Wavelength converter and method for manufacturing the same, optical network node device

Abstract

The application provides a wavelength converter, an optical network node device and a preparation method of the wavelength converter, which can be applied to scenarios such as wavelength division optical communication networks. The wavelength converter comprises a cladding, a plurality of ring structures and a graphene piece, the plurality of ring structures are located in an internal space surrounded by the cladding, and at least part of the graphene piece is located in an optical wave transmission area, and the optical wave transmission area is located in the internal space. The wavelength converter of the application combines and utilizes the wide-spectrum ultra-low dispersion and optical field binding capacity of the optical fiber composed of the cladding and the ring structure, and the dispersion-free, wide-band low-loss transmission characteristics and ultra-high third-order nonlinear coefficient of the graphene piece, the conversion bandwidth can reach 461 nm, and the conversion efficiency can reach -21.7 dB.

Description

Technical Field

[0001] This application relates to the field of optical technology, and in particular to a wavelength converter and its fabrication method, and an optical network node device. Background Technology

[0002] In recent years, with the development of technology and the large-scale application of wavelength division multiplexing (WDM), the capacity of optical network node devices has been increasing. Optical cross-connects (OXCs) are widely deployed in WDM optical communication networks, but wavelength blocking may occur, affecting the overall network throughput. Existing optical-electrical-optical wavelength conversion methods involve electrical conversion, which has inherent disadvantages such as high power consumption, complex structure, and slow response rate. In contrast, all-optical wavelength conversion utilizes analog conversion of optical signals, without involving electrical conversion, and has advantages such as low power consumption, simple structure, transparent modulation format, and high response rate. In all-optical wavelength conversion, it is necessary to design a nonlinear optical device with high conversion efficiency and wide conversion bandwidth. From a physical perspective, the nonlinear optical device is required to have both high nonlinear effect and low dispersion characteristics. Existing nonlinear optical devices have low conversion efficiency and narrow conversion bandwidth. Summary of the Invention

[0003] This application provides a wavelength converter, an optical network node device, and a method for fabricating the wavelength converter. The wavelength converter of this application combines and utilizes the broadband ultra-low dispersion and optical field confinement capability of optical fiber composed of cladding and ring structure, as well as the dispersion-free, broadband low-loss transmission characteristics and ultra-high third-order nonlinear coefficient of graphene components. The conversion bandwidth can reach 461nm and the conversion efficiency can reach -21.7dB.

[0004] In a first aspect, this application provides a wavelength converter, including a cladding, a plurality of ring structures and graphene components, wherein the cladding surrounds and forms an internal space, the plurality of ring structures are located within the internal space, and at least a portion of the graphene components are located in the region for light wave transmission, the region for light wave transmission being located within the internal space.

[0005] Optical fibers composed of a cladding and multiple ring structures exhibit an anti-resonance effect. This anti-resonance effect refers to the phenomenon where light of a specific wavelength range is reflected by the ring structure due to the Fabry-Perot cavity effect, where the specific wavelength range is proportional to the thickness of the ring structure. In this application, light of a specific wavelength range, after being irradiated by the ring structure, is confined within the core region formed by the ring structure. In this application, the core region is used for optical wave transmission, and light propagates within the core region using air as a medium. Propagation using air as a medium has extremely low dispersion values. Therefore, the optical fiber composed of a cladding and multiple ring structures in this application has low dispersion values ​​and strong light field confinement capabilities, resulting in high conversion bandwidth.

[0006] The graphene element has a sheet-like structure, and the graphene within it exhibits dispersion-free and broadband low-loss transmission characteristics. The graphene element exhibits a third-order nonlinear effect, which refers to the change in the physical properties of the graphene element after strong light irradiation, affecting the phase change of the light wave. When two different wavelengths of light are incident on the graphene element, the stronger light of the two wavelengths triggers the third-order nonlinear effect in the graphene, leading to four-wave mixing to generate light of a new wavelength. The third-order nonlinear effect of the graphene affects the four-wave mixing effect. The larger the third-order nonlinear coefficient of the nonlinear medium, the stronger the third-order nonlinear effect and the stronger the four-wave mixing effect. In this application, the third-order nonlinear coefficient of the graphene is eight orders of magnitude higher than that of silicon dioxide fiber, thus exhibiting higher conversion efficiency and effectively improving optical wave conversion efficiency.

[0007] In this application, the wavelength conversion principle of the wavelength converter is as follows: When the signal light and pump light pass through the optical wave converter, part of the pump light and part of the signal light pass through the graphene device. Under the third-order nonlinear effect of graphene in the graphene device, the two pump photons in the pump light disappear to generate one signal photon and one idler photon. The signal light will affect the phase and wavelength of the signal photon and the idler photon during the wavelength conversion process of the graphene device. That is, the generated signal photon has the same phase and wavelength as the original signal light. The signal photon and the original signal light are superimposed to generate a signal light with enhanced power. All the idler photons generated continuously constitute the idler light, and the phase of the idler light is opposite to that of the signal light. During this process, the pump light will attenuate (or the power of the pump light will decrease) and be output as the attenuated pump light.

[0008] In this wavelength conversion process, the conversion efficiency is proportional to the product of the pump optical power and the third-order nonlinear coefficient of the graphene. Given a fixed pump optical power, the graphene component used in this application has a large third-order nonlinear coefficient, thereby improving the wavelength conversion efficiency. Conversion efficiency is expressed as a multiple of the output idler optical power divided by the input signal optical power, measured in dB.

[0009] In this wavelength conversion process, the conversion bandwidth is proportional to the product of the pump light power, the third-order nonlinear coefficient of graphene, and the reciprocal of the dispersion value of the optical fiber. The optical fiber in the reciprocal of the dispersion value is an optical fiber composed of cladding and multiple ring structures. The lower the dispersion value, the larger the third-order nonlinear coefficient, and the larger the pump light power, the larger the conversion bandwidth. The optical fiber composed of cladding and multiple ring structures provided in this application has an extremely low dispersion value, thereby improving the conversion bandwidth.

[0010] The conversion bandwidth is defined as |signal wavelength - idler wavelength|, which is the absolute value of the difference between the signal wavelength and the idler wavelength. The larger the conversion bandwidth, the wider the range of wavelengths that can be converted, and the wider the range of wavelengths that can be selected in specific applications.

[0011] The pump light described in this application refers to a continuous high-power laser with a power range of 0.5W-4W. If the power is too low, the conversion bandwidth cannot be obtained. The pump light described in this application is preferably around 1550nm, while ordinary visible light is too far from the pump light wavelength, resulting in low power and ineffective wavelength conversion.

[0012] In specific application scenarios, the target wavelength to be converted may have multiple wavelengths, meaning the wavelength of the converted idler light may have multiple wavelengths. In this application, the wavelength of the idler light can be adjusted by controlling the wavelength of the pump light. During the wavelength conversion process, the wavelength converter generates one signal photon and one idler photon by the disappearance of two pump photons. According to the law of conservation of energy, 2 / λ 泵 =1 / λ 信 +1 / λ 闲 ;λ 泵 λ represents the wavelength of the pump photon. 信 λ represents the wavelength of the signal photon. 闲 λ represents the wavelength of the idler photon. 泵 The larger λ is 闲 The larger the wavelength, the more the wavelength of the idler light can be adjusted by controlling the wavelength of the pump light.

[0013] In one possible implementation of the first aspect, multiple annular structures are tangent to the inner surface of the cladding, and the portions of each annular structure facing away from the cladding constitute a negative curvature surface. The negative curvature refers to the negative rate of rotation of the tangent direction angle about a point on the curve with respect to the arc length.

[0014] In one possible implementation of the first aspect, the graphene element is fixed to the cladding. The edge of the graphene element can be fixed to the cladding at any position. The edge of the graphene element can be fixed to a position near the inner surface of the cladding, or the edge of the graphene element can be fixed to a position near the outer surface of the cladding.

[0015] In one possible implementation of the first aspect, there is a gap between two adjacent ring structures, through which the graphene element passes. Specifically, there are multiple gaps between multiple ring structures, through which the graphene element passes, or through two of the gaps.

[0016] In one possible implementation of the first aspect, a first end of the graphene element is connected to the cladding layer, and a second end of the graphene element is located within the core region. The graphene element performs wavelength conversion on incident light through the second end located within the core region. Specifically, the graphene element includes a first end, a second end, and a connecting segment connecting the first end and the second end, the connecting segment being located within a gap. In this embodiment, the first end, the second end, and the connecting segment are all made of graphene. In other embodiments, the second end located within the core region can be made of graphene, while the first end and the connecting segment can be made of other non-graphene materials, such as ultrathin glass, which can save on the cost of graphene; in some embodiments, the second end and the connecting segment can be made of graphene, while the first end is made of other materials.

[0017] In other embodiments, graphene material can be bonded to an ultrathin carrier, such as ultrathin glass. Since graphene is generally thin, bonding it to the ultrathin carrier prevents the graphene component from shifting and affecting the light conversion effect. Specifically, graphene material can be bonded to the portion of the ultrathin carrier corresponding to the second end, or to the portion corresponding to the second end and the connecting section, or the entire ultrathin carrier can be bonded with graphene material.

[0018] In this application, the cladding material is one of silicon dioxide, soft glass, or plastic; the ring structure is made of silicon dioxide.

[0019] In one possible implementation of the first aspect, the graphene element portion passing through the gap is spaced apart from the annular structures on both sides of the gap. In this application, the walls of the annular structures are very thin and easily broken; spacing the graphene element from the annular structures avoids damaging the annular structures.

[0020] In one possible implementation of the first aspect, there is a gap between two adjacent annular structures, and the width of each gap between the multiple annular structures is equal. In this application, the multiple annular structures confine light within the fiber core region, and the width of the gap between the annular structures is preferably set to 0.1 μm-10 μm to better confine the light within the fiber core region and prevent light leakage from the gaps.

[0021] In one possible implementation of the first aspect, the wavelength converter has two graphene elements, which are respectively inserted into two gaps. In other embodiments, the wavelength converter may also have three or more graphene elements, with the multiple graphene elements inserted into different gaps. Specifically, the multiple graphene elements may be evenly distributed within the internal space.

[0022] In one possible implementation of the first aspect, a plurality of annular structures have a first gap and a second gap disposed opposite to each other, and a graphene element passes through the first gap and the second gap. In this embodiment, the graphene element passes through the first gap and the second gap in parallel, and the graphene element is planar. In some embodiments, the graphene element passes through the two gaps in a curved manner, for example, passing through two adjacent gaps in a curved manner, or passing through two spaced-apart gaps in a curved manner.

[0023] In one possible implementation of the first aspect, the two ends of the graphene element are connected to the cladding layer, and the graphene element passes through the core region. The graphene element performs wavelength conversion on incident light through a portion located within the core region. Specifically, the graphene element includes a first end, a second end, and a main body portion connecting the first and second ends. The first and second ends are fixedly connected to the cladding layer. The main body portion includes a first connecting segment, a second connecting segment, and a central segment connecting the first and second connecting segments. The central segment is located within the core region, the first connecting segment is located within a first gap, and the second connecting segment is located within a second gap. The graphene element performs wavelength conversion on incident light through the central segment located within the core region. In this embodiment, the first end, the second end, and the main body portion are all made of graphene. In other embodiments, only the central segment may be made of graphene, while other parts may be made of other materials, such as ultrathin glass; or the main body portion may be made of graphene, while other parts may be made of other materials. In this embodiment, the two ends of the graphene element are fixed to the cladding layer. In some implementations, the wavelength converter includes two graphene elements, one of which is fixed at both ends to the cladding, and the other of which is fixed at one end to the cladding.

[0024] In one possible implementation of the first aspect, the cladding layer has a first through-hole and a second through-hole penetrating both opposite surfaces of the cladding layer. The first through-hole and a first gap are radially corresponding, and the second through-hole and a second gap are radially corresponding. The graphene element passes through the first through-hole and the second through-hole. The radial direction is the direction from the inner surface of the cladding layer towards the center of the internal space. The first and second through-holes can be formed by laser penetration. In a preferred embodiment, the extension lines of the central axes of the first and second through-holes overlap. In another preferred embodiment, the central axes of the first through-hole, the first gap, the second gap, and the second through-hole overlap to facilitate the smooth insertion of the graphene element.

[0025] In one possible implementation of the first aspect, the wavelength converter further includes an encapsulation component for fixing the graphene element to the cladding. When the graphene element is fixed to the cladding via its first end, the first end can be connected and fixed to the cladding via the encapsulation component; when the graphene element is fixed to the cladding via its first and second ends, the first and second ends can be connected and fixed to the cladding via the encapsulation component.

[0026] In one possible implementation of the first aspect, the encapsulation component is formed by curing liquid adhesive or by laser ablation.

[0027] In one possible implementation of the first aspect, the encapsulation component includes a first encapsulation sub-component and a second encapsulation sub-component. A first end is fixedly connected to the cladding layer via the first encapsulation sub-component, and a second end is fixedly connected to the cladding layer via the second encapsulation sub-component. Specifically, a portion of the first encapsulation sub-component is connected to the outer surface of the cladding layer adjacent to a first through-hole, and a portion of the first encapsulation sub-component is located in the first through-hole and connected to the first end of the graphene component; a portion of the second encapsulation sub-component is connected to the outer surface of the cladding layer adjacent to a second through-hole, and a portion of the second encapsulation sub-component is located in the second through-hole and connected to the second end of the graphene component.

[0028] In one possible implementation of the first aspect, the graphene component includes a first graphene sub-component and a second graphene sub-component, which are arranged along the axial direction of the cladding. The axial direction refers to the direction of the cladding rotation center axis, and is perpendicular to the radial direction. In this embodiment, the graphene component includes two graphene sub-components; in other embodiments, the graphene component may include three or more graphene sub-components.

[0029] In one possible implementation of the first aspect, the orthographic projections of the first graphene sub-component and the second graphene sub-component onto the cross-section of the cladding have a predetermined angle. The cross-section of the cladding is perpendicular to the axial direction and parallel to the radial direction. In other embodiments, when the graphene component comprises three or more graphene sub-components, an angle may be provided between each graphene sub-component.

[0030] In one possible implementation, the axial length of the graphene element is 2mm-20mm. If the graphene element is too long, it increases pump light loss, causing pump light attenuation and a decrease in pump light power. Since the conversion efficiency of the wavelength converter is proportional to the product of the pump light power and the third-order nonlinear coefficient of the graphene element, a decrease in pump light power further affects the conversion efficiency. Conversely, if the graphene element is too short, maximum conversion efficiency cannot be achieved. Setting the axial length of the graphene element within the aforementioned range yields better conversion performance. When the graphene element comprises two or more graphene sub-elements, the total length of the two or more graphene sub-elements is 2mm-20mm.

[0031] The radial width of the graphene component ranges from 100 μm to 300 μm. Specifically, the radial width of the graphene component can be set according to the size of the cladding or ring structure.

[0032] The thickness of the graphene element ranges from 0.5 nm to 10 nm. The thickness direction of the graphene element is perpendicular to both its width and length directions. Excessive thickness of the graphene element increases pump light loss and attenuation, resulting in decreased pump light power and consequently affecting conversion efficiency. Setting the graphene element thickness within the aforementioned range yields better conversion performance.

[0033] In this application, the cladding is preferably cylindrical, and the annular structure is tubular. The inner diameter of the cladding ranges from 50μm to 100μm, the outer diameter ranges from 100μm to 500μm, and the thickness ranges from 50μm to 400μm. The inner diameter of the annular structure ranges from 10μm to 40μm, and the wall thickness ranges from 375nm to 750nm.

[0034] In one possible implementation of the first aspect, multiple ring structures are symmetrically distributed on both sides of the graphene element. This symmetrical distribution reduces light propagation loss within the core region 11.

[0035] In one possible implementation of the first aspect, the inner surface of the cladding has a radial cross-section that is polygonal, with each annular structure tangent to each side of the polygon. In this embodiment, the polygon is hexagonal, and there are six annular structures, each tangent to one of the six sides of the hexagon. In another embodiment, when the polygon is octagonal, there are eight annular structures, each tangent to one of the eight sides of the octagon.

[0036] In one possible implementation of the first aspect, the ring structure includes a first sub-ring structure and a second sub-ring structure. The inner diameter of the first sub-ring structure is larger than the outer diameter of the second sub-ring structure. The second sub-ring structure is tangent to the first sub-ring structure and tangent to the first sub-ring structure at a first tangent point. The first sub-ring structure is tangent to the inner surface of the cladding at a second tangent point, and the first and second tangent points coincide. In this embodiment, the ring structure consists of two sub-ring structures. When light waves are incident on the wall of the first sub-ring structure, after passing through the Fabry-Perot cavity effect, part of the light waves pass through the wall and are incident on the outer wall of the second sub-ring structure. Part of the light waves, after passing through the wall of the second sub-ring structure, are reflected back to the wall of the first sub-ring structure after passing through the Fabry-Perot cavity effect. This is equivalent to some light waves undergoing two Fabry-Perot cavity effects before entering the fiber core region, which can increase the light intensity in the fiber core region. In other embodiments, the first and second tangent points may not coincide.

[0037] In one possible implementation of the first aspect, the radial cross-section of the annular structure is elliptical, with the major axis of the ellipse pointing towards the center of the fiber core region. In another embodiment, the minor axis of the ellipse points towards the center of the fiber core region.

[0038] In some embodiments, the ring structure includes a third sub-ring structure and a fourth sub-ring structure, wherein the shape of the third sub-ring structure differs from the shape of the fourth sub-ring structure, and multiple third sub-ring structures and multiple fourth sub-ring structures are distributed alternately. For example, the third sub-ring structure is a small ring, and the fourth sub-ring structure is a large ring; or, the third sub-ring structure is a ring, and the fourth sub-ring structure is a double ring; or, the third sub-ring structure is an ellipse, and the fourth sub-ring structure is a ring, etc.

[0039] In this application, the number of ring structures 120 is preferably 6 or 8. In other embodiments, other numbers are also possible.

[0040] Secondly, this application provides an optical network node device, including the wavelength converter described above.

[0041] In one possible implementation of the second aspect, the optical network node device includes a pump laser, an optical amplifier, a first filter, a signal source, an optical multiplexer, and a second filter. The pump laser is used to generate a first pump light; the optical amplifier is used to amplify the power of the first pump light; the first filter is used to filter out the radiation signal generated by the optical amplifier when the first pump light is amplified. The first pump light is preferably a laser with continuous high power, the power range of the first pump light is 0.5W-4W, and the wavelength of the first pump light is preferably 1550nm; the signal source is used to emit... The first signal light has a wavelength of 1548 nm. In some embodiments, the wavelength of the first signal light can be 850 nm, or around 1550 nm and 850 nm. The optical multiplexer is used to integrate the first signal light and the first pump light into the same optical fiber for transmission. The optical multiplexer can be an optical coupler. After receiving the first signal light and the first pump light, the wavelength converter generates a second pump light, a second signal light, and an idler light. The second filter is used to filter out the second pump light and the second signal light from the second pump light, the second signal light, and the idler light to obtain the idler light.

[0042] Thirdly, this application provides a method for fabricating a wavelength converter, the method comprising:

[0043] A cladding layer is provided, which surrounds and forms an internal space, within which multiple annular structures are formed. Specifically, the annular structures are formed by placing annular preforms within the internal space and then heating and stretching the annular preforms. During the stretching process, the annular structures are connected and fixed to the inner surface of the cladding layer.

[0044] Through-holes are formed by slotting in the cladding. Specifically, a laser can be used to slot from the outer surface of the cladding to the inner surface to form through-holes. The axial length of the through-hole matches the axial length of the graphene component. The laser can be a femtosecond laser, which allows for more precise slotting within the cladding. When the graphene component is fixed to the cladding at only one end, a first through-hole can be formed on only one side of the cladding. When both ends of the graphene component are fixed to the cladding, a first through-hole and a second through-hole can be formed on both sides of the cladding, respectively.

[0045] The graphene element is installed within the internal space via the through-hole, with at least a portion of the graphene element located within the light wave transmission region, which is also located within the internal space. The positional relationship between the graphene element, the cladding, and the ring structure is as described above and will not be repeated here. When inserting the graphene element into the internal space, it is necessary to avoid physical damage to the graphene element from contacting the cladding and ring structure.

[0046] The graphene element is fixed to the cladding by an encapsulation component. Attached Figure Description

[0047] Figure 1 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0048] Figure 2 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0049] Figure 3 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0050] Figure 4 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0051] Figure 5 This is a schematic diagram illustrating wavelength conversion using an application wavelength converter according to one embodiment of this application;

[0052] Figure 6 This is a schematic diagram of the structure of an optical network node device provided in one embodiment of this application;

[0053] Figure 7 This is a schematic diagram of a wavelength division optical communication network provided in one embodiment of this application;

[0054] Figure 8 This is a schematic diagram of an optical network node device provided in one embodiment of the present application applied in a wavelength division optical communication network;

[0055] Figure 9This is a schematic diagram of an optical network node device provided in one embodiment of the present application applied in a wavelength division optical communication network;

[0056] Figure 10 This is a schematic diagram of an optical network node device provided in one embodiment of the present application applied in a wavelength division optical communication network;

[0057] Figure 11 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0058] Figure 12 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0059] Figure 13 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0060] Figure 14 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0061] Figure 15 This is a three-dimensional schematic diagram of a wavelength converter provided in one embodiment of this application, omitting the ring structure;

[0062] Figure 16 This is a three-dimensional schematic diagram of a wavelength converter provided in one embodiment of this application, omitting the ring structure;

[0063] Figure 17 The wavelength converter provided in one embodiment of this application omits a radial cross-sectional view of the annular structure;

[0064] Figure 18 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0065] Figure 19 This is a three-dimensional schematic diagram of a wavelength converter provided in one embodiment of this application;

[0066] Figure 20 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0067] Figure 21 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0068] Figure 22 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0069] Figure 23 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0070] Figure 24 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0071] Figure 25 This is a radial cross-sectional view of a wavelength converter provided in one embodiment of this application;

[0072] Figure 26 This is a simulation diagram of the normalized electric field of a wavelength converter provided in one embodiment of this application;

[0073] Figure 27 yes Figure 26 Light intensity distribution maps for each region;

[0074] Figure 28 This is a schematic diagram of a wavelength converter performing wavelength conversion according to a comparative embodiment of this application;

[0075] Figure 29 This is a schematic diagram of a wavelength converter performing wavelength conversion according to a comparative embodiment of this application;

[0076] Figure 30 This is a schematic diagram of a wavelength converter performing wavelength conversion according to a comparative embodiment of this application;

[0077] Figure 31 This is a flowchart of a method for fabricating a wavelength converter according to one embodiment of this application. Detailed Implementation

[0078] The embodiments of this application are described below with reference to the accompanying drawings.

[0079] For ease of understanding, the English abbreviations and related technical terms used in the embodiments of this application will be explained and described below.

[0080] Graphene is a two-dimensional material consisting of a hexagonal honeycomb lattice of carbon atoms, only one atom thick.

[0081] Wavelength conversion: refers to the technology of transferring signals carrying service information from one wavelength to another at intermediate nodes in an all-optical network.

[0082] Fabry-Perot cavity effect: also known as the Fabry-Perot resonant cavity effect, is composed of two parallel plane mirrors. Light can travel back and forth multiple times in the resonant cavity, producing a resonance enhancement effect. The light that can produce resonance enhancement is light whose phase increases by an integer multiple of 2π for one period of transmission between the two mirrors.

[0083] Four-wave mixing is a type of optical wave coupling effect generated by the interaction of the real part of the third-order polarization of the optical fiber medium. It is caused by the interaction of different wavelengths, resulting in the generation of so-called mixing products or new optical waves in the sidebands at other wavelengths. This interaction may occur between signals in a multi-channel system.

[0084] QPSK (Quadrature Phase Shift Keying): Quadrature phase shift keying.

[0085] QAM (Quadrature Amplitude Modulation): Quadrature amplitude modulation.

[0086] PAM (Pulse Amplitude Modulation): Pulse amplitude modulation.

[0087] OOK (On-Off Keying): Binary amplitude keying.

[0088] Evanescent field: The interference between the incident wave and the reflected wave forms a standing wave distribution in the incident region. Although all the power is reflected back, there is still a light field in the second medium. Its field strength disappears rapidly with the increase of distance to the boundary. Such a vanishing field that does not carry energy is called an evanescent field.

[0089] This application provides a wavelength converter, an optical network node device, and a method for fabricating the wavelength converter. The wavelength converter is used in wavelength division multiplexing (WDM) optical communication networks to perform wavelength conversion and resolve wavelength conflicts in network links. Using the wavelength converter of this application, wavelength conversion can be performed at high speed, with high efficiency and transparent format transformation of service signals.

[0090] The wavelength converter provided in this application includes a cladding, multiple ring structures, and a graphene element. The cladding surrounds and forms an internal space, the multiple ring structures are located within the internal space, and at least a portion of the graphene element is located in the region of light transmission, which is also located within the internal space. This wavelength converter combines and utilizes the broadband ultra-low dispersion and light field confinement capabilities of optical fibers composed of cladding and ring structures, as well as the dispersion-free, broadband low-loss transmission characteristics and ultra-high third-order nonlinear coefficient of the graphene element, achieving a conversion bandwidth of 461 nm and a conversion efficiency of -21.7 dB.

[0091] Please see Figure 1This application provides a wavelength converter 10, including a cladding 110, a plurality of ring structures 120, and a graphene element 200. The cladding 110 surrounds and forms an internal space 12, and the plurality of ring structures 120 are located within the internal space 12. At least a portion of the graphene element 200 is located in the region for light wave transmission, which is located within the internal space 12. In this embodiment, the region commonly surrounded by the plurality of ring structures 120 is a fiber core region 11, which is used for light wave transmission. The surrounding region includes a region surrounded by the plurality of ring structures 120 with gaps between each ring structure 120. Please refer to [link to relevant documentation]. Figure 2 In this embodiment, the core region 11 is preferably a region surrounded by a plurality of annular structures 120 at points closest to the center of the cladding 110. Please refer to [link / reference]. Figure 3 In some other embodiments, the core region 11 may be a region surrounded by a plurality of annular structures 120 near the center of the cladding 110.

[0092] The cladding 110 has an internal space 12 in the middle. In this embodiment, the cladding 110 is cylindrical (e.g., ...). Figure 1 As shown in the diagram, both the inner surface 111 and the outer surface 112 of the cladding 110 are cylindrical. In some embodiments, the outer surface 112 of the cladding 110 can be a polygonal columnar shape, and the inner surface 111 is cylindrical. In some embodiments, the outer surface 112 of the cladding 110 can be cylindrical, and the inner surface 111 is a polygonal columnar shape (e.g., ...). Figure 20 As shown in the figure, the cladding 110 is used to provide support for the annular structure 120.

[0093] In this embodiment, the annular structure 120 is a microcapillary structure, and there are 6 annular structures 120 (e.g., Figure 1 As shown, six annular structures 120 are evenly distributed inside the cladding 110, and each annular structure 120 is tangent to the inner surface 111 of the cladding 110. The annular structure 120 is formed by heating and stretching an annular preform. During the stretching process, the annular structure 120 is connected and fixed to the inner surface 111 of the cladding 110.

[0094] In this application, the optical fiber 100, composed of a cladding 110 and multiple ring structures 120, exhibits an anti-resonance effect. This anti-resonance effect refers to the phenomenon where light of a specific wavelength range is reflected by the ring structure 120 due to the Fabry-Perot cavity effect. The specific wavelength range is proportional to the thickness of the ring structure 120. In this application, light of a specific wavelength range, after being irradiated by the ring structure 120, is confined within the core region 11 formed by the ring structure 120. In this application, the core region 11 is used for optical wave transmission, and the light propagates within the core region 11 using air as a medium. Propagation using air as a medium results in extremely low dispersion.

[0095] The optical fiber 100 composed of cladding 110 and multiple ring structures 120 in this application has a low dispersion value and a strong light field confinement ability, which makes it have a high conversion bandwidth capability.

[0096] Furthermore, multiple annular structures 120 are tangent to the inner surface of the cladding 110, and the portion of each annular structure 120 facing away from the cladding 110 constitutes a negative curvature surface. The negative curvature refers to the negative rate of rotation of the tangent direction angle about a point on a curve with respect to the arc length. For example... Figure 4 As shown, in Figure 4 The surface of part E between two adjacent annular structures 120 is a negative curvature surface, and the surface of part E is located on the outer surface of the annular structure 120.

[0097] In this application, the graphene element 200 has a sheet-like structure, and the graphene in the graphene element 200 possesses dispersion-free and broadband low-loss transmission characteristics. The graphene element 200 exhibits a third-order nonlinear effect, which refers to the change in the physical properties of the graphene element 200 itself after being irradiated by strong light, affecting the phase change of the light wave. When two different wavelengths of light are incident on the graphene element 200, the strong light of the two different wavelengths will induce the third-order nonlinear effect of the graphene, thereby causing four-wave mixing to generate light of a new wavelength. The third-order nonlinear effect of graphene affects the four-wave mixing effect. The larger the third-order nonlinear coefficient of the nonlinear medium, the stronger the third-order nonlinear effect and the stronger the four-wave mixing effect. The third-order nonlinear coefficient of graphene is eight orders of magnitude higher than that of silicon dioxide fiber, thus exhibiting higher conversion efficiency and effectively improving the optical wave conversion efficiency.

[0098] Please see Figure 5In this application, the wavelength conversion principle of the wavelength converter 10 is as follows: When the signal light L1 and the pump light L2 pass through the wavelength converter 10, part of the pump light L2 and part of the signal light L1 pass through the graphene device 200. Under the third-order nonlinear effect of graphene in the graphene device 200, the two pump photons in the pump light L2 disappear to generate one signal photon and one idler photon. The signal light L1 will affect the phase and wavelength of the signal photon and the idler photon during the wavelength conversion process of the graphene device 200. That is, the generated signal photon has the same phase and wavelength as the original signal light L1. The signal photon and the original signal light L1 are superimposed to generate the signal light L3 with enhanced power. All the idler photons generated continuously constitute the idler light L4. The phase of the idler light L4 is opposite to the phase of the signal light L3. During this process, the pump light L2 will attenuate (or the power of the pump light L2 will decrease) and be output as the attenuated pump light L5.

[0099] In this wavelength conversion process, the conversion efficiency is proportional to the product of the pump light L2 power and the third-order nonlinear coefficient of the graphene. Given a fixed pump light L2 power, the graphene in the graphene element 200 used in this application has a large third-order nonlinear coefficient, thereby improving the wavelength conversion efficiency. The conversion efficiency is expressed as a multiple of the output idler light L4 power divided by the input signal light L1 power, and is measured in dB.

[0100] In this wavelength conversion process, the conversion bandwidth is proportional to the product of the pump light L2 power, the third-order nonlinear coefficient of graphene, and the reciprocal of the dispersion value of the optical fiber 100. The optical fiber 100 in the reciprocal of the dispersion value is composed of a cladding 110 and multiple ring structures 120. The lower the dispersion value, the larger the third-order nonlinear coefficient, and the larger the pump light L2 power, the larger the conversion bandwidth. The optical fiber 100 provided in this application, composed of a cladding 110 and multiple ring structures 120, has an extremely low dispersion value, thereby improving the conversion bandwidth.

[0101] Wherein, the conversion bandwidth = |signal light wavelength - idler light wavelength|, that is, the absolute value of the difference between the wavelength of signal light L1 and the wavelength of idler light L4; the larger the value of the conversion bandwidth, the larger the range of wavelengths that can be converted, and the wider the range of selectable wavelengths in specific applications.

[0102] For example, if the wavelength of signal light L1 is 1550nm and the conversion bandwidth is 20nm, then the wavelength range that signal light L1 can be converted is 1540nm-1560nm; when the conversion bandwidth is 200nm, then the wavelength range that signal light L1 can be converted is 1450nm-1650nm, with more wavelength channels available for conversion. Therefore, the larger the conversion bandwidth, the better.

[0103] The pump light L2 mentioned in this application refers to a continuous high-power laser with a power range of 0.5W-4W. If the power is too low, the conversion bandwidth cannot be obtained. The pump light L2 mentioned in this application is preferably around 1550nm. However, ordinary visible light is too far from the wavelength of the pump light L2, resulting in low power and ineffective wavelength conversion.

[0104] In specific application scenarios, the target wavelength to be converted may have multiple wavelengths, meaning the converted idler light L4 may have multiple wavelengths. In this application, the wavelength of the idler light L4 can be adjusted by controlling the wavelength of the pump light L2. During the wavelength conversion process, the wavelength converter 10 generates one signal photon and one idler photon by the disappearance of two pump photons. According to the law of conservation of energy, 2 / λ 泵 =1 / λ 信 +1 / λ 闲 ;λ 泵 λ represents the wavelength of the pump photon. 信 λ represents the wavelength of the signal photon. 闲 λ represents the wavelength of the idler photon. 泵 The larger λ is 闲 The larger the wavelength of the pump light L4, the more the wavelength of the idler light L2 can be adjusted by controlling the wavelength of the pump light L4.

[0105] Please see Figure 6This application also provides an optical network node device 20, which includes the wavelength converter 10 as described above. Specifically, the optical network node device 20 includes a pump laser 21, an optical amplifier 22, a first filter 23, a signal source 24, an optical multiplexer 25, and a second filter 26. The pump laser 21 generates a first pump light L0; the optical amplifier 22 amplifies the power of the first pump light L0; the first filter 23 filters out the radiation signal generated by the optical amplifier 22 when the first pump light L0 is amplified. The first pump light L2 after amplification and filtering out the radiation signal is denoted as L2. The first pump light L2 is preferably a continuous high-power laser, and the power range of the first pump light L2 is 0.5W- 4w, the wavelength of the first pump light L2 is preferably 1550nm; the signal source 24 is used to emit the first signal light L1, the wavelength of the first signal light L1 is 1548nm, in some embodiments, the wavelength of the first signal light L1 can be 850nm, or near 1550nm and 850nm; the optical multiplexer 25 is used to integrate the first signal light L1 and the first pump light L2 into the same optical fiber for transmission, the optical multiplexer 25 can be an optical coupler; after receiving the first signal light L1 and the first pump light L2, the wavelength converter 10 generates the second pump light L5, the second signal light L3 and the idler light L4; the second filter 26 is used to filter out the second pump light L5 and the second signal light L3 from the second pump light L5, the second signal light L3 and the idler light L4 to obtain the idler light L4.

[0106] In one application scenario, the optical network node device 20 of this application can be used as an OXC node in a wavelength division multiplexing (WDM) optical communication network 30 to resolve wavelength conflicts in the network link. In other words, the optical network node device 20 of this application is used as an OXC node to perform wavelength conversion. Figure 7As shown, the wavelength division multiplexing (WDM) optical communication network 30 includes a transmitter 101, a first node 102, a second node 103, and a receiver 104. The transmitter 101 transmits signal light with a wavelength of λ0. The first node 102 includes at least one input port and at least three output ports. The signal light with wavelength λ0 is output from the three output ports after passing through the input port of the first node 102. The second node 103 includes at least three input ports that are connected to the three output ports of the first node 101, and at least one output port. The three input ports of the second node 103 and the three output ports of the first node 101 are connected to each other. Three paths should be connected to form a first path a, a second path b, and a third path c. Each of the first path a, the second path b, and the third path c has a communication channel available for optical transmission with wavelengths of λ0, λ1, λ2, and λ3. When the second path b is interrupted due to a fault, and all four wavelength communication channels of the third path c are occupied, only the communication channel with wavelength λ1 in the first path a is not occupied. In this case, if it is necessary to transmit the service information with wavelength λ0 from the transmitting end 101 to the receiving end 104, an optical network node device 20 as described in this application can be added between the transmitting end 101 and the first node 102.

[0107] like Figure 8 As shown, an optical network node device 20 is added between the transmitter 101 and the first node 102. The output of the transmitter 101 is connected to the input of the signal source 24 in the optical network node device 20, and the input of the first node 102 is connected to the output of the second filter 26 in the optical network node device 20. The light wave carrying the service signal has a wavelength of λ0 (equivalent to...). Figure 5 The signal wave L2 is emitted from the transmitter 101 and converted into a signal wave with wavelength λ1 after passing through the optical network node device 20 (equivalent to...). Figure 5The idle frequency optical L4 in the first path (path b) is used to transfer the service signal to a signal wave with wavelength λ1. Due to the interruption of the second path b, all four wavelength communication channels on the third path c are occupied, while only the communication channels of λ0, λ2, and λ3 are occupied in the first path a, and the communication channel of λ1 is not occupied. At this time, the rerouting control transmits the signal wave with wavelength λ1 from the first path a to deliver the service signal. The signal wave with wavelength λ1 is transmitted from the second node 103 to the receiving end 104. In some other application scenarios, an optical network node device 20 of this application can be added between the second node 103 and the receiving end 104 to convert the signal wave with wavelength λ1 into a signal wave with wavelength λ0, and then transmit the signal wave with wavelength λ0 to the receiving end 104. In this way, the signal waves of the transmitting end 101 and the receiving end 104 can be kept consistent. The wavelength converter 10 in the optical network node device 20 provided in this application is used to realize all-optical wavelength conversion, which can convert service signals at high speed, high efficiency and transparent format. The transparent format means that it is applicable to various modulation formats of signals, such as QPSK, QAM, PAM or OOK. Various modulation signals can use this technical solution.

[0108] In some other implementations, the converted wavelength can be controlled by adjusting the wavelength of the pump light. For example, when only a communication channel of λ4 is available, the wavelength of the pump light can be adjusted so that the wavelength of the converted idler light is λ4.

[0109] It should be noted that each path between the first node 102 and the second node 103 may also have other nodes, such as... Figure 9 As shown, a third node 105 is provided on the first path a, a fourth node 106 is provided on the second path b, and a fifth node 107 is provided on the third path c. In some embodiments, the communication channel included in each path between the first node 102 and the second node 103 may also be configured to support transmission of two, three, or more wavelengths. In some embodiments, the path between the first node 102 and the second node 103 is not limited to the first path a, the second path b, and the third path c, but may include more paths.

[0110] It should be noted that in the wavelength division optical communication network 30, the transmitter 101 can also be used as the receiver of the upstream network, and the receiver 104 can also be used as the transmitter of the downstream network.

[0111] In some implementations, the sending end 101 can be a host, and the receiving end 104 can be a terminal. See also... Figure 10The optical network node device 20 is applied in a specific wavelength division multiplexing (WDM) optical communication network 30 scenario. In this scenario, the host acts as the transmitter 101 of the WDM optical communication network 30. The host is connected to the first node device, the optical network node device, and the controller. The optical network node device is also connected to the first node device. There are three communication lines between the first node device and the second node device: a first communication line, a second communication line, and a third communication line. The second node device is also connected to the terminal and the controller. The terminal acts as the receiver of the WDM optical communication network 30. When the host transmits a signal wave carrying a service signal, the controller first controls the signal wave to be transmitted directly from the host to the first node device. When the third communication line is interrupted, the channel of the second communication line is full, and the wavelength of the remaining channel of the first communication line is inconsistent with the wavelength of the signal wave transmitted by the host, the signal wave cannot be transmitted to the terminal. At this time, the controller controls the signal wave transmitted by the host to undergo wavelength conversion through the optical network node device before being transmitted to the first node device. The wavelength to be converted by the optical network node device can be determined according to the wavelength of the remaining channel in the first communication line. After wavelength conversion by the optical network node equipment, the signal wave can be transmitted to the second node equipment via the first communication line, and then to the terminal via the second node equipment.

[0112] In one possible implementation of the wavelength converter 10 of this application, a graphene element 200 is fixed to a cladding 110. The edge of the graphene element 200 can be fixed to the cladding 110 at any position. In some embodiments, the edge of the graphene element 200 is fixed to a position of the cladding 110 near the inner surface 111 (e.g., Figure 11 As shown), in other embodiments, the edge of the graphene element 200 is fixed to the cladding 110 near the outer surface 112 (e.g., as shown). Figure 1 (As shown).

[0113] Please see Figure 12 In one embodiment, a gap 130 is provided between two adjacent annular structures 120, and the graphene element 200 passes through at least one gap 130. In this embodiment, a plurality of gaps 130 are provided between a plurality of annular structures 120, and the graphene element 200 passes through one of the gaps 130.

[0114] In one possible implementation, the first end 210 of the graphene element 200 is connected to the cladding 110, and the second end 220 of the graphene element 200 is located within the core region 11. The graphene element 200 performs wavelength conversion on the incident light through the second end 200 located within the core region 11. Specifically, the graphene element 200 includes a first end 210, a second end 220, and a connecting segment 230 connecting the first end 210 and the second end 220, the connecting segment 230 being located within the gap 130. In this embodiment, the first end 210, the second end 220, and the connecting segment 230 are all made of graphene. In other embodiments, the second end 220 located in the core region 11 may be made of graphene, while the first end 210 and the connecting segment 230 may be made of other non-graphene materials, such as ultra-thin glass, which can save the cost of graphene materials; in some embodiments, the second end 220 and the connecting segment 230 may be made of graphene, while the first end 210 may be made of other materials.

[0115] In other embodiments, the graphene material can be bonded to an ultrathin carrier, such as ultrathin glass. Since graphene is generally thin, bonding it to the ultrathin carrier prevents the graphene component 200 from shifting and affecting the light conversion effect. Specifically, the graphene material can be bonded to the portion of the ultrathin carrier corresponding to the second end 220, or to the portion of the ultrathin carrier corresponding to the second end 220 and the connecting segment 230, or the entire ultrathin carrier can be bonded with graphene.

[0116] In this application, the cladding 110 is made of silicon dioxide, soft glass, or plastic; the annular structure 120 is made of silicon dioxide.

[0117] In one possible implementation, the portion of the graphene element 200 passing through the gap 130 is spaced apart from the annular structures 120 on both sides of the gap 130. In this application, the walls of the annular structures 120 are very thin and easily broken. By spaced the graphene element 200 from the annular structures 120, damage to the annular structures 120 can be avoided.

[0118] In one possible implementation, there is a gap between two adjacent annular structures 120, and each gap 130 between the plurality of annular structures 120 has an equal width. In this application, the plurality of annular structures 120 confine light within the fiber core region 11, and the width of the gap 130 between the annular structures 120 is preferably set to 0.1μm-10μm to better confine the light within the fiber core region 11 and prevent light leakage from the gap 130.

[0119] Please see Figure 13In one embodiment, the wavelength converter 10 has two graphene elements 200, which are respectively inserted into two gaps 130. In other embodiments, the wavelength converter 10 may also have three or more graphene elements 200, with the multiple graphene elements 200 inserted into different gaps 130. Specifically, the multiple graphene elements 200 are evenly distributed within the internal space 12.

[0120] Please refer to it again. Figure 1 In one embodiment, a plurality of annular structures 120 are provided with a first gap 131 and a second gap 132 disposed opposite to each other, and the graphene element 200 passes through the first gap 131 and the second gap 132. In this embodiment, the graphene element 200 passes through the first gap 131 and the second gap 132 in parallel, and the graphene element 200 is planar. In some embodiments, the graphene element 200 passes through the two gaps 130 in a curved shape, for example, passing through two adjacent gaps 130 in a curved shape, or passing through two spaced-apart gaps 130 in a curved shape.

[0121] In one possible implementation, the graphene element 200 is connected to the cladding 110 at both ends and passes through the core region 11. The graphene element 200 performs wavelength conversion on the incident light through a portion located within the core region 11. Specifically, the graphene element 200 includes a first end 210, a second end 220, and a main body portion 240 connecting the first end 210 and the second end 220. The first end 210 and the second end 220 are fixedly connected to the cladding 110. The main body portion 240 includes a first connecting segment 241, a second connecting segment 242, and a central segment 243 connecting the first connecting segment 241 and the second connecting segment 242. The central segment 243 is located within the core region 11, the first connecting segment 241 is located within a first gap 131, and the second connecting segment 242 is located within a second gap 132. The graphene element 200 performs wavelength conversion on the incident light through the central segment 243 located within the core region 11. In this embodiment, the first end 210, the second end 220, and the main body 240 are all made of graphene. In other embodiments, only the central segment 243 may be made of graphene, while other parts may be made of other materials, such as ultrathin glass; or the main body 240 may be made of graphene, while other parts may be made of other materials. In this embodiment, both ends of the graphene element 200 are fixed to the cladding 110. In some embodiments, the wavelength converter 10 includes two graphene elements 200, one of which has both ends fixed to the cladding 110, and the other has one end fixed to the cladding 110 (e.g., ...). Figure 14 (As shown).

[0122] Please refer to it again. Figure 1In this embodiment, the cladding 110 is provided with a first through hole 113 and a second through hole 114 penetrating the two opposing surfaces of the cladding 110. The first through hole 113 and the first gap 131 are radially corresponding, and the second through hole 114 and the second gap 132 are radially corresponding. The graphene component 200 passes through the first through hole 113 and the second through hole 114. The radial direction y is the direction from the inner surface 111 of the cladding 110 toward the center of the internal space 12 (e.g., ...). Figure 15 (As shown). The first through hole 113 and the second through hole 114 can be formed by laser penetration. In a preferred embodiment, the extension lines of the central axes of the first through hole 113 and the second through hole 114 overlap. In another preferred embodiment, the central axes of the first through hole 113, the first gap 131, the second gap 132 and the second through hole 114 overlap to facilitate the smooth insertion of the graphene component 200.

[0123] In one possible implementation, the wavelength converter 10 further includes an encapsulation component 300 for securing the graphene element 200 to the cladding 110. When the graphene element 200 is secured to the cladding 110 via its first end 210, the first end 210 can be connected and secured to the cladding 110 via the encapsulation component 300 (e.g., ...). Figure 12 (As shown); when the graphene component 200 is fixed to the cladding 110 via the first end 210 and the second end 220, the first end 210 and the second end 220 can be connected and fixed to the cladding 110 via the encapsulation component 300 (as shown). Figure 1 (As shown).

[0124] In one possible implementation, the encapsulation component 300 is formed by curing liquid adhesive or by laser ablation.

[0125] Please refer to it again. Figure 1 The encapsulation component 300 includes a first encapsulation sub-component 310 and a second encapsulation sub-component 320. A first end 210 is fixedly connected to the cladding layer 110 via the first encapsulation sub-component 310, and a second end 220 is fixedly connected to the cladding layer 110 via the second encapsulation sub-component 320. Specifically, a portion of the first encapsulation sub-component 310 is connected to the outer surface 112 of the cladding layer 110 adjacent to the first through-hole 113, and a portion of the first encapsulation sub-component 310 is located in the first through-hole 113 and connected to the first end 210 of the graphene component 200. A portion of the second encapsulation sub-component 320 is connected to the outer surface 112 of the cladding layer 110 adjacent to the second through-hole 114, and a portion of the second encapsulation sub-component 320 is located in the second through-hole 114 and connected to the second end 220 of the graphene component 200.

[0126] Please see Figure 15In one embodiment, the graphene component 200 includes a first graphene sub-component 250 and a second graphene sub-component 260, which are arranged along the axial direction z of the cladding 110. The axial direction z refers to the direction of the rotational center axis of the cladding 110, and is perpendicular to the radial direction y. In this embodiment, the graphene component 200 includes two graphene sub-components; in other embodiments, the graphene component 200 may include three or more graphene sub-components.

[0127] Please see Figure 16 and Figure 17 In one embodiment, the first graphene sub-component 250 and the second graphene sub-component 260 have a predetermined included angle α when projected onto the cross-section of the cladding 110. The cross-section of the cladding 110 is perpendicular to the axial direction z and parallel to the radial direction y. In other embodiments, when the graphene component 200 includes three or more graphene sub-components, a certain included angle can be provided between each graphene sub-component.

[0128] Please see Figure 19 In this application, the length L of the graphene element 200 along the axial direction z is 2mm-20mm. If the length of the graphene element 200 is too long, it will increase the loss of the pump light L2, causing pump light L2 attenuation and a decrease in pump light L2 power. Since the conversion efficiency of the wavelength converter 10 is proportional to the product of the pump light L2 power and the third-order nonlinear coefficient of the graphene element 200, a decrease in pump light L2 power will affect the conversion efficiency. If the length of the graphene element 200 is too short, the maximum conversion efficiency cannot be obtained. Setting the axial length L of the graphene element 200 within the above-mentioned range results in better conversion performance. When the graphene element 200 includes two or more graphene sub-elements (e.g., ...), ... Figure 15 and Figure 16 As shown), the total length of two or more graphene sub-components is 2mm-20mm.

[0129] Please see Figure 18 The width W of the graphene component 200 along the radial direction y is 100μm-300μm. Specifically, the width W of the graphene component 200 along the radial direction y can be set according to the size of the cladding 110 or the annular structure 120.

[0130] Please refer to it again. Figure 19 The thickness t of the graphene element 200 ranges from 0.5 nm to 10 nm. The thickness direction of the graphene element 200 is perpendicular to both its width and length directions. Excessive thickness of the graphene element 200 will increase the loss of pump light L2, leading to pump light L2 attenuation and a decrease in pump light L2 power, thus affecting the conversion efficiency. Setting the thickness t of the graphene element 200 within the aforementioned range results in better conversion performance.

[0131] In this application, the cladding 110 is preferably cylindrical, and the annular structure 120 is tubular. The inner diameter d of the cladding 110 ranges from 50 μm to 100 μm, the outer diameter D of the cladding 110 ranges from 100 μm to 500 μm, and the thickness of the cladding 110 ranges from 50 μm to 400 μm. The inner diameter r of the annular structure 120 ranges from 10 μm to 40 μm, and the wall thickness s of the annular structure 120 ranges from 375 nm to 750 nm.

[0132] In one possible implementation, multiple ring structures 120 are symmetrically distributed on both sides of the graphene element 200. The symmetrical distribution can reduce the light propagation loss within the core region 11.

[0133] Please see Figure 20 In one embodiment, the inner surface 111 of the cladding 110 has a polygonal cross-section along the radial direction, with each annular structure 120 tangent to each side of the polygon. In this embodiment, the polygon is hexagonal, and there are six annular structures 120, each tangent to one of the six sides of the hexagon. In another embodiment, when the polygon is octagonal, there are eight annular structures 120, each tangent to one of the eight sides of the octagon.

[0134] Please see Figure 21 In one embodiment, the annular structure 120 includes a first sub-annular structure 121 and a second sub-annular structure 122. The inner diameter of the first sub-annular structure 121 is larger than the outer diameter of the second sub-annular structure 122. The second sub-annular structure 121 is tangent to the first sub-annular structure 121 and is tangent to the first sub-annular structure 121 at a first tangent point O1. The first sub-annular structure 121 is tangent to the inner surface 110 of the cladding 110 at a second tangent point O2. The first tangent point O1 and the second tangent point O2 coincide. In this embodiment, the annular structure 120 consists of two sub-annular structures. When light waves are incident on the wall of the first sub-annular structure 121, after passing through the Fabry-Perot cavity effect, part of the light waves pass through the wall and are incident on the outer wall of the second sub-annular structure 122. Part of the light waves, after passing through the wall of the second sub-annular structure 122, are reflected back to the wall of the first sub-annular structure 121 after passing through the Fabry-Perot cavity effect. This is equivalent to some light waves undergoing two Fabry-Perot cavity effects before entering the fiber core region 11, which can increase the light intensity within the fiber core region 11. In other embodiments, the first tangent point O1 and the second tangent point O2 may not coincide.

[0135] Please see Figure 22In one embodiment, the annular structure 120 has an elliptical cross-section along the radial direction, with the major axis of the ellipse pointing towards the center of the core region 11. In another embodiment, the minor axis of the ellipse points towards the center of the core region 100.

[0136] In some embodiments, the ring structure 120 includes a third sub-ring structure 123 and a fourth sub-ring structure 124, wherein the shape of the third sub-ring structure 123 differs from the shape of the fourth sub-ring structure 124, and the plurality of third sub-ring structures 123 and the plurality of fourth sub-ring structures 124 are distributed at intervals. For example, please refer to Figure 23 The third sub-ring structure 123 is a small ring, and the fourth sub-ring structure 124 is a large ring; or, please refer to Figure 24 The third sub-ring structure 123 is a circular ring, and the fourth sub-ring structure 124 is a double circular ring; or, the third sub-ring structure 123 is an ellipse, and the fourth sub-ring structure 124 is a circular ring, etc.

[0137] In this application, the number of ring structures 120 is preferably 6 or 8 (e.g., Figure 25 (As shown). In other embodiments, the number may be other than the given number.

[0138] To illustrate that the wavelength converter 10 in this application has high conversion efficiency and wide conversion bandwidth, one embodiment of the wavelength converter 10 (such as...) will be described. Figure 1 As shown, simulation software was used to simulate the technical effect. The inner diameter d of the cladding 110 was selected as 100 μm, the outer diameter D of the cladding 110 was 200 μm, the thickness of the cladding 110 was 100 μm, and 6 annular structures 120 were attached to the inner surface wall of the cladding 110. The parameters of the 6 annular structures 120 were the same. The inner diameter r of the annular structure 120 was 30 μm, the wall thickness s of the annular structure 120 was 585 nm, the thickness t of the graphene part 200 was 5 nm, the radial width W of the graphene part 200 was 200 μm, and the axial length L of the graphene part 200 was 5 mm.

[0139] Figure 26 The diagram shows a simulation of the normalized electric field of the wavelength converter 10. Arrow f indicates the polarization direction of the electric field, and e indicates the light intensity of light passing through the core region 11 on both sides of the graphene component 200. Figure 27 The figure shows the normalized electric field distribution along the radial direction of the core region 11. Figure 27 x-axis represents Figure 26 Distance from left to right Figure 27 The vertical axis represents the corresponding Figure 26 The light intensity at each lateral position, combined with Figure 26 and Figure 27It can be seen that the light intensity is greatest at position e. From position e to position 200 of the graphene component, the light intensity first decreases and then increases, reaching its maximum value at position 200. The normalized electric field simulation does not consider the cladding 110 of the wavelength converter 10. This is because the light is confined within the core region 11 by the ring structure 120, and the light field is not distributed within the cladding 110. Therefore, the cladding 110 can be ignored in the simulation, reducing the computational load. Simultaneously, since the light field is mainly distributed within the core region 11, the width of the graphene component 200 can be set to 80 μm, and the graphene component 200 can be only placed within the gap 130 between the core region 11 and the ring structure 120. This simplification does not affect the simulation results and reduces the computational load. The simulation results show that the loss of the wavelength converter 10 is 9.7 dB / cm, and the effective nonlinear coefficient of the air binding between the graphene component 200 and the optical fiber 100 is 2396.47 / (W·km).

[0140] Based on the simulation parameters of loss and effective nonlinear coefficient, assuming the pump light wavelength is 1550nm, the dispersion of the fiber 100 composed of cladding 110 and multiple ring structures 120 is 1ps / nm / km, and the pump light powers are 1W, 1.5W and 2W respectively, the conversion efficiency and conversion bandwidth are calculated respectively.

[0141] The conversion efficiency can be calculated using the method described in the literature Zhou, Hao, Tingyi Gu, James F. McMillan, Nicholas Petrone, Arend Van Der Zande, James C. Hone, Mingbin Yu et al. "Enhanced four-wave mixing in graphene-silicon slow-light photonic crystal waveguides." Applied Physics Letters 105, no. 9 (2014): 091111. The conversion bandwidth can be obtained from the absolute wavelength difference between the signal light and the pump light when the conversion efficiency decreases by 3 dB. The calculation results are shown in Table 1 below.

[0142] Table 1

[0143] Pump optical power (W) Conversion bandwidth (nm) Conversion efficiency (dB) 1 340.8 -27.74 1.5 407.2 -24.21 2 461 -21.7

[0144] The calculated conversion bandwidth can reach up to 461nm, and the conversion efficiency can reach -21.7dB.

[0145] To illustrate that the wavelength converter 10 in this application has a better wavelength conversion effect, the following three comparative embodiments are also provided.

[0146] In Comparative Example 1, please refer to Figure 28 The wavelength converter 10a uses micro / nano fiber 400 as the transmission medium, combined with graphene 500. The micro / nano fiber 400 is placed on a substrate 600, and graphene 500 is then covered on the surface of the micro / nano fiber 400 away from the substrate 600. When signal light and pump light are transmitted to the micro / nano fiber 400, due to the poor light field confinement capability of the micro / nano fiber 400, some of the signal light and pump light are coupled into the graphene 500 via an evanescent field. The pump light excites the third-order nonlinear effect of the graphene 500, and through four-wave mixing with the signal light, generates idler light, which then transfers the signal light's service information onto the idler light. The micro / nano fiber 400 itself has a large dispersion value, resulting in a final wavelength conversion bandwidth of only 4.5 nm, a maximum conversion efficiency of only -28 dB, and a loss of 20 dB, which is relatively high.

[0147] In Comparative Example 2, please refer to Figure 29 The wavelength converter 10b uses a silicon photonic crystal film 700 as a conductive medium and combines it with graphene 500. The graphene 500 is attached to the surface of the silicon photonic crystal film 700. When the signal light and pump light are transmitted in the silicon photonic crystal film 700, the silicon photonic crystal film 700 also has strong evanescent field characteristics. Some of the signal light and pump light will couple into the graphene 500 and excite its third-order nonlinear effect. The pump light and signal light generate idler light through four-wave mixing, and the signal light service information is transferred to the idler light. The wavelength converter 10b has a final wavelength conversion bandwidth of only 17nm and a conversion efficiency of -23dB.

[0148] In Comparative Example 3, please refer to Figure 30 The wavelength converter 10c combines a solid fiber 800 end face with a graphene 500. The graphene 500 is clamped between the two solid fiber 800 end faces via a fiber clamp 900. Signal light and pump light are coupled from the solid fiber 800 end faces and enter the graphene 500, exciting a third-order nonlinear effect in the graphene 500. This generates idler light through four-wave mixing, transferring the signal light's service information onto the idler light. Finally, the signal light, pump light, and idler light exit through the other solid fiber 800 end face. Due to the short interaction distance between the light and the graphene 500, and the high dispersion and loss of the solid fiber 700, the wavelength conversion bandwidth in this wavelength converter 10c is only 12nm, and the maximum conversion efficiency is only -27dB.

[0149] The wavelength converter 10 of this application combines and utilizes the broadband ultra-low dispersion and light field confinement capability of the optical fiber 100 composed of cladding 110 and ring structure 120, as well as the dispersion-free, broadband low-loss transmission characteristics and ultra-high third-order nonlinear coefficient of the graphene component 200. The conversion bandwidth can reach up to 461nm and the conversion efficiency can reach -21.7dB. In particular, the conversion bandwidth is significantly greater than that of the comparative examples 1 to 3 mentioned above, indicating that the wavelength converter 10 of this application has better wavelength conversion effect.

[0150] Please see Figure 31 and Figure 1 This application also provides a method for fabricating a wavelength converter 10, including steps S100, S200, S300, and S400. Detailed steps are described below.

[0151] In step S100, a cladding layer 110 is provided, which surrounds and forms an internal space 12, within which a plurality of annular structures 120 are formed. In this embodiment, the annular structure 120 is formed by placing an annular preform in the internal space 12 and then heating and stretching the annular preform. During the stretching process, the annular structure 120 is connected and fixed to the inner surface 111 of the cladding layer 110.

[0152] Step S200: A through-hole is formed by slotting in the cladding 110. Preferably, a laser is used to slot from the outer surface 112 to the inner surface 111 of the cladding 110 to form the through-hole. The axial length of the through-hole matches the axial length of the graphene element 200. The laser can be a femtosecond laser, which allows for more precise slotting within the cladding 110. When the graphene element 200 is fixed to the cladding 110 only at one end, a first through-hole 113 can be formed only on one side of the cladding 110 (e.g., ...). Figure 12 As shown), when the two ends of the graphene component 200 are fixed to the cladding 110, a first through hole 113 and a second through hole 114 can be formed on both sides of the cladding 110 respectively (as shown). Figure 1 (As shown).

[0153] In step S300, the graphene component 200 is installed within the internal space 12 via a through-hole, with at least a portion of the graphene component 200 located within the light wave transmission region of the internal space 12. The positional relationship between the graphene component 200, the cladding 110, and the annular structure 120 is as described above and will not be repeated here. When inserting the graphene component 200 into the internal space 12, it is necessary to avoid physical damage to the graphene component 200 from contacting the cladding 110 and the annular structure 120.

[0154] In step S400, the graphene component 200 is fixed to the cladding layer 110 using the encapsulation component 300. The specific fixing method is as described above and will not be repeated here.

[0155] The wavelength converter, optical network node device, and fabrication method of the wavelength converter provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and embodiments of this application. The description of the embodiments above is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in specific embodiments and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A wavelength converter, characterized by, The wavelength converter comprises a cladding, a plurality of annular structures and a graphene member, the cladding surrounds to form an inner space, the plurality of annular structures are located in the inner space, the plurality of annular structures collectively surround a region as a core region, the core region is used for light wave transmission, and at least part of the graphene member is located in the core region.

2. The wavelength converter of claim 1, wherein, The plurality of annular structures are tangent to the inner surface of the cladding, and each of the plurality of annular structures constitutes a negative curvature surface away from part of the surface of the cladding.

3. The wavelength converter of claim 1, wherein, The graphene member is fixed to the cladding.

4. The wavelength converter of claim 1, wherein, There is a gap between two adjacent annular structures, and the graphene member passes through at least one of the gaps.

5. The wavelength converter of claim 4, wherein, A first end of the graphene member is connected to the cladding, and a second end of the graphene member is located in the core region.

6. The wavelength converter of claim 5, wherein, A graphene member part passing through the gap is spaced apart from the annular structures on both sides of the gap.

7. The wavelength converter of claim 1, wherein, There is a gap between two adjacent annular structures, and the width of each gap between the plurality of annular structures is equal.

8. The wavelength converter of claim 1, wherein, There are oppositely arranged first and second gaps between the plurality of annular structures, and the graphene member passes through the first and second gaps.

9. The wavelength converter of claim 8, wherein, Both ends of the graphene member are connected to the cladding, and the graphene member passes through the core region.

10. The wavelength converter of claim 9, wherein, The wavelength converter further comprises a packaging component for fixing the graphene member to the cladding.

11. The wavelength converter of claim 10, wherein, The packaging component is formed by curing liquid glue or ablation of the packaging component by laser.

12. The wavelength converter of claim 1, wherein, The graphene member comprises a first graphene sub-member and a second graphene sub-member, and the first graphene sub-member and the second graphene sub-member are arranged along the axial direction of the cladding.

13. The wavelength converter of claim 12, wherein, The first graphene sub-member and the second graphene sub-member have a preset included angle in the orthographic projection of the cross section of the cladding.

14. The wavelength converter of claim 1, wherein, The thickness of the graphene member is in the range of 0.5 nm to 10 nm, and the length of the graphene member along the axial direction is in the range of 2 mm to 20 mm.

15. The wavelength converter of claim 1, wherein, The plurality of annular structures are symmetrically distributed on both sides of the graphene member.

16. The wavelength converter of any of claims 1-15, wherein, The inner surface of the cladding has a polygonal structure in the radial cross section, and each of the annular structures is tangent to each side of the polygon.

17. The wavelength converter of any of claims 1-15, wherein, The annular structure comprises a first sub-annular structure and a second sub-annular structure, the inner diameter of the first sub-annular structure is greater than the outer diameter of the second sub-annular structure, the second sub-annular structure is inscribed in the first sub-annular structure and tangent to the first sub-annular structure at a first tangent point, the first sub-annular structure is tangent to the inner surface of the cladding at a second tangent point, and the first tangent point coincides with the second tangent point.

18. An optical network node device, characterized by The optical network node device comprises the wavelength converter according to any one of claims 1 to 17.

19. The optical network node device of claim 18, wherein, The optical network node device further comprises: a pump laser for generating first pump light; an optical amplifier for amplifying the power of the first pump light; a first filter for filtering out the radiation signal generated by the optical amplifier when the first pump light passes through the optical amplifier; a signal source for emitting first signal light; an optical multiplexer for integrating the first signal light and the amplified first pump light into the same optical fiber for transmission; The wavelength converter generates second pump light, second signal light and idler light after receiving the first signal light and the amplified first pump light; The second filter is configured to filter out the second pump light and the second signal light from the second pump light, the second signal light and the idler light, and obtain the idler light.

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