Underground optical signal transmission system and method

Abstract

The invention relates to the technical field of optical signal processing, in particular to an underground optical signal transmission system and method, and the system comprises an optical signal generation device which is used for generating an optical signal in an X polarization direction and transmitting the optical signal to a polarization state regulation and control device through a polarization maintaining optical fiber; the polarization state regulation and control device is used for regulating the polarization state of the optical signal to obtain a candidate optical signal and transmitting the candidate optical signal to the total reflection device; the total reflection device is used for performing total reflection on the candidate optical signal to obtain a total reflection optical signal; the total reflection light signal is transmitted to a signal processing unit through a polarization maintaining optical fiber; and the signal processing unit is used for carrying out polarization state detection on the total reflection light signal to obtain target polarization state information of the total reflection light signal. The system reduces the problems of optical signal damage, attenuation and the like, and improves the reliability and stability of the whole system.

Description

Technical Field

[0001] The present invention relates to the technical field of optical signal processing, and in particular to a downhole optical signal transmission system and method in the technical field of optical signal processing. Background Art

[0002] In underground operations, with the continuous development of intelligent mining technologies, the demand for high-speed, accurate transmission of large amounts of data is becoming increasingly urgent. Traditional electrical signal transmission methods face numerous challenges in the complex underground environment, such as severe electromagnetic interference and limited transmission bandwidth. In contrast, optical signal transmission, with its advantages of high bandwidth and low loss, has gradually become a research hotspot for underground data transmission.

[0003] However, the downhole optical signal transmission optical path structure in the related technology has poor high temperature resistance, reflection efficiency and stability in the signal reflection link, resulting in large transmission loss and attenuation of the optical signal, and thus low accuracy in polarization state detection of the optical signal. Summary of the Invention

[0004] The purpose of the present invention is to provide a downhole optical signal transmission system and method, and the technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present invention provides a downhole optical signal transmission system, the system comprising:

[0006] An optical signal generating device is used to generate an optical signal in an X-polarization direction and transmit it to a polarization state control device through a polarization-maintaining optical fiber;

[0007] The polarization state regulating device is used to adjust the polarization state of the optical signal to obtain a candidate optical signal, and transmit the candidate optical signal to the total reflection device;

[0008] The total reflection device is used to perform total reflection on the candidate optical signal to obtain a total reflection optical signal; and transmit the total reflection optical signal to the signal processing unit through the polarization-maintaining optical fiber;

[0009] The signal processing unit is used to perform polarization state detection on the total reflection light signal to obtain target polarization state information of the total reflection light signal.

[0010] In a second aspect, an embodiment of the present invention provides a method for transmitting downhole optical signals, the method comprising:

[0011] Generate an optical signal in the X-polarization direction;

[0012] adjusting the polarization state of the optical signal to obtain a candidate optical signal;

[0013] Totally reflecting the candidate optical signal to obtain a total reflected optical signal;

[0014] Polarization state detection is performed on the total reflected light signal to obtain target polarization state information of the total reflected light signal.

[0015] The present invention has the following beneficial effects: in a downhole signal transmission system, an optical signal in the X-polarization direction is generated by an optical signal generating device and transmitted to a polarization state control device through a polarization-maintaining optical fiber; thereafter, the polarization state control device adjusts the polarization state of the optical signal to obtain a candidate optical signal, and transmits the candidate optical signal to a total reflection device; so that the candidate optical signal is totally reflected by the total reflection device to obtain a totally reflected optical signal; thus, by totally reflecting the candidate optical signal by the total reflection device, the totally reflected optical signal sent to the signal processing unit can be made more accurate, reducing damage and attenuation of the optical signal. Finally, the polarization state of the totally reflected optical signal is detected by the signal processing unit to obtain target polarization state information of the totally reflected optical signal; thus, since the accuracy of the totally reflected optical signal received by the signal processing unit is high, the accuracy of the target polarization state information detected by the signal processing unit is high, thereby improving the reliability and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the structure of a downhole optical signal transmission system provided in the related art;

[0018] Figure 2 This is a schematic diagram of the structure of a downhole optical signal transmission system provided by an embodiment of the present invention;

[0019] Figure 3 1 is another structural diagram of a downhole optical signal transmission system provided by an embodiment of the present invention;

[0020] Figure 4 This is another schematic diagram of the structure of a downhole optical signal transmission system provided by an embodiment of the present invention;

[0021] Figure 5 1 is a schematic diagram of the structure of a signal processing unit provided in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the implementation process of a downhole optical signal transmission method provided by an embodiment of the present invention;

[0023] Figure 7 It is a structural diagram of a computer device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a method for downhole optical signal transmission according to the present invention, including its specific implementation, structure, features, and effectiveness. In the following description, references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0025] In the description of the embodiments of the present invention, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present invention, "multiple" refers to two or more than two.

[0026] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to imply or suggest relative importance or implicitly indicate the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0027] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0028] In some embodiments, there are still key technical bottlenecks in downhole optical signal transmission. On the one hand, the high-temperature environment downhole poses a serious threat to the normal operation of the laser. The materials and structures of conventional lasers are prone to performance degradation at high temperatures. For example, high temperatures can cause deformation of the optical resonant cavity structure inside the laser, reduced quantum efficiency of the active area material, and difficulty in heat dissipation, making it impossible for the laser to stably emit high-quality optical signals or even unable to work, thereby cutting off the source of optical signal transmission. On the other hand, although high-temperature resistant quantum dot lasers can maintain a certain working state in a high-temperature environment, they have obvious deficiencies in high-speed signal propagation. The special physical mechanism of quantum dot lasers will cause problems such as complex carrier dynamics and limited modulation bandwidth during high-speed modulation, resulting in signal transmission rates that are difficult to meet the requirements of complex downhole operations for real-time transmission of large amounts of data.

[0029] In addition, the optical signal transmission optical path structure in the related technology also has some limitations. For example, in the signal reflection link, the commonly used optical fiber loop structure may have room for improvement in terms of high temperature resistance, reflection efficiency and stability. Figure 1 As shown, the laser 101 generates an X-polarized optical signal, which is transmitted to the PZT through a polarization-maintaining optical fiber to adjust the polarization state of the optical signal. The optical signal after the polarization state is adjusted is then transmitted to the signal processing unit 103 through the optical fiber loop 102 through the polarization-maintaining optical fiber. Due to the limitations of the optical fiber loop 102, the accuracy of the optical signal transmitted to the signal processing unit 103 is low.

[0030] Based on this, the embodiment of the present invention provides a downhole optical signal transmission system that can effectively overcome the impact of high temperature environments on lasers, achieve high-speed signal transmission of high-temperature resistant quantum dot lasers, and optimize the optical path structure to improve the overall system performance. The following is a detailed description of a specific scheme of a downhole optical signal transmission system provided by the present invention in conjunction with the accompanying drawings. Figure 2 , which shows a schematic structural diagram of a downhole optical signal transmission system provided by one embodiment of the present invention. The system 200 includes:

[0031] The optical signal generating device 201 is used to generate an optical signal in the X polarization direction and transmit it to the polarization state control device through the polarization-maintaining optical fiber.

[0032] Here, the optical signal generating device 201 can be implemented by a laser. An optical signal in the X-polarization direction is generated by the laser. The working principle of the downhole optical signal transmission system is to precisely control the optical signal based on the polarization characteristics of light. The system starts with a laser. As a light source, the laser has a high degree of polarization specificity and emits linearly polarized light at any angle. This beam of light with a specific polarization angle then enters the polarization-maintaining optical fiber. The polarization-maintaining optical fiber can simultaneously support stable transmission of light in the X and Y polarization directions. Moreover, in the absence of external interference factors, the polarization-maintaining optical fiber can effectively maintain the initial polarization state of the light, so that the X-polarized light emitted from the laser can be transmitted in the optical fiber with extremely low loss and extremely high polarization fidelity. In some possible implementations, the optical signal can be transmitted in parallel through multiple polarization-maintaining optical fibers to improve transmission efficiency.

[0033] The polarization state regulating device 202 is used to adjust the polarization state of the optical signal to obtain a candidate optical signal, and transmit the candidate optical signal to the total reflection device.

[0034] Here, the polarization state control device 202 can be implemented by lead zirconate titanate piezoelectric ceramics (Pb(Zr1-xTiO3), PZT). When the optical signal is successfully transmitted to the PZT in the polarization-maintaining optical fiber, the PZT becomes the core component for controlling the polarization state of the light. When the non-polarization-maintaining optical fiber placed on the wall of the box is not squeezed, its polarization state remains unchanged, for example, it still remains in the X direction, just like when it is transmitted in the polarization-maintaining optical fiber, the polarization state does not change. However, once the PZT squeezes the non-polarization-maintaining optical fiber placed on the wall of the box, the refractive index of the optical fiber changes, which in turn causes the polarization angle of the optical signal to change, for example, from the original X polarization angle to the Y polarization angle.

[0035] In some possible implementations, the polarization state adjustment device 202 includes: a first piezoelectric ceramic, a second piezoelectric ceramic, and a third piezoelectric ceramic; wherein:

[0036] The first piezoelectric ceramic is used to adjust the phase difference of the optical signal propagating in two orthogonal directions based on a first pressure, so as to convert the optical signal into linearly polarized light.

[0037] Here, the first piezoelectric ceramic adjusts the phase difference of the optical signal propagating in two orthogonal directions to 90° based on the first pressure, thereby converting the optical signal into linearly polarized light. For example, when an optical fiber placed on the wall of a box is squeezed by the PZT, stress birefringence will be generated. The degree of birefringence is related to the applied pressure. For the first PZT (i.e., the first piezoelectric ceramic), to produce a similar The effect of the wave plate is to convert the input light into linearly polarized light.

[0038] The second piezoelectric ceramic is configured to adjust the first pressure to obtain a second pressure; and to rotate the linearly polarized light based on the second pressure to obtain an intermediate optical signal;

[0039] Here, the second piezoelectric ceramic adjusts the phase difference of the linearly polarized light propagating in two orthogonal directions to 180° based on the second pressure, so as to rotate the linearly polarized light and obtain the intermediate optical signal; for example, the second PZT (i.e., the second piezoelectric ceramic) generates a similar (where λ represents the wavelength of the optical signal) The wave plate rotates the polarization direction of the optical signal by 90° between the fast axis and the slow axis, thereby adjusting the polarization direction of the linearly polarized light.

[0040] The third piezoelectric ceramic is used to adjust the second pressure to obtain a third pressure; and based on the third pressure, adjust the polarization state of the intermediate optical signal to obtain the candidate optical signal.

[0041] Here, the third piezoelectric ceramic adjusts the phase difference of the candidate optical signal propagating in two orthogonal directions to 90° based on the third pressure, so as to adjust the polarization state of the intermediate optical signal and obtain the candidate optical signal.

[0042] In some possible implementations, the third PZT (ie, the third piezoelectric ceramic) produces a similar The effect of the wave plate is to further change the polarization state of the optical signal from the state adjusted by the second PZT (i.e., the polarization state of the intermediate optical signal), and ultimately to achieve the effect of adjusting the polarization state to any desired polarization state, just like the effect of using two wave plates in succession and a wave plate combination.

[0043] According to the birefringence theory, when an optical fiber is subjected to a certain pressure P, a refractive index difference Δn will be generated in the two orthogonal directions (fast axis and slow axis) of the optical fiber. The relationship between this refractive index difference and pressure can be expressed by the elastic coefficient P of the material. ij To express, that is (where n is the original refractive index of the optical fiber). The function of the wave plate is to generate phase difference between the light propagating along the fast axis and the slow axis. (L1 is the length of the first PZT corresponding to the box wall fiber (the squeezed part), that is, the length of the first PZT. λ is the wavelength of the incident light, and n is the original refractive index of the fiber). Adjust P1 so that The second PZT is to produce The effect of the wave plate is to adjust the pressure P2 applied to the optical fiber to produce a phase difference between the light propagating in the fast axis and the slow axis. The third PZT is to produce The effect of the wave plate is to adjust the pressure P3 applied to the optical fiber to produce a phase difference between the light propagating in the fast axis and the slow axis. Thus, the polarization state of the intermediate optical signal is adjusted by the phase difference to obtain a candidate optical signal.

[0044] In practice, a precise pressure sensor is required to monitor the pressure applied by the PZT, combined with a device for detecting the polarization state of light. Based on the difference between the detected polarization state and the target polarization state, a feedback control system adjusts the PZT drive voltage, thereby adjusting the pressures P1, P2, and P3 to achieve precise polarization control. In this way, the first, second, and third piezoelectric ceramics can precisely adjust the polarization state of the optical signal.

[0045] The total reflection device 203 is configured to perform total reflection on the candidate optical signal to obtain a total reflection optical signal; and transmit the total reflection optical signal to the signal processing unit via a polarization-maintaining optical fiber.

[0046] Here, the total reflection device includes: a total reflection mirror with a surface coating or a prism with an isosceles right triangle cross section; wherein:

[0047] The surface-coated total reflection mirror is used to prepare a metal or multi-layer thin film on the surface of a preset material to totally reflect the candidate light signal to obtain a totally reflected light signal;

[0048] like Figure 3 As shown, the laser 31 generates an optical signal in the X-polarization direction, which is transmitted to the PZT through a polarization-maintaining fiber for polarization adjustment to obtain a candidate optical signal. The candidate optical signal is then totally reflected by a total reflection mirror 32, and the totally reflected optical signal is transmitted to the signal processing unit 33 through the polarization-maintaining fiber.

[0049] The prism having an isosceles right triangle cross section is used to perform total reflection on the candidate optical signal based on the geometric shape and refractive index of the prism to obtain a total reflection optical signal.

[0050] like Figure 4 As shown, laser 41 generates an X-polarized optical signal, which is transmitted to the PZT via a polarization-maintaining fiber for polarization adjustment to obtain a candidate optical signal. The candidate optical signal is then totally reflected by a total reflection prism 42, which is then transmitted to a signal processing unit 43 via a polarization-maintaining fiber. In this way, by totally reflecting the candidate optical signal through a total reflection prism or a total reflection mirror and then transmitting it to the signal processing unit via a polarization-maintaining fiber, optical signal attenuation can be reduced, thereby improving accuracy.

[0051] In conventional downhole optical systems, optical fiber loops are commonly used for optical signal transmission and processing. However, these loops are prone to bending and breaking, and the light attenuation increases with fiber length. This system innovatively replaces the fiber loop with a total internal reflection structure, addressing the attenuation problem and preventing the breakage of the fiber loop. Total internal reflection structures primarily come in two forms: those with metal or multi-layer thin films on the surface, and those with an isosceles right triangle cross-section. Surface-coated total internal reflection structures utilize metal or multi-layer thin films deposited on a specific material, leveraging the optical properties of the films to cause total internal reflection of light. This structure offers advantages in downhole applications, such as its compact size and ease of installation in confined spaces, while also effectively reducing optical signal loss during transmission. Total internal reflection prisms utilize their geometric shape and refractive index to achieve total internal reflection of light. Prisms offer high reflection efficiency and stability, making them suitable for harsh underground environments, such as high humidity and dust, ensuring stable optical signal transmission. By employing a total internal reflection structure, the system overcomes potential damage and signal attenuation issues that can plague optical fiber loops in complex underground environments, improving the reliability and stability of the entire optical system.

[0052] The signal processing unit 204 is configured to perform polarization state detection on the total reflected light signal to obtain target polarization state information of the total reflected light signal.

[0053] Here, the signal processing unit undertakes the important task of accurately detecting and judging the polarization angle of the light returning from the well. The signal processing unit adopts advanced photoelectric detection technology and intelligent algorithms, which can quickly and accurately analyze the polarization angle information of the light. The light squeezed by the PZT is first divided into the X direction and the Y direction by the PBS, and then enters the corresponding PD respectively to obtain the size of the light signal in the X and Y directions. If it is detected that there is only a light signal in the X direction and no light signal in the Y direction, the signal processing unit will output a signal of 0; conversely, if it is detected that there is no light signal in the X direction and there is a light signal in the Y direction, the signal processing unit will output a signal of 1. Through this ingenious design, with the help of the size of the force applied by PZT, the effective monitoring of the polarization state of light and signal conversion are realized, and a complete, efficient and accurate principle system for the regulation and detection of the polarization state of light is constructed. Such as Figure 5 As shown, the signal processing unit 204 includes: a polarizing beam splitter (PBS) 51, photodetectors (PD1 and PD2) and a calculation module 52;

[0054] The polarization beam splitter PBS 51 is used to separate the total reflected light signal into polarized light signals in two directions perpendicular to each other.

[0055] Here, PBS 51 accurately decomposes the input polarized light (i.e., the totally reflected light signal) into two beams along the X and Y directions according to its polarization characteristics. In other words, after passing through the PBS, the original polarized light beam is separated into two mutually perpendicular directions, thereby providing optical signals in different directions for subsequent processing.

[0056] The photodetectors (PD1 and PD2) are used to convert the polarized light signal into an electrical signal.

[0057] Here, there are two photodetectors (i.e. Figure 5 PD1 and PD2 are shown. One photodetector detects the intensity of light in the X direction, while the other detects the intensity of light in the Y direction. These two photodetectors convert the optical signal into a corresponding electrical signal, thereby obtaining the specific quantitative values of light in the X and Y directions, facilitating subsequent numerical calculations and other operations.

[0058] The calculation module 52 is configured to determine target polarization state information of the total reflected light signal based on the electrical signal.

[0059] Here, first of all, the magnitude values of the light in the X direction and the Y direction detected by the two PDs are obtained. Then, the tangent function (tan) in the trigonometric function is used for calculation. Specifically, by calculating the value of the tan function (this value is determined based on the ratio of the light magnitudes in the X and Y directions, that is, tanθ=Y direction light magnitude / X direction light magnitude, where θ is the angle based on the X direction), the magnitude of the angle θ based on the X direction is obtained. Then, a correspondence between the magnitude of the angle θ and the numerical range of 0-256 is established. For example, through some kind of linear mapping or pre-set rules, the specific value of each angle θ can find a unique corresponding value in the range of 0-256, so that the angle information can be converted into a specific coded value.

[0060] In an embodiment of the present invention, in a downhole signal transmission system, an optical signal in the X-polarization direction is generated by an optical signal generating device and transmitted to a polarization state control device through a polarization-maintaining optical fiber; thereafter, the polarization state control device adjusts the polarization state of the optical signal to obtain a candidate optical signal, and transmits the candidate optical signal to a total reflection device; so that the candidate optical signal is totally reflected by the total reflection device to obtain a totally reflected optical signal; in this way, by totally reflecting the candidate optical signal by the total reflection device, the totally reflected optical signal sent to the signal processing unit can be made more accurate, reducing problems such as damage and attenuation of the optical signal. Finally, the polarization state of the totally reflected optical signal is detected by the signal processing unit to obtain the target polarization state information of the totally reflected optical signal; in this way, since the accuracy of the totally reflected optical signal received by the signal processing unit is high, the accuracy of the target polarization state information detected by the signal processing unit is high, thereby improving the reliability and stability of the entire optical system.

[0061] In some possible implementations, the downhole optical signal transmission system further includes: a data conversion unit;

[0062] a data conversion unit, configured to convert the input initial coded data into an initial polarization state control signal based on a preset mapping relationship, and apply the initial polarization state control signal to the polarization state adjustment device; wherein the preset mapping relationship is used to represent the correspondence between the polarization angle of the optical signal and the coding value range;

[0063] The polarization state adjustment device is further configured to adjust the polarization state of the optical signal based on the initial polarization state control signal to obtain the candidate optical signal;

[0064] The signal processing unit is further configured to restore the target polarization state information of the total reflected light signal into target coded data based on the preset mapping relationship.

[0065] To further improve system performance, downhole signals are mapped one-to-one to codes ranging from 0 to 256, establishing a direct mapping between signals and digital codes. Furthermore, the polarization state of light is incorporated into the coding system, creating a precise one-to-one mapping between polarization angles ranging from 0 to 90 degrees and values from 0 to 256, creating a pre-defined mapping. For example, code 0 corresponds to a light signal propagating only in the X-polarization direction, while code 256 represents light propagating only in the Y-polarization direction. This mapping allows the polarization angle of light to carry information.

[0066] During the transmission of optical signals underground, the data conversion unit converts the input initial coded data into an initial polarization state control signal according to a preset mapping relationship, and applies the initial polarization state control signal to the polarization state adjustment device.

[0067] Here, the initial coded data is the coded data corresponding to the set target polarization state. By converting the input initial coded data into an initial polarization state control signal, the polarization state adjustment device can adjust the polarization state of the optical signal according to the initial polarization state control signal. Specifically, the polarization state adjustment device adjusts the polarization state of the optical signal based on the initial polarization state control signal to obtain the candidate optical signal. Finally, the signal processing unit, based on the preset mapping relationship, restores the target polarization state information of the fully reflected optical signal to the target coded data, thereby improving the transmission efficiency of the optical signal.

[0068] In a specific example, taking 8-bit data transmission as an example, each 8-bit data is assigned a specific polarization state. Specifically, the precise action of the PZT on the optical signal enables the corresponding conversion between polarization state and data. Different degrees of PZT compression cause the polarization angle of the light to change, thereby carrying different data information. Downhole, the data is converted into an optical signal with the corresponding polarization state according to a pre-defined correspondence, and then transmitted through the polarization-maintaining fiber. At the receiving end, the signal processing unit accurately detects the polarization state of the light and, based on pre-defined encoding rules, converts the polarization state back into 8-bit data, thus ensuring accurate transmission and restoration of the data. This encoding method fully utilizes the polarization properties of light, greatly improving the utilization rate of the optical channel and enhancing the signal's resistance to interference during transmission. Each 8-bit data is precisely assigned a specific polarization state. The core of this process lies in the mechanism by which the PZT acts on light. As a piezoelectric material, PZT undergoes varying degrees of mechanical deformation when different voltages are applied, which in turn squeezes the passing light to varying degrees, ultimately changing the polarization angle of the light. By precisely controlling PZT, it is possible to finely adjust the polarization state of light, allowing the light to carry specific data information.

[0069] At the downhole transmitter, the data processing system converts 8-bit data into corresponding polarization control signals based on pre-set coding rules. These signals are then applied to the PZT via a drive circuit. The PZT acts on the light according to the control signal, converting the data into an optical signal with the corresponding polarization state, which is then coupled into the optical fiber for transmission. At the receiver, the signal processing unit uses a polarization beam splitter and photodetector to accurately detect the polarization state of the received optical signal. The detection equipment separates the optical signal according to its polarization direction and converts it into an electrical signal. By analyzing and processing the electrical signal, the polarization angle of the light is determined. The detected polarization angle is then converted back into 8-bit data based on pre-set coding rules. This process requires the signal processing unit at the receiver to have a high degree of accuracy and stability to ensure that the data sent by the transmitter can be accurately restored.

[0070] In some possible implementations, to further increase the transmission rate, parallel transmission can be performed through multiple optical fibers. Based on this, the data conversion unit divides the initial coded data according to the number of the multiple optical fibers to obtain multiple divided coded data. The multiple divided coded data correspond to the multiple optical fibers one-to-one. Based on the preset mapping relationship, the multiple divided coded data corresponding to the multiple optical fibers are converted into multiple initial polarization state control signals.

[0071] The signal processing unit converts the multiple initial polarization state control signals into multiple intermediate coded data based on the preset mapping relationship, and fuses the multiple intermediate coded data to obtain the target coded data.

[0072] Here, in order to further improve the transmission rate and meet the needs of scenarios such as underground that have extremely high requirements for signal transmission reliability, the embodiment of this invention adopts a solution of 4 optical fibers transmitting 32-bit data in parallel. At the transmitting end, the data conversion unit distributes the 32-bit data to the 4 optical fibers according to specific rules. The specific distribution method is: the 32-bit data is evenly divided into 4 groups, that is, a plurality of divided encoded data are obtained; each group of 8 bits corresponds to one optical fiber. Each optical fiber converts the corresponding 8-bit data into a coding mode according to the polarization state at different angles. For example, the first optical fiber may be responsible for transmitting the upper 8 bits of data, and transmits it in the optical fiber by converting these 8-bit data into an optical signal with a specific polarization state.

[0073] At the receiving end, the signal processing unit independently receives, detects, analyzes, and decodes the signal from each optical fiber. The signal processing unit accurately detects and analyzes the polarization state of the optical signal in the corresponding fiber. It then processes the electrical signal using a digital signal processing algorithm to extract the polarization state information it carries. Next, according to encoding rules, the polarization state information is converted back into 8-bit data. Finally, the 8-bit data decoded by the four processing units is combined to produce the complete 32-bit data.

[0074] This parallel transmission method not only significantly increases the transmission rate, but also provides redundancy and fault tolerance due to the simultaneous transmission of data along multiple optical fibers. If one optical fiber fails or is disturbed, the other three fibers can continue to transmit data, ensuring data integrity and reliability. For example, if a fiber experiences signal attenuation or distortion due to downhole environmental factors, the receiving end's processing unit can analyze and process the data from the other three fibers, utilizing redundant information to recover lost or erroneous data and ensure the accuracy of the final 32-bit data received. This redundant fault-tolerance mechanism is particularly important in the complex downhole environment, effectively ensuring the stability and reliability of signal transmission and meeting the requirements of high-reliability scenarios.

[0075] The embodiment of the present invention provides a method for transmitting optical signals underground. Figure 6 , combined with Figure 6 The steps shown are explained below:

[0076] 601, generate an optical signal in the X polarization direction.

[0077] Here, a laser is used to generate an optical signal in the X-polarization direction and transmit it through a polarization-maintaining optical fiber.

[0078] 602. Adjust the polarization state of the optical signal to obtain a candidate optical signal.

[0079] Here, the polarization state of the optical signal is adjusted by the PZT to obtain a candidate optical signal.

[0080] 603 : Perform total reflection on the candidate optical signal to obtain a total reflection optical signal.

[0081] Here, the candidate optical signal is totally reflected by a total reflection device to obtain a totally reflected optical signal.

[0082] 604 : Perform polarization state detection on the totally reflected light signal to obtain target polarization state information of the totally reflected light signal.

[0083] Here, first, the total reflection light signal is separated into a first polarized light signal and a second polarized light signal that are perpendicular to each other; for example, the total reflection light signal is separated into two beams of light along the X direction and the Y direction by using a PBS. The light along the X direction is the first polarized light signal, and the light along the Y direction is the second polarized light signal. Afterwards, the first polarized light signal and the second polarized light signal are converted into a first electrical signal and a second electrical signal respectively; for example, two photodetectors are used to convert the first polarized light signal and the second polarized light signal into corresponding electrical signals, thereby obtaining the quantized values of the light in the X and Y directions, so as to facilitate subsequent numerical calculations and other operations. Finally, based on the first electrical signal and the second electrical signal, the target polarization state information of the total reflection light signal is determined. For example, after obtaining the magnitude values of the first electrical signal and the second electrical signal, the polarization angle of the total reflection light signal, i.e., the target polarization state information, is calculated by using the tangent function (tan) in the trigonometric function.

[0084] In some possible implementations, the polarization angle θ between the first and second electrical signals is determined, using the first electrical signal as a reference: tanθ = Y-axis light intensity / X-axis light intensity. This polarization angle serves as the target polarization state information for the total reflection optical signal. By employing a total reflection structure to fully reflect the candidate optical signal, polarization state detection can be performed on the total reflection optical signal. This overcomes potential damage and signal attenuation issues that may arise with optical fiber loops in complex underground environments, improving the reliability and stability of the entire optical system.

[0085] Optionally, the transmission medium can be a wired link (for example, but not limited to, coaxial cable, optical fiber and digital subscriber line (DSL)) or a wireless link (for example, but not limited to, wireless Fidelity (WIFI), Bluetooth and mobile device network). It should be noted that the system provided in the above embodiment is only illustrated by the division of the above functional modules. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the computer device can be divided into different functional modules to complete all or part of the functions described above. In addition, the method embodiments provided in the above embodiments belong to the same concept. The specific implementation process is detailed in the method embodiments, which will not be repeated here.

[0086] Figure 7 FIG. 1 is a schematic diagram of the structure of a computer device provided by an embodiment of the present invention. For example, Figure 7As shown, the computer device 700 includes: a memory 701, a processor 702, and a computer program 703 stored in the memory 701 and running on the processor 702, wherein when the processor 702 executes the computer program 703, the computer device can execute any one of the downhole optical signal transmission methods introduced above.

[0087] In addition, an embodiment of the present invention also protects a system, which may include a memory and a processor, wherein the memory stores an executable program code, and the processor is used to call and execute the executable program code to perform a downhole optical signal transmission method provided by an embodiment of the present invention. This embodiment can divide the system into functional modules according to the above method example. For example, it can correspond to each functional module, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware. It should be noted that the division of modules in this embodiment is schematic and is only a logical function division. There may be other division methods in actual implementation. It should be noted that all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0088] It should be understood that the system provided in this embodiment is used to execute the above-mentioned downhole optical signal transmission method, and therefore can achieve the same effect as the above-mentioned implementation method. In the case of an integrated unit, the system may include a processing module and a storage module. Specifically, when the system is applied to a device, the processing module can be used to control and manage the actions of the device. The storage module can be used to support the device in executing mutual program codes, etc. Specifically, the processing module can be a processor or a controller, which can implement or execute various exemplary logic blocks, modules and circuits described in conjunction with the disclosure of the present invention. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of digital signal processing (DSP) and a microprocessor, etc., and the storage module can be a memory.

[0089] In addition, the system provided by the embodiments of the present invention may specifically be a chip, component, or module. The chip may include a connected processor and memory; the memory is used to store instructions. When the processor calls and executes the instructions, the chip can execute a downhole optical signal transmission method provided by the above embodiment. The system, computer-readable storage medium, computer program product, or chip provided by this embodiment is used to execute the corresponding method provided above. Therefore, the beneficial effects achieved by the system can refer to the beneficial effects of the corresponding method provided above and will not be repeated here.

[0090] Through the description of the above embodiments, those skilled in the art can understand that, for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional modules as needed, that is, the internal structure of the system is divided into different functional modules to complete all or part of the functions described above. In the embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely schematic. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or units, which can be electrical, mechanical or other forms.

[0091] It should be noted that the above-mentioned order of the embodiments of the present invention is for description only and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or may be advantageous. The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments. The above content is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered within the scope of protection of the present invention.

Claims

1. A downhole optical signal transmission system, characterized in that: The downhole optical signal transmission system comprises: An optical signal generating device is used to generate an optical signal in an X-polarization direction and transmit it to a polarization state control device through a polarization-maintaining optical fiber; The polarization state regulating device is used to adjust the polarization state of the optical signal to obtain a candidate optical signal, and transmit the candidate optical signal to the total reflection device; The total reflection device is used to perform total reflection on the candidate optical signal to obtain a total reflection optical signal; and transmit the total reflection optical signal to the signal processing unit through the polarization-maintaining optical fiber; The signal processing unit is used to perform polarization state detection on the total reflection light signal to obtain target polarization state information of the total reflection light signal.

2. The downhole optical signal transmission system according to claim 1, characterized in that: The downhole optical signal transmission system further includes: a data conversion unit; The data conversion unit is configured to convert the input initial coded data into an initial polarization state control signal based on a preset mapping relationship, and apply the initial polarization state control signal to the polarization state adjustment device; wherein the preset mapping relationship is used to represent the correspondence between the polarization angle of the optical signal and the coding value range; The polarization state adjustment device is further configured to adjust the polarization state of the optical signal based on the initial polarization state control signal to obtain the candidate optical signal; The signal processing unit is further configured to restore the target polarization state information of the total reflected light signal into target coded data based on the preset mapping relationship.

3. The downhole optical signal transmission system according to claim 2, characterized in that: The polarization-maintaining optical fiber includes: a plurality of optical fibers; The data conversion unit is further configured to divide the initial coded data according to the number of the plurality of optical fibers to obtain a plurality of divided coded data; wherein the plurality of divided coded data corresponds one-to-one to the plurality of optical fibers; and based on the preset mapping relationship, convert the plurality of divided coded data corresponding to the plurality of optical fibers into a plurality of initial polarization state control signals; The signal processing unit is further configured to convert the multiple initial polarization state control signals into multiple intermediate coded data based on the preset mapping relationship, and fuse the multiple intermediate coded data to obtain the target coded data.

4. The downhole optical signal transmission system according to claim 1, characterized in that: The total reflection device comprises: a total reflection mirror with a surface coating or a prism with an isosceles right triangle cross section; wherein: The surface-coated total reflection mirror is used to prepare a metal or multi-layer thin film on the surface of a preset material to perform total reflection on the candidate light signal; or The prism having an isosceles right triangle cross section is used to perform total reflection on the candidate optical signal based on the geometric shape and refractive index of the prism.

5. The downhole optical signal transmission system according to claim 1, characterized in that: The polarization state adjustment device includes: a first piezoelectric ceramic, a second piezoelectric ceramic and a third piezoelectric ceramic; wherein: The first piezoelectric ceramic is configured to adjust a phase difference between propagation of the optical signal in two orthogonal directions based on a first pressure, so as to convert the optical signal into linearly polarized light; The second piezoelectric ceramic is configured to adjust the first pressure to obtain a second pressure; and to rotate the linearly polarized light based on the second pressure to obtain an intermediate optical signal; The third piezoelectric ceramic is used to adjust the second pressure to obtain a third pressure; and based on the third pressure, adjust the polarization state of the intermediate optical signal to obtain the candidate optical signal.

6. The downhole optical signal transmission system according to claim 5, characterized in that: The first piezoelectric ceramic is further configured to adjust the phase difference of the optical signal propagating in two orthogonal directions to 90° based on the first pressure, so as to convert the optical signal into linearly polarized light; The second piezoelectric ceramic is further configured to adjust the phase difference of the linearly polarized light propagating in two orthogonal directions to 180° based on the second pressure, so as to rotate the linearly polarized light and obtain the intermediate optical signal; The third piezoelectric ceramic is further configured to adjust the phase difference of the candidate optical signal propagating in two orthogonal directions to 90° based on the third pressure, so as to adjust the polarization state of the intermediate optical signal and obtain the candidate optical signal.

7. The downhole optical signal transmission system according to claim 1, characterized in that: The signal processing unit includes: a polarization beam splitter, configured to separate the total reflected light signal into polarized light signals in two directions perpendicular to each other; a photodetector, configured to convert the polarized light signal into an electrical signal; A calculation module is used to determine target polarization state information of the total reflected light signal based on the electrical signal.

8. A method for transmitting optical signals downhole, characterized in that: The downhole optical signal transmission method comprises: Generate an optical signal in the X-polarization direction; adjusting the polarization state of the optical signal to obtain a candidate optical signal; Totally reflecting the candidate optical signal to obtain a total reflected optical signal; Polarization state detection is performed on the total reflected light signal to obtain target polarization state information of the total reflected light signal.

9. The downhole optical signal transmission method according to claim 8, characterized in that: The performing polarization state detection on the totally reflected light signal to obtain target polarization state information of the totally reflected light signal includes: Separating the total reflected light signal into a first polarized light signal and a second polarized light signal perpendicular to each other; converting the first polarized light signal and the second polarized light signal into a first electrical signal and a second electrical signal respectively; Based on the first electrical signal and the second electrical signal, target polarization state information of the totally reflected light signal is determined.

10. The downhole optical signal transmission method according to claim 9, characterized in that: The determining, based on the first electrical signal and the second electrical signal, target polarization state information of the totally reflected light signal includes: Determining a polarization angle between the first electrical signal and the second electrical signal based on the first electrical signal; Based on the polarization angle, target polarization state information of the totally reflected light signal is determined.

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