Electric control variable optical attenuator based on multistage wedge-shaped liquid crystal box and attenuation control method

Abstract

The invention discloses an electrically-controlled variable optical attenuator based on a multistage wedge-shaped liquid crystal box and an attenuation control method, the attenuator comprises a laser, the laser provides an incident light signal, the divergent incident light signal is converted into a collimated parallel light beam through a collimator, the collimated parallel light beam is subjected to deflection modulation through a multistage wedge-shaped liquid crystal box module, and the modulated light beam is converted into a modulated light beam; the multi-channel liquid crystal controller is coupled to the output optical fiber through the optical fiber coupler, and generates and outputs driving voltage signals capable of being independently adjusted to the N-stage wedge-shaped liquid crystal box module, so that each wedge-shaped liquid crystal box in the multi-stage wedge-shaped liquid crystal box module is independently controlled; the control method comprises the steps of receiving a target instruction, querying a system-level relationship, distributing a deflection task, querying a device-level relationship, outputting a driving signal and performing closed-loop feedback correction. According to the invention, a large attenuation range is obtained, and at the same time, millisecond-level and even sub-millisecond-level rapid response is realized; the precision, the linearity and the usability of attenuation control are improved, and the control complexity is reduced.

Description

Technical Field

[0001] This invention relates to dimmable light control, and more particularly to an electrically controlled dimmable light attenuator and attenuation control method based on a multi-stage wedge liquid crystal cell. Background Technology

[0002] Variable optical attenuators (VOAs) are indispensable key components in optical fiber communication networks, primarily responsible for the precise and dynamic management of power levels in optical channels. They play a crucial role in optical transmitter power control, channel equalization, receiver saturation prevention, optical performance monitoring, and system gain flattening. As optical networks evolve towards dynamic reconfiguration and intelligent flexibility, higher performance requirements are being placed on VOAs: faster response times, lower power consumption, higher reliability, more compact size, and lower polarization dependence. Traditional mechanically adjustable attenuators (such as MEMS types) achieve attenuation by physically moving light-blocking plates or changing fiber alignment. While technologically mature, they suffer from issues such as wear and tear on moving parts, poor shock resistance, and slow response times (typically above milliseconds). Thermo-optical VOAs utilize thermal effects to change the waveguide refractive index, but they have high power consumption, limited response speed, and are susceptible to environmental temperature fluctuations. Magneto-optical VOAs, based on the Faraday effect, require complex and stable magnetic field generators, resulting in high costs and difficulty in integration.

[0003] Liquid crystal-based VOAs (LC-VOA) have attracted widespread attention due to their advantages such as no moving parts, fully electronic control, low power consumption, and ease of integration. The closest existing technology to this invention is an adjustable optical attenuator based on a single wedge-shaped liquid crystal cell combined with a polarization-independent structure or directly used for beam deflection. Its core lies in utilizing the electrically controlled deflection characteristics of a single wedge-shaped liquid crystal cell to modulate the optical path. Although the above-mentioned scheme based on a single-stage wedge-shaped liquid crystal cell achieves electrically tunable attenuation without mechanical moving parts and has the potential to be insensitive to polarization, it has limitations: a limited deflection range and dynamic range. The maximum deflection angle that a single wedge-shaped liquid crystal cell can produce is limited by the birefringence range of the liquid crystal material and the maximum wedge difference in the cell thickness. To obtain a sufficiently large deflection angle, it may be necessary to increase the wedge angle or cell thickness difference, but this will bring problems in response speed, uniformity, or driving voltage, which limits the maximum attenuation dynamic range of the attenuator; the contradiction between response speed and cell thickness: the response time of liquid crystal is proportional to the square of the cell thickness. In order to obtain significant phase modulation or deflection effect, a certain cell thickness is required for a single stage, which severely restricts the response speed of the device and makes it difficult to meet the requirements of high-speed optical networks for fast power regulation; control accuracy and linearity: the deflection angle control of a single stage may require high voltage control accuracy, and the relationship between voltage, deflection angle and attenuation may be non-linear, increasing the difficulty of precise attenuation control; limited performance optimization space: the single-stage structure lacks flexibility in performance improvement. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an electrically controlled adjustable light attenuator based on a multi-stage wedge-shaped liquid crystal cell and an attenuation control method.

[0005] Technical Solution: The electrically controlled adjustable optical attenuator based on multi-stage wedge liquid crystal cells of the present invention is characterized by comprising a laser, a collimator, an N-stage wedge liquid crystal cell module, an optical fiber coupler, and a multi-channel liquid crystal controller; the laser provides an incident light signal, which is converted into a collimated parallel beam by the collimator, and the collimated parallel beam is deflected and modulated by the multi-stage wedge liquid crystal cell module, and coupled to the output optical fiber by the optical fiber coupler; the multi-channel liquid crystal controller generates and outputs an independently adjustable driving voltage signal to the N-stage wedge liquid crystal cell module, thereby independently controlling each wedge liquid crystal cell in the multi-stage wedge liquid crystal cell module.

[0006] Furthermore, the N-level wedge liquid crystal cell module is composed of multiple single-level wedge liquid crystal cells.

[0007] Furthermore, the single-stage wedge-shaped liquid crystal cell includes a substrate, spacers, an alignment layer, and a transparent electrode. There is a substrate at the top and bottom, and the spacers, alignment layer, and transparent electrode are arranged in the middle from top to bottom. The inner side of the spacers is configured as a nematic liquid crystal layer. The cell thickness is controlled by changing the wedge angle by using spacers of different sizes.

[0008] Furthermore, the transparent electrode is made of indium tin oxide material with a thickness of 100-200 nm, a sheet resistance of 20-50 Ω, and an electrode pattern that is a full-surface electrode.

[0009] Furthermore, the alignment layer is made of polyimide material and is treated with a friction alignment technique to give the liquid crystal molecules a pretilt angle of 2°-5°.

[0010] The electrically controlled adjustable light attenuation control method based on a multi-level wedge liquid crystal cell described in this invention includes the following steps:

[0011] (1) Upon receiving the target command, the control unit receives an externally input target attenuation value A from the communication interface. target ;

[0012] (2) Query the system-level relationship, calculate the total deflection angle, and the control unit accesses the lookup table or mathematical model pre-stored in the non-volatile memory. The lookup table stores the attenuation A and the required total deflection angle ∑Δθ. req The correspondence;

[0013] (3) Assign deflection tasks. The control unit runs the deflection task assignment algorithm and assigns the total deflection angle ∑Δθ obtained in step (2). req The N-stage wedge-shaped liquid crystal cells are decomposed and allocated to the cascaded structure.

[0014] (4) Query the device-level relationships, calculate the driving voltage, and the control unit accesses its memory again, which pre-stores the voltage-deflection angle relationship curve for each single-stage wedge liquid crystal cell; calculate the digital voltage value based on the voltage-deflection angle relationship curve.

[0015] (5) Output drive signal. The control unit, through its digital-to-analog converter channel, converts the calculated digital voltage values ​​[V1, V2, ..., V...] into digital voltage values ​​[V1, V2, ..., V...]. n Converted into a corresponding analog voltage signal;

[0016] (6) Closed-loop feedback correction: The closed-loop negative feedback system works continuously to ensure long-term high precision and stability of attenuation.

[0017] Further, step (2) includes:

[0018] (2.1) The relationship curve between the total deflection angle and the attenuation was obtained through experimental calibration: A = f(∑Δθ);

[0019] (2.2) The control unit uses A target Using an index, a search and interpolation calculation are performed in the lookup table to calculate the total beam deflection angle ∑Δθ required to achieve the desired attenuation. req ;

[0020] (2.3) A new key intermediate variable ∑Δθ is obtained. req And store it in memory.

[0021] Further, step (3) includes:

[0022] (3.1) Calculate a deflection angle combination (Δθ1, Δθ2, ..., Δθ) n ), such that Δθ1+Δθ2+...+Δθ n =∑Δθ req ;

[0023] (3.2) Select either balanced allocation or master-slave allocation based on the allocation strategy; Balanced allocation: Δθ n =∑Δθ req / N, where N is the number of stages in the wedge-shaped liquid crystal cell; master-slave allocation: the first M stages are set as coarse adjustment units, responsible for a large deflection range; the last NM stages are set as fine adjustment units, responsible for fine correction;

[0024] (3.3) A set of target deflection angle values ​​[Δθ1, Δθ2, ..., Δθ] is obtained. n ].

[0025] Furthermore, the voltage-deflection angle relationship in step (4) is: Δθ i =g i (V i ), i = 1, 2, ..., n, representing the number of liquid crystal cells, Δθ i V is the deflection angle. i For the applied voltage, g i () represents the deflection relationship; the control unit uses the assigned target deflection angle Δθ i Using the input as the reference, query the corresponding voltage-deflection curve and calculate the required voltage value V. i Finally, a set of digital voltage values ​​[V1, V2, ..., V] is obtained. n ].

[0026] Further, step (6) includes:

[0027] (6.1) Monitoring: The photodetector at the system output converts the optical power into an electrical signal in real time, which is then read back to the control unit via an analog-to-digital converter;

[0028] (6.2) Comparison: The control unit compares the read-back optical power value with A. target The corresponding expected optical power values ​​are compared to calculate the real-time error of the attenuation.

[0029] (6.3) Correction: The control unit uses a correction algorithm to generate a small voltage adjustment δV based on the real-time error in step (6.2). i ;

[0030] (6.4) Adjustment: Add the adjustment amount to the original output voltage, i.e., V inew =V i +δV i , and re-output.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0032] (1) By cascading multiple levels, the total deflection task is decomposed, breaking through the limitations of single-level structure on deflection angle and attenuation range, and achieving a larger dynamic range of attenuation.

[0033] (2) By adopting a multi-level thin box design, the total deflection requirement is distributed to N cascaded thin boxes, which solves the contradiction between large dynamic range and fast response speed. While obtaining a large attenuation range, it achieves a fast response at the millisecond or even sub-millisecond level.

[0034] (3) It provides a precise control mechanism that combines "coarse adjustment" and "fine adjustment". The previous stage can provide a large deflection step (coarse adjustment), and the later stage can provide fine deflection fine adjustment (fine adjustment). By digitally controlling the combination of voltages at each stage, the target deflection angle can be approximated more flexibly and linearly, thereby achieving high precision and high repeatability control of the attenuation and simplifying the control algorithm.

[0035] (4) The multi-level modular design brings great design flexibility. The deflection range and attenuation dynamic range can be easily expanded by adding or removing levels, and the overall performance can be customized and optimized according to different application scenarios. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of an electrically controlled tunable light attenuator based on a multi-stage wedge-shaped liquid crystal cell.

[0037] Figure 2 A schematic diagram of a single-stage wedge-shaped liquid crystal cell;

[0038] Figure 3 This is a schematic diagram illustrating the principle of beam deflection.

[0039] Figure 4 The flowchart shows a method for electrically controlled tunable light attenuation control based on a multi-stage wedge liquid crystal cell.

[0040] Figure 5 This is a structural diagram of a four-level two-dimensional deflection system;

[0041] Figure 6 This is a schematic diagram of the superposition of multiple deflection angles;

[0042] Figure 7 This is a structural diagram of a two-stage one-dimensional deflection system. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, the present invention includes a laser 1, a collimator 2, an N-stage wedge liquid crystal cell module 3, an optical fiber coupler 4, and a multi-channel liquid crystal controller 5. The laser 1 provides an incident light signal, which is converted into a collimated parallel beam by the collimator 2. The collimated parallel beam is deflected and modulated by the multi-stage wedge liquid crystal cell module 3 and coupled to the output optical fiber by the optical fiber coupler 4. The multi-channel liquid crystal controller 5 generates and outputs an independently adjustable driving voltage signal to the N-stage wedge liquid crystal cell module 3, thereby independently controlling each wedge liquid crystal cell in the multi-stage wedge liquid crystal cell module 3. The laser 1 provides an incident light signal and can be a DFB laser or other semiconductor laser. The collimator 2 converts the divergent beam output by the laser into a collimated parallel beam. The N-stage wedge liquid crystal cell module 3 is composed of N (N≥2) cascaded wedge liquid crystal cells, each of which is independently controlled. The optical fiber coupler 4 couples the deflected and modulated beam to the output optical fiber. The multi-channel liquid crystal controller 5 generates and outputs an independently adjustable driving voltage signal to each stage of the wedge liquid crystal cell.

[0045] like Figure 2 As shown, the N-level wedge liquid crystal cell module 3 is composed of multiple single-level wedge liquid crystal cells. Each single-level wedge liquid crystal cell includes a substrate 31, spacers 32, an alignment layer 33, and a transparent electrode 34. A substrate 31 is placed at the top and bottom, with spacers 32, alignment layer 33, and transparent electrode 34 arranged sequentially from top to bottom in the middle. A nematic liquid crystal layer 35 is set inside the spacers 32. The cell thickness is controlled by changing the wedge angle through spacers 32 of different sizes. The substrate structure consists of an upper planar substrate and a lower planar substrate. The transparent electrode is made of indium tin oxide (ITO) material with a thickness of 100-200 nm and a sheet resistance of 20-50 Ω. The electrode pattern is a full-surface electrode to ensure electric field uniformity. Alignment layer: Made of polyimide material, treated with tribo-alignment technology to create a pretilt angle of 2°-5° for the liquid crystal molecules; Liquid crystal material: Nematic liquid crystal, such as Merck's E7 series, with parameters: Δn = 0.22, Δε = 13.8, rotational viscosity γ1 = 0.2 Pa·s; Cell thickness control: The cell thickness (wedge angle) is controlled by changing the wedge angle by using spacers 32 of different sizes.

[0046] like Figure 3 The diagram illustrates the deflection principle of a light beam passing through a wedge-shaped liquid crystal cell. The physical mechanism of beam deflection involves independently controlling the voltage applied to each stage of the wedge-shaped liquid crystal cell to change the orientation of its liquid crystal molecules, thereby continuously adjusting its effective refractive index n. effDue to the wedge-shaped structure of the liquid crystal cell, the change in refractive index causes the emitted light beam to produce a controllable deflection angle Δθ.

[0047] Initial (maximum decay) state: When no voltage is applied to any of the liquid crystal cells (V=0), the liquid crystal molecules at each level are aligned parallel to the substrate, n eff =n e (Maximum value). The deflection angle Δθ generated at each stage at this point. i At its maximum, after multiple deflection stages are superimposed, the total deflection angle ∑Δθ reaches its maximum value, the beam deviates significantly from the fiber center, the coupling efficiency is lowest, and the attenuation is maximum; Operating (attenuation adjustment) state: when voltage is applied to each stage, the liquid crystal molecules begin to stand upright, n eff From n e To n o This decreases; this results in a deflection angle Δθ per stage. i (V) decreases accordingly. By precisely controlling the combination of voltages at each stage, the total deflection angle ∑Δθ can be precisely controlled to decrease from its maximum value downwards, causing the beam to gradually approach the optimal coupling angle of the optical fiber, thereby improving coupling efficiency and reducing attenuation; minimum attenuation state: when a saturation voltage is applied to all liquid crystal cells, the liquid crystal molecules are perpendicular to the substrate, n eff =n o (Minimum value). At this point, the total deflection angle ∑Δθ is at its minimum, the beam is closest to the ideal alignment state, the coupling efficiency is the highest, and the attenuation (insertion loss) is minimal. Therefore, through voltage control, continuous adjustment from maximum to minimum attenuation is achieved, and multi-stage cascading greatly expands the controllable range and accuracy of the total deflection angle. For example... Figure 6 As shown, the principle of superimposing multi-level deflection angles is demonstrated.

[0048] like Figure 4 As shown, the electrically controlled adjustable light attenuation control method based on a multi-level wedge liquid crystal cell according to the present invention includes the following steps:

[0049] (1) Upon receiving the target command, the control unit receives an externally input target attenuation value A from the communication interface. target ;

[0050] (2) Query the system-level relationship, calculate the total deflection angle, and the control unit accesses the lookup table or mathematical model pre-stored in the non-volatile memory. The lookup table stores the attenuation A and the required total deflection angle ∑Δθ. req The correspondence;

[0051] (2.1) The relationship curve between the total deflection angle and the attenuation was obtained by experimental calibration, which describes "how large the total deflection angle is needed to produce the corresponding attenuation".

[0052] (2.2) The control unit uses A targetUsing an index, a search and interpolation calculation are performed in the lookup table to calculate the total beam deflection angle ∑Δθ required to achieve the desired attenuation. req ;

[0053] (2.3) A new key intermediate variable ∑Δθ is obtained. req And store it in memory.

[0054] (3) Assign deflection tasks. The control unit runs the deflection task assignment algorithm and assigns the total deflection angle ∑Δθ obtained in step (2). req The N-stage wedge-shaped liquid crystal cells are decomposed and allocated to the cascaded structure.

[0055] (3.1) Calculate a deflection angle combination (Δθ1, Δθ2, ..., Δθ) n ), such that Δθ1+Δθ2+...+Δθ n =∑Δθ req ;

[0056] (3.2) Select either balanced allocation or master-slave allocation based on the allocation strategy; Balanced allocation: Δθ n =∑Δθ req / N, where N is the number of stages in the wedge-shaped liquid crystal cell; master-slave allocation: the first M stages are set as coarse adjustment units, responsible for a large deflection range; the last NM stages are set as fine adjustment units, responsible for fine correction;

[0057] (3.3) A set of target deflection angle values ​​[Δθ1, Δθ2, ..., Δθ] is obtained. n ].

[0058] Furthermore, the voltage-deflection angle relationship in step (4) is: Δθ i =g i (V i ), i = 1, 2, ..., n, representing the number of liquid crystal cells, Δθ i V is the deflection angle. i For the applied voltage, g i () represents the deflection relationship; the control unit uses the assigned target deflection angle Δθ i Using the input as the reference, query the corresponding voltage-deflection curve and calculate the required voltage value V. i Finally, a set of digital voltage values ​​[V1, V2, ..., V] is obtained. n ].

[0059] (4) Query the device-level relationship, calculate the driving voltage, and the control unit accesses its memory again, which contains the voltage-deflection angle relationship curve of each single-level wedge liquid crystal cell; calculate the digital voltage value based on the voltage-deflection angle relationship curve.

[0060] (5) Output drive signal. The control unit, through its digital-to-analog converter channel, converts the calculated digital voltage values ​​[V1, V2, ..., V...] into digital voltage values ​​[V1, V2, ..., V...]. n The electric field is converted into corresponding analog voltage signals. These analog voltage signals are amplified and buffered by a driving circuit (which may contain operational amplifiers) and then applied independently and in parallel to the electrodes of the corresponding wedge-shaped liquid crystal cell. Under the influence of the electric field, the liquid crystal cell begins to change molecular orientation, and the entire process is completed.

[0061] (6) Closed-loop feedback correction: The closed-loop negative feedback system works continuously to ensure long-term high precision and stability of the attenuation.

[0062] (6.1) Monitoring: The photodetector at the system output converts the optical power into an electrical signal in real time, which is then read back to the control unit via an analog-to-digital converter;

[0063] (6.2) Comparison: The control unit compares the read-back optical power value with A. target The corresponding expected optical power values ​​are compared to calculate the real-time error of the attenuation.

[0064] (6.3) Correction: The control unit uses a correction algorithm to generate a small voltage adjustment δV based on the real-time error in step (6.2). i ;

[0065] (6.4) Adjustment: Add the adjustment amount to the original output voltage, i.e., V inew =V i +δV i , and re-output.

[0066] Preferred implementation scheme

[0067] Example 1: Two-stage one-dimensional deflection system

[0068] like Figure 7 As shown, the implementation scheme of the two-level one-dimensional deflection system is illustrated.

[0069]

[0070] Level 1: Wedge angle θ1 = 1.5°, responsible for a large range of deflection (coarse adjustment).

[0071] Second level: Wedge angle θ2 = 0.5°, responsible for fine-tuning within a small range.

[0072] Response time: in milliseconds (including rise and fall times)

[0073] Example 2: Four-level two-dimensional deflection system

[0074] like Figure 5 As shown, the implementation scheme of a four-level two-dimensional deflection system is illustrated.

[0075]

[0076] Device 1: Laser

[0077] Component 2: Collimator

[0078] Device 3: LC box X1

[0079] Function: To achieve the first-stage deflection of the beam in the X direction.

[0080] Wedge orientation: The liquid crystal molecules are aligned (optical axis) along the X-axis, thus the resulting phase gradient is along the X-axis, causing the light beam to deflect in the XZ plane.

[0081] Control signal: determined by voltage V x1 Control the deflection amount.

[0082] Device 4: LC box Y1

[0083] Function: To achieve the first-stage deflection of the beam in the Y direction.

[0084] Wedge orientation: The liquid crystal molecules are aligned (optical axis) along the Y-axis, thus the resulting phase gradient is along the Y-axis, causing the light beam to deflect in the YZ plane.

[0085] Control signal: determined by voltage V y1 Control the deflection amount.

[0086] Device 5: LC box x2

[0087] Function: To achieve a second-order deflection of the beam in the X direction. It works in conjunction with device 1 (LC cell X1) to achieve polarization-independent X-direction deflection, and can superimpose the deflection angles to achieve a larger result.

[0088] Wedge direction: Same as device 1, along the X-axis.

[0089] Control signal: determined by voltage V x2 Control the deflection amount.

[0090] Device 6: LC box Y2

[0091] Function: To achieve the second-order deflection of the beam in the Y direction. It works in conjunction with device 2 (LC cell Y1) to jointly complete the polarization-independent Y-direction deflection, and can superimpose the deflection angles to achieve a larger result.

[0092] Wedge direction: Same as device 2, along the Y-axis.

[0093] Control signal: determined by voltage V y2

[0094] Control the deflection amount:

[0095] X-direction deflection: Levels 1 and 3, wedge-shaped direction along the X-axis

[0096] Y-direction deflection: Levels 2 and 4, wedge-shaped direction along the Y-axis

[0097] This multi-stage liquid crystal deflection system has the following advantages:

[0098] Polarization independent: It can efficiently handle incident light of any polarization state, which is key to its application in communication and laser systems; Two-dimensional large-angle deflection: Through multi-stage cascading, a much larger deflection angle can be achieved than a single stage; No moving mechanical parts: Deflection is entirely controlled by electrical signals, resulting in high speed, no wear, and long lifespan; Therefore, it is very suitable for the following scenarios: Multiple fiber port selection: By providing V {x1} V {y1} V {x2} V {y2} By applying different combinations of voltages, the laser beam can be precisely deflected to the end face of any fiber in the fiber array, enabling dynamic optical path switching.

[0099] Spatial optical coupling systems can be used for precise pointing and tracking of light beams in free-space optical communication, or for efficiently coupling light beams into single-mode optical fibers (precise alignment is required).

[0100] Workflow: After collimation, the laser beam becomes parallel light and passes sequentially through liquid crystal cells 1 to 4. The beam aligned with the orientation of the liquid crystal molecules, i.e., the e-beam, is modulated. Liquid crystal cells 1 and 3 modulate the e-beam on the X-axis component, while liquid crystal cells 2 and 4 modulate the e-beam on the Y-axis component. Ultimately, this results in a two-way beam deflection, where a beam is deflected separately along the X and Y axes. The system controls the four voltages (V... x1 V y1 V x2 V y2 Each beam is independently controlled in two dimensions to deflect the beam at a specific angle, ultimately coupling the beam precisely into a specific port of the fiber array.

[0101] To achieve unsplitting of a beam of light and deflection along both the X and Y axes, polarization dependence needs to be introduced. This means the light passing through the collimator needs to be processed by a polarization device, ensuring its polarization direction aligns with the orientation direction of liquid crystal cell 1.

[0102] In addition, compared to the previous scheme, the rubbing direction of liquid crystal cells 2 and 4 needs to be consistent with that of liquid crystal cells 1 and 3, but the direction of thickness change remains consistent with the previous scheme; this is to allow only e-light to be modulated, that is, only one beam of light changes.

[0103] Compared to the scheme in Example 1, in Example 2 the outgoing light does not split into two beams, but due to polarization dependence, there will be energy loss of the incident light and a decrease in coupling efficiency.

[0104] This invention decomposes the overall deflection task through multi-level cascading. Each level provides a deflection component Δθ. i N-order deflection angles can be superimposed (∑Δθ) i This allows for a total deflection range far exceeding that of a single-stage structure without significantly altering the single-stage material and geometric parameters, thereby achieving a larger attenuation dynamic range (e.g., >40dB).

[0105] A multi-level thin-box design is used to distribute the total deflection requirement to N cascaded thin boxes, each with a thickness d. multi Much smaller than the equivalent single-stage large box thickness d single (d multi <<d single Since τ∝d 2 The response speed of a single-stage thin box is much faster than that of a single-stage thick box. The total system response time is determined by the slowest stage, but it can still be kept at a very fast level (e.g., <10ms), successfully decoupling the coupling relationship between "large deflection" and "fast response".

[0106] The multi-stage cascaded architecture itself provides a precise control mechanism that combines "coarse adjustment" and "fine adjustment." Earlier stages can provide large deflection steps (coarse adjustment), while later stages can provide fine deflection adjustments (fine adjustment). By digitally controlling the combination of voltage stages, the target deflection angle can be approximated more flexibly and linearly, thereby achieving high-precision and high-repeatability control of attenuation and simplifying the control algorithm.

[0107] Multi-stage modular design offers tremendous design flexibility, allowing for easy expansion of deflection and attenuation dynamic range by adding or removing stages. Different materials or cell thicknesses can be selected for different stages of the liquid crystal cell to specifically optimize particular parameters (e.g., high-Δn liquid crystal is used in the front stage for wide-range deflection, while low-viscosity liquid crystal is used in the rear stage for rapid and fine adjustment). This flexibility is unmatched by single-stage fixed structures.

Claims

1. An electrically controlled variable optical attenuator based on a multi-stage wedge-shaped liquid crystal cell, characterized in that, It comprises a laser (1), a collimator (2), an N-stage wedge-shaped liquid crystal cell module (3), a fiber coupler (4) and a multi-channel liquid crystal controller (5); the laser (1) provides an incident light signal, the collimator (2) converts the divergent incident light signal into a collimated parallel light beam, the collimated parallel light beam is deflected and modulated by the multi-stage wedge-shaped liquid crystal cell module (3), and is coupled into an output optical fiber through the fiber coupler (4); the multi-channel liquid crystal controller (5) generates and outputs independently adjustable driving voltage signals to the N-stage wedge-shaped liquid crystal cell module (3), so as to independently control each wedge-shaped liquid crystal cell in the multi-stage wedge-shaped liquid crystal cell module (3).

2. The multi-stage wedge liquid crystal cell based electrically controlled variable optical attenuator according to claim 1, wherein, The N-stage wedge-shaped liquid crystal cell module (3) is composed of a plurality of single-stage wedge-shaped liquid crystal cells.

3. The electrically controlled variable optical attenuator based on a multi-stage wedge liquid crystal cell according to claim 2, characterized in that, The single-stage wedge-shaped liquid crystal cell comprises a substrate (31), a spacer (32), an alignment layer (33) and a transparent electrode (34), each of which is provided with a substrate (31) on the upper and lower sides, and the spacer (32), the alignment layer (33) and the transparent electrode (34) are sequentially arranged from top to bottom in the middle, the inner side of the spacer (32) is provided with a nematic liquid crystal layer (35), and the cell thickness is controlled by changing the wedge angle size through spacers (32) of different sizes.

4. An electrically controlled variable optical attenuator based on a multi-stage wedge liquid crystal cell according to claim 3, characterized in that, The transparent electrode (34) is made of indium tin oxide material, the thickness is 100-200 nm, the square resistance is 20-50 Ω, and the electrode pattern is a full-surface electrode.

5. An electrically controlled variable optical attenuator based on a multi-stage wedge liquid crystal cell according to claim 3, wherein, The alignment layer (33) is made of polyimide material, and the rubbing orientation technology is used to process the liquid crystal molecules to generate a pre-tilt angle of 2°-5°.

6. A method of electrically controlled adjustable optical attenuation control based on a multi-stage wedge liquid crystal cell, implemented by using the electrically controlled adjustable optical attenuator based on a multi-stage wedge liquid crystal cell according to any one of claims 1-5, characterized in that, It comprises the following steps: (1) receiving a target command, the control unit receives a target attenuation value A inputted from the communication interface target ; (2) Query the system level relationship, calculate the total deflection angle, the control unit accesses the pre-stored query table or mathematical model in the non-volatile memory, the query table stores the corresponding relationship between the attenuation A and the required total deflection angle ∑Δθ req ; (3) Distribute the deflection task, the control unit runs the deflection task distribution algorithm, the total deflection angle ∑Δθ obtained in step (2) is distributed to each deflection task of the N-level wedge-shaped liquid crystal cell in the cascade req decomposing the distribution to the N-stage wedge-shaped liquid crystal cell in the cascade (4) querying the device-level relationship, calculating the driving voltage, and the control unit accessing its memory again, in which the voltage-deflection angle relationship curve of each single-stage wedge-shaped liquid crystal cell is pre-stored; According to the voltage-deflection angle relationship curve, the digital voltage value is calculated (5) an output drive signal, through which the control unit converts the calculated digital voltage values [V1, V2,..., Vn] into corresponding analog voltage signals via its digital-to-analog converter channel; n ] into corresponding analog voltage signals via its digital-to-analog converter channel; (6) closed-loop feedback correction, the closed-loop negative feedback system continuously works to ensure long-term high precision and stability of the attenuation amount.

7. A method of electrically controlling the light attenuation control of a multi-stage wedge liquid crystal cell based on claim 6, characterized in that, The step (2) comprises: (2.1) obtaining the relationship curve A=f(∑Δθ) between the total deflection angle and the attenuation amount through experimental calibration; (2.2) The control unit calculates the total beam deflection angle ∑Δθ required to achieve the desired attenuation amount A target req ;​ (2.3) a new key intermediate variable ∑Δθ is obtained req and stored in memory.

8. The method of electrically controlled adjustable optical attenuation control based on a multi-stage wedge liquid crystal cell according to claim 6, characterized in that, The step (3) comprises: (3.1) a set of deflection angles (Δθ1, Δθ2,..., Δθ n ) is calculated such that Δθ1+ Δθ2+... + Δθ n =∑Δθ req ; (3.2) According to the distribution strategy, choose equal distribution or master-slave distribution; Equal distribution: Δθ n =∑Δθ req / N, N is the number of wedge-shaped liquid crystal cell; Master-slave distribution: Set the first M stages as coarse adjustment unit, responsible for large deflection range; The last N-M stages are fine adjustment unit, responsible for fine correction; (3.3) a set of target values of the deflection angle [Δθ1, Δθ2,..., Δθ n ] is obtained.

9. The method of controlling the electrically adjustable optical attenuation of a multistage wedge liquid crystal cell according to claim 6, wherein, The step (4) voltage-deflection angle relationship is: Δθ i = g i (V i ), i = 1, 2,..., n, represents the number of liquid crystal boxes, Δθ i is the deflection angle, V i is the applied voltage, g i () is the deflection relationship; the control unit inputs the target deflection angle Δθ i assigned, queries its corresponding voltage-deflection curve, and inversely calculates the voltage value V i to be applied; finally a set of digital voltage values [V1, V2,..., V n ] is obtained.

10. The method of controlling the electrically adjustable optical attenuation based on the multistage wedge-shaped liquid crystal cell according to claim 6, characterized in that, The step (6) comprises: (6.1) monitoring: the photodetector at the output end of the system converts the optical power into an electrical signal in real time, which is read back to the control unit through an analog-to-digital converter; (6.2) comparison: the control unit compares the read-back optical power value with A target The corresponding expected optical power values are compared and the real-time error of the attenuation amount is calculated; (6.3) Correction: The control unit employs a correction algorithm to generate a small voltage adjustment δV from the real-time error of step (6.2) i ; (6.4) Adjustment: The adjustment amount is added to the original output voltage, i.e. V inew = V i + δV i and output again.

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