CN114911009A - Optical fiber filter - Google Patents
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- CN114911009A CN114911009A CN202210461331.XA CN202210461331A CN114911009A CN 114911009 A CN114911009 A CN 114911009A CN 202210461331 A CN202210461331 A CN 202210461331A CN 114911009 A CN114911009 A CN 114911009A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
Abstract
An optical fiber filter comprising: the optical fiber comprises a first single-mode optical fiber and a first optical fiber head component, the second optical fiber comprises a second single-mode optical fiber and a second optical fiber head component, and the first optical fiber head component is opposite to the second optical fiber head component; the light incident from the first single-mode fiber enters the second fiber after passing through the first single-mode fiber and/or the first fiber head assembly after being focused and collimated, and the light incident from the second single-mode fiber enters the first fiber after passing through the second single-mode fiber and/or the second fiber head assembly after being focused and collimated. The invention can carry out focusing and collimating treatment on the divergent light and reduce the light loss.
Description
Technical Field
The invention relates to the technical field of photoelectricity, in particular to an optical fiber filter.
Background
In the field of optoelectronics, fiber filters may be used to separate the desired wavelength from the fiber, and light other than this wavelength will be rejected. Taking a tunable fiber Fabry-Perot (F-P) filter as an example, the basic structure of the Fabry-Perot filter comprises a pair of parallel high reflecting mirrors and a Fabry-Perot cavity between the high reflecting mirrors.
In the prior art, a tunable fabry-perot filter based on an all-fiber structure is generally fabricated using a multi-beam fabry-perot interferometer formed on end faces of two optical fibers. The fiber resonator formed at the end faces of the two fibers needs to meet mode matching, otherwise, because the light emitted from the fibers is divergent, a large amount of light escapes when the light is reflected back and forth in the F-P cavity for multiple times, and cannot enter the other fiber, so that the loss of transmitted light is large.
There is a need for a fiber filter that can focus and collimate divergent light to reduce optical loss.
Disclosure of Invention
The invention aims to provide an optical fiber filter which can perform focusing and collimating treatment on divergent light and reduce light loss.
To solve the above technical problem, an embodiment of the present invention provides an optical fiber filter, including: the optical fiber comprises a first single-mode optical fiber and a first optical fiber head component, the second optical fiber comprises a second single-mode optical fiber and a second optical fiber head component, and the first optical fiber head component is opposite to the second optical fiber head component; the light incident from the first single-mode fiber enters the second fiber after passing through the first single-mode fiber and/or the first fiber head assembly after being focused and collimated, and the light incident from the second single-mode fiber enters the first fiber after passing through the second single-mode fiber and/or the second fiber head assembly after being focused and collimated.
Optionally, the first fiber head assembly is a first multimode fiber coaxial with the first single-mode fiber, and/or the second fiber head assembly is a second multimode fiber coaxial with the second single-mode fiber: the fiber core of the first end of the first multimode fiber is welded with the fiber core of the first single-mode fiber, and the fiber core of the first end of the second multimode fiber is welded with the fiber core of the second single-mode fiber; wherein the second end of the first multimode optical fiber is opposite the second end of the second multimode optical fiber.
Optionally, the first multimode optical fiber further includes a first multimode optical fiber external connection layer, and the second multimode optical fiber further includes a second multimode optical fiber external connection layer; the first multimode optical fiber external connection layer is welded with the first single-mode optical fiber external connection layer in the process of welding the fiber core of the first end of the first multimode optical fiber with the fiber core of the first single-mode optical fiber; and in the process of welding the fiber core of the first end of the second multimode optical fiber with the fiber core of the second single-mode optical fiber, welding the external connection layer of the second multimode optical fiber with the external connection layer of the second single-mode optical fiber.
Optionally, the first single-mode fiber further includes a first single-mode fiber external connection layer, and the second single-mode fiber further includes a second single-mode fiber external connection layer; the peripheral circumference of the first single-mode optical fiber external connection layer is consistent with that of the first multimode optical fiber external connection layer, and the peripheral circumference of the second single-mode optical fiber external connection layer is consistent with that of the second multimode optical fiber external connection layer.
Optionally, the first optical fiber head assembly further comprises a first reflective film, and the first reflective film is located at the end face of the second end of the first multimode optical fiber; the second fiber optic head assembly further comprises a second reflective film positioned at an endface of a second end of the second multimode optical fiber; the reflectivity of the first reflecting film and the reflectivity of the second reflecting film are both higher than a preset reflectivity threshold value.
Optionally, the first multimode fiber and/or the second multimode fiber is a graded-index multimode fiber; the length of the first multimode fiber is determined according to the graded index period of the first multimode fiber, and the length of the second multimode fiber is determined according to the graded index period of the second multimode fiber; wherein the greater the graded index period of the first multimode optical fiber, the greater the length of the first multimode optical fiber; the larger the graded-index period of the second multimode optical fiber, the larger the length of the second multimode optical fiber.
Optionally, the length of the first multimode optical fiber is (N +1/4) times the graded-index period of the first multimode optical fiber; the second multimode optical fiber has a length that is (N +1/4) times the graded-index period of the second multimode optical fiber; wherein N is a positive integer.
Optionally, the end of the core of the first single-mode optical fiber has a first recess, and the first optical fiber head assembly includes a first reflective film, where the first reflective film is attached to an inner surface of the first recess; and/or the end part of the fiber core of the second single-mode optical fiber is provided with a second concave part, the second optical fiber head assembly comprises a second reflecting film, and the second reflecting film is attached to the inner surface of the second concave part; the light incident from the first single-mode fiber enters the second fiber after passing through the first concave part and the focusing collimation of the first reflection film, and the light incident from the second single-mode fiber enters the first fiber after passing through the second concave part and the focusing collimation of the second reflection film.
Optionally, a vertex of the first recessed portion is located at a center of a fiber core end of the first single-mode fiber, an inner surface of the first recessed portion is axisymmetric, and a symmetry axis of the first recessed portion is consistent with an axial direction of the first single-mode fiber within a preset length; the top point of the second concave part is positioned at the center of the end part of the fiber core of the second single-mode fiber, the inner surface of the second concave part is axisymmetric, and the symmetry axis is consistent with the axial direction of the second single-mode fiber within a preset length; the fiber core end face of the first single-mode fiber is opposite to and parallel to the fiber core end face of the second single-mode fiber.
Optionally, the first single-mode fiber further includes a first fiber external connection layer, and the first reflective film is attached to an end face of the first fiber external connection layer; the second single mode fiber further comprises a second optical fiber external connection layer, and the second reflection film is attached to the end face of the second optical fiber external connection layer.
Optionally, a quotient between a depression depth of the first depression and a core diameter of the first single-mode fiber is selected from: 0.1 to 2; a quotient between a depression depth of the second depression and a core diameter of the second single mode fiber is selected from: 0.1 to 2.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
in the embodiment of the invention, the first optical fiber head assembly and the second optical fiber head assembly which are opposite to each other are adopted, so that the light incident from the first single-mode fiber enters the second optical fiber after passing through the focusing collimation of the first single-mode fiber and/or the first optical fiber head assembly, the light incident from the second single-mode fiber enters the first optical fiber after passing through the focusing collimation of the second single-mode fiber and/or the second optical fiber head assembly, the focusing collimation treatment can be performed on the divergent light, the output of the parallel light beam with larger light beam diameter is facilitated, and the light loss is reduced while the light collimation effect is obtained.
Further, first fiber head subassembly be with first multimode fiber that first single mode fiber is coaxial, and/or, second fiber head subassembly be with second multimode fiber that second single mode fiber is coaxial, and the fibre core of first multimode fiber's first end with the fibre core butt fusion of first single mode fiber, the fibre core of second multimode fiber's first end with the fibre core butt fusion of second single mode fiber to can form the fibre core that changes from thin to thick, help when forming focus collimation effect, enlarge beam diameter. Compared with the prior art that the self-focusing lens is adopted, the multi-mode optical fiber self-focusing optical fiber has the problems of large size, high requirement on optical alignment, deviation of emergent light from the axis of the optical fiber and the like.
Further, the first fiber head assembly comprises a first reflecting film, and the first reflecting film is attached to the inner surface of the first recess; the second optical fiber head component comprises a second reflecting film, and the second reflecting film is attached to the inner surface of the second concave part; wherein, follow the light that first single mode fiber incides passes through first depressed part with get into behind the focus collimation of first reflection film the second optic fibre, follow the light that second single mode fiber incides passes through the second depressed part with get into behind the focus collimation of second reflection film first optic fibre to can form the fibre core tip of the single mode fiber of sectional area from big to small change, help enlarging beam diameter, obtain the effect of focus collimation simultaneously. Compared with the prior art that the self-focusing lens is adopted, the single-mode optical fiber self-focusing lens has the problems of large size, high requirement on optical alignment, deviation of emergent light from the axis of the optical fiber and the like.
Drawings
FIG. 1 is a schematic cross-sectional view of an optical fiber filter according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of another optical fiber filter according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of another optical fiber filter according to an embodiment of the present invention;
fig. 4 is a schematic perspective view of the optical fiber filter of fig. 3.
Description of reference numerals:
the optical fiber module comprises first optical fibers 11, 21, 31, second optical fibers 12, 22, 32, first single-mode optical fibers 111, 211, 311, second single-mode optical fibers 121, 221, 321, a first fiber head assembly 112, a second fiber head assembly 122, first multi-mode optical fibers 212, second multi-mode optical fibers 222, first single-mode optical fiber external connection layers 213, 313, second single-mode optical fiber external connection layers 223, 323, a first multi-mode optical fiber external connection layer 214, a second multi-mode optical fiber external connection layer 224, first reflection films 215, 315, second reflection films 225, 325, a first concave portion 314 and a second concave portion 324.
Detailed Description
As described above, in the related art, a tunable fabry-perot filter based on an all-fiber structure is generally fabricated using a multi-beam fabry-perot interferometer formed on end surfaces of two optical fibers. The fiber resonator formed at the end faces of the two fibers needs to meet mode matching, otherwise, because the light emitted from the fibers is divergent, a large amount of light escapes when the light is reflected back and forth in the F-P cavity for multiple times, and cannot enter the other fiber, so that the loss of transmitted light is large.
In particular, the tunable optical fiber Fabry-Perot filter is a core element in optical communication, optical fiber sensing and optical fiber measurement systems, and is an excellent optical fiber device for continuously scanning wavelength. One of the main applications of tunable fiber Fabry-Perot filters is in the field of fiber optic sensors. The optical wavelength and the optical spectrum are important sensing parameters, and the tunable optical fiber Fabry-Perot filter is a core element for acquiring wavelength and optical spectrum signals. A Fiber Bragg Grating (FBG) sensor and a Fiber fabry-perot sensor are two typical point type Fiber sensors, and the main scheme of signal demodulation is realized by acquiring the spectrum of the sensor. The tunable optical fiber Fabry-Perot filter is used for demodulating the wavelength of the FBG and the cavity length of the Fabry-Perot sensor, and the tunable optical fiber Fabry-Perot filter has the advantages of high detection sensitivity, wide wavelength range, convenience in multiplexing and the like.
In the field of optical communication, a tunable fiber Fabry-Perot filter plays a critical role in communication channel monitoring and promotion of an all-optical network architecture. As the number of Dense Wavelength Division Multiplexing (DWDM) optical channels increases, it becomes important how to efficiently utilize the transmission bandwidth of the optical fiber. The efficiency of optical communication can be greatly improved if optical-to-optical conversion can be directly performed at a node; however, it is difficult for a fixed wavelength optical device in an optical network to cope with high-speed optical transmission and optical blockage. The tunable optical fiber Fabry-Perot can screen out different wavelengths in the optical performance monitor for processing, filter the noise of the optical amplifier to reduce the adverse effect, and complete dynamic locking of a channel, output of a lower channel and the like, so that the framework of an optical communication network is simplified, the flexibility and efficiency of an optical communication system are improved, and the development of an all-optical network is promoted.
The tunable fiber Fabry-Perot filter can also be used in a continuous tunable fiber laser, the wavelength tuning range of the tunable fiber Fabry-Perot filter can cover the gain range of an erbium-doped fiber, and the tuning of the output wavelength of the fiber laser by the tunable fiber Fabry-Perot filter is almost the only reliable choice at present. Meanwhile, the tunable optical fiber Fabry-Perot filter can be used for spectral analysis, and is applied to the fields of environmental protection, scientific instruments, biomedicine and the like, such as environmental gas monitoring, analytical chemistry, atomic emission spectrum detection, fluorescence spectrum detection, optical coherence tomography and the like.
In the prior art, a tunable fabry-perot filter based on an all-fiber structure generally comprises a pair of parallel high-reflection mirrors, and a fabry-perot cavity between the high-reflection mirrors. The transmission characteristic of the Fabry filter is an Airy Function (Airy Function), when the optical length of the Fabry cavity is integral multiple of half wavelength, the corresponding wavelength meets the resonance condition of the Fabry cavity, and the Fabry filter has the maximum transmissivity; parameters of the Fabry-Perot filter, such as the refractive index of a medium in the cavity or the cavity length, are tuned, and the corresponding resonant wavelength is changed, so that the tuning of the transmission wavelength is realized.
The inventor of the invention finds that the optical fiber resonant cavity formed on the end faces of the two optical fibers needs to meet the mode matching, otherwise, because the light emitted from the optical fibers is divergent, a large amount of light escapes when the optical fibers are repeatedly reflected back and forth in the F-P cavity, and cannot enter the other optical fiber, so that the loss of the transmitted light is large. In particular, from a mode matching perspective, the mode field diameter of an optical fiber should be comparable to the width of the resonant mode of the F-P cavity for light to be efficiently coupled into another optical fiber. The mismatch between the fiber mode and the resonant mode does not affect the quality factor Q of the cavity, i.e. the finesse (Finess) of the fiber fabry-perot interferometer, but has a crucial effect on the transmission loss of the cavity. Low transmission losses can only be achieved if the modes of the fiber and the resonant cavity are matched as closely as possible.
The inventor of the present invention has found through research that, in the prior art, when the light emitted from the optical fiber is changed into parallel light, a self-focusing lens is usually adopted to change the light emitted from the optical fiber into parallel light, and the light is converged by the self-focusing lens at the receiving end and then enters the single-mode optical fiber. The size of the self-focusing lens used in the technology is large, the self-focusing lens is actually equivalent to a glass device, the requirement on optical alignment is extremely high, light rays emitted by the self-focusing lens are not transmitted along the axis of the optical fiber but deviate from the axis of the optical fiber, and a Fabry-Perot cavity is difficult to form between the end faces of the two self-focusing lenses.
In the embodiment of the invention, the first optical fiber head assembly and the second optical fiber head assembly which are opposite to each other are adopted, so that the light incident from the first single-mode fiber enters the second optical fiber after passing through the focusing collimation of the first single-mode fiber and/or the first optical fiber head assembly, the light incident from the second single-mode fiber enters the first optical fiber after passing through the focusing collimation of the second single-mode fiber and/or the second optical fiber head assembly, the focusing collimation treatment can be performed on the divergent light, the output of the parallel light beam with larger light beam diameter is facilitated, and the light loss is reduced while the light collimation effect is obtained.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a schematic cross-sectional structure diagram of an optical fiber filter according to an embodiment of the present invention. The fiber filter may include opposing first and second optical fibers 11 and 12.
The first optical fiber 11 may include a first single-mode optical fiber 111 and a first fiber head assembly 112, the second optical fiber 12 may include a second single-mode optical fiber 121 and a second fiber head assembly 122, and the first fiber head assembly 112 may be opposite to the second fiber head assembly 122.
The light incident from the first single-mode fiber 111 enters the second optical fiber 12 after passing through the focusing collimation of the first single-mode fiber 111 and/or the first fiber head assembly 112, and the light incident from the second single-mode fiber 121 enters the first optical fiber 11 after passing through the focusing collimation of the second single-mode fiber 121 and/or the second fiber head assembly 122.
In the embodiment of the present invention, the first fiber head assembly 112 and the second fiber head assembly 122 which are opposite to each other are adopted, so that light incident from the first single-mode fiber 111 enters the second fiber 12 after passing through the focusing collimation of the first single-mode fiber 111 and/or the first fiber head assembly 112, light incident from the second single-mode fiber 121 enters the first fiber 11 after passing through the focusing collimation of the second single-mode fiber 121 and/or the second fiber head assembly 122, and the divergent light can be subjected to the focusing collimation treatment, which is beneficial to outputting a parallel light beam with a larger light beam diameter, and light loss is reduced while obtaining a light collimation effect.
Further, in a specific implementation manner of the embodiment of the present invention, the first fiber optic head assembly 112 and/or the second fiber optic head assembly 122 may be a multi-mode fiber, and the multi-mode fiber is used to generate the focusing and collimating effects.
In which, fig. 1 shows that a fiber interference cavity of the fiber filter may be formed between the first fiber head assembly 112 and the second fiber head assembly 122, and the fiber interference cavity has a cavity length d.
Further, by adjusting the cavity length d, the wavelength scanning range of the fiber filter can be adjusted.
As a non-limiting example, the cavity length d is selected from 5 microns to 100 microns, corresponding to a wavelength sweep range of 12nm to 240nm for the fiber filter.
Referring to fig. 2, fig. 2 is a schematic cross-sectional structure diagram of another optical fiber filter according to an embodiment of the present invention.
In the other fiber filter, the first fiber head assembly may be a first multimode fiber 212 coaxial with the first single mode fiber 211, and/or the second fiber head assembly may be a second multimode fiber 222 coaxial with the second single mode fiber 221.
The core of the first end of the first multimode optical fiber 212 is welded with the core of the first single-mode optical fiber 211, and the core of the first end of the second multimode optical fiber 222 is welded with the core of the second single-mode optical fiber 221; wherein a second end of the first multimode optical fiber 212 is opposite a second end of the second multimode optical fiber 222.
In the embodiment of the present invention, the first fiber head assembly may be a first multimode fiber 212 coaxial with the first single-mode fiber 211, and/or the second fiber head assembly is a second multimode fiber 222 coaxial with the second single-mode fiber 221, and a core of the first end of the first multimode fiber 212 is fusion-spliced with a core of the first single-mode fiber 211, and a core of the first end of the second multimode fiber 222 is fusion-spliced with a core of the second single-mode fiber 221, so that a core varying from thin to thick may be formed, which is helpful to form a focus collimation effect and simultaneously expand a beam diameter. Compared with the prior art that the self-focusing lens is adopted, the multi-mode optical fiber self-focusing optical fiber has the problems of large size, high requirement on optical alignment, deviation of emergent light from the axis of the optical fiber and the like.
Further, the first single mode fiber 211, the first multimode fiber 212, the second single mode fiber 221, and the second multimode fiber 222 may be gold-plated fibers.
Further, the first multimode optical fiber 212 may further include a first multimode optical fiber external connection layer 214, and the second multimode optical fiber 222 may further include a second multimode optical fiber external connection layer 224; wherein the first multimode optical fiber outer connection layer 214 is fusion-connected with the outer connection layer of the first single mode optical fiber 211 in the process of fusion-connecting the core of the first end of the first multimode optical fiber 212 with the core of the first single mode optical fiber 211; in the process of fusing the core of the first end of the second multimode optical fiber 222 and the core of the second single-mode optical fiber 221, the second multimode optical fiber external connection layer 224 is fused with the external connection layer of the second single-mode optical fiber 221.
As shown in fig. 2, after the core of the first multimode fiber 212 is fused with the first single mode fiber 211, the core of the first multimode fiber 212 shows a change from thin to thick, and the first multimode fiber external connection layer 214 is closely attached to the core of the first multimode fiber 212, so that the cross section of the first multimode fiber external connection layer 214 is annular, and the cross section area changes from large to small (from left to right in fig. 2). Similarly, the cross-section of the second multimode fiber outer cladding 224 is also circular and the cross-sectional area varies from large to small (from right to left in fig. 2).
Further, the first single-mode fiber 211 may further include a first single-mode fiber external connection layer 213, and the second single-mode fiber 221 may further include a second single-mode fiber external connection layer 223; the peripheral circumference of the first single-mode optical fiber external connection layer 213 is identical to the peripheral circumference of the first multimode optical fiber external connection layer 214, and the peripheral circumference of the second single-mode optical fiber external connection layer 223 is identical to the peripheral circumference of the second multimode optical fiber external connection layer 224.
Specifically, the first single-mode fiber external connection layer 213, the second single-mode fiber external connection layer 223, the first multimode fiber external connection layer 214, and the second multimode fiber external connection layer 224 may be of a multilayer structure, and may include, for example, a fiber cladding layer, and may further include a fiber coating layer.
It should be noted that, in the embodiment of the present invention, the structural composition of the first single-mode fiber external connection layer 213, the second single-mode fiber external connection layer 223, the first multimode fiber external connection layer 214, and the second multimode fiber external connection layer 224 may not be limited.
Further, the first fiber head assembly 21 may further include a first reflective film 215, and the first reflective film 215 is located at an end face of the second end of the first multimode fiber 212; the second fiber optic head assembly 22 may further include a second reflective film 225, the second reflective film 225 being positioned at an end face of the second end of the second multimode optical fiber 222; the reflectivities of the first reflective film 215 and the second reflective film 225 may be higher than a predetermined threshold value.
Wherein the reflectivity of the first reflective film 215 and the second reflective film 225 may be determined according to the fineness of the optical fiber filter, which may be selected from the following, as a non-limiting example: 2 to 10000, the reflectivity of the first reflective film 215 and the second reflective film 225 may be selected from: 4% to 99.999%.
Further, the first multimode fiber 212 and the first single mode fiber 211 after fusion splicing can be fixedly placed in the first ferrule (not shown) and also can be fixedly placed in the first glass capillary (not shown); the fused second multimode optical fiber 222 and the second single mode optical fiber 221 may be fixedly disposed in a second ferrule (not shown) and may also be fixedly disposed in a second glass capillary (not shown).
It is understood that the first single mode fiber 211 may have a first single mode fiber outer cladding 213, and the first multimode fiber 212 may have a first multimode fiber outer cladding 214, such that the first single mode fiber outer cladding 213 and the first multimode fiber outer cladding 214 are fixedly disposed within the first ferrule or the first glass capillary. Similarly, the second single-mode fiber external connection layer 223 and the second multi-mode fiber external connection layer 224 may be fixedly disposed in the second ferrule or the second glass capillary.
Further, glue may be used for fixation.
Still further, the first reflective film 215 may cover not only the end face of the first multimode optical fiber 212 but also the end face of the first ferrule or the first glass capillary; the second reflective film 225 may cover not only the end surface of the second multimode optical fiber 222 but also the end surface of the second ferrule or the second glass capillary.
Further, the first reflective film 215 and the second reflective film 225 may be coated.
Further, the length of the first multimode optical fiber 212 may be determined according to suitable parameters.
It should be noted that, when the first multimode optical fiber 212 and the first single-mode optical fiber 211 after fusion splicing are fixedly placed in the first ferrule or the first glass capillary, the length of the first multimode optical fiber 212 can be shortened by grinding the end face of the first ferrule or the first glass capillary, and simultaneously, the grinding of the end face of the first multimode optical fiber 212 is realized. Likewise, the length of the second multimode optical fiber 222 may be shortened by grinding the endface of the second ferrule or second glass capillary while grinding the endface of the second multimode optical fiber 222 is achieved.
In a specific implementation of the embodiment of the present invention, the first multimode fiber 212 and/or the second multimode fiber 222 may be a graded-index multimode fiber, which may have a graded-index period.
Wherein the length of the first multimode fiber 212 may be determined according to the graded index period of the first multimode fiber 212, and the length of the second multimode fiber 222 may be determined according to the graded index period of the second multimode fiber 222; wherein the greater the graded index period of the first multimode optical fiber 212, the greater the length of the first multimode optical fiber 212; the larger the graded-index period of the second multimode optical fiber 222, the larger the length of the second multimode optical fiber 222.
Still further, the length of the first multimode optical fiber 212 may be (N +1/4) times the graded-index period of the first multimode optical fiber 212, and the length of the second multimode optical fiber 222 may be (N +1/4) times the graded-index period of the second multimode optical fiber 222. Wherein N is a positive integer.
In particular, the graded index period of a multimode fiber may also be referred to as the pitch.
The lengths of the first multimode optical fiber 212 and the second multimode optical fiber 222 may be a quarter pitch, or may be one or more complete pitches (i.e., N pitches above) plus a quarter pitch.
In the embodiment of the invention, the quarter pitch is adopted, so that the invention has the characteristics of small volume, simple and compact structure, low cost, wide application range and good light condensation effect.
In the embodiment of the present invention, a method for forming an optical fiber filter is also disclosed, and the optical fiber filter may be the optical fiber filter described above and shown in fig. 2. The first optical fiber will be described below as an example.
The method for forming the optical fiber filter may include: performing fusion welding treatment on a fiber core of a first single-mode fiber and a fiber core of a first end of a first multimode fiber, and cutting off a second end of the first multimode fiber at a first preset distance from a fusion welding point; filling a fixed connecting material in the through hole of the first ferrule, inserting the cut first multimode optical fiber and the first single-mode optical fiber into the through hole of the first ferrule, and exposing the second end face of the first multimode optical fiber; and grinding the second end face of the first multimode optical fiber, and stopping grinding when the length of the first multimode optical fiber is shortened to a preset length.
Further, the method may further include: the fiber end face is polished.
Still further, the method may further comprise: and plating a first reflecting film on the second end face of the ground first multimode optical fiber to obtain the first optical fiber head assembly.
Further, the fiber core of the first single-mode fiber and the fiber core of the first end of the first multimode fiber may be fusion-spliced by using an optical fiber fusion splicer.
Further, the first preset distance may be selected from 0.1mm to 10mm, for example 1 mm.
In particular, after cleaving the second end of the first multimode optical fiber, a first multimode optical fiber may be formed with a distal end of the first single mode optical fiber having a length of about a first predetermined distance.
Further, the first ferrule may be a fiber optic ferrule.
Further, the fixing and connecting material may be glue.
In an embodiment of the present invention, to form a fiber tunable fabry-perot filter, opposing first and second optical fibers may be mounted on a piezoelectric sensor driven structure and aligned to form low-loss multi-beam interference between the first and second reflective films. And the distance between the first reflecting film and the second reflecting film is changed by applying voltage through the piezoelectric sensor, so that the wavelength of the light is changed, and the wavelength tuning is formed.
The piezoelectric sensor may be, for example, a piezoelectric ceramic.
Referring to fig. 3 and 4 in combination, fig. 3 is a schematic cross-sectional structure diagram of another optical fiber filter according to an embodiment of the present invention, and fig. 4 is a schematic perspective structure diagram of the optical fiber filter in fig. 3.
Specifically, the end of the core of the first single mode fiber 311 may have a first recess 314, and the first fiber head assembly may include a first reflective film 315, wherein the first reflective film 315 is attached to the inner surface of the first recess 314; and/or the core end of the second single-mode optical fiber 321 has a second recess 324, and the second fiber head assembly may include a second reflective film 325, wherein the second reflective film 325 is attached to the inner surface of the second recess 324; light incident from the first single-mode fiber 311 enters the second optical fiber 32 after passing through the first recess 314 and the first reflective film 315, and light incident from the second single-mode fiber 321 enters the first optical fiber 31 after passing through the second recess 324 and the second reflective film 325.
Specifically, since the first concave portion 314 and the second concave portion 324 are provided, a core having a circular cross section and a cross-sectional area varying from large to small can be formed, and taking the example that light incident from the first single mode fiber 311 passes through the first concave portion 314, the light is focused toward the edge along the variation of the cross-section of the core, thereby enlarging the beam diameter and obtaining the effect of focusing and collimating.
It should be noted that, for more details regarding the first reflective film 315 and the second reflective film 325, please refer to the description of the first reflective film 215 and the second reflective film 225 in fig. 2 and the description thereof will not be repeated herein.
In the embodiment of the present invention, the first fiber head assembly includes a first reflective film 315, and the first reflective film 315 is attached to the inner surface of the first recess 314; the second fiber head assembly comprises a second reflective film 325, and the second reflective film 325 is attached to the inner surface of the second recess 324; the light incident from the first single-mode fiber 311 enters the second fiber 32 after passing through the first recess 314 and the first reflective film 315 for focusing and collimation, and the light incident from the second single-mode fiber 321 enters the first fiber 31 after passing through the second recess 324 and the second reflective film 325 for focusing and collimation, so that a fiber core of the single-mode fiber with a sectional area changing from large to small can be formed, the expansion of the beam diameter is facilitated, and meanwhile, the focusing and collimation effect is obtained. Compared with the prior art that the self-focusing lens is adopted, the single-mode optical fiber self-focusing lens has the problems of large size, high requirement on optical alignment, deviation of emergent light from the axis of the optical fiber and the like.
Further, the first single-mode fiber 311 and the second single-mode fiber 312 may be gold-plated fibers.
Further, the vertex of the first concave portion 314 is located at the center of the end of the core of the first single-mode optical fiber 311, the inner surface of the first concave portion 314 is axisymmetric, and the symmetry axis is consistent with the axial direction of the first single-mode optical fiber 311 within a preset length; the vertex of the second concave portion 324 is located at the center of the core end of the second single-mode optical fiber 321, the inner surface of the second concave portion 324 is axisymmetric, and the axis of symmetry is consistent with the axial direction of the second single-mode optical fiber 321 within a preset length; the core end surface of the first single mode fiber 311 is opposite to and parallel to the core end surface of the second single mode fiber 321.
Specifically, since the apex of the first recess 314 is located at the center of the end of the core of the first single-mode optical fiber 311, it is possible to form a core of a single-mode optical fiber having a circular ring-shaped cross section and a cross-sectional area varying from large to small.
Because the symmetry axis is consistent with the axial direction of the first single-mode fiber 311 within the preset length, the emergent light can be consistent with the axial direction of the first single-mode fiber 311, and therefore self-focusing and self-aligning effects are further formed.
The first recess 314 and the second recess 324 may be formed on the core of the optical fiber by Micro-electro-mechanical system (MEMS) process.
Further, the first single-mode optical fiber 311 may further include a first single-mode optical fiber external connection layer 313, and the first reflective film 315 is attached to an end face of the first single-mode optical fiber external connection layer 313; the second single-mode fiber 321 further comprises a second single-mode fiber external connection layer 323, and the second reflection film 325 is attached to an end face of the second single-mode fiber external connection layer 323.
Specifically, the first single-mode fiber external connection layer 313 and the second single-mode fiber external connection layer 323 may be both of a multilayer structure, and may include, for example, a fiber cladding layer, and may further include a fiber coating layer.
In specific implementation, the first single-mode fiber 311 may be inserted into the first external single-mode fiber layer 313 and fixed by gluing, and the second single-mode fiber 321 may be inserted into the second external single-mode fiber layer 323 and fixed by gluing.
Furthermore, the end faces of the first single-mode optical fiber external connection layer 313 and the second single-mode optical fiber external connection layer 323 can be subjected to polishing treatment.
Further, a quotient between a depression depth of the first depression 314 and a core diameter of the first single mode fiber 311 may be selected from: 0.1 to 2.
Still further, the quotient may be selected from 0.8 to 1.2, for example 1.
The quotient between the recess depth of the second recess 324 and the core diameter of the second single mode fiber 321 may be selected from: 0.1 to 2.
Still further, the quotient may be selected from 0.8 to 1.2, for example 1.
In the embodiment of the present invention, a method for forming an optical fiber filter is also disclosed, where the optical fiber filter may be the optical fiber filter described above and shown in fig. 3 and 4. The first optical fiber will be described below as an example.
The method for forming the optical fiber filter may include: filling a fixed connecting material in the through hole of the first ferrule, inserting a first single mode fiber into the through hole of the first ferrule, and exposing the end face of the first single mode fiber; grinding the end face of the first single-mode optical fiber; a first recess is formed in an end face of the first single mode optical fiber.
Still further, the method may further comprise: and plating a first reflection film on the end face of the first single-mode optical fiber and the inner surface of the first concave part to obtain the first optical fiber head assembly.
Still further, the fixed connection material may be glue.
Further, a first recess may be formed in an end surface of the first single-mode optical fiber using a MEMS process.
It should be understood that the term "and/or" herein is merely one type of association relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein indicates that the former and latter associated objects are in an "or" relationship.
The "plurality" appearing in the embodiments of the present application means two or more.
The descriptions of the first, second, etc. appearing in the embodiments of the present application are only for illustrating and differentiating the objects, and do not represent the order or the particular limitation of the number of the devices in the embodiments of the present application, and do not constitute any limitation to the embodiments of the present application.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. An optical fiber filter, comprising:
the optical fiber comprises a first single-mode optical fiber and a first optical fiber head component, the second optical fiber comprises a second single-mode optical fiber and a second optical fiber head component, and the first optical fiber head component is opposite to the second optical fiber head component;
the light incident from the first single-mode fiber enters the second fiber after passing through the first single-mode fiber and/or the first fiber head assembly after being focused and collimated, and the light incident from the second single-mode fiber enters the first fiber after passing through the second single-mode fiber and/or the second fiber head assembly after being focused and collimated.
2. The fiber filter of claim 1, wherein the first fiber optic head assembly is a first multimode fiber coaxial with the first single mode fiber, and/or wherein the second fiber optic head assembly is a second multimode fiber coaxial with the second single mode fiber:
the fiber core of the first end of the first multimode fiber is welded with the fiber core of the first single-mode fiber, and the fiber core of the first end of the second multimode fiber is welded with the fiber core of the second single-mode fiber;
wherein the second end of the first multimode optical fiber is opposite the second end of the second multimode optical fiber.
3. The fiber filter of claim 2, wherein the first multimode fiber further comprises a first multimode fiber outer cladding layer, and the second multimode fiber further comprises a second multimode fiber outer cladding layer; the first multimode optical fiber external connection layer is welded with the first single-mode optical fiber external connection layer in the process of welding the fiber core of the first end of the first multimode optical fiber with the fiber core of the first single-mode optical fiber; and in the process of welding the fiber core of the first end of the second multimode optical fiber with the fiber core of the second single-mode optical fiber, welding the external connection layer of the second multimode optical fiber with the external connection layer of the second single-mode optical fiber.
4. The fiber filter of claim 3, wherein the first single mode fiber further comprises a single mode fiber outer cladding layer, and wherein the second single mode fiber further comprises a second single mode fiber outer cladding layer;
the peripheral circumference of the first single-mode optical fiber external connection layer is consistent with that of the first multimode optical fiber external connection layer, and the peripheral circumference of the second single-mode optical fiber external connection layer is consistent with that of the second multimode optical fiber external connection layer.
5. The optical fiber filter according to claim 2,
the first fiber optic head assembly further comprises a first reflective film positioned at an endface of the second end of the first multimode optical fiber;
the second fiber optic head assembly further comprises a second reflective film positioned at an endface of a second end of the second multimode optical fiber;
the reflectivity of the first reflecting film and the reflectivity of the second reflecting film are both higher than a preset reflectivity threshold value.
6. The fiber filter according to claim 2, wherein the first multimode fiber and/or the second multimode fiber is a graded-index multimode fiber;
the length of the first multimode fiber is determined according to the graded index period of the first multimode fiber, and the length of the second multimode fiber is determined according to the graded index period of the second multimode fiber;
wherein the greater the graded index period of the first multimode optical fiber, the greater the length of the first multimode optical fiber;
the larger the graded-index period of the second multimode optical fiber, the larger the length of the second multimode optical fiber.
7. The optical fiber filter according to claim 6,
the length of the first multimode optical fiber is (N +1/4) times the graded-index period of the first multimode optical fiber;
the second multimode optical fiber has a length that is (N +1/4) times the graded-index period of the second multimode optical fiber;
wherein N is a positive integer.
8. The fiber optic filter of claim 1, wherein the core end of the first single mode fiber has a first recess, the first fiber optic head assembly comprising a first reflective film, the first reflective film conforming to an inner surface of the first recess;
and/or the presence of a gas in the gas,
the end part of the fiber core of the second single-mode optical fiber is provided with a second sunken part, the second optical fiber head component comprises a second reflecting film, and the second reflecting film is attached to the inner surface of the second sunken part;
the light incident from the first single-mode fiber enters the second fiber after passing through the first concave part and the focusing collimation of the first reflection film, and the light incident from the second single-mode fiber enters the first fiber after passing through the second concave part and the focusing collimation of the second reflection film.
9. The optical fiber filter according to claim 8,
the top point of the first concave part is positioned at the center of the end part of the fiber core of the first single-mode optical fiber, the inner surface of the first concave part is axisymmetric, and the symmetry axis is consistent with the axial direction of the first single-mode optical fiber within a preset length;
the top point of the second concave part is positioned at the center of the end part of the fiber core of the second single-mode fiber, the inner surface of the second concave part is axisymmetric, and the symmetry axis is consistent with the axial direction of the second single-mode fiber within a preset length;
the fiber core end face of the first single mode fiber is opposite to and parallel to the fiber core end face of the second single mode fiber.
10. The optical fiber filter according to claim 8,
the first single-mode optical fiber further comprises a first optical fiber external connection layer, and the first reflection film is attached to the end face of the first optical fiber external connection layer;
the second single mode fiber further comprises a second optical fiber external connection layer, and the second reflection film is attached to the end face of the second optical fiber external connection layer.
11. The optical fiber filter according to claim 8,
a quotient between a depression depth of the first depression and a core diameter of the first single mode fiber is selected from: 0.1 to 2;
a quotient between a depression depth of the second depression and a core diameter of the second single mode fiber is selected from: 0.1 to 2.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116661067A (en) * | 2023-07-31 | 2023-08-29 | 光越科技(深圳)有限公司 | Optical fiber adjustable filter |
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