifter in the optical switch S1 when different voltages are output from the control port C1 according to the formula P = V 2 / R. The power corresponds to the voltage one - to - one, where P: power; V: voltage; R: resistance. Draw a power - spectral standard deviation curve; this power - spectral standard deviation curve changes periodically, and the voltage corresponding to the minimum value point on the curve is the calibration value for making the optical switch S1 in the through or cross state, and the states of the optical switch S1 calibrated by the voltages corresponding to any two adjacent minimum value points are different.

[0013] (2.2) Output the calibrated voltage to the optical switch S1 through the control port C1 to make it in the through or cross state; in the same way as the calibration process of the optical switch S1, output the scanning step voltage to the optical phase shifter in the optical switch S2 through the control port C2 of the voltage source array, and calculate the through or cross state voltage of the optical switch S2 according to the change data of the spectral standard deviation; output the calibrated voltage to the optical switches S1 - S2 through the control ports C1 - C2 to make them in the through or cross state. In the same way as the calibration process of the optical switch S1, output the scanning step voltage to the optical phase shifter in the optical switch S3 through the control port C3 of the voltage source array, and calculate the through or cross state voltage of the optical switch S3 according to the change data of the spectral standard deviation; repeat the above process, output the calibrated voltage to the optical switches S1 - S i Output to the optical switches S1 - S i Output the calibrated voltage to make it in the through or cross state through the control port C of the voltage source array i+1 Output to the optical switch S i+1 Output the scanning step voltage to the optical phase shifter in it, and calculate the through or cross state voltage of the optical switch S i+1 where i is greater than or equal to 3 and less than or equal to n - 1;

[0014] (2.3) Respectively output the calibrated voltage to the optical switches S1 to S n through C1 to C n to make them in the through or cross state, and output the scanning step voltage through the control port C of the voltage source array n+1 to control the optical phase shifter in the optical switch S n+1 The spectral analyzer tests the interference spectrum output from the Out1 port of the optical switch switching delay line when different voltages are output through the control port C n+1 Calculate the standard deviation of each spectrum, calculate the resistance value of the optical phase shifter in the optical switch S n+1 and calculate the power loaded on the optical phase shifter in the optical switch S n+1 when different voltages are output through the control port C n+1 to plot the power - spectral standard deviation curve; this power - standard deviation curve changes periodically, and the voltages corresponding to the maximum and minimum points are the calibrated values for making the optical switch S n+1 in the through or cross state, and the states of the optical switch S n+1 corresponding to the voltages at the maximum and minimum points are different.

[0015] Furthermore, in step (4), the method for distinguishing the through or cross state voltages of each stage of optical switches is as follows:

[0016] (4.1) For each stage of optical switches S1 to S n+1Reserve a pair of calibration voltages that can be in a through or cross state, and n + 1 optical switches S1 to S n+1 Form 2 n+1 different combinations of calibration voltage values, and each combination of voltage values corresponds to a transmission path of the optical signal in the optical switch switching delay line;

[0017] (4.2) Input a preset fixed-wavelength laser into the input port of the optical switch switching delay line In, and load the 2 n+1 different combinations of calibration voltage values to the optical switches S1 to S n+1 respectively. Among them, when the 2 n combinations of calibration voltage values are applied, there is no optical signal output from the Out1 port of the optical switch switching delay line, and the optical signal is output from the Out2 port. Discard these 2 n combinations of calibration voltage values, and the remaining 2 n combinations of calibration voltage values correspond to 2 n different transmission paths of the optical signal in the optical switch switching delay line;

[0018] (4.3) Input a fixed-wavelength laser into the input port of the optical switch switching delay line In, and load any one of the remaining 2 n different combinations of calibration voltage values to the optical switches S1 to S n+1 respectively. Test the delay amount of the optical switch switching delay line. The delay amount of each transmission path is a preset fixed value, and determine the transmission path of the optical signal in the optical switch switching delay line according to the measured delay amount;

[0019] (4.4) The through or cross state of each stage of the optical switch corresponding to the transmission path is fixed. According to the test delay result, distinguish the voltage in the through state and the voltage in the cross state from the pair of calibration voltages reserved for each stage of the optical switches S1 to S n+1 respectively.

[0020] Furthermore, the optical transmission medium of the optical switch switching delay line is not limited to optical fiber or on-chip integrated optical waveguide.

[0021] Furthermore, the wavelength range of the interference spectrum is an integer multiple of the maximum free spectral range of the delay line.

[0022] Furthermore, the optical switch is not limited to the MZI-type 4-port structure.

[0023] Beneficial effects: Compared with the existing calibration technical solutions, the technical solution of the present invention has the following beneficial technical effects:

[0024] The technical solution of the present invention utilizes the interference spectrum characteristics of the output of the optical switch switching delay line, and calibrates the optical switch control voltage in the optical switch switching delay line without introducing a special structure, effectively reducing the difficulty of chip design, tape-out, and packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a test system diagram for the method of calibrating the optical switch control voltage in the optical switch switching delay line provided by the present invention;

[0026] Figure 2 It is a transmission path diagram of the optical signal in the delay line when the total delay of the delay line is 0 ps and 93 ps;

[0027] Figure 3 It is a schematic structural diagram of a 2×2 MZI optical switch;

[0028] Figure 4 It is the interference spectrum of a 5-order optical switch switching delay line;

[0029] Figure 5 It is a relationship diagram between the standard deviation of the spectral data at the Out port and the driving power of the optical switch S1;

[0030] Figure 6 It is a relationship diagram between the standard deviation of the spectral data at the Out port and the driving power of the optical switch S6;

[0031] Figure 7 It is the transmission path of the optical signal in the optical switch switching delay line when the delay of the optical switch switching delay line is 9 ps at this time. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0033] Figure 1This is a test system diagram for calibrating the control voltage of an optical switch in an optical switch switching delay line by utilizing the interference spectrum characteristics of the output of the optical switch switching delay line without introducing a special structure in the present invention. The control voltages of six optical switches (S1 to S6) in a 5th-order optical switch switching delay line are calibrated through a voltage source array, a wavelength-tunable laser, a spectrum analyzer, and a delay test system. When a broadband light source is input from the In port on the left side of the optical switch switching delay line, the splitting ratio of the optical switches (S1 to S6) is controlled by the scanning step voltage output by the voltage source array, and the interference degree of the interference spectrum output from the Out1 port on the right side of the optical switch switching delay line will change accordingly. The control voltage of the optical switch in the delay line can be calibrated according to the change of the interference degree of the interference spectrum. The present invention utilizes the interference spectrum characteristics of the output of the optical switch switching delay line to calibrate the control voltage of each-stage optical switch in the optical switch switching delay line without introducing an additional special structure. The optical switch switching delay line is a binary topological structure. The 5th-order optical switch switching delay line includes six optical switches and a pair of delay waveguides for each stage. Each pair of delay waveguides contains two optical waveguides with different lengths, and the corresponding delay differences of the two optical waveguides are 3 ps, 6 ps, 12 ps, 24 ps, and 48 ps respectively. The two optical waveguides are respectively connected to two ports of the optical switch, and different optical waveguides are selected through the optical switch switching to achieve a total of 32 delay amounts with a total delay difference of 0 ps, 3 ps, 6 ps, 9 ps... 93 ps. When the total delay amount of the delay line is 0 ps and 93 ps, the transmission paths of the optical signals in the delay line are respectively as Figure 2 shown in (a) and (b) in

[0034] Figure 3 shows the structure of an optical switch Mach-Zehnder interferometer (MZI) type optical switch, which consists of two 2×2 optical beam splitters as input and output, and two straight waveguides as the two arms of the MZI structure. An optical phase shifter is provided on one or both arms to control the optical switch to be in the "through" or "cross" state to select different optical transmission paths. Each optical switch has 4 ports, namely the upper left, lower left, upper right, and lower right ports. If the optical signal is defined to be transmitted from left to right, the upper left to lower right and lower left to upper right are the cross states, and the upper left to upper right and lower left to lower right are the through states; if the optical signal is defined to be transmitted from right to left, the upper right to lower left and lower right to upper left are the cross states, and the upper right to upper left and lower right to lower left are the through states.

[0035] Figure 4 shows the interference spectrum of a 5th-order optical switch switching delay line containing six optical switches. The FSR follows formula (1):

[0036]

[0037] Where, Ng is the group refractive index of the optical waveguide, ΔL is the length difference of the delay line, λ is the wavelength, and the maximum FSR of the fifth-order optical switch switching delay line obtained by theoretical calculation and experiment is both 2.6 nm.

[0038] The present invention proposes a calibration method for the optical switch control voltage in an optical switch switching delay line, and the method includes the following steps:

[0039] (1) Arrange a voltage source array, a wavelength tunable laser, and a spectrum analyzer on the optical switch switching delay line to form an optical switch drive voltage-spectrum monitoring system;

[0040] (2) Change the drive voltage of the optical switch through the voltage source array, synchronously calculate the standard deviation of the interference spectrum output by the delay line, and calculate the through or cross state voltage of each stage of the optical switch according to the change data of the spectrum standard deviation;

[0041] (3) Connect the output port Out1 of the optical switch switching delay line to the delay test system;

[0042] (4) Distinguish the through or cross state voltage of each stage of the optical switch according to the delay test result of the optical switch switching delay line.

[0043] Among them, the connection method of the optical switch drive voltage (power)-spectrum monitoring system described in step (1) is as follows:

[0044] The wavelength tunable laser is input to the In input port of the optical switch switching delay line, the control ports (C1 to C6) of the voltage source array are connected to the optical switches (S1 to S6) in the optical switch switching delay line in one-to-one correspondence, and the right output port Out1 of the optical switch switching delay line is connected to the spectrum analyzer;

[0045] First, calibrate the optical switch S1. Connect the Out1 port on the right side of the delay line to the spectrum analyzer, apply a scanning drive voltage of 0 V to 10 V to the optical phase shifter in the optical switch S1 through the control port C1 of the voltage source array, with a voltage step of 0.01 V. For each loaded voltage value, the spectrum analyzer tests the interference spectrum with a wavelength range of 1568.7 nm to 1571.3 nm output from the Out1 port on the right side of the optical switch switching delay line; calculate the standard deviation of each spectrum; test the resistance value of the optical phase shifter in the optical switch S1 to be 1200 Ω, and according to the formula P = V 2 / R, calculate the power loaded on the optical phase shifter in the optical switch S1 when different voltages are output from the control port C1; as Figure 5As shown, a "power - spectral standard deviation" curve is plotted; this "power - spectral standard deviation" curve varies periodically, and the voltage (power) corresponding to the minimum value point is the calibration value that makes the optical switch S1 in the "through" or "cross" state, and the states of the optical switch S1 calibrated by the voltages (powers) corresponding to any two adjacent minimum value points are different. In the scanning drive voltage range of 0V to 10V, 2.19V, 5.25V, 7.34V, and 9.03V are the calibration values that make the optical switch S1 in the "through" or "cross" state. If 2.19V and 7.34V make the optical switch S1 in the "through" state, then 5.25V and 9.03V make the optical switch S1 in the "cross" state; conversely, if 2.19V and 7.34V make the optical switch S1 in the "cross" state, then 5.25V and 9.03V make the optical switch S1 in the "through" state. To reduce the overall power consumption of the device, the voltage values 2.19V and 5.25V are retained as the initial calibration values for the "through" or "cross" state of the optical switch S1. However, which of the voltage values 2.19V and 5.25V can make the optical switch S1 in the "through" state and which can make the optical switch S1 in the "cross" state cannot be determined temporarily. After obtaining the initial calibration values of all optical switches, they can be distinguished through delay tests.

[0046] Next, the optical switch S2 is calibrated. Through the control port C1, the voltage value (2.19V or 5.25V, and the actually loaded voltage is 2.19V) calibrated in the previous step to make the optical switch S1 in the "through" or "cross" state is output to the optical switch S1, so that the optical switch S2 is in a fixed "through" or "cross" state. Similar to the calibration method of the optical switch S1, the voltage value that makes the optical switch S2 in the "through" or "cross" state is calibrated. The pair of initial calibration values retained for the optical switch S2 to be in the "through" or "cross" state are 1.88V and 4.86V.

[0047] Using the same method, the voltage values that make the optical switches S3 - S5 in the "through" or "cross" state are calibrated by the above - mentioned method.

[0048] The calibration method of the optical switch S6 is slightly different from that of the optical switches S1 - S5. First, through the control ports C1 to C5, the voltage values calibrated in the previous step to make the optical switches S1 to S5 in the "through" or "cross" state are output to the optical switches S1 to S5; through the control port C6 of the voltage source array, a scanning step voltage is output to control the optical phase shifter in the optical switch S6, and the spectral analyzer tests the interference spectrum output from the Out1 port on the right side of the switching delay line when different voltages are output from the control port C6, and calculates the standard deviation of each spectrum; the resistance value of the optical phase shifter in the optical switch S6 is measured to be approximately 1150Ω. According to the formula P = V 2 / R, calculate the power loaded onto the optical phase shifter in the optical switching point S6 when different voltages are output from the control port C6; as Figure 6 shown, plot the "power - spectral standard deviation" curve; this "power - standard deviation" curve changes periodically, and the voltages (powers) corresponding to the maximum and minimum points are the calibration values that make the optical switch S6 in the "through" or "cross" state, and the states of the optical switch S6 calibrated by the voltages (powers) corresponding to the maximum and minimum points are different. In the scanning drive voltage range of 0V to 10V, 2.39V, 5.36V, 7.58V, and 8.97V are the calibration values that make the optical switch S6 in the "through" or "cross" state. If 2.39V and 7.58V make the optical switch S6 in the "through" state, then 5.36V and 8.97V make the optical switch S6 in the "cross" state; conversely, if 2.39V and 7.58V make the optical switch S6 in the "cross" state, then 5.36V and 8.97V make the optical switch S6 in the "through" state. Retain 2.39V and 5.36V as the initial calibration values for making the optical switch S6 in the "through" or "cross" state. Retain a pair of initial calibration voltages for each stage of optical switch (S1 - S6) to make it in the "through" or "cross" state as shown in Table 1.

[0049]

[0050] Table 1 Retain a pair of initial calibration voltages for each stage of optical switch (S1 - S6) to make it in the "through" or "cross" state.

[0051] The 6 optical switches (S1 - S6) in Table 1 can form 2 6 kinds of different combinations of calibration voltage values, and each combination of voltage values corresponds to a delay transmission path of the optical switch switching delay line. Input a 1 - path fixed - wavelength laser into the left - hand In port of the optical switch switching delay line, and load the 2 6 kinds of different combinations of calibration voltage values onto the optical switches (S1 - S6) respectively. Among them, in the case of 2 5 kinds of combinations of calibration voltage values, there is no optical signal output from the right - hand Out1 port of the optical switch switching delay line (the optical signal is output from the Out2 port), discard these 2 5 = 32 kinds of combinations of calibration voltage values; the remaining 2 5 = 32 kinds of combinations of calibration voltage values correspond to 32 different transmission paths of the optical signal in the optical switch switching delay line. The "through", "cross" states of each stage of optical switch in the delay lines corresponding to these remaining 32 different delay transmission paths and the total delay of the delay line are shown in Table 2.

[0052] Optical switch 1 Optical switch 2 Optical switch 3 Optical switch 4 Optical switch 5 Optical switch 6 Delay amount Cross Through Through Through Through Cross 0 ps Through Cross Through Through Through Cross 3 ps Cross Cross Cross Through Through Cross 6 ps Through Through Cross Through Through Cross 9 ps Cross Through Cross Cross Through Cross 12 ps Through Cross Cross Cross Through Cross 15 ps Cross Cross Through Cross Through Cross 18 ps Through Through Through Cross Through Cross 21 ps Cross Through Through Cross Cross Cross 24 ps Through Cross Through Cross Cross Cross 27 ps Cross Cross Cross Cross Cross Cross 30 ps Through Through Cross Cross Cross Cross 33 ps Cross Through Cross Through Cross Cross 36 ps Through Cross Cross Through Cross Cross 39 ps Cross Cross Through Through Cross Cross 42 ps Through Through Through Through Cross Cross 45 ps Cross Through Through Through Cross Through 48 ps Through Cross Through Through Cross Through 51 ps Cross Cross Cross Through Cross Through 54 ps Through Through Cross Through Cross Through 57 ps Cross Through Cross Cross Cross Through 60 ps Through Cross Cross Cross Cross Through 63 ps Cross Cross Through Cross Cross Through 66 ps Through Through Through Cross Cross Through 69 ps Cross Through Through Cross Through Through 72 ps Through Cross Through Cross Through Through 75 ps Cross Cross Cross Cross Through Through 78 ps Through Through Cross Cross Through Through 81 ps Cross Through Cross Through Through Through 84 ps Through Cross Cross Through Through Through 87 ps Cross Cross Through Through Through Through 90 ps Through Through Through Through Through Through 93 ps

[0053] Table 2 shows the "through" and "cross" states of the optical switches at all levels in the delay lines corresponding to 32 different delay transmission paths and the total delay of the delay lines.

[0054] Next, by measuring the delay, further distinguish which of the pair of initial calibrated voltages reserved for each optical switch (S1 - S6) makes the optical switch in the "through" state and which makes it in the "cross" state. Input a laser with a fixed wavelength into the In port on the left side of the optical switch switching delay line, connect the Out1 port on the right side of the optical switch switching delay line to the delay test system, and load any one of the remaining 2 5 different combinations of calibrated voltage values (the actual voltages loaded on S1 - S6 are 5.25V, 4.86V, 2.34V, 2.74V, 3.3V, and 2.39V) onto the optical switches (S1 - S6). The measured delay of the optical switch switching delay line at this time is 9 ps. The delay of each delay transmission path is designed. Determine the transmission path of the optical signal in the optical switch switching delay line at this time according to the measured delay as Figure 7 shown. At this time, the optical switches (S1 - S6) at all levels in the delay line are in the "through", "through", "cross", "through", "through", and "cross" states respectively. Therefore, the actual voltages 5.25V, 4.86V, 2.34V, 2.74V, 3.3V, and 2.39V loaded on the optical switches S1 - S6 are the voltages that make the optical switches S1 - S6 in the "through", "through", "cross", "through", "through", and "cross" states respectively. Thus, the voltages 2.19V, 1.88V, 5.56V, 5.84V, 6.04V, and 5.36V are the voltages that make the optical switches S1 - S6 in the "cross", "cross", "through", "cross", "cross", and "through" states respectively. The distinguished voltages that make the optical switches S1 - S6 in the "through" or "cross" state are shown in Table 3. Thus, the calibration of the control voltages of the optical switches at all levels in the optical switch switching delay line is completed.

[0055]

[0056] Table 3 shows the distinguished voltages that make the optical switches S1 - S6 in the "through" or "cross" state.

[0057] The present invention utilizes the output interference spectrum characteristics of the optical switch switching delay line to calibrate the control voltage of the optical switch in the optical switch switching delay line without introducing additional special structures, effectively reducing the difficulty of chip design, tape - out, and packaging.

[0058] The specific implementation methods described above further elaborate on the purpose and technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention's solution and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calibration method for the control voltage of an optical switch in an optical switch switching delay line, characterized in that, Including the following steps: (1) Arrange a voltage source array, a wavelength tunable laser, and a spectral analyzer on the optical switch switching delay line to form an optical switch drive voltage - spectral monitoring system; (2) Change the drive voltage of the optical switch through the voltage source array, synchronously calculate the standard deviation of the interference spectrum output by the delay line, and calculate the through or cross state voltages of each level of the optical switch according to the change data of the spectral standard deviation; (3) Connect the output port Out1 of the optical switch switching delay line to the delay test system; (4) Distinguish the through or cross state voltages of each level of the optical switch according to the delay test results of the optical switch switching delay line.

2. The calibration method of the optical switch control voltage in an optical switch switching delay line according to claim 1, wherein, In step (1), the connection mode of the optical switch driving voltage - spectrum monitoring system is as follows: The wavelength - tunable laser is connected to the input port of the In of the optical switch switching delay line, and the control ports C1 - C of the voltage source array are n+1 connected to the optical switches S1 - S in the optical switch switching delay line one by one, and the output port Out1 of the optical switch switching delay line is connected to the spectrum analyzer, where n≥1. n+1 ​ 3. The calibration method of the optical switch control voltage in an optical switch switching delay line according to claim 2, wherein In step (2), the method for calculating the through or cross state voltages of each level of the optical switch according to the change data of the spectral standard deviation is as follows: (2.1) Output a scanning step voltage to the optical phase shifter in the optical switch S1 through the control port C1 of the voltage source array, and the spectral analyzer tests the interference spectrum output by the Out1 port of the delay line at different voltages; Calculate the standard deviation of each spectrum; test the resistance value of the optical phase shifter in the optical switch S1, and calculate the power applied to the optical phase shifter in the optical switch S1 when different voltages are output at the control port C1 according to the formula P = V 2 / R. The power corresponds to the voltage one by one, where P is power, V is voltage, and R is resistance. Plot the power-spectrum standard deviation curve; the power-spectrum standard deviation curve changes periodically, and the voltage corresponding to the minimum value point on the curve is the calibration value for making the optical switch S1 in the through or cross state, and the states of the optical switch S1 calibrated by the voltages corresponding to any two adjacent minimum value points are different; (2.2) Output the calibrated voltage to the optical switch S1 through the control port C1 to make it in the through or cross state; the same as the calibration process of the optical switch S1, output the scanning step voltage to the optical phase shifter in the optical switch S2 through the control port C2 of the voltage source array, and calculate the through or cross state voltage of the optical switch S2 according to the change data of the spectral standard deviation; output the calibrated voltage to the optical switches S1 - S2 through the control ports C1 - C2 to make them in the through or cross state. The same as the calibration process of the optical switch S1, output the scanning step voltage to the optical phase shifter in the optical switch S3 through the control port C3 of the voltage source array, and calculate the through or cross state voltage of the optical switch S3 according to the change data of the spectral standard deviation; repeat the above process, output the calibrated voltage to the optical switches S1 - S i Output the calibrated voltage to the optical switches S1 - S i to make them in the through or cross state, and output the scanning step voltage to the optical phase shifter in the optical switch S i+1 through the control port C i+1 of the voltage source array, and calculate the through or cross state voltage of the optical switch S i+1 where i is greater than or equal to 3 and less than or equal to n - 1; (2.3) respectively pass through C1 to C n Output calibrated voltages to make the optical switches S1 to S n in a through or cross state, and through the control ports C of the voltage source array n+1 Output scanning step voltages to control the optical switches S n+1 in the optical phase shifter, and the spectral analyzer tests the control ports C n+1 Output the interference spectra output from the Out1 port of the switching delay line when different voltages are applied, calculate the standard deviation of each spectrum, and calculate the optical switches S n+1 in the resistance value of the optical phase shifter, and calculate the control ports C n+1 Output the power applied to the optical phase shifter in the optical switches S n+1 when different voltages are applied to plot the power-spectral standard deviation curve; this power-standard deviation curve changes periodically, and the voltages corresponding to the maximum and minimum points are the calibration values that make the optical switches S n+1 in a through or cross state, and the optical switches S calibrated by the voltages corresponding to the maximum and minimum points n+1 are in different states.

4. The calibration method of the optical switch control voltage in an optical switch switching delay line according to claim 1, wherein In step (4), the method for distinguishing the through or cross state voltages of each level of the optical switch is as follows: (4.1) For each level of optical switches S1 to S n+1 Reserve a pair of calibration voltages that keep them in a through or cross state. For n + 1 optical switches S1 to S n+1 Form 2 n+1 Different combinations of calibration voltage values, and each combination of voltage values corresponds to a transmission path of the optical signal in the optical switch switching delay line; (4.2) Input a preset fixed-wavelength laser into the input port of the optical switch switching delay line In, and load two n+1 different combinations of calibration voltage values to the optical switches S1 to S n+1 respectively. Among them, when the two n combinations of calibration voltage values are applied, no optical signal is output from the Out1 port of the optical switch switching delay line, and the optical signal is output from the Out2 port. Discard these two n combinations of calibration voltage values, and the remaining two n combinations of calibration voltage values correspond to two n different transmission paths of the optical signal in the optical switch switching delay line; (4.3) Input 1 path of fixed-wavelength laser into the In input port of the optical switch switching delay line, and load any one of the remaining 2 n combinations of different calibration voltage values to optical switches S1 to S n+1 , test the delay amount of the optical switch switching delay line. The delay amount of each transmission path is a pre-designed fixed value, and determine the transmission path of the optical signal in the optical switch switching delay line at this time according to the measured delay amount; (4.4) The on / off states of the optical switches at all levels corresponding to the transmission path are fixed. According to the test delay results, from each level of optical switch S1 to S n+1 A pair of reserved calibrated voltages are used to distinguish the voltage in the through state and the voltage in the cross state.

5. A calibration method for the optical switch control voltage in an optical switch switching delay line according to claim 1, characterized in that: The optical transmission medium of the optical switch switching delay line is an optical fiber or an on - chip integrated optical waveguide.

6. A calibration method for the optical switch control voltage in an optical switch switching delay line according to claim 1, characterized in that: The wavelength range of the interference spectrum is an integer multiple of the maximum free spectral range of the delay line.

7. A calibration method for the optical switch control voltage in an optical switch switching delay line according to claim 1, characterized in that: The optical switch is not limited to the MZI - type 4 - port structure.

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