A method and apparatus for controlling the delay of long optical fibers

Abstract

This invention discloses a method for controlling the delay of long optical fibers. The invention tightly winds long optical fibers into a barrel-shaped fiber loop and controls a temperature control element located at the bottom of the fiber loop using a dual PID temperature control method: First, a first PID controller is used to precisely control the temperature control element, configured with an overshoot of 15±5℃ relative to the target temperature, allowing the fiber delay of the fiber loop to be quickly controlled to a stable state; then, a second PID controller is used to perform temperature compensation control on the temperature control element, compensating for changes in the ambient monitored temperature and ensuring that the monitored temperature inside the fiber loop closely tracks the compensated target temperature. This invention also discloses a long optical fiber delay control device. Compared to existing technologies, this invention not only achieves rapid control of optical fiber delay but also achieves stable delay over a wide temperature range, while also possessing advantages such as small size, low cost, and simple control structure.

Description

Technical Field

[0001] This invention relates to a method and apparatus for controlling the delay of long optical fibers. Background Technology

[0002] As an essential material in the field of optics, the stability of optical fibers is a crucial factor for practical engineering applications. Controlling fiber stability primarily involves controlling the actual optical path length, which is mainly affected by changes in the fiber's refractive index and its physical elongation. Among the many factors influencing the fiber's refractive index, temperature and vibration have the most significant impact. Therefore, temperature control of optical fibers is an indispensable aspect of their engineering applications.

[0003] In the field of temperature control, high efficiency and good real-time performance are crucial factors. PID control, with its strong stability and real-time performance, has been widely used in temperature control systems, such as PID temperature control in fiber optic gyroscopes. However, PID control still has its limitations for fiber optic temperature control. For example, PID parameters are difficult to select, and improper selection can lead to a series of problems such as excessive overshoot, excessively long temperature control time, and slow heating rate. Moreover, a single PID temperature control cannot compensate for temperature changes in the real-time environment of the fiber optic cable.

[0004] Temperature compensation is another challenge in fiber optic delay control. In engineering applications, temperature compensation is a crucial factor that researchers must consider. Current temperature compensation methods primarily rely on establishing compensation optimization models. With technological advancements, solutions such as BP neural network-based temperature compensation models, chaotic particle swarm optimization theory, and RBF neural network error estimation have been proposed to address the temperature compensation problem. However, these methods are complex and difficult to adapt to engineering applications. Therefore, a temperature control method capable of rapid temperature control of long optical fibers and real-time feedback compensation to ambient temperature is urgently needed. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of existing long fiber delay control technology based on temperature control, and to provide a long fiber delay control method that can not only achieve rapid control of fiber delay, but also achieve fiber delay stability over a wide temperature range. At the same time, it also has the advantages of small size, low cost and simple control structure.

[0006] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0007] A method for controlling the delay of long optical fibers involves tightly winding long optical fibers into a barrel-shaped fiber loop and controlling a temperature control element located at the bottom of the fiber loop using a dual PID temperature control method to achieve delay control of the long optical fiber: First, a first PID controller is used to precisely control the temperature control element, configured to have an overshoot of 15±5℃ relative to the target temperature, so that the fiber delay of the fiber loop is quickly controlled to a stable state; then, a second PID controller is used to perform temperature compensation control on the temperature control element, compensating for the target temperature based on changes in the ambient monitored temperature, and ensuring that the monitored temperature inside the fiber loop closely tracks the compensated target temperature.

[0008] Furthermore, the barrel-shaped fiber optic ring and the temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

[0009] Furthermore, a first temperature sensor located on the upper surface inside the fiber optic ring is used to obtain the monitoring temperature inside the fiber optic ring, and a second temperature sensor located on the outer surface of the high-insulation thermal insulation material is used to obtain the ambient monitoring temperature.

[0010] Based on the same inventive concept, the following technical solutions can also be obtained:

[0011] A long fiber delay control device, comprising:

[0012] An optical fiber loop is formed by tightly winding long optical fibers into a barrel shape.

[0013] A temperature control element is located at the bottom of the fiber optic ring;

[0014] A control unit is used to perform dual PID temperature control on the temperature control element to achieve delay control of the long optical fiber. The control unit includes a first PID controller and a second PID controller. During temperature control, the first PID controller is first used to precisely control the temperature control element. The first PID controller is configured to have an overshoot of 15±5℃ relative to the target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state. Then, the second PID controller is used to perform temperature compensation control on the temperature control element, compensating for the target temperature according to the change in the ambient monitored temperature, and ensuring that the monitored temperature inside the optical fiber ring closely tracks the compensated target temperature.

[0015] Furthermore, the barrel-shaped fiber optic ring and the temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

[0016] Furthermore, the long fiber delay control device also includes:

[0017] The first temperature sensor is located on the upper surface inside the fiber optic ring to acquire the monitoring temperature inside the fiber optic ring; the second temperature sensor is located on the outer surface of the high-insulation material to acquire the ambient monitoring temperature.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] This invention achieves a more compact and smaller structure for the entire long optical fiber delay control device by tightly winding long optical fibers into a barrel-shaped fiber ring and placing a temperature control element at the bottom of the fiber ring. Simultaneously, based on the temperature field distribution characteristics of this fiber ring structure, a dual PID temperature control scheme is designed: one PID control is used for precise temperature control at the front end, employing PID overshoot to quickly bring the long optical fiber delay to a stable state, turning the disadvantage of PID overshoot into an advantage, saving power consumption, and accelerating the fiber stabilization process; the other PID control is used for real-time compensation for the impact of ambient temperature fluctuations after the long optical fiber temperature has stabilized. Compared to existing long optical fiber temperature control schemes, this invention offers faster delay control, a wider controllable temperature range, and a simple and easy-to-implement PID control method with low implementation cost, making it highly practical. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a specific embodiment of the long fiber delay control device of the present invention;

[0021] Figure 2 This is a schematic diagram of the control structure of a dual PID temperature control system;

[0022] Figure 3 The graph shows the change of the corresponding fiber length over time in a conventional PID temperature control without PID overshoot.

[0023] Figure 4 The graph shows the change of fiber length over time in PID temperature control with added PID overshoot.

[0024] Figure 5 This is a cross-sectional view of a single-layer fiber optic ring at a certain cross-section.

[0025] Figure 6 A simplified schematic diagram of the temperature field distribution in the fiber optic ring. Detailed Implementation

[0026] In optical fiber delay control, the relationship between optical fiber delay τ and optical fiber length L can be expressed as:

[0027]

[0028] In the formula, n is the refractive index of the optical fiber at the current ambient temperature, and c is the speed of light.

[0029] The relationship between the refractive index n of the optical fiber and the change in ambient temperature ΔT can be simply expressed as:

[0030] n=n0+γΔT (2)

[0031] In the formula, n is the refractive index of the optical fiber at the current temperature, n0 is the refractive index of the optical fiber at the initial temperature, γ is the influence coefficient of temperature on the refractive index of the optical fiber, and ΔT=T-T0 represents the temperature difference between the current temperature value and the initial temperature value.

[0032] Therefore, in environments with changing temperatures, the refractive index of optical fibers will be affected by temperature, which in turn will affect the fiber delay. Thus, controlling the delay of optical fibers requires first controlling the temperature of the optical fibers.

[0033] Existing single-PID fiber optic temperature control schemes suffer from problems such as excessively long temperature control time and slow heating rate, and cannot achieve temperature compensation control. On the other hand, existing temperature compensation control schemes based on BP neural network temperature compensation models, chaotic particle swarm optimization theory, and RBF neural network error estimation have the disadvantages of system complexity, high implementation difficulty, and high system cost.

[0034] To address the aforementioned issues, the present invention proposes a solution by tightly winding long optical fibers into a barrel-shaped fiber loop and placing a temperature control element at the bottom of the fiber loop. This results in a more compact and smaller overall structure for the long optical fiber delay control device. Furthermore, based on the temperature field distribution characteristics of this fiber loop structure, a dual PID temperature control scheme is designed: one PID control path is used for precise temperature control at the front end, employing PID overshoot to quickly bring the long optical fiber temperature to a stable state, turning the disadvantage of PID overshoot into an advantage, saving power consumption, and accelerating the fiber temperature stabilization process; the other PID control path is used for real-time compensation for the impact of ambient temperature fluctuations after the long optical fiber temperature has stabilized.

[0035] The long fiber delay control method proposed in this invention is as follows:

[0036] Long optical fibers are tightly wound into a barrel-shaped fiber loop, and a temperature control element located at the bottom of the fiber loop is controlled using the following dual PID temperature control method to achieve delay control of the long optical fiber: First, a first PID controller is used to precisely control the temperature control element. The first PID controller is configured to have an overshoot of 15±5℃ relative to the target temperature, so that the fiber delay of the fiber loop is quickly controlled to a stable state; then, a second PID controller is used to perform temperature compensation control on the temperature control element, compensating for the target temperature according to the change in the ambient monitored temperature, and ensuring that the monitored temperature inside the fiber loop closely tracks the compensated target temperature.

[0037] Furthermore, the barrel-shaped fiber optic ring and the temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

[0038] Furthermore, a first temperature sensor located on the upper surface inside the fiber optic ring is used to obtain the monitoring temperature inside the fiber optic ring, and a second temperature sensor located on the outer surface of the high-insulation thermal insulation material is used to obtain the ambient monitoring temperature.

[0039] The long fiber delay control device proposed in this invention includes:

[0040] An optical fiber loop is formed by tightly winding long optical fibers into a barrel shape.

[0041] A temperature control element is located at the bottom of the fiber optic ring;

[0042] A control unit is used to perform dual PID temperature control on the temperature control element to achieve delay control of the long optical fiber. The control unit includes a first PID controller and a second PID controller. During temperature control, the first PID controller is first used to precisely control the temperature control element. The first PID controller is configured to have an overshoot of 15±5℃ relative to the target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state. Then, the second PID controller is used to perform temperature compensation control on the temperature control element, compensating for the target temperature according to the change in the ambient monitored temperature, and ensuring that the monitored temperature inside the optical fiber ring closely tracks the compensated target temperature.

[0043] Furthermore, the barrel-shaped fiber optic ring and the temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

[0044] Furthermore, the long fiber delay control device also includes:

[0045] The first temperature sensor is located on the upper surface inside the fiber optic ring and is used to obtain the monitoring temperature inside the fiber optic ring.

[0046] The second temperature sensor is installed on the outer surface of the high-insulation material to obtain the ambient temperature.

[0047] In the above technical solutions, the fiber optic ring can be wound in a single-layer or multi-layer manner depending on the actual length of the long optical fiber, space constraints, and other conditions; the temperature control element can be flexibly selected from electrothermal films, semiconductor temperature control elements, etc., depending on the specific target temperature, actual ambient temperature, and cost.

[0048] To facilitate public understanding, the technical solution of the present invention will be described in detail below through a specific embodiment and in conjunction with the accompanying drawings:

[0049] The structure of the long fiber delay control device in this embodiment is as follows: Figure 1 As shown, a long optical fiber is tightly wound into a barrel-shaped fiber ring with one or more layers. A heating film is placed at the bottom of the fiber ring. The fiber ring and the heating film are placed inside an aluminum box with good thermal conductivity. The gaps inside the aluminum box are filled with a high thermal conductivity filling material, and the outside of the aluminum box is wrapped with a high thermal insulation material. A first temperature sensor is set on the upper surface inside the fiber ring to obtain the monitoring temperature inside the fiber ring. A second temperature sensor is set on the outer surface of the high thermal insulation material to obtain the ambient monitoring temperature. A control component (not shown in the figure) is connected to the power drive module of the heating film, and the temperature of the fiber ring is controlled by controlling the driving power of the heating film.

[0050] To achieve low-cost, rapid temperature control and wide-temperature-range temperature compensation control, the control component of this invention employs, as follows: Figure 2 The dual PID temperature control structure shown uses two parallel PID controllers to form a PID precision temperature control system and a PID temperature compensation control system. During temperature control, the PID precision temperature control system first uses the feedback temperature from the first temperature sensor to precisely control the temperature control element. This system is configured with an overshoot of 15±5℃ relative to the target temperature, allowing the fiber optic delay of the fiber optic ring to quickly stabilize. Then, based on the feedback temperature from the first temperature sensor and the ambient temperature changes reported by the second temperature sensor, the PID temperature compensation control system performs temperature compensation control on the temperature control element. It compensates for the target temperature based on changes in the monitored ambient temperature, ensuring that the monitored temperature inside the fiber optic ring closely tracks the compensated target temperature.

[0051] In the initial PID precise temperature control process, the fiber optic cable needs to reach a stable state quickly. However, during the heating process, there is a significant time delay between the measured stable temperature state and the stable state of the fiber optic cable. Figure 3 It can be seen that when the temperature begins to stabilize, the fiber optic cable is still in a state of rapid elongation and requires a considerable amount of time to reach a stable state. This time is very disadvantageous in practical applications, so reducing the stabilization time requires improvements to the temperature control program. In this invention, since the temperature control uses PID feedback control, the temperature curve will have an overshoot due to the presence of the I value during actual temperature control. This overshoot is usually an unwanted process in PID control and typically needs to be smoothed out through optimization. However, in the temperature control process of the fiber optic ring of this invention, due to the delay between the fiber optic cable and the temperature, this overshoot curve becomes particularly important for rapid control of the fiber optic delay. Therefore, this invention takes the opposite approach, deliberately increasing the overshoot in the first half of the temperature control process. Extensive experiments have shown that the optimal overshoot is 15±5℃. Within this overshoot time, the full-power output time of the power drive is longer, which can compensate for the delay in the fiber optic ring temperature, thereby achieving rapid stabilization of the fiber optic ring. Figure 4 As shown, after the fiber optic ring undergoes PID temperature overshoot, compared to... Figure 3 In the non-overshooting fiber elongation process, the overshooting system exhibits a significantly faster and more stable control effect. This invention cleverly transforms the overshoot process—a process that traditionally requires suppression in PID control—into an advantage in fiber optic ring temperature control, greatly accelerating the delay stabilization process of the fiber optic ring.

[0052] After precise temperature control of the fiber optic ring, this invention provides temperature compensation control for internal temperature changes under external environmental temperature disturbances after the temperature field has stabilized. This enables the fiber optic ring to quickly compensate for temperature fluctuations under external environmental temperature disturbances, ensuring stable delay and preventing external interference. The temperature compensation control principle is explained in detail below:

[0053] like Figure 5 As shown, for a single-layer optical fiber, the number of turns N can be expressed as:

[0054]

[0055] D is the diameter of a single optical fiber, r1 is the inner diameter of the fiber loop, and r2 is the outer diameter of the fiber loop.

[0056] Total length L of a single-layer fiber optic ring c This can be expressed as:

[0057]

[0058] Since the refractive index of the fiber optic loop changes at different temperatures, this change in refractive index affects the actual optical path length L that light travels in the fiber optic loop. cx It will change. The actual optical path can be expressed as:

[0059]

[0060] In the above formula, L c n is the total length of a single-layer fiber optic ring. x is the refractive index of the optical fiber at the current temperature.

[0061] like Figure 6 As shown, the height of the device is h, the temperature value of the upper surface measuring point is T1, and the temperature value of the lower surface measuring point is T0. s Let n be the temperature value at a certain height s in an optical fiber loop device with height h. s Let T be the refractive index of the optical fiber at that temperature. Since the initial simulation of the device model showed that the internal temperature field was a linear temperature change process, and due to uniform heating at the bottom, the temperature decreased uniformly with increasing height. Therefore, the temperature value T at height x is... x The refractive index n(x) can be expressed by the following equations:

[0062]

[0063] n(x)=n s +[T x -T s ]·k (7)

[0064] In the formula, k is a constant representing the influence coefficient of temperature on the refractive index of the fiber ring.

[0065] From the above formula, the actual optical path length of light in a single-layer fiber ring at height x can be obtained as follows:

[0066]

[0067] For the entire fiber optic ring delay control device with height h, since the diameter of each fiber is D, the number of layers i in the entire fiber optic ring is:

[0068]

[0069] Then the number of fiber layers m at height x can be expressed as:

[0070] x=m·D (10)

[0071] Therefore, the actual optical path L that light travels within the entire fiber optic loop is... sum for:

[0072]

[0073]

[0074] In a practical device, since h >> D, we can obtain Therefore, the actual optical path L that light travels within the entire fiber optic loop is... sum It can be written as:

[0075]

[0076] The final actual optical path length within the fiber optic ring is:

[0077]

[0078] To maintain the insensitivity of the fiber optic loop delay control device to external temperature changes, due to T s The temperature is taken at any given altitude; it is a constant. Therefore, as long as T0 + T1 in the above formula is a constant value, L can be guaranteed. sum The constancy of.

[0079] Therefore, the target temperature can be compensated based on the change in ambient temperature collected by the second temperature sensor, and the internal temperature of the fiber optic ring collected by the first temperature sensor can be used as feedback. The power of the heating film can be controlled by the PID temperature compensation control system, so that the monitored temperature inside the fiber optic ring closely tracks the compensated target temperature, thus achieving stable time-delay temperature compensation.

[0080] The long fiber delay control device of the present invention has the advantages of fast and accurate temperature control, simple structure, small size and low cost, and can be widely used in devices with high requirements for fiber delay, such as optoelectronic oscillators and fiber optic gyroscopes.

Claims

1. A method for controlling the delay of long optical fibers, characterized in that, Long optical fibers are tightly wound into a barrel-shaped fiber loop, and a temperature control element located at the bottom of the fiber loop is controlled using the following dual PID temperature control method to achieve delay control of the long optical fiber: First, a first PID controller is used to precisely control the temperature control element. The first PID controller is configured to have an overshoot of 15±5℃ relative to the target temperature, so that the fiber delay of the fiber loop is quickly controlled to a stable state; then, a second PID controller is used to perform temperature compensation control on the temperature control element: the target temperature is compensated based on the change in the ambient monitored temperature. The collected internal monitored temperature of the fiber loop is used as feedback, and the second PID controller performs temperature compensation control on the temperature control element, so that the monitored temperature inside the fiber loop closely tracks the compensated target temperature.

2. The long fiber delay control method as described in claim 1, characterized in that, The barrel-shaped fiber optic ring and temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

3. The long fiber delay control method as described in claim 2, characterized in that, The monitoring temperature inside the fiber optic ring is obtained using a first temperature sensor located on the upper surface inside the fiber optic ring, and the ambient monitoring temperature is obtained using a second temperature sensor located on the outer surface of the high-insulation thermal insulation material.

4. A long fiber delay control device, characterized in that, include: An optical fiber loop is formed by tightly winding long optical fibers into a barrel shape. A temperature control element is located at the bottom of the fiber optic ring; A control unit is used to perform dual PID temperature control on the temperature control element to achieve delay control of the long optical fiber. The control unit includes a first PID controller and a second PID controller. During temperature control, the first PID controller is first used to precisely control the temperature control element. The first PID controller is configured to have an overshoot of 15±5℃ relative to the target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state. Then, the second PID controller is used to perform temperature compensation control on the temperature control element: the target temperature is compensated according to the change in the ambient monitored temperature. The monitored temperature inside the optical fiber ring is used as feedback, and the second PID controller performs temperature compensation control on the temperature control element, so that the monitored temperature inside the optical fiber ring closely tracks the compensated target temperature.

5. The long fiber delay control device as described in claim 4, characterized in that, The barrel-shaped fiber optic ring and temperature control element are encapsulated in a shell of high thermal conductivity material, and the internal gaps are filled with high thermal conductivity filler material; the shell of high thermal conductivity material is wrapped with high thermal insulation material.

6. The long fiber delay control device as described in claim 5, characterized in that, Also includes: The first temperature sensor is located on the upper surface inside the fiber optic ring and is used to obtain the monitoring temperature inside the fiber optic ring. The second temperature sensor is installed on the outer surface of the high-insulation material to obtain the ambient temperature.

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