WO2012006936A1 - Fibre-optic coil for fibre-optic gyroscope - Google Patents

Abstract

The present invention relates to a fibre-optic coil for a fibre-optic gyroscope comprising a sensing frame and polarization-maintaining optical fibres (PMF) wound around the sensing frame, characterized in that said PMF are a PMF ribbon formed by 2×n PM fibres bonded in parallel (wherein n is 1, 2, 3…), thus forming a PMF ribbon with 2×n cores. The PMF ribbon, after being wound, has the heads and tails of adjacent fibres in the two ends thereof joined by melting, with the head end of the first fibre and the tail end of the last fibre being used respectively as the input end and the output end of the fibre-optic coil. The present invention can significantly improve the quality and speed of winding of such fibre-optic coils, enhance the performance indices and winding efficiency of the fibre-optic coils, improve the geometric control accuracy and temperature performance of the looped fibres, and enhance the temperature stability and the accuracy indices of the fibre-optic coils. The present invention simplifies the winding process for the fibre-optic coils, has a simple and reliable winding method that has good reproducibility, and also improves winding efficiency.

Description

 Optical fiber ring for fiber optic gyroscope Technical field

The invention relates to an optical fiber ring for a fiber optic gyroscope, belonging to the technical field of fiber optic gyroscopes.

Background technique

Born in 1976, fiber optic gyroscope is a new type of sensor that uses optical fiber sensing technology to measure the spatial inertial rotation rate. It has developed into a new mainstream instrument with epoch-making characteristics in the field of inertial technology. It is developed with the mechanical gyroscope commonly used in recent years. Compared with the laser gyro, the application range is larger, the cost is low, the volume is small, and the weight is light. The application prospect of fiber optic gyroscope is very broad. It is not only used for aircraft and ship navigation, missile guidance, high-precision attitude control of spacecraft, but also for the guidance of high-class cars, as well as robots and automation control systems. .

The fiber optic ring is the sensing element of the fiber optic gyroscope. The basic requirement for it is that the extinction ratio is larger and the reciprocity is better. How to wind high-quality fiber optic ring is very important for the development of fiber optic gyroscope. There are many winding methods, such as spiral winding method, quadrupole winding method, anti-quadrupole winding method, and eight-pole winding method. The core of such a variety of winding methods is to achieve the reciprocity of the fiber loop and suppress the shup effect.

US Patent No. 5848213, Low shupe bias fiber optic rotation Sensor coil, A method for using a fiber-wound loop is disclosed, that is, a loop is used with a fiber, and the heads of the strap are welded together in a certain order, and a loop is formed after the loop. This ensures that the fibers are parallel when looping. In this method, a large number of fiber fusion splice joints are added during the winding process of the loop, which may result in unstable performance of the sensing coil. At the same time, using this method to wind the fiber coil, there is no good way to ensure the reciprocity of the two rotation directions, and the temperature stability of the fiber coil is not improved.

Other related domestic and foreign patents mainly involve how to add silver powder, carbon powder and other materials to the fixing glue of the optical fiber ring to improve the temperature conduction performance of the ring, or use different winding methods to improve the temperature stability of the ring. According to years of research and experiments, the performance of the fiber loop using the four-pole winding method is the best in terms of temperature stability. Therefore, the current gyro fiber ring uses the four-pole winding method, and other winding methods are fresh. Used. However, due to the limitation of the shape of the cylindrical fiber, there are many difficulties in the tension control, fiber misalignment and length symmetry control of the fiber loop during the winding process, which makes it difficult to achieve a good consistency of the final fiber loop quality. And stability, affecting the mass production of fiber optic gyroscope products. Therefore, improving the performance of fiber optic rings is one of the keys to the development of fiber optic gyroscopes.

technical problem

The technical problem to be solved by the present invention is to provide an optical fiber ring for a fiber optic gyroscope which can improve the stress and temperature sensitivity of the optical fiber ring and improve the manufacturing process and precision index thereof in view of the deficiencies of the above prior art.

Technical solution

The technical solution adopted by the present invention to solve the above-mentioned problems is to include a sensing skeleton and a polarization maintaining optical fiber wound on the sensing skeleton, wherein the polarization maintaining optical fiber is a polarization maintaining optical fiber ribbon, The polarization-maintaining optical fiber ribbon is formed by 2×n polarization-maintaining fibers juxtaposed and bonded, n is 1, 2, 3..., and constitutes a polarization-maintaining optical fiber ribbon with a core number of 2×n, and two polarization-maintaining optical fiber ribbons after winding The end and end of the adjacent fibers in the end are melted and connected, and the first end of the first fiber and the tail end of the last fiber respectively serve as the input end and the output end of the fiber ring.

According to the above scheme, the polarization-maintaining optical fiber ribbon is formed by two or four polarization-maintaining fibers being juxtaposed and bonded to form a 2-core or 4-core polarization-maintaining optical fiber ribbon.

According to the above scheme, the polarization-maintaining optical fiber ribbon is formed by the polarization-maintaining optical fiber passing through the adhesive and being cured by ultraviolet light; the adhesive is a resin, and the thermal expansion coefficient of the resin is linear with the temperature change within the operating temperature range of the optical fiber loop. relationship.

According to the above solution, the polarization maintaining fiber is a Panda type polarization maintaining fiber, a bow tie type polarization maintaining fiber, an elliptical cladding type polarization maintaining fiber, an elliptical core type polarization maintaining fiber or a photonic crystal polarization maintaining fiber.

According to the above scheme, the method of winding the polarization-maintaining optical fiber ribbon on the sensing skeleton is a quadrupole winding method, a spiral winding method, an inverse quadrupole winding method or an eight-pole winding method.

According to the above scheme, the layers of the polarization-maintaining optical fiber ribbons wound on the sensing skeleton are closely juxtaposed, and the upper and lower polarization-maintaining optical fiber ribbons are aligned up and down corresponding to the respective windings.

According to the above scheme, the polarization-maintaining optical fiber ribbon is a 2-core polarization-maintaining optical fiber ribbon, and is wound on the sensing skeleton by a quadrupole winding method, that is, the length of the polarization-maintaining optical fiber ribbon is divided into two, and the midpoint is to be polarization-maintained. The fiber ribbon is divided into left and right sections. The left section is wound from the midpoint of the ribbon to the first layer of the loop from left to right on the sensing skeleton, and then the right section is taken from the midpoint of the ribbon. The second layer of the ring is wound from left to right on the skeleton, and then the third layer of the ring is wound from right to left, and then the left fiber is wound on the sensing skeleton to wrap the fourth layer of the ring from right to left. Then, the fifth layer of the loop is wound from left to right, and each of the two layers of the left and right sections alternates until the number of turns designed, and the last layer is wound from right to left by the left fiber ribbon. The optical fiber ribbons on the left and right sections are equally wound on the sensing skeleton; the optical fibers at the ends of the left and right optical fibers are separated, and then one fiber and the right segment of the left end are separated. The other fiber at the end is fused, and the connected fiber is fixed on the surface of the fiber ring with a curing glue, and the remaining two fiber ends are used as light. The input and output ends of the loop. In the above description, left and right can be interchanged.

According to the above scheme, the optical fiber ribbon wound on the sensing skeleton is bonded and positioned by the curing adhesive.

Beneficial effect

The beneficial effects of the invention are as follows: 1. Reducing the length of the fiber to be wound: when using a 2×n core number of polarization-maintaining fiber ribbon, the length of the fiber ribbon to be wound is only 1/1 of the length of the fiber required by the loop. (2×n). Since the fiber ring generally uses the quadrupole winding method, the stress control and position control requirements of the fiber to be wound are extremely strict, so shortening the fiber length can greatly improve the winding quality and winding speed of the fiber ring, and improve the fiber ring. The performance index and winding efficiency of the ring; and the invention has better length symmetry, so that the quality of the finally wound fiber ring ring achieves better consistency and stability. 2. The control precision of the wound fiber is improved: The characteristics of the cylindrical structure of the optical fiber, in the winding process of the optical fiber ring, the upper optical fiber can only be located in the gap of the lower optical fiber, that is, the upper optical fiber is located in the V-shaped groove formed by the lower optical fiber and there is a transition intersection, as shown in FIG. 2 Shown. At this intersection, the fibers are overlapped and the stress control is difficult. By using the polarization-maintaining optical fiber ribbon of the present invention, the upper and lower layers of the optical fibers can be stacked in parallel, and the surface of each layer is smooth and flat, effectively avoiding the intersection problem of the single optical fiber winding. Therefore, the polarization-maintaining optical fiber ribbon proposed by the invention can improve the geometric control precision of the wound optical fiber, further improve the performance index of the optical fiber loop; 3. Improve the temperature performance of the optical fiber loop: using the polarization-maintaining optical fiber ribbon of the invention, The process control is stable, and the optical fiber ribbons are vertically and stably connected in parallel. Therefore, in the fabrication of the optical fiber loop, the use of the cured adhesive can be greatly reduced, and the curing adhesive inevitably has thermal expansion in the use temperature range of the optical fiber loop. The problem will have a great influence on the temperature stability of the fiber ring. Therefore, reducing the use of the curing glue can effectively improve the temperature stability of the fiber ring and improve the accuracy of the fiber ring; 4. Simplify the fiber ring. The winding process, the winding method is simple and reliable, the repeatability is good, and the winding efficiency is also improved.

DRAWINGS

FIG. 1 is a schematic diagram of an ideal four-pole winding fiber arrangement. In the figure, 1 is a single fiber, and 2 and 3 are respectively two ends of a single fiber, which are also input and output ends of the fiber ring.

2 is a schematic view showing the arrangement of a conventional single-fiber four-pole wound optical fiber. In the figure, 4 is a V-shaped groove formed by adjacent fibers of the same layer, and 5 is a cured glue distributed between the wound optical fibers.

FIG. 3 is a schematic structural view of a double-core polarization-maintaining optical fiber ribbon according to the present invention

4 is a schematic structural view of a four-core polarization-maintaining optical fiber ribbon according to the present invention.

FIG. 5 is a schematic diagram of the fiber ribbon segmentation of the present invention (synchronized by two mid-points on two fiber-distributing disks).

Figure 6 is a schematic view of a four-pole winding process starting from the midpoint of the optical fiber ribbon in one embodiment of the present invention.

FIG. 7 is a partial schematic view showing a partial arrangement of a 2-core optical fiber with a four-pole wound coil according to the present invention.

FIG. 8 is a schematic cross-sectional structural view of a 2-core polarization-maintaining optical fiber ribbon ring according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1:

Two pairs of polarization-maintaining fibers 1 of the same type are bonded together by resin and UV-cured to form a double-core polarization-maintaining optical fiber ribbon 6. After preparing a two-core (2-core) polarization-maintaining optical fiber ribbon, the optical fiber ribbon on the optical fiber disk is divided into two. Half to another identical fiber optic disk, resulting in this midpoint 9 with a ribbon, the midpoint being the symmetrical midpoint required to wind the loop, starting from the midpoint of the coil . Using the quadrupole winding method, the fiber ribbons on the two fiber-optic discs are sequentially wound onto the sensing skeleton 10 from the symmetrical midpoint. Figures 4 and 5 show the key steps of the quadrupole winding method. The two-core polarization-maintaining optical fiber ribbon 6 is divided into two left and right segments, which are wound around the left and right fiber distributor disks 7, 8. The midpoint of the fiber ribbon is 9 in the figure. Then, the wire-shaped sensing bobbin and the two fiberizing discs are mounted on the fiber loop winding device, and the double-core fiber ribbon is wound on the sensing bobbin 10 from the midpoint 9 as shown in FIG. When the fiber on the right splitter disc 8 is wound, the left splitter tray 7 and the sensing skeleton 10 are synchronized and revolved, that is, the left splitter tray 7 and the sensing skeleton 10 remain relatively stationary, and the sensing skeleton is rotated around the fiber, right. The splitter disc 8 is discharged; likewise, when the optical fiber on the left splitter tray 7 is wound, the right splitter disc 8 and the sensing bobbin 10 remain relatively stationary. The optical fiber ribbon 6 is finally wound on the bobbin 10 by alternately winding the optical fiber ribbon on the fiber separation tray. Each of the layers of the polarization-maintaining optical fiber ribbons wound on the sensing skeleton is closely arranged side by side, and the upper and lower polarization-maintaining optical fiber ribbons are vertically aligned with each other and closely stacked. The winding method is that the fiber ribbon on one of the first and last layers of the fiber-optic disk is wound on the skeleton, and then the fiber ribbon on the other fiber-optic disk is wound on the two layers. Each of the two layers of left and right fiber ribbons are alternated until the number of turns designed is completed, wherein the first layer and the last layer are both wound by the left (or right) fiber, so that the left, The right fiber ribbon has the same number of winding turns on the sensing skeleton. The winding process is strictly in accordance with the requirements of the quadrupole symmetrical winding method. After the winding, one end of the double-core polarization-maintaining optical fiber ribbon is cut, and then one of the two ends of the optical fiber is cross-fused and welded together to form a fiber loop 11 with two symmetrical spiral structures on the left and right sides. Fig. 7 is a schematic view of a double-core polarization-maintaining optical fiber ribbon wound optical fiber ring, the fiber is wound on the skeleton 10, wherein the outermost two layers of optical fiber ribbons are adjacent to the right side of the skeleton and are two polarization-maintaining optical fiber ribbons. Ends. In order to obtain a complete polarization-maintaining fiber loop, the upper and lower ends of the fiber with the "X" mark are fused together, and the remaining two pins with the "+" mark are used for the fiber loop. Input and output. Such a fiber optic ring having a fiber length twice the length of the fiber ribbon is wound. After the welding is completed, the welded head is sealed and bonded to the side of the coil bobbin by the resin used in the belt, and the welding point can basically serve as a symmetrical midpoint of the entire sensing coil, but in order to avoid the occurrence of the welding point Small symmetrical reflection interference requires the fusion point to avoid the true center of symmetry.

In this embodiment, a polarization-maintaining fiber working at a wavelength of 1550 nm and having a mode field diameter of 6 μm and a cladding diameter of 125 μm is firstly subjected to a double-core strip, and the coated layer of the optical fiber has a diameter of 250 μm and has a long side with a rear rectangle and a long side ( The d value in Fig. 3 is 510 μm. The double-core and back-wound fiber is wound on the sensing skeleton as shown in FIG. 7 by using a quadrupole winding method, and the size of the sensing skeleton needs to ensure that the inner width is an integral multiple of (d value) 510 μm, and the depth of the groove In order to have a fiber thickness (b value) of 4 times an integral multiple of 250 μm, the requirements of these parameters are all to meet the need to ensure quadrupole symmetry. The parameters selected in this embodiment are the inner width of the skeleton (a value) of 20.4 mm and the skeleton depth (c value) of 20 mm. The parameters of the fiber loop obtained after the inner groove of the skeleton is completely filled are: room temperature polarization crosstalk -26 dB. The temperature stability of the crosstalk was measured by the fiber loop, and the measurement conditions were as follows: the temperature was uniformly increased from -40 ° C to +60 ° C, and the temperature change rate was 2 ° C / min, and the measurement showed that the full-temperature crosstalk change was 3.5 dB. The ambient temperature crosstalk size and full-text crosstalk variation of the fiber loop can meet the application requirements of medium precision fiber optic gyroscopes. Compared with fiber loops wound with a single fiber, the ambient temperature crosstalk is generally between -22dB and -26dB, and the full-temperature crosstalk variation is generally greater than 7dB. Therefore, compared with the fiber loop wound by the double-core polarization-maintaining fiber ribbon, the temperature stability of the fiber loop wound by the single fiber is poor.

Embodiments of the invention

Example 2-8:

In the embodiment 2-8, the same parallel strip structure design is adopted, and the winding of the fiber loop is also carried out by the quadrupole symmetrical winding method, and the parameters of the strip, the parameters of the loop skeleton and the winding of the fiber loop are The polarization crosstalk parameters are as follows.

Example 1: b = 250 μm, d = 510 μm, a = 20.4 mm, c = 20 mm, room temperature crosstalk -26 dB, full temperature crosstalk change 3.5 dB.

Example 2: b = 248 μm, d = 505 μm, a = 20.2 mm, c = 19.84 mm, room temperature crosstalk - 25.8 dB, full temperature crosstalk change of 2.8 dB.

Example 3: b = 250 μm, d = 502 μm, a = 20.08 mm, c = 20 mm, room temperature crosstalk - 26.2 dB, full temperature crosstalk change 3.3 dB.

Example 4: b = 252 μm, d = 504 μm, a = 20.16 mm, c = 20.16 mm, room temperature crosstalk - 25.9 dB, full temperature crosstalk change 3.8 dB.

Example 5: b = 247 μm, d = 500 μm, a = 20 mm, c = 19.76 mm, room temperature crosstalk - 26.8 dB, full temperature crosstalk change of 2.9 dB.

Example 6: b = 249 μm, d = 505 μm, a = 20.2 mm, c = 19.92 mm, room temperature crosstalk - 27.2 dB, full temperature crosstalk change 3.2 dB.

Example 7: b = 251 μm, d = 504 μm, a = 20.16 mm, c = 20.08 mm, room temperature crosstalk - 27.1 dB, full temperature crosstalk change 3.1 dB.

Example 8: b = 253 μm, d = 507 μm, a = 20.28 mm, c = 20.24 mm, room temperature crosstalk - 26.9 dB, full temperature crosstalk change 2.6 dB.

The full-text measurement conditions are the same as in the first embodiment.

It can be seen from the above data that the use of the polarization-maintaining optical fiber ribbon winding optical fiber ring of the present invention keeps the normal-temperature crosstalk size relatively stable, and the full-temperature crosstalk variation is about 3 dB, and the distribution is concentrated. It is shown that the fiber loop wound by the polarization-maintaining optical fiber ribbon of the invention has the characteristics of stable performance and good batching, and is of great significance for the batch development and production of the fiber optic gyroscope, and the polarization-maintaining optical fiber ribbon proposed by the invention is used at the same time. The full-temperature crosstalk variation of the wound fiber ring is much smaller than the full-temperature crosstalk variation of the ring wound by a single polarization-maintaining fiber, which can fully meet the requirements of the medium-precision fiber optic gyroscope.

Claims (7)

What is claimed is: 1. A fiber optic ring for a fiber optic gyroscope, comprising: a sensing skeleton and a polarization maintaining fiber wound on the sensing skeleton, wherein the polarization maintaining fiber is a polarization maintaining fiber ribbon, and the The partial fiber ribbon is formed by 2×n polarization-maintaining fibers juxtaposed, n is 1, 2, 3..., and the polarization-maintaining fiber ribbon with the core number 2×n is formed, and the two polarization-maintaining fiber ribbons are wound. The first and second ends of the adjacent fibers are melted and connected, and the first end of the first fiber and the tail end of the last fiber respectively serve as the input end and the output end of the fiber ring. 2. The fiber optic ring for a fiber optic gyroscope according to claim 1, wherein the polarization-maintaining fiber ribbon is formed by two or four polarization-maintaining fibers juxtaposed to form a 2-core or 4-core warranty. Partial fiber ribbon. The optical fiber ring for a fiber optic gyroscope according to claim 1 or 2, wherein the polarization-maintaining optical fiber ribbon is formed by a polarization-maintaining optical fiber through an adhesive and cured by ultraviolet light; the adhesive is a resin. The coefficient of thermal expansion of the resin is linear with the temperature change over the temperature range of the fiber loop. The fiber optic ring for a fiber optic gyroscope according to claim 1 or 2, wherein the polarization maintaining fiber is a Panda type polarization maintaining fiber, a bow tie type polarization maintaining fiber, an elliptical cladding type polarization maintaining fiber, Elliptical core type polarization-maintaining fiber or photonic crystal type polarization-maintaining fiber. The optical fiber ring for a fiber optic gyroscope according to claim 1 or 2, wherein the polarization-maintaining optical fiber ribbon is wound on the sensing skeleton by a quadrupole winding method, a spiral winding method, and a reverse Quadrupole winding or eight-pole winding method. The fiber optic ring for a fiber optic gyroscope according to claim 5, wherein each of the layers of the polarization-maintaining optical fiber ribbon wound on the sensing skeleton is closely juxtaposed, and the upper and lower layers are respectively arranged. The polarization-maintaining fiber ribbon is aligned up and down for each circle. 7. The fiber optic ring for a fiber optic gyroscope according to claim 1, wherein said polarization maintaining fiber ribbon is a 2-core polarization-maintaining fiber ribbon and is wound on a sensing skeleton by a quadrupole winding method. The length of the polarization-maintaining fiber ribbon is divided into two. The mid-point is used to divide the polarization-maintaining fiber ribbon into left and right segments. First, the left segment is wound from the midpoint of the fiber ribbon to the sensing skeleton from left to right. Layer loop, then the right segment is wound from the midpoint of the ribbon to the second layer of the ring from left to right on the sensing skeleton, and then the third layer of the ring is wound from right to left, and then the left fiber ribbon is taken The fourth layer of loops is wound from right to left on the sensing skeleton, and the fifth layer of loops is wound from left to right. Each of the two layers of left and right sections alternates until the finished design is completed. Number, wherein the last layer is wound from right to left by the left fiber ribbon, so that the left and right fiber ribbons are equally wound on the sensing skeleton; the left and right fiber ribbons are terminated at both ends The fibers are separated, and then one fiber of the left end is fused to another fiber of the right end, and the connected fiber is cured and glued. Surface of the fiber ring in the circle, the remaining two fiber ends as input and output side optical fiber segment loops.

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