A dual-core photonic crystal fiber wavelength splitter with liquid crystal filled single polarization output

Abstract

The present invention discloses a liquid crystal filled single polarization output dual-core photonic crystal fiber wavelength beam splitter, which includes: a core region and a cladding region, wherein the core region and the cladding region are filled with pure quartz glass substrate material; the core region includes a central air hole, two first air holes, two second air holes, two third air holes, and eight fourth air holes; the cladding region is located in the outer layer of the core region, and the cladding region includes a plurality of fifth air holes evenly arranged, wherein the diameter of the fifth air holes is d6, the hole spacing is a0, and the fifth air holes are arranged in a regular hexagonal structure. This beam splitter introduces liquid crystal material, is shorter than a full air hole type photonic crystal fiber, has better light transmission effect, is simpler in structure than a beam splitter based on the SPR effect, is easy to manufacture, and has lower cost.

Description

Technical Field

[0001] The invention relates to the field of optical fiber communication, and in particular to a double-core photonic crystal optical fiber wavelength splitter with liquid crystal filling and single polarization output. Background Art

[0002] Optical fiber is the most important part of optical communication system as the medium for optical signal transmission. For current communication system, wavelength division multiplexing (WDM) technology plays an important role in optical communication system. In WDM system, wavelength splitter plays an important role.

[0003] The wavelength beam splitter with single polarization output not only supports the transmission of light in a certain polarization direction to avoid inter-mode crosstalk, but also can separate the light of two typical communication wavelengths, 1310nm and 1550nm, so it is more suitable for the current WDM system. At present, people mainly adopt the following solutions when designing such beam splitters:

[0004] (1) Based on all-air-hole photonic crystal fiber. The single-polarization output wavelength beam splitter designed with this scheme is usually based on the traditional photonic crystal fiber, with a birefringent structure constructed in its core and cladding regions. Its light-guiding mechanism is the same as that of the traditional photonic crystal fiber. In addition, the core of this type of beam splitter is formed by the lack of air holes, just like the traditional photonic crystal fiber, and because its core region is used to construct a birefringent structure, its core is generally not a regular circle. However, due to the low birefringence of this type of beam splitter, it often requires a long fiber length to separate the two typical communication wavelengths of 1310nm and 1550nm, which cannot meet the needs of device miniaturization.

[0005] (2) Based on the surface plasmon resonance (SPR) effect. The basic principle is to fill metal wires near the fiber core, or to plate a metal layer, and use the SPR effect to make a certain polarization mode of the fiber core mode resonate with the plasma polarization mode of the metal surface at two wavelengths of 1310nm and 1550nm, thereby losing a certain polarization mode of the core mode. The metal used in this type of beam splitter is mostly gold. This type of photonic crystal fiber polarization beam splitter is not only expensive in material, but also very difficult to manufacture. Summary of the invention

[0006] In view of the above technical problems, the purpose of the present invention is to provide a liquid crystal filled single polarization output dual-core photonic crystal fiber wavelength splitter for use in a WDM system to separate the two wavelengths of 1310nm and 1550nm, and to achieve this through the following technical solutions:

[0007] A liquid crystal filled single polarization output double-core photonic crystal fiber wavelength splitter, comprising: a core region and a cladding region, wherein the core region and the cladding region are filled with pure quartz glass substrate material;

[0008] The core area includes a central air hole, two first air holes, two second air holes, two third air holes, and eight fourth air holes; wherein the central air hole is located in the center of the core area, and the diameter of the central air hole is d1; the two first air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a1, the two first air holes are filled with nematic liquid crystals, and the first air holes filled with nematic liquid crystals serve as the core of the optical fiber, and the diameters of the two first air holes are both d2; the two second air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a1. The horizontal distance is a2, and the diameters of the two second air holes are both d3; the two third air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a3, and the diameters of the two third air holes are both d4; the four fourth air holes are arranged on the upper side of the central air hole in the vertical direction, and the other four fourth air holes are arranged on the lower side of the central air hole in the vertical direction, and the four fourth air holes located on the upper and lower sides of the central air hole are horizontally arranged and the vertical distance from the central air hole is a4, the diameters of the eight fourth air holes are all d5, and the horizontal spacing between two adjacent fourth air holes in the transverse direction is a0;

[0009] The cladding region is located in the outer layer of the core region, and the cladding region includes a plurality of evenly arranged fifth air holes, the diameters of the fifth air holes are all d6, the hole spacings are all a0, and the fifth air holes are arranged in a regular hexagonal structure.

[0010] Optionally, the diameter d1 of the central air hole ranges from 0.95 to 1.05 um.

[0011] Optionally, a horizontal distance a1 between the first air hole and the central air hole ranges from 1.795 to 1.805 um.

[0012] Optionally, the diameter d2 of the first air hole ranges from 0.595 to 0.605 um.

[0013] Optionally, a horizontal distance a2 between the second air hole and the central air hole ranges from 4.49 to 4.51 um.

[0014] Optionally, the second air hole diameter d3 has a value range of 0.795-0.805 um.

[0015] Optionally, a horizontal distance a3 between the third air hole and the central air hole is in a range of 7.195-7.205 um; a diameter d4 of the third air hole is in a range of 0.795-0.805 um.

[0016] Optionally, the fourth air hole diameter d5 has a value range of 3.349-3.351 um.

[0017] Optionally, a vertical distance a4 between the fourth air hole and the central air hole ranges from 3.116 to 3.118 um.

[0018] Optionally, the value range of a0 is 3.598-3.602 um; the value range of the fifth air hole diameter d6 is 0.998-1.002 um.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] (1) This beam splitter introduces liquid crystal material, which is shorter than the all-air hole photonic crystal fiber and has better light transmission effect. It is simpler in structure, easier to manufacture, and has lower cost than the beam splitter based on the SPR effect.

[0021] (2) The communication band of this beam splitter is wider, and single polarization output can be achieved in the entire O+E+S+C+L+U communication band.

[0022] (3) Since the fiber core is filled with nematic liquid crystal material, when the liquid crystal is rotated at an angle of 90°, the length of the optical fiber is only 2.38 mm, and the crosstalk noise is only -68.18 dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a cross-sectional view of the liquid crystal filled single polarization output dual-core photonic crystal fiber wavelength splitter of the present invention.

[0025] Figure 2 The diagram is a relationship diagram of the mode refractive index of the liquid crystal filled single polarization output dual-core photonic crystal optical fiber wavelength splitter of the present invention as a function of wavelength.

[0026] Figure 3 It is the relationship between the normalized energy of the liquid crystal filled single polarization output double-core photonic crystal optical fiber wavelength beam splitter of the present invention and the length of the beam splitter.

[0027] In the figure, 1 is the central air hole, 2 is the air hole filled with liquid crystal, 3 is two air holes at a distance a2 from the central air hole in the horizontal direction, 4 is two air holes at a distance a3 from the central air hole in the horizontal direction, 5 is eight large air holes at a distance a4 from the central air hole in the vertical direction, 6 is the cladding area air hole, and 7 is a pure quartz glass substrate. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, a liquid crystal filled single polarization output dual-core photonic crystal fiber wavelength splitter comprises: a core region and a cladding region, wherein the core region and the cladding region are filled with a pure quartz glass substrate material 7;

[0030] The core area includes a central air hole 1, two first air holes 2, two second air holes 3, two third air holes 4, and eight fourth air holes 5; wherein the central air hole is located in the center of the core area, and the diameter of the central air hole is d1; the two first air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a1, the two first air holes are filled with nematic liquid crystals, and the first air holes filled with nematic liquid crystals serve as the core of the optical fiber, and the diameters of the two first air holes are both d2; the two second air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a2, and the two The diameters of the two air holes are both d3; the two third air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a3, and the diameters of the two third air holes are both d4; the four fourth air holes are arranged on the upper side of the central air hole in the vertical direction, and the other four fourth air holes are arranged on the lower side of the central air hole in the vertical direction. The four fourth air holes located on the upper and lower sides of the central air hole are horizontally arranged and the vertical distance from the central air hole is a4. The diameters of the eight fourth air holes are both d5, and the horizontal spacing between two adjacent fourth air holes in the horizontal direction is a0; wherein, the diameter of the fourth air hole is larger than that of the first air hole, the second air hole, and the third air hole.

[0031] The cladding region is located in the outer layer of the core region, and the cladding region includes a plurality of evenly arranged fifth air holes 6, the fifth air holes have a diameter of d6, the hole spacing is a0, and the fifth air holes are arranged in a regular hexagonal structure. Compared with other arrangements, the photonic crystal fiber with a cladding arranged in a regular hexagonal structure has a more stable structure and is easier to draw.

[0032] Optionally, the diameter d1 of the central air hole has a value range of 0.95-1.05 um. The difference between the diameter d1 of the central air hole and the diameter of the first air hole constitutes a double refraction effect.

[0033] Optionally, the horizontal distance a1 between the first air hole and the central air hole is in the range of 1.795-1.805 um. The step distance difference between the first air hole and the surrounding air holes constitutes a birefringence effect.

[0034] Optionally, the value range of the diameter d2 of the first air hole is 0.595-0.605 um. The difference between the diameter of the first air hole and the diameters of the surrounding air holes constitutes a birefringence effect.

[0035] Optionally, the horizontal distance a2 between the second air hole and the central air hole is in the range of 4.49-4.51 um. Optionally, the diameter d3 of the second air hole is in the range of 0.795-0.805 um.

[0036] Optionally, a horizontal distance a3 between the third air hole and the central air hole is in a range of 7.195-7.205 um; a diameter d4 of the third air hole is in a range of 0.795-0.805 um.

[0037] Optionally, the diameter d5 of the fourth air hole is in the range of 3.349-3.351 um. Optionally, the vertical distance a4 between the fourth air hole and the central air hole is in the range of 3.116-3.118 um.

[0038] Optionally, the value range of a0 is 3.598-3.602 um; the value range of the fifth air hole diameter d6 is 0.998-1.002 um.

[0039] The differences in diameter and distance of the air holes in the above structure make the core structure have a good birefringence effect, which facilitates the transmission of optical signals, reduces noise, and improves transmission efficiency.

[0040] like Figure 1As shown, 1 is the central air hole; 2 is the two cores of the optical fiber; 3 is two air holes at a2 on both sides of the central air hole in the horizontal direction; 4 is two air holes at a3 on both sides of the central air hole in the horizontal direction; 5 is eight large air holes at a4 distance from the central air hole in the vertical direction; 6 is the cladding air hole; 7 is the pure quartz glass substrate. The two cores are nematic liquid crystals filled with high birefringence materials in the air holes, and the cores are regular circles. In addition, air holes of different sizes are introduced around the cores to increase the structural birefringence of the core area. Therefore, the birefringence of the present invention can be regarded as the combined effect of the high birefringence material (nematic liquid crystal E7) and the artificially constructed core area structural birefringence. The refractive index of liquid crystal is higher than that of quartz. Therefore, from the perspective of a single core, its transmission mechanism is the same as that of a traditional single-mode optical fiber, which is total internal reflection. From the perspective of the dual-core structure, the present invention is supermode transmission. Therefore, the present invention belongs to a hybrid light guiding mechanism. According to the coupled mode theory, in a dual-core structure, a mode coupling effect will occur between the two cores, forming a total of 4 supermodes.

[0041] like Figure 2 As shown, the rotation angle of the liquid crystal molecules can be controlled by an external electric field. When the rotation angle of the liquid crystal is 90°, the present invention utilizes a mode cutoff method to couple and cut off the two supermodes in the x polarization direction with the fundamental space filling mode at a wavelength less than 0.99 μm, leaving only the two supermodes in the y polarization direction. The optical fiber can achieve single polarization output in the wavelength range of 0.99 μm to 1.86 μm, which covers the entire O+E+S+C+L+U communication band.

[0042] like Figure 3 As shown, when the fiber length is 2.38mm, the energy of the 1310nm light reaches the maximum in one fiber core, while the 1550nm light reaches the maximum in the other fiber core, and the two crosstalk noises are -68.18dB.

[0043] Embodiment 1: The radius d1 of the central air hole is in the range of 0.95um. The distance a1 between the two fiber cores and the left and right sides of the central air hole in the horizontal direction is in the range of 1.795um, and the diameter d2 of the fiber core is in the range of 0.595um. The distance a2 between the two air holes and the left and right sides of the central air hole in the horizontal direction is in the range of 4.49um, and the diameter d3 is in the range of 0.795um. The distance a3 between the two air holes and the left and right sides of the central air hole in the horizontal direction is in the range of 7.195um, and the diameter d4 is in the range of 0.795um. The distance a4 between the eight air holes and the upper and lower sides of the central air hole in the vertical direction is in the range of 3.116um, and the distance d4 is in the range of 3.349um. The diameter d6 of the air holes in the cladding area is in the range of 0.998um. The air hole spacing a0 in the cladding area is in the range of 3.598um.

[0044] Embodiment 2: The radius d1 of the central air hole is in the range of 1.05um. The distance a1 between the two fiber cores and the left and right sides of the central air hole in the horizontal direction is in the range of 1.805um, and the diameter d2 of the fiber core is in the range of 0.605um. The distance a2 between the two air holes and the left and right sides of the central air hole in the horizontal direction is in the range of 4.51um, and the diameter d3 is in the range of 0.805um. The distance a3 between the two air holes and the left and right sides of the central air hole in the horizontal direction is in the range of 7.205um, and the diameter d4 is in the range of 0.805um. The distance a4 between the eight air holes and the upper and lower sides of the central air hole in the vertical direction is in the range of 3.118um, and the distance d4 is in the range of 3.351um. The diameter d6 of the air holes in the cladding area is in the range of 1.002um. The air hole spacing Λ0 in the cladding area is in the range of 3.602um.

[0045] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0046] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid crystal filled single polarization output dual core photonic crystal fiber wavelength splitter, Features include: A core region and a cladding region, wherein the core region and the cladding region are filled with pure quartz glass substrate material; The core area includes a central air hole, two first air holes, two second air holes, two third air holes, and eight fourth air holes; wherein the central air hole is located in the center of the core area, and the diameter of the central air hole is d1; the two first air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a1, the two first air holes are filled with nematic liquid crystals, and the first air holes filled with nematic liquid crystals serve as the core of the optical fiber, and the diameters of the two first air holes are both d2; the two second air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a1. The horizontal distance is a2, and the diameters of the two second air holes are both d3; the two third air holes are respectively arranged on the left and right sides of the central air hole in the horizontal direction, and the horizontal distance from the central air hole is a3, and the diameters of the two third air holes are both d4; the four fourth air holes are arranged on the upper side of the central air hole in the vertical direction, and the other four fourth air holes are arranged on the lower side of the central air hole in the vertical direction, and the four fourth air holes located on the upper and lower sides of the central air hole are horizontally arranged and the vertical distance from the central air hole is a4, the diameters of the eight fourth air holes are all d5, and the horizontal spacing between two adjacent fourth air holes in the transverse direction is a0; The cladding region is located in the outer layer of the core region, and the cladding region includes a plurality of fifth air holes evenly arranged, the diameters of the fifth air holes are all d6, the hole spacings are all a0, and the fifth air holes are arranged in a regular hexagonal structure; The diameter d1 of the central air hole has a value range of 0.95-1.05um; The horizontal distance a1 between the first air hole and the central air hole ranges from 1.795 to 1.805 um.

2. The beam splitter according to claim 1, Features: The value range of the first air hole diameter d2 is 0.595-0.605 um.

3. The beam splitter according to claim 1, Features: The horizontal distance a2 between the second air hole and the central air hole ranges from 4.49 to 4.51 um.

4. The beam splitter according to claim 1, Features: The value range of the second air hole diameter d3 is 0.795-0.805 um.

5. The beam splitter according to claim 1, Features: The horizontal distance a3 between the third air hole and the central air hole is in the range of 7.195-7.205 um; the diameter d4 of the third air hole is in the range of 0.795-0.805 um.

6. The beam splitter according to claim 1, Features: The value range of the fourth air hole diameter d5 is 3.349-3.351 um.

7. The beam splitter according to claim 1, Features: The vertical distance a4 between the fourth air hole and the central air hole ranges from 3.116 to 3.118 um.

8. The beam splitter according to claim 1, Features: The value range of a0 is 3.598-3.602 um; the value range of the fifth air hole diameter d6 is 0.998-1.002 um.

Images