Multi-channel optical fiber precision delay line and implementation method thereof

Abstract

A multi-channel fiber optic precision delay line and its implementation method are disclosed. By controlling the winding method and flipping direction of the fiber, the optical path difference of each fiber core channel can be precisely controlled, thereby achieving multi-channel precision delay.

Description

Technical Field

[0001] This invention relates to a technology in the field of optical fiber, specifically a multi-channel optical fiber precision delay line and its implementation method. Background Technology

[0002] Optical fiber, as an information transmission medium, possesses advantages such as light weight, small size, and strong resistance to electromagnetic interference, making it a promising application in phased arrays requiring long delay times. With technological advancements, modern communications demand ever-increasing transmission capacity, necessitating fiber optic delay lines with larger transmission capacities and higher precision. Engineering requirements demand delay difference measurement accuracy on the order of ps or sub-ps.

[0003] The current manufacturing technology for fiber optic units is limited in its inability to be applied to scenarios with high integration requirements, such as data centers and delay lines used in radar. Bundling multiple optical fibers together would increase the size, which is inconsistent with the current trend of high integration. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention proposes a multi-channel fiber precision delay line and its implementation method. By controlling the winding method and flipping direction of the fiber, precise control of the optical path difference of each fiber core channel can be achieved, thus realizing multi-channel precision delay.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a method for implementing a multi-channel fiber optic precision delay line. By setting the rotation angle and winding method of the peripheral fiber cores around the central axis or the central fiber core, the optical path difference of each fiber core channel can be precisely controlled, thereby obtaining multi-channel precision delay.

[0007] The distance between the peripheral fiber core and the central axis is called the intercore distance.

[0008] The winding methods include: winding without reversing the angle and winding while reversing.

[0009] The aforementioned non-flip angle winding refers to the following: when winding a multi-core optical fiber into a circle, no flipping operation is performed on the optical fiber, so that the position of each fiber core on the end face of the multi-core optical fiber remains unchanged. That is, on the end face of the multi-core optical fiber, a polar coordinate system is established with the center of the end face as the center, and the polar diameter and polar angle of each fiber core remain unchanged.

[0010] The aforementioned simultaneous winding and flipping refers to: while winding the multi-core optical fiber into a loop, the winding end is flipped with the optical fiber as the axis of rotation. That is, after winding L meters of optical fiber, ① the optical fiber is twisted clockwise or counterclockwise according to the flipping angle θ, ② winding L meters of optical fiber, ③ twisting the optical fiber counterclockwise or clockwise according to the flipping angle θ, and repeating the winding until an integer multiple of L of optical fiber is completed.

[0011] The precise control of the optical path difference includes winding without flipping the angle and winding while flipping.

[0012] The precise control of optical path difference through non-flipping angle winding refers to the following: When a multi-core optical fiber with a length of L1 meters, a core refractive index of n, and a core spacing of r is wound once without flipping, the optical path difference of the middle core is nL1, which depends on the length of the multi-core optical fiber. The optical path difference of the peripheral cores is n·2π·r·cos(θ1)·L1 / L3+nL1, where θ1 is the central angle of the peripheral core. In other words, the required optical path difference can be obtained by controlling the number of winding turns and the length of the optical fiber without flipping, thus achieving precise control of the optical path difference and obtaining the required delay.

[0013] The precise control of optical path difference through simultaneous flipping and winding refers to the following: a multi-core optical fiber with a length of L1 meters, a core refractive index of n, and a core spacing of r meters, is flipped θ degrees every L2 meters and wound once every L3 meters. The optical path difference between the peripheral cores and the central core is then calculated as follows: Where: θ1 is the central angle of the peripheral core, which makes the optical path difference between each fiber core channel very close, that is, the optical path difference between the peripheral core and the middle core is very small, thus making the delay between each fiber core very small and realizing multi-channel precise delay.

[0014] This invention relates to a multi-channel optical fiber precision delay line prepared by the above method, wherein the cladding contains multiple fiber cores that can serve as channels for signal transmission. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the implementation method of the present invention;

[0016] Figure 2 This is a schematic diagram of the cross-section of the optical fiber of the present invention;

[0017] In the diagram: central core 201, peripheral cores 202-20N;

[0018] Figure 3 (a) Optical fiber end face view during the flipping process; (b) Top view of the optical fiber during the winding process after one flip.

[0019] In the diagram: central core 301, peripheral cores 302-304;

[0020] Figure 4 This is an end-face diagram of a seven-core optical fiber structure;

[0021] In the diagram: central core 401, peripheral cores 402-207;

[0022] Figure 5 for Figure 4A schematic diagram showing the relationship between the time delay difference between peripheral core 402 and intermediate core 401 and the flip angle;

[0023] Figure 6 for Figure 4 Schematic diagram showing the relationship between the time delay difference and the flip angle between peripheral core 405 and intermediate core 401;

[0024] Figure 7 for Figure 4 A schematic diagram showing the relationship between the time delay difference and the flip angle between the peripheral core 407 and the central core when they flip 2, 3, or 4 times per revolution.

[0025] Figure 8 This is an end-face diagram of a four-core optical fiber structure;

[0026] In the diagram: Virtual central core 801, peripheral cores 802-205;

[0027] Figure 9 for Figure 8 A schematic diagram showing the relationship between the time delay difference between the peripheral core 802 and the intermediate core 801 and the flip angle. Detailed Implementation

[0028] Example 1

[0029] like Figure 2 As shown, this embodiment relates to a multi-channel fiber precision delay line, including: a central core 201 and peripheral cores 202 to 20N evenly distributed around it, the distance between the peripheral core 201 and the central core 201, i.e. the inter-core distance, is rμm.

[0030] In this embodiment, r is 60 μm.

[0031] This embodiment relates to a method for implementing a five-channel fiber optic precision delay line, specifically including:

[0032] Step 1: Establish a rectangular coordinate system with the central core 301 as the origin and the third peripheral core 304 and the central core 301 as the horizontal axis. The second peripheral core 303 is the position of the first peripheral core 302 after being flipped by θ degrees. After each flip, it is wrapped half a circle. Then, after the nth flip and half a circle, the optical path difference between the first peripheral core 302 and the central core 301 in this half circle is s = n1·π·r1 = n1·π·r_os(θ1-nθ), where: r1 = r_os(θ1-nθ), is the horizontal coordinate of the second peripheral core 303 in the rectangular coordinate system after flipping by θ, which represents the distance between the core 303 and the central core in the horizontal direction after flipping; n1 is the refractive index of the fiber core; r is the distance between the cores; θ1 is the central angle between the first peripheral core 302 and the third peripheral core 304; and n is the number of flips.

[0033] Step 2, as follows Figure 3As shown in b, for a multi-core optical fiber of length L1 meters, it is flipped every L2 meters during winding, and half a turn is wound after each flip. After a total of L1 / L2 flips, the total optical path difference between the peripheral core 302 and the middle core 301 is: This allows us to obtain the time delay difference.

[0034] Where: n1 is the refractive index of the fiber core, and v is the speed of light.

[0035] When only winding without flipping, for a multi-core optical fiber of length L1 meters, one wrap is made every L3 meters. The optical path differences between the middle core 301 and the peripheral core 302 after winding L1 / L3 turns are s1 = n1·L1 and s2 = n1·2π(π + r·cos(θ1))L1 / L3, respectively. From this, the time delay generated without flipping can be obtained as follows: Where R is the winding radius, which is defined as the distance from the center core to the center of the loop after winding, and its value is L3 / 2π.

[0036] Example 2

[0037] like Figure 4 As shown, this embodiment relates to a method for implementing a seven-core optical fiber, specifically including:

[0038] Step 1: In the flipped end view, the flip angle θ is taken as 1 to 360°. Each core has a refractive index of 1.4520 and an intercore distance r of 60 μm.

[0039] Step 2: Wind the optical fiber 100 times, flipping it twice after each turn, each time by θ degrees, that is, flipping it by θ degrees every 0.5m.

[0040] according to Figure 4 The fiber delay difference obtained by the method is as follows: Figure 5 As shown in the figure, the horizontal axis represents the time delay difference between the first peripheral core 402 and the middle core 401, and the vertical axis represents the flip angle. When the flip angle is a multiple of 9, the time delay difference is 0, that is:

[0041] ① When the rotation is k times per revolution, and each rotation is d degrees, and a total of L revolutions are made, then when the total number of rotation degrees kdL is an integer multiple of 2π, the time delay difference between each peripheral core and the middle core is 0 under ideal conditions.

[0042] ② When the flip angle is 0, that is, without flipping, the multi-core fiber is directly wound, and the time delay difference between the first peripheral core 402 and the middle core 401 after 100 turns is 90.5ps.

[0043] Similarly, the relationship between the time delay difference between the fourth peripheral core 405 and the intermediate core 401 and the flip angle can be obtained. For example... Figure 6As shown.

[0044] From the above, we can see that the relationship diagrams of the first peripheral core 402 and the fourth peripheral core 405, the second peripheral core 403 and the fifth peripheral core 406 are opposite, and the relationship diagrams of the third peripheral core 404 and the sixth peripheral core 407 are opposite. That is, when the flip angle is a multiple of 9, the time delay difference is 0.

[0045] When the seven-core fiber is not flipped during the winding process, and assuming that the radius of the loop after winding is 0.1m, that is, the length of each loop of fiber is 0.2πm, and the number of windings is 100, the time delay of the middle core 401 is 0.3μs. Among the time delay differences between the other peripheral cores and the middle core, the third peripheral core 404 and the sixth peripheral core 407 have the largest time delay differences, which are 181ps and -181ps respectively. The second peripheral core 403 and the fourth peripheral core 405 have the same time delay of 90.5ps, and the first peripheral core 402 and the fifth peripheral core 406 have the same time delay of -90.5ps. Therefore, by controlling the number of windings and the radius, that is, the fiber length, any desired time delay can be obtained.

[0046] The above describes the scenario where the rotation occurs twice per revolution, for a total of 100 revolutions. When the rotation occurs three or four times per revolution, with each rotation at the same angle, the result is shown in the diagram below, using the same principle as core 101.

[0047] Based on the previously obtained relationship, when the fiber core flips 3 times per revolution, the time delay difference is 0 when the flip angle is a multiple of 6; when the fiber core flips 4 times per revolution, the time delay difference is 0 when the flip angle is a multiple of 9. Simulation results also verify this. As can be seen from the figure, as the number of flips per revolution increases, the fluctuation of the time delay difference becomes smaller. This is because with the increase of the number of flips per revolution, the central angle corresponding to the arc traversed by the fiber core after each flip becomes smaller, thereby reducing the optical path difference of the fiber core, and thus the fluctuation of the time delay difference is also smaller.

[0048] Example 3

[0049] like Figure 8 As shown, for a four-core fiber, for ease of calculation in the case of flipping, it is assumed that there is a virtual intermediate core 101 used to calculate the time delay difference between the other four peripheral cores and the virtual intermediate core. The specific steps in this embodiment include:

[0050] Step 1: Take the flip angle θ as a range from 1 to 360°. The core has a refractive index of 1.4520 and the distance between adjacent cores is 60 μm.

[0051] Step 2: Wind the optical fiber 100 times, rotating it twice after each rotation, each rotation being θ degrees, i.e., rotating it θ degrees every 0.5m, to obtain a four-core optical fiber. Its time delay difference is as follows: Figure 9 As shown.

[0052] As shown in the figure, the time delay difference between each channel and the middle core of the four-core optical fiber in this embodiment is basically the same as that of the seven-core optical fiber, which is concentrated in the range of -4 to 4 ps. Similarly, when the winding process does not flip, the required time delay difference can be obtained by controlling the length of the optical fiber.

[0053] The simulation results above show that when the fiber is flipped during the winding process, the time delay difference between each fiber core can reach -4 to 4 ps, which is an improvement of two orders of magnitude compared to when it is not flipped. This achieves precise delay for each channel. Without flipping, the required delay can be obtained by controlling the length of the fiber, enabling precise control of multi-channel delay.

[0054] Compared with existing technologies, this method can improve the delay accuracy of each channel by two orders of magnitude, and the delay difference between channels can be controlled in the picosecond range. It also has a high degree of integration.

[0055] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for implementing a multi-channel fiber optic precision delay line, characterized in that, By setting the flipping angle and winding method of the peripheral core around the central core, the optical path difference of each fiber core channel can be precisely controlled, thereby obtaining multi-channel precise delay. The winding methods include: winding without turning the angle and winding while turning; The aforementioned non-flip angle winding refers to the following: when winding a multi-channel optical fiber into a circle, no flipping operation is performed, so that the position of each fiber core on the end face of the multi-channel optical fiber remains unchanged. That is, on the end face of the multi-channel optical fiber, a polar coordinate system is established with the center of the end face as the center, and the polar diameter and polar angle of each fiber core remain unchanged. The aforementioned winding and flipping refers to: while winding the multi-channel optical fiber into a loop, the winding end is flipped with the multi-channel optical fiber as the pivot. That is, after winding L meters of multi-channel optical fiber, ① the multi-channel optical fiber is twisted clockwise or counterclockwise according to the flipping angle θ, ② winding L meters of multi-channel optical fiber, ③ twisting the multi-channel optical fiber counterclockwise or clockwise according to the flipping angle θ, and the winding is completed after the loop is wound to an integer multiple of L. The precise control of the optical path difference includes winding without flipping the angle and winding while flipping; The precise control of optical path difference by the non-flip angle winding refers to: a length of... A multi-channel optical fiber with a core refractive index of n and an intercore spacing of r is wound once without flipping. For a multi-channel optical fiber with a middle core, the optical path difference between the middle core and the middle core is n. That is, the optical path difference depends on the length of the multi-channel fiber, while the optical path difference of the peripheral core is... ,in: The central angle between the peripheral cores is the optical path difference obtained by controlling the number of turns of the winding and the length of the multi-channel fiber without flipping, so as to achieve precise control of the optical path difference and thus obtain the required delay. The precise control of the optical path difference through simultaneous winding and flipping refers to the following: the length is... Meter, core refractive index A multi-channel optical fiber with an inter-core spacing of r meters, arranged at intervals of... The meter flips θ degrees, each If the rice is flipped and wound once, the optical path difference between the outer core and the middle core is... ,in: The central angle of the peripheral core is set to make the optical path difference between each fiber core channel very close, that is, the optical path difference between the peripheral core and the middle core is very small, thus making the delay between each fiber core very small and realizing precise delay of multiple channels.

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