Porous optical fiber and supercontinuum generator

Abstract

The embodiment of the utility model discloses a porous optical fiber and a super-continuum spectrum generator, and belongs to the technical field of optical fiber communication, the porous optical fiber comprises a cladding part and a glycerol fiber core, and the cladding part comprises a fiber core area and a non-fiber-core area surrounding the fiber core area; the fiber core hole is arranged in the fiber core area. The glycerol fiber core is filled in the fiber core hole, and the refractive index of the glycerol fiber core is greater than that of the cladding part; the plurality of first air holes are arranged in the non-fiber core area around the fiber core hole at intervals; the multiple second air holes surround the first air holes and are formed in the non-fiber-core area at intervals, and the fiber core holes, the first air holes and the second air holes are different in hole diameter. According to the porous optical fiber, the problem of fiber core cavitation can be solved, the spectrum broadening efficiency can be remarkably improved, spectrum distortion can be effectively avoided, transmission loss is reduced, and stable spectrum output in a wide temperature range can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical fiber communication, and in particular to a porous optical fiber and a supercontinuum generator. BACKGROUND

[0002] Supercontinuum (SC) is a phenomenon that the spectrum of a narrowband laser pulse is dramatically broadened by the interaction of group velocity dispersion and nonlinear optical effects (such as self-phase modulation, four-wave mixing, soliton frequency shift, etc.) when the laser pulse propagates in a nonlinear medium.

[0003] In the early days, solid-state crystals were often used as nonlinear media in supercontinuum generation technology. However, solid-state crystals have the problems of low nonlinear coefficient and high energy consumption.

[0004] At present, by filling nonlinear liquids (such as ethanol and carbon tetrachloride) in an optical fiber as a nonlinear medium, some limitations of solid-state crystals can be overcome to some extent.

[0005] However, using nonlinear liquids as nonlinear media has the problems of solidification at low temperature and high vapor pressure at high temperature. The temperature range adaptability of existing nonlinear liquids is limited, which can easily lead to fiber core cavitation, causing spectral distortion and dramatic increase in transmission loss. CONTENT OF THE INVENTION

[0006] A first aspect of the present application discloses a porous optical fiber, comprising:

[0007] a cladding part, the cladding part comprising a core region and a non-core region surrounding the core region;

[0008] a core hole provided in the core region;

[0009] a glycerol core filled in the core hole, the refractive index of the glycerol core being greater than the refractive index of the cladding part;

[0010] a plurality of first air holes arranged at intervals around the core hole in the non-core region;

[0011] a plurality of second air holes arranged at intervals around the first air holes in the non-core region, wherein the hole diameters of the core hole, the first air holes and the second air holes are different.

[0012] In a possible implementation, the hole diameter of the core hole is d0, and the hole diameter of the second air hole is d2, and d0>d2 is satisfied.

[0013] In a possible implementation, the hole diameter of the first air hole is d1, and d0>d2>d1 is satisfied.

[0014] In a possible implementation, the cladding part is a zinc selenide cladding.

[0015] In a possible implementation, the porous optical fiber further comprises a protective layer, which is arranged on the cladding portion.

[0016] In a possible implementation, the porous optical fiber further comprises a functional coating, which is coated on the hole wall of each second air hole.

[0017] In a possible implementation, the functional coating comprises a fluorocarbon coating, a graphene coating, or a fluorocarbon / graphene composite coating.

[0018] In a possible implementation, the thickness of the functional coating is t, and 0.5 μm≤t≤1.0 μm is satisfied.

[0019] In a possible implementation, the number of core holes is one, and the core hole is located at the center of the core region.

[0020] In a possible implementation, the number of core holes is at least two, and the at least two core holes are symmetrically arranged around the center of the core region.

[0021] In a possible implementation, the porous optical fiber further comprises an encapsulating member, which is arranged at both ends of the cladding portion to seal the core hole.

[0022] A second aspect of the present application discloses a supercontinuum generator, comprising the porous optical fiber as disclosed in any of the above implementations.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The porous optical fiber of the present application adopts a glycerol core, which has very excellent temperature range adaptability and can solve the problem of core cavitation. At the same time, the glycerol core has an ultrahigh refractive index, which can significantly improve the spectral broadening efficiency, effectively avoid spectral distortion, reduce transmission loss, and help to realize stable spectral output in a wide temperature range. At the same time, the core hole, the first air hole, and the second air hole are arranged from the center to the edge of the cladding portion, i.e., inwardly and outwardly, respectively, and the hole diameters of the three are different. Through the coordination of different hole diameters, the dispersion can be effectively constrained, so that the dispersion is as flat as possible, further reducing the loss and improving the nonlinear efficiency of the glycerol core.

[0025] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only constitute some of the embodiments of the present application, and other drawings can also be obtained by those of ordinary skill in the art without any creative effort based on these drawings.

[0027] Figure 1 A cross-sectional view of a holey optical fiber provided by an embodiment of the present application;

[0028] Figure 2 A structural schematic view of a supercontinuum generator provided by an embodiment of the present application.

[0029] Explanation of reference signs:

[0030] 1 holey optical fiber; 11 cladding part; 12 core hole; 13 glycerol core; 14 first air hole; 15 second air hole; 16 protective layer;

[0031] 2 supercontinuum generator; 21 pump source; 22 first gradient refractive index optical fiber; 23 polarizer; 24 Faraday rotator; 25 analyzer; 26 second gradient refractive index optical fiber; 27 optical spectrum analyzer. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments only constitute some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0033] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0034] In addition, in addition to being used to indicate the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. Those of ordinary skill in the art can understand the specific meaning of these terms in the present application according to the specific situation.

[0035] In addition, the terms "mount", "set", "provided with", "connected", "linked" should be interpreted broadly. For example, it can be fixed connection, detachable connection, or integral structure; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication between two devices, elements or components. The specific meaning of the above terms in the present application can be understood according to the specific circumstances by those skilled in the art.

[0036] In addition, the terms "first", "second" and the like are mainly used to distinguish different devices, elements or components (the specific type and structure may be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "multiple" is two or more.

[0037] Embodiments of the first aspect of the present application disclose a kind of porous optical fiber 1, as shown in Figure 1 The cladding portion 11 includes a core region and a non-core region surrounding the core region. The core hole 12 is provided in the core region. The glycerol core 13 is filled in the core hole 12, and the refractive index of the glycerol core 13 is greater than the refractive index of the cladding portion 11. The plurality of first air holes 14 is arranged at intervals in the non-core region around the core hole 12. The plurality of second air holes 15 is arranged at intervals in the non-core region around the first air holes 14, wherein the hole diameters of the core hole 12, the first air hole 14 and the second air hole 15 are different.

[0038] In this embodiment, the porous optical fiber 1 includes a cladding portion 11, a core hole 12, a glycerol core 13, a plurality of first air holes 14 and a plurality of second air holes 15. The cladding portion 11 includes a core region and a non-core region, the core region is located at the center position, and the non-core region is arranged at the periphery of the core region. The core hole 12 is provided in the core region, and the core hole 12 is used to accommodate the glycerol core 13. The glycerol core 13 has the characteristics of high boiling point, low freezing point and extremely low vapor pressure, and has very excellent temperature range adaptability, which can solve the problem of core cavitation. At the same time, the glycerol core 13 has ultra-high refractive index, which can significantly improve the spectral broadening efficiency, effectively avoid spectral distortion, reduce transmission loss, and help to realize stable spectral output in a wide temperature range. The glycerol core 13 is prepared from glycerol, and the glycerol core 13 is in a viscous liquid state. According to Snell's law, when light is emitted from a high refractive index medium to a low refractive index medium, total reflection occurs when the critical angle is exceeded. When the refractive index of the glycerol core 13 is greater than the refractive index of the cladding portion 11, a refractive index difference is formed, and the light can continue to reflect forward in the optical fiber, realizing efficient transmission of optical signals.

[0039] The first air holes 14 are arranged in the non-fiber core area around the fiber core hole 12, and the second air holes 15 are arranged in the non-fiber core area around the first air holes 14.

[0040] That is, the fiber core hole 12, the first air holes 14 and the second air holes 15 are arranged from the center to the edge of the cladding part 11, respectively, and the diameters of the three are different, and the dispersion can be effectively constrained through the coordination of different diameters, so that the dispersion is as flat as possible, further reducing the loss and improving the nonlinear efficiency of the glycerol fiber core 13.

[0041] Specifically, the number of surrounding layers of the first air holes 14 is less than that of the second air holes 15. As shown in the figure, Figure 1 the number of surrounding layers of the first air holes 14 is 1, and the number of surrounding layers of the second air holes 15 is 3. Alternatively, the number of surrounding layers of the first air holes 14 is 2, and the number of surrounding layers of the second air holes 15 is 3.

[0042] It is worth noting that each layer of the first air holes 14 and the second air holes 15 adopts a hexagonal symmetric arrangement design.

[0043] In a possible implementation, the diameter of the fiber core hole 12 is d0, and the diameter of the second air hole 15 is d2, which satisfies: d0>d2.

[0044] In this embodiment, the diameter of the fiber core hole 12 is larger than that of the second air hole 15. Since the second air hole 15 is distributed at the periphery of the cladding part 11, when the diameter of the relatively outer second air hole 15 is smaller, the restriction ability of the cladding part 11 to the optical signal is stronger, which can reduce the loss of the optical signal, help to form a low-leakage and high-localization light transmission mode, and improve the transmission efficiency of the optical fiber.

[0045] In a possible implementation, the diameter of the first air hole 14 is d1, which satisfies: d0>d2>d1.

[0046] In this embodiment, the diameter of the first air hole 14 between the fiber core hole 12 and the second air hole 15 satisfies the above relationship, that is, the diameter of the first air hole 14 is the smallest, and the dispersion can be effectively constrained through the first air hole 14, so that the dispersion is as flat as possible.

[0047] At the same time, the diameter of the fiber core hole 12 is the largest, which can effectively concentrate the optical field energy in the center of the optical fiber, reduce the interface scattering and bending loss, thereby reducing the light guiding loss and improving the nonlinear action efficiency.

[0048] In a possible implementation, the cladding part 11 is a zinc selenide cladding.

[0049] In this embodiment, the cladding part 11 is composed of a zinc selenide cladding, wherein the glycerol core 13 and the zinc selenide cladding realize a thermal compensation design of the optical fiber. The negative thermal optical coefficient of glycerol and the positive thermal optical coefficient of zinc selenide can offset the temperature variation stress, and realize the effect of inhibiting spectral drift. Preferably, the thickness of the cladding part 11 is the radial distance between the outer edge of the cladding and the hole wall of the core hole 12. Preferably, the thickness of the cladding part 11 is less than 20 μm, so as to ensure good mode field localization capability and mechanical strength. The zinc selenide belongs to a crystal material, and has high Young's modulus and good thermal stability.

[0050] At the same time, the glycerol core 13 can strengthen the nonlinear interaction of the optical field and the medium by means of the molecular level hydrogen bond network, and in addition, the glycerol core 13 has an ultrahigh nonlinear refractive index, which can significantly improve the nonlinear coefficient of the porous optical fiber 1. For example, in the 2 μm-5 μm waveband, the infrared transmission window of the glycerol core 13 cooperates with the wide infrared transmission characteristics of the zinc selenide cladding, and can cover the 3 μm-5 μm atmospheric window and part of the molecular fingerprint region.

[0051] In a possible implementation, the porous optical fiber 1 further comprises a protective layer 16 arranged on the cladding part 11. The protective layer 16 can adopt a fluoropolymer, such as Teflon-FEP. The protective layer 16 has the characteristics of low moisture absorption, corrosion resistance, softness, and bendability.

[0052] In a possible implementation, the porous optical fiber 1 further comprises a functional coating layer coated on the hole wall of each second air hole 15.

[0053] In this embodiment, the functional coating layer coated on the hole wall of the second air hole 15 has three functions. The first function is to enhance the mechanical stability. For example, the functional coating layer can strengthen the mechanical stability and strength of the cladding part 11, reduce the risk of air hole collapse, block the erosion of corrosive media to the cladding part 11, and prolong the service life of the optical fiber. The second function is to improve the temperature variation resistance. The functional coating layer has a low thermal expansion coefficient, which is helpful for the balance of the thermal compensation structure and avoids the deformation of the cladding microstructure under temperature variation. The third function is to effectively resist corrosion and pollution. The second air hole 15 is located at the outer layer of the cladding part 11, and directly contacts the air or the boundary of the cladding of the optical fiber, and is easily affected by moisture and chemical corrosion. The addition of the functional coating layer can improve the reliability of the optical fiber.

[0054] In a possible implementation, the functional coating layer can be a fluorocarbon coating layer.

[0055] In a possible implementation, the functional coating layer can be a graphene coating layer.

[0056] In a possible implementation, the functional coating layer can be a fluorocarbon / graphene composite coating layer.

[0057] In this embodiment, the fluorocarbon / graphene composite coating is a high-performance protective coating formed by combining graphene nanomaterials with fluorocarbon resin. It combines the physicochemical advantages of both and is widely used in heavy-duty corrosion protection, weather resistance, and functionalization fields. Specifically, in the fluorocarbon / graphene composite coating, fluorocarbon resin serves as the matrix and graphene as the reinforcing phase.

[0058] Specifically, fluorocarbon resin molecules contain a large number of high-energy CF bonds, exhibiting the following characteristics: chemical inertness (resistance to acids, alkalis, salt spray, and solvent corrosion); weather resistance (resistance to UV aging, with a gloss retention rate >90%). Graphene is dispersed in the resin in the form of nanosheets (0.8-1.2 nm thick), serving functions including: physical barrier (layered structure fills coating pores, extending the penetration path of corrosive media); electrical and thermal conductivity (enhancing the coating's static dissipation ability and heat dissipation efficiency); and mechanical reinforcement (high specific surface area increases the bonding force between the resin and the matrix, improving adhesion to 12 MPa-15 MPa). The ratio of fluorocarbon resin to graphene can use conventional ratios, such as a typical graphene addition of 0.01 wt%-0.15 wt%, as excessive amounts can lead to agglomeration.

[0059] In one possible implementation, the thickness of the functional coating is t, which satisfies: 0.5μm≤t≤1.0μm.

[0060] In one possible implementation, the number of core holes 12 is one, and the core hole 12 is located at the center of the core region.

[0061] In one possible implementation, the number of core holes 12 is at least two, and the at least two core holes 12 are symmetrically arranged around the center of the core region.

[0062] In one possible implementation, the porous optical fiber 1 further includes encapsulation components disposed at both ends of the cladding portion 11 to seal the core holes 12.

[0063] In this embodiment, the two ends of the cladding portion 11 are also provided with encapsulation components, which can seal the core hole 12 and prevent the glycerol core 13 from falling out of the core hole 12.

[0064] For example, the encapsulation component can be UV-curable epoxy resin.

[0065] In a specific embodiment, the porous optical fiber 1 disclosed in this application uses a glycerol core 13 to fill the core hole 12, with the glycerol core 13 as the core nonlinear medium, a zinc selenide cladding, and a functional coating in the outer second pore 15. This solves the problems of core voiding, narrowing of spectral window, and high peak power dependence of traditional optical fibers under extreme temperatures, and achieves stable spectral output in a wide temperature range.

[0066] Specifically, the glycerol core 13 can significantly expand the temperature range, and its extremely low vapor pressure characteristics can solve the problem of core cavitation caused by the condensation of nonlinear substances at low temperatures or the volatilization of nonlinear substances at high temperatures in traditional optical fibers. Meanwhile, in combination with the corrosion resistance of the fluorocarbon / graphene composite coating to the zinc selenide cladding layer, the fluorocarbon / graphene composite coating can significantly improve the mechanical stability of the optical fiber under extreme temperature changes. At the same time, the synergistic design of the glycerol core 13, the zinc selenide cladding layer, and the fluorocarbon / graphene composite coating can suppress the spectral center wavelength shift caused by temperature changes to a very low level, ensuring the long-term reliable operation of the optical fiber in an industrial-grade wide temperature range environment.

[0067] In addition, the glycerol core 13 has good chemical inertness and oxidation resistance, and the viscosity and transmittance decay is extremely low during long-term high-temperature operation. The fluorocarbon / graphene coating maintains the structural integrity of the zinc selenide cladding layer under salt spray corrosion and thermal cycle impact through the microcapsule self-repairing mechanism and high bonding strength, and blocks the corrosion of the corrosion medium to the pore structure.

[0068] A second aspect of the present application discloses an ultra-continuous spectrum generator 2, as shown in Figure 2 comprising the porous optical fiber 1 disclosed in any of the above embodiments.

[0069] In this embodiment, the ultra-continuous spectrum generator 2 comprises the porous optical fiber 1 disclosed in any of the above embodiments, thus having all the beneficial effects of the porous optical fiber 1, which will not be repeated here.

[0070] Specifically, the ultra-continuous spectrum generator 2 comprises a pump source 21, a first gradient refractive index optical fiber 22, a polarizer 23, a Faraday rotator 24, an analyzer 25, a second gradient refractive index optical fiber 26, and a spectrometer 27, and the working process of the ultra-continuous spectrum generator 2 is as follows:

[0071] (1) The pump source 21 first emits femtosecond pulses with a center wavelength of 3.54 µm, a pulse width of 100 fs, and a peak power of 5 kW;

[0072] (2) The femtosecond pulses then enter the first gradient refractive index optical fiber 22 for mode filtering and collimation, and the linear polarization direction is locked by the polarizer 23, and then passes through the Faraday rotator 24 to complete a 45° non-reciprocal rotation to isolate feedback;

[0073] (3) The light beam after the above pretreatment is coupled into the porous optical fiber 1 with a glycerol core and a zinc selenide cladding layer, and in a light path of 10 cm, the group velocity dispersion, self-phase modulation, Raman effect, and four-wave mixing cooperate to broaden the 3.54 µm narrowband pump pulses to a 3~5 µm broadband supercontinuum spectrum;

[0074] (4) The expanded light beam is collimated and aberration-corrected again by the second GRIN fiber 26, and finally enters the spectrometer 27 after passing through the polarizer 25 to select the polarization component, and the output spectrum is detected in real time to determine whether it completely covers the target waveband, and the pump condition is adjusted through closed-loop feedback to ensure stable performance.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A holey optical fiber, characterized in that, The porous optical fiber comprises: a cladding part, the cladding part comprising a core region and a non-core region surrounding the core region; a core hole provided in the core region; a glycerol core filled in the core hole, the glycerol core having a refractive index greater than that of the cladding part; a plurality of first air holes arranged at intervals around the core hole in the non-core region; a plurality of second air holes arranged at intervals around the first air holes in the non-core region, wherein the core hole, the first air holes and the second air holes have different hole diameters.

2. The porous optical fiber according to claim 1, wherein: the core hole has a hole diameter d0, and the second air holes have a hole diameter d2, and d0>d2 is satisfied.

3. The porous optical fiber according to claim 2, wherein: the first air holes have a hole diameter d1, and d0>d2>d1 is satisfied.

4. The porous optical fiber according to claim 1, wherein: the cladding part is a zinc selenide cladding; and the porous optical fiber further comprises a protective layer arranged on the cladding part.

5. The holey optical fiber according to any one of claims 1 to 4, characterized in that, The porous optical fiber further comprises: a functional coating layer coated on the hole wall of each of the second air holes.

6. The porous optical fiber according to claim 5, wherein: the functional coating layer comprises a fluorocarbon coating layer, a graphene coating layer or a fluorocarbon / graphene composite coating layer.

7. The porous optical fiber according to claim 5, wherein: the functional coating layer has a thickness t, and 0.5 μm≤t≤1.0 μm is satisfied.

8. The porous optical fiber according to any one of claims 1 to 4, wherein: the core hole is one, and the core hole is located at the center of the core region; or the core hole is at least two, and the at least two core holes are arranged symmetrically around the center of the core region.

9. The holey optical fiber according to any one of claims 1 to 4, characterized in that, The porous optical fiber further comprises: an encapsulating member arranged at both ends of the cladding part to seal the core hole.

10. An supercontinuum generator characterized in that, The porous optical fiber according to any one of claims 1 to 9. ​

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