Long optical fiber delay control method and device

Abstract

The invention discloses a long optical fiber delay control method. A long optical fiber is tightly wound into a barrel-shaped optical fiber ring, and a temperature control element arranged at the bottom of the optical fiber ring is controlled through the following dual PID temperature control method: firstly, a first PID controller is used for accurately controlling the temperature control element, and the first PID controller is configured to have overshoot of 15 + / -5 DEG C with the target temperature; the optical fiber delay of the optical fiber ring is quickly controlled to a stable state; and then a second PID controller is used to carry out temperature compensation control on the temperature control element, the target temperature is compensated according to the variation of the environment monitoring temperature, and the monitoring temperature in the optical fiber ring closely tracks the compensated target temperature. The invention further discloses a long optical fiber delay control device. Compared with the prior art, the optical fiber delay control device not only can realize rapid control of optical fiber delay, but also can realize delay stability of the optical fiber in a large temperature range, and has the advantages of small size, low cost and simple control structure.

Description

Technical Field

[0001] The invention relates to a long optical fiber delay control method and device. Background Art

[0002] As an essential material in the field of optics, the stability of optical fiber is a crucial factor in practical engineering applications. The control of optical fiber stability mainly lies in the control of the actual optical path of the optical fiber, which is mainly affected by the change of the optical fiber refractive index and the physical elongation of the optical fiber. Among the many factors that affect the refractive index of the optical fiber, temperature and vibration have the most important influence. Therefore, temperature control of optical fiber is an indispensable part of optical fiber in engineering applications.

[0003] For the field of temperature control, high efficiency and good real-time performance are very important factors. PID control has been widely used in temperature control systems due to its strong stability and real-time performance, such as PID temperature control used in fiber optic gyroscopes. However, for fiber optic temperature control, PID control still has its own shortcomings. For example, PID parameters are difficult to select, and unreasonable selection will cause a series of problems such as large overshoot, too long temperature control time, and too slow heating speed. Moreover, for the temperature field changes of optical fibers in real-time environments, a single PID temperature control cannot achieve temperature compensation adjustment.

[0004] Temperature compensation is another difficulty in controlling optical fiber delay. When optical fiber is used in engineering applications, temperature compensation is a factor that researchers must consider. The current temperature compensation method is to perform temperature compensation by establishing a compensation optimization model. With the development of technology, temperature compensation models based on BP neural networks, chaotic particle swarm optimization theory, RBF neural network estimation errors and other solutions have been proposed to solve the problem of temperature compensation. However, the above methods are relatively complex and difficult to mismatch in engineering application scenarios. Therefore, there is an urgent need for a temperature control method that can achieve rapid temperature control of long optical fibers and realize real-time feedback compensation for ambient temperature. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing long optical fiber delay control technology based on temperature control, and to provide a long optical fiber delay control method, which can not only realize the rapid control of optical fiber delay, but also realize the delay stability of optical fiber in a large temperature range, and at the same time 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 technical problems:

[0007] A method for controlling the delay of a long optical fiber, wherein a long optical fiber is tightly wound into a barrel-shaped optical fiber ring, and a temperature control element arranged at the bottom of the optical fiber ring is controlled by the following dual PID temperature control method to achieve the delay control of the long optical fiber: first, a first PID controller is used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with a target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state; then a second PID controller is used to perform temperature compensation control on the temperature control element, and the target temperature is compensated according to the change in the environmental monitoring temperature, so that the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature.

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

[0009] Furthermore, a first temperature sensor disposed on the inner upper surface of the optical fiber ring is used to obtain the monitoring temperature inside the optical fiber ring, and a second temperature sensor disposed on the outer surface of the high thermal insulation material is used to obtain the environmental monitoring temperature.

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

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

[0012] Fiber optic loops, formed by tightly winding a long optical fiber into a barrel shape;

[0013] A temperature control element is arranged at the bottom of the optical fiber ring;

[0014] A control component is used to perform dual PID temperature control on a temperature control element to achieve delay control of the long optical fiber; the control component includes a first PID controller and a second PID controller; when performing temperature control, the first PID controller is first used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with 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 environmental monitoring temperature, and the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature.

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

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

[0017] The first temperature sensor is arranged on the upper surface of the fiber optic ring to obtain the monitoring temperature inside the fiber optic ring; the second temperature sensor is arranged on the outer surface of the high thermal insulation material to obtain the environmental monitoring temperature.

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

[0019] The present invention makes the structure of the entire long optical fiber delay control device more compact and smaller in size by tightly winding a long optical fiber into a barrel-shaped optical fiber ring and arranging a temperature control element at the bottom of the optical fiber ring; at the same time, according to the temperature field distribution characteristics of the optical fiber ring with this structure, a dual PID temperature control scheme is designed for it: one PID control is used for precise temperature control of the front section, and PID overshoot is used to make the long optical fiber delay quickly reach a stable state, which converts the disadvantage of PID's easy overshoot into an advantage, saves power consumption, and speeds up the stabilization process of the optical fiber; the other PID is used for real-time compensation of the influence of ambient temperature when the ambient temperature fluctuates after the temperature of the long optical fiber is stabilized; compared with various existing long optical fiber temperature control schemes, the present invention has a faster delay control speed, a wider controllable temperature range of the delay, a simple and easy-to-implement PID control method, a low implementation cost, and great practical value. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0022] Figure 3 This is a diagram showing the change of the corresponding optical fiber length over time in conventional PID temperature control without PID overshoot;

[0023] Figure 4 This is a diagram showing the change of the corresponding optical fiber length over time in the PID temperature control with PID overshoot;

[0024] Figure 5 A cross-sectional view of a single-layer optical fiber ring at a certain cross section of the optical fiber ring;

[0025] Figure 6 This is a simplified schematic diagram of the temperature field distribution of the optical fiber ring. DETAILED DESCRIPTION

[0026] In the delay control of optical fiber, the relationship between the optical fiber delay τ and the 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 fiber refractive index n and the current ambient temperature change 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 an environment with changing temperature, the refractive index of the optical fiber will be affected by the temperature, and thus the optical fiber delay will also be affected. Therefore, to control the delay of the optical fiber, the temperature of the optical fiber must be controlled first.

[0033] The existing single PID fiber optic temperature control solution has problems such as too long temperature control time and too slow heating speed, and it is impossible to achieve temperature compensation control; while the existing temperature compensation control solutions such as BP neural network-based temperature compensation model, chaotic particle swarm optimization theory, and RBF neural network estimation error have the disadvantages of complex system, great implementation difficulty, and high system cost.

[0034] To solve the above problems, the solution of the present invention is to tightly wind the long optical fiber into a barrel-shaped optical fiber ring and set a temperature control element at the bottom of the optical fiber ring, so that the structure of the entire long optical fiber delay control device is more compact and the volume is smaller; at the same time, according to the temperature field distribution characteristics of the optical fiber ring of this structure, a dual PID temperature control scheme is designed for it: one PID control is used for precise temperature control of the front section, and PID overshoot is used to make the temperature of the long optical fiber quickly reach a stable state, turning the disadvantage of PID's easy overshoot into an advantage, saving power consumption, and accelerating the stabilization process of the optical fiber temperature; the other PID is used for real-time compensation of the influence of ambient temperature when the ambient temperature fluctuates after the temperature of the long optical fiber is stabilized.

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

[0036] A long optical fiber is tightly wound into a barrel-shaped optical fiber ring, and a temperature control element arranged at the bottom of the optical fiber ring is controlled by the following dual PID temperature control method to achieve delay control of the long optical fiber: first, a first PID controller is used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with the target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state; then a second PID controller is used to perform temperature compensation control on the temperature control element, and the target temperature is compensated according to the change of the environmental monitoring temperature, so that the monitored temperature inside the optical fiber ring closely tracks the compensated target temperature.

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

[0038] Furthermore, a first temperature sensor disposed on the inner upper surface of the optical fiber ring is used to obtain the monitoring temperature inside the optical fiber ring, and a second temperature sensor disposed on the outer surface of the high thermal insulation material is used to obtain the environmental monitoring temperature.

[0039] The long optical fiber delay control device proposed by the present invention comprises:

[0040] Fiber optic loops, formed by tightly winding a long optical fiber into a barrel shape;

[0041] A temperature control element is arranged at the bottom of the optical fiber ring;

[0042] A control component is used to perform dual PID temperature control on a temperature control element to achieve delay control of the long optical fiber; the control component includes a first PID controller and a second PID controller; when performing temperature control, the first PID controller is first used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with 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 environmental monitoring temperature, and the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature.

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

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

[0045] A first temperature sensor is disposed on the upper surface of the optical fiber ring and is used to obtain a monitoring temperature inside the optical fiber ring;

[0046] The second temperature sensor is arranged on the outer surface of the high thermal insulation material and is used to obtain the environmental monitoring temperature.

[0047] In the above technical solution, the fiber optic ring can be wound in a single-layer or multi-layer manner according to the actual length of the long optical fiber, space limitations and other conditions; the temperature control element can flexibly select electric heating film, semiconductor temperature control element, etc. according to the specific target temperature, actual ambient temperature and cost.

[0048] In order to facilitate public understanding, the technical solution of the present invention is described in detail below through a specific embodiment and in conjunction with the accompanying drawings:

[0049] The structure of the long optical 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 optical fiber ring with a single layer or multiple layers, and a heating thermal film is arranged at the bottom of the optical fiber ring; the optical fiber ring and the heating thermal film are placed in an aluminum box which is a good thermal conductor, the gap in the aluminum box is 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 arranged on the upper surface of the inner part of the optical fiber ring, and is used to obtain the monitoring temperature inside the optical fiber ring; a second temperature sensor is arranged on the outer surface of the high thermal insulation material, and is used to obtain the environmental monitoring temperature; a control component (not shown in the figure) is connected to a power driving module of the heating thermal film, and the temperature of the optical fiber ring is controlled by controlling the driving power of the heating thermal film.

[0050] In order to realize low-cost rapid temperature control and temperature compensation control over a wide temperature range, the control component of the present invention adopts Figure 2 The dual PID temperature control structure shown in the figure, through two parallel PID controllers, respectively constitutes a PID precise temperature control system and a PID temperature compensation control system; when performing temperature control, the PID precise temperature control system is first used to precisely control the temperature control element according to the feedback temperature of the first temperature sensor, and the PID precise temperature control system is configured to have an overshoot of 15±5°C with the target temperature, so that the optical fiber delay of the optical fiber ring can be quickly controlled to a stable state; then, based on the feedback temperature of the first temperature sensor and the ambient temperature change fed back by the second temperature sensor, the PID temperature compensation control system is used to perform temperature compensation control on the temperature control element, and the target temperature is compensated according to the change of the ambient monitoring temperature, so that the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature.

[0051] In the initial PID precise temperature control process, the optical fiber length needs to be able to quickly reach a stable state. However, during the heating process, there is a large time delay between the measured temperature stable state and the optical fiber stable state. Figure 3 It can be seen that when the temperature begins to reach a stable state, the length of the optical fiber is still in a rapid elongation state, and it will take a long time to reach a stable state. This period of time is very unfavorable for practical applications, so compressing the stabilization time requires improving the temperature control program. In the present invention, since the temperature control adopts PID feedback control, in the actual temperature control process, due to the existence of the I value, the temperature curve will have an overshoot overshoot. This temperature is usually a process that the system does not need in the PID control process. It is usually necessary to flatten this overshoot through optimization. However, in the temperature control process of the optical fiber ring of the present invention, due to the delay process between the optical fiber and the temperature, this overshoot curve becomes particularly important for the rapid control of the optical fiber delay. Therefore, the present invention goes the other way and deliberately increases the overshoot in the first half of the temperature control process. After a large number of experiments, it is found that the optimal overshoot is 15±5℃. During this overshoot time, the full power output time of the power drive is longer, which can compensate for the delay of the optical fiber ring temperature, thereby achieving the effect of rapid stabilization of the optical fiber ring. Figure 4 As shown in the figure, after the PID temperature over-adjustment, the fiber ring Figure 3 In the process of fiber elongation without overshoot, the system after overshoot obviously shows the effect of fast and stable control. The present invention uses overshoot, a process that needs to be suppressed in the traditional PID control process, to cleverly turn disadvantages into advantages in the temperature control of the fiber ring, greatly accelerating the delayed stabilization process of the fiber ring.

[0052] After the fiber optic ring is precisely temperature controlled, the present invention performs temperature compensation control on the internal temperature change under the condition of external ambient temperature interference after the temperature field is stabilized, so that the fiber optic ring can quickly perform temperature compensation under the external ambient temperature interference, ensuring that the fiber optic ring delay remains stable and is not disturbed by the outside world. The temperature compensation control principle is described in detail below:

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

[0054]

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

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

[0057]

[0058] Since the refractive index of the fiber ring changes at different temperatures, the change in the fiber refractive index will cause the actual optical path L of the light in the fiber ring to change. cx will change. The actual optical path can be expressed as:

[0059]

[0060] In the above formula, L c is the total length of a single-layer fiber ring, n 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 temperature measuring point is T1, the temperature value of the lower surface temperature measuring point is T0, T s is the temperature value at a certain height s in the optical fiber ring device with a height of h, n s is the refractive index of the optical fiber at this temperature. Since the device model has been obtained in the initial simulation process that the temperature field inside the device is a linear temperature change process, due to uniform heating at the bottom, the temperature is a uniform decreasing process when the height increases. Therefore, at a temperature value T of height x x and the refractive index n(x) can be expressed as the following equations:

[0062]

[0063] n(x)=n s +[T x -T s ]·k (7)

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

[0065] From the above formula, we can get the actual optical path of light in a single-layer fiber ring at a height of x:

[0066]

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

[0068]

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

[0070] x=m·D (10)

[0071] Therefore, the actual optical distance L that the light travels in the entire fiber ring is sum for:

[0072]

[0074] In the actual device, since h>>D, we can get Therefore, the actual optical distance L that the light travels in the entire fiber ring is sum can be written as:

[0075]

[0076] The actual optical path of the light in the final fiber ring is:

[0077]

[0078] In order to keep the fiber optic ring delay control device insensitive to external temperature changes, due to T s is the temperature value at any height, which is a constant. Therefore, as long as T0+T1 in the above formula is a constant value, L sum of constant.

[0079] Therefore, the set target temperature can be compensated according to the change of the ambient monitoring temperature collected by the second temperature sensor, and the internal monitoring temperature of the optical fiber ring collected by the first temperature sensor is used as feedback. The heating film power is controlled by the PID temperature compensation control system, so that the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature, thereby achieving stable delayed temperature compensation.

[0080] The long optical 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 optical fiber delay, such as optoelectronic oscillators and optical fiber gyroscopes.

Claims

1. A long optical fiber delay control method, characterized in that: A long optical fiber is tightly wound into a barrel-shaped optical fiber ring, and a temperature control element arranged at the bottom of the optical fiber ring is controlled by the following dual PID temperature control method to achieve delay control of the long optical fiber: first, a first PID controller is used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with the target temperature, so that the optical fiber delay of the optical fiber ring is quickly controlled to a stable state; then a second PID controller is used to perform temperature compensation control on the temperature control element, and the target temperature is compensated according to the change of the environmental monitoring temperature, so that the monitored temperature inside the optical fiber ring closely tracks the compensated target temperature.

2. The long optical fiber delay control method according to claim 1, characterized in that: The barrel-shaped optical fiber ring and the temperature control element are encapsulated in a high thermal conductivity material shell, and the internal space is filled with a high thermal conductivity filling material; the outside of the high thermal conductivity material shell is wrapped with a high thermal insulation material.

3. The long optical fiber delay control method according to claim 2, characterized in that: A first temperature sensor disposed on the upper surface of the fiber optic ring is used to obtain the monitoring temperature inside the fiber optic ring, and a second temperature sensor disposed on the outer surface of the high thermal insulation material is used to obtain the environmental monitoring temperature.

4. A long optical fiber delay control device, characterized in that: include: Fiber optic loops, formed by tightly winding a long optical fiber into a barrel shape; A temperature control element is arranged at the bottom of the optical fiber ring; A control component is used to perform dual PID temperature control on a temperature control element to achieve delay control of the long optical fiber; the control component includes a first PID controller and a second PID controller; when performing temperature control, the first PID controller is first used to accurately control the temperature control element, and the first PID controller is configured to have an overshoot of 15±5°C with 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 environmental monitoring temperature, and the monitoring temperature inside the optical fiber ring closely tracks the compensated target temperature.

5. The long optical fiber delay control device as claimed in claim 4, characterized in that: The barrel-shaped optical fiber ring and the temperature control element are encapsulated in a high thermal conductivity material shell, and the internal space is filled with a high thermal conductivity filling material; the outside of the high thermal conductivity material shell is wrapped with a high thermal insulation material.

6. The long optical fiber delay control device as claimed in claim 5, characterized in that: Also includes: A first temperature sensor is disposed on the upper surface of the optical fiber ring and is used to obtain a monitoring temperature inside the optical fiber ring; The second temperature sensor is arranged on the outer surface of the high thermal insulation material and is used to obtain the environmental monitoring temperature.

Images