CN114563840B - Ultra-wideband flat all-fiber circular polarizer and manufacturing method thereof - Google Patents
Ultra-wideband flat all-fiber circular polarizer and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to an ultra-wideband flat all-fiber circular polarizer and a manufacturing method thereof, wherein the manufacturing method comprises the following steps: according to a first phase matching condition which is satisfied by coupling a fiber core fundamental mode to a high-order cladding mode by a double-spiral chiral long-period fiber grating, calculating a grating period range when the fiber core fundamental mode works at a dispersion turning point; introducing chirp into the double-helix chiral long-period fiber grating to obtain the double-helix chirped chiral long-period fiber grating; acquiring a grating period of each grating section in the double-helix chirped chiral long-period fiber grating according to the grating period range; establishing a target coupling equation of the double-helix chirped chiral long-period fiber grating in a local coordinate system; according to the amplitude relation between the output end and the input end of the grating segment, calculating the length of each grating segment by combining a target coupling equation; and manufacturing the all-fiber circular polarizer according to the grating period and length. The manufacturing method can manufacture the all-fiber circular polarizer with flat working bandwidth, wider bandwidth, small volume and low cost.
Description
Technical Field
The invention belongs to the technical field of optical fiber type passive devices, and particularly relates to an ultra-wideband flat all-optical fiber type circular polarizer and a manufacturing method thereof.
Background
The circular polarization technology has important application in the fields of optical fiber sensing, optical fiber communication and the like. The polarization characteristic of circularly polarized light has important research significance and application value in the aspects of underwater optical communication, optical fiber gyroscopes, optical fiber current sensors, polarization imaging and the like. Usually, the circular polarization polarizer is composed of discrete components, so that the whole optical network has the defects of large volume, difficult integration, large insertion loss, unstable operation and the like. With the deep research and application requirements, higher requirements are put on the functions and performances of the circularly polarized light modulation device. In recent years, optical fiber type circular polarizers have become a research hot spot, and the related performance parameters are rapidly optimized. Since the optical fiber type circular polarizer has: the optical fiber type circular polarizer has the advantages of simple structure, easy manufacture and many excellent and unique circular polarization and sensing characteristics, and more research groups are devoted to the manufacture and application research of the optical fiber type circular polarizer.
However, the current circular polarizer has a very narrow bandwidth (several nanometers) and uneven power, so that not only the spectral efficiency, the communication capacity, the detection precision and the applicability of a communication system are weakened, but also the problem that the working index/performance of a device is drastically reduced due to the fact that the working band is shifted along with the change of the environment exists. These factors limit the popularization and application of circular polarizers in all-optical communication, sensing, and modulation systems. Meanwhile, the appearance of the optical fiber type circular polarizer brings hopes for the design of the high-performance circular polarizer, and more importantly, the optical fiber type circular polarizer provides possibility for the transmission of circular polarized light in an all-optical fiber system. Therefore, the research on the optical fiber type circular polarizer attracts the important attention of a plurality of known universities and research institutions at home and abroad. However, the related researches have been gradually developed, and researches on a broadband flat optical fiber type circular polarizer which is urgently needed have not been reported yet. In view of the above, the design and implementation of an all-fiber circular polarizer with ultra-wideband flat characteristics is a very intensive research subject.
In the prior art, the following techniques are generally used to generate circularly polarized light: circular polarization glass, polarization beam splitter prism, spatial light modulator, spiral polarization-preserving fiber, etc. However, the circular polarizers implemented by the above-mentioned technologies are large in volume, relatively expensive, narrow in operating bandwidth and uneven in power, and most circular polarizers require complex spatial structures, have serious dispersion effects of device performance, and cannot realize all-optical fiber in all-optical communication systems.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an ultra-wideband flat all-fiber circular polarizer and a manufacturing method thereof. The technical problems to be solved by the invention are realized by the following technical scheme:
the embodiment of the invention provides a manufacturing method of an ultra-wideband flat all-fiber round polarizer, which comprises the following steps:
calculating a grating period range of the double-helix chiral long-period fiber grating when the double-helix chiral long-period fiber grating works at a dispersion turning point according to a first phase matching condition which is met by the double-helix chiral long-period fiber grating to couple a fiber core fundamental mode to a high-order cladding mode;
introducing chirp into the double-helix chiral long-period fiber grating to obtain the double-helix chirped chiral long-period fiber grating;
acquiring a grating period of each grating section in the double-helix chirped chiral long-period fiber grating according to the grating period range, wherein the grating period changes along with the position of a fiber shaft;
establishing a target coupling equation under the interaction between a right-handed circularly polarized fiber core mode and a left-handed circularly polarized cladding mode in the double-helix chirped chiral long-period fiber grating in a local coordinate system;
according to the amplitude relation between the output end and the input end of the grating segment, the length of each grating segment is calculated by combining the target coupling equation;
and manufacturing the all-fiber circular polarizer according to the grating period and the length.
In one embodiment of the present invention, the first phase matching condition is:
λ res ＝(n eff,01 -n eff,0n )Λ
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
In one embodiment of the invention, the grating period of each of the grating segments is:
Λ＝Λ 0 +cz
wherein, lambda 0 The initial period of the chirp period is represented by z, the axial position of the optical fiber is represented by z, the value of z ranges from 0 to L, c=delta lambda/L, c represents the chirp coefficient, and delta lambda represents the total period variation of the chirped grating.
In one embodiment of the present invention, establishing a target coupling equation between a right-handed circularly polarized core mode and a left-handed circularly polarized cladding mode in the double-helix chirped long period fiber grating in a local coordinate system includes:
establishing a circular polarization mode coupling equation of the first coordinate system, the second coordinate system polarization fiber core mode and the cladding mode in the local coordinate system;
based on the mutual coupling effect between the right-handed circularly polarized fiber core mode and the left-handed circularly polarized cladding mode, and the fiber core fundamental mode LP of the double-helix chirped chiral long-period fiber grating 01 Coupled to higher order cladding modes LP 0n And simplifying the circular polarization mode coupling equation to obtain the target coupling equation under the satisfied second phase matching condition.
In one embodiment of the invention, the circular polarization mode coupling equation is:
where both κ and κ' represent coupling coefficients, τ (τ=2π/P) represents the twist rate,p represents the pitch of the optical fiber,indicating the amplitude of the right-handed circularly polarized core layer,/->Indicating the amplitude of the right-handed circularly polarized core layer,/->Represents the amplitude of the left-hand circularly polarized core and cladding, +.>Indicating the amplitude, beta, of the right-handed circularly polarized core and cladding co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of> The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
In one embodiment of the present invention, the second phase matching condition is:
λ res ＝(n eff,01 -n eff,0n )Λ(z)
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, z represents the fiber axis position, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
In one embodiment of the invention, the target coupling equation is:
where κ denotes the coupling coefficient, τ (τ=2π/P) denotes the turn ratio, P denotes the fiber pitch,indicating the amplitude of the right-handed circularly polarized core and cladding, +.>Indicating the amplitudes of the left-hand circularly polarized core and cladding; beta co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of> The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
In one embodiment of the present invention, the amplitude relationship is:
wherein A is co (z M+1 ) Representing the amplitude of the output end core mould, A cl (z M+1 ) Representing the output end cladding mode amplitude, F i Matrix element representing the ith grating segment, A co (z 1 ) =1 represents initial conditions of core die, a cl (z 1 ) =0 denotes the cladding mode initial condition, a ij Two mode coupling coefficients in a matrix element representing the ith grating segment, k representing the coupling strength, σ representing the imaginary part of the coupling strength, z i+1 Representing the length of the i+1st segment grating, z i The i-th segment grating length is represented, i represents the grating number.
Another embodiment of the present invention provides an ultra-wideband flat all-fiber circular polarizer, which is a double-spiral chirped-type chiral long-period fiber grating formed by sequentially connecting a plurality of double-spiral chiral long-period fiber gratings, wherein,
each section of the double-helix chiral long-period fiber grating works in a preset range at two sides of a dispersion turning point, and the grating period of the double-helix chirped chiral long-period fiber grating changes along with the position of an optical fiber shaft.
In one embodiment of the present invention, the grating period of each section of the double-spiral chiral long-period fiber grating gradually increases or decreases as the position of the fiber shaft increases.
Compared with the prior art, the invention has the beneficial effects that:
in the manufacturing method of the invention, the grating period range is obtained when the double-helix chiral long-period fiber grating works at the dispersion turning point, so that the full-fiber circular polarizer with ultra-wideband circular polarization filtering characteristic can be realized, and the chirp is introduced into the double-helix chiral long-period fiber grating, so that the full-fiber circular polarizer with flat filtering characteristic can be realized, thereby manufacturing the full-fiber circular polarizer with flat working bandwidth, wider bandwidth, small volume and low cost.
Drawings
FIG. 1 is a schematic flow chart of a method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to an embodiment of the present invention;
FIG. 2 is a diagram of a right-handed double-helix chiral long-period fiber grating according to an embodiment of the present invention;
fig. 3 a-3 b are schematic diagrams of a right-hand double-helix chiral long-period fiber grating phase matching curve according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a transmission spectrum of right-handed circularly polarized light in a right-handed double-helix chiral long-period fiber grating operating at a dispersion turning point according to an embodiment of the present invention;
fig. 5 a-5 b are schematic structural diagrams of two kinds of double-helix chirped chiral long-period fiber gratings according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a dual-spiral chirped chiral long-period fiber grating obtained by melt-twisting a polarization maintaining fiber according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of axial refractive index modulation of a dual-spiral chirped chiral long-period fiber grating according to an embodiment of the present invention;
fig. 8 is a transmission spectrum diagram of a dual-spiral chirped chiral long-period fiber grating according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
Example 1
Referring to fig. 1, fig. 1 is a schematic flow chart of a manufacturing method of an ultra-wideband flat all-fiber circular polarizer according to an embodiment of the present invention. The manufacturing method of the ultra-wideband flat all-fiber round polarizer comprises the following steps:
s1, according to the double-helix chiral long-period fiber grating, a fiber core fundamental mode LP 01 Coupled to higher order cladding modes LP 0n And calculating the grating period range of the double-helix chiral long-period fiber grating when the double-helix chiral long-period fiber grating works at the dispersion turning point according to the satisfied first phase matching condition.
Referring to fig. 2, fig. 2 is a structural diagram of a right-hand double-helix chiral long period fiber grating according to an embodiment of the present invention. In fig. 2, a polarization maintaining fiber (e.g., panda-type polarization maintaining fiber) in a molten state is twisted at a high speed, and the twisted fiber core forms a spiral path, thereby forming a double-spiral chiral long-period fiber grating.
It should be noted that, the optical fiber shown in fig. 2 is only a schematic diagram, the dual-spiral chiral long period fiber grating includes a fiber core, a stress region and a cladding, the fiber core is located at the center of the cladding, the stress region is located inside the cladding, the stress region forms a dual-spiral path, and the surface of the cladding forms an uneven shape.
In this embodiment, the double-helix chiral long-period fiber grating may be a right-hand double-helix chiral long-period fiber grating or a left-hand double-helix chiral long-period fiber grating.
Unlike traditional long period fiber grating, the double-spiral chiral long period fiber grating combines the fiber core fundamental mode LP 01 Coupled to higher order cladding modes LP 0n Above, it satisfies the first phase matching condition:
λ res ＝(n eff,01 -n eff,0n )Λ (1)
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
Further, the resonant cladding mode of each order of the double-helix chiral long period fiber grating can be calculated according to the first phase matching condition of the formula (1). In this embodiment, the resonant cladding mode of the first 14 orders (i.e. m=2 to 15) of the double-spiral chiral long period fiber grating is calculated according to the first phase matching condition of the formula (1), for convenience, the resonant cladding mode is given by a phase matching curve, please refer to fig. 3a to fig. 3b, fig. 3a to fig. 3b are schematic diagrams of the phase matching curve of the right-hand chiral long period fiber grating provided by the embodiment of the present invention, in which fig. 3a is the phase matching curve of the cladding mode with the cladding mode order of m=2 to 8, fig. 3b is the phase matching curve of the cladding mode with the cladding mode order of m=9 to 15, and in the drawing, the black dots represent the dispersion turning points of the phase matching curve.
As can be seen from fig. 3a, the slope of each curve is always positive for cladding modes m=2 to 8. Whereas in fig. 3b, the cladding modes of m=9 to 15 change from positive to negative in slope, there is a point where the slope is infinite, as shown by the black point in fig. 3b, which is called the dispersion turning point of the fiber grating. It is apparent that each of the dispersion turning points corresponds to the maximum grating period of each resonant cladding mode. For the cladding mode with m more than or equal to 9, when the grating period is smaller than the grating period at the dispersion turning point, the slope of the curve is changed from positive to negative, and one grating period corresponds to two resonance wavelengths at different positions, namely a double resonance phenomenon is generated. Then, along with the increase of the grating period, two different resonant wavelength positions are simultaneously close to the resonant wavelength position at the dispersion turning point, and are overlapped to one point when the grating period is increased to the grating period at the dispersion turning point, namely the resonant wavelength position corresponding to the dispersion turning point. In this case, the resonance peak at the dispersion turning point has a wider bandwidth than that at the single resonance due to the mutual superposition of the double resonance peaks.
Further, the resonance peak bandwidth of the fiber grating can be expressed as:
in the formula (2), deltalambda 3dB 3-dB bandwidth, L grating length and delta n representing resonant peak of fiber grating g Indicating the difference in group refractive index between the core and cladding.
As can be seen from (2), the closer the resonance wavelength is to the dispersion turning point of the fiber grating, the group refractive index difference Deltan between the core and the cladding g The smaller and thus the broader the resonance peak bandwidth of the fiber grating.
Therefore, by designing grating parameters of the double-helix chiral long-period fiber grating, the fiber grating works at a dispersion turning point of a high-radial-order cladding mode, and can effectively generate an ultra-wideband circular polarization mode. In the embodiment, the grating period range of the double-helix chiral long-period fiber grating is set, so that the fiber grating works near the dispersion turning point; in other words, when the double-helix chiral long-period fiber grating works near the dispersion turning point, a wider resonance peak bandwidth can be realized, so that the grating period corresponding to the dispersion turning point is used as a grating period range in a certain range on both sides of the grating period. Specifically, the grating period range can be set according to actual requirements, the larger the period range is, the wider the working bandwidth is, but the weaker the coupling strength is in the range which is far from the corresponding period of the dispersion turning point, for example, the period at the dispersion turning point of the double-helix chiral long-period fiber grating is 160 μm, 159-161 μm can be selected as the grating period range, and the 3dB bandwidth-200 nm can be obtained. The twisting speed of the polarization maintaining fiber for melt twisting can be determined by the grating period range.
Further, taking a right-hand double-helix chiral long period fiber grating as an example, according to the first phase matching condition of formula (1), the core mold (LP 01 ) With cladding mode (LP) 0,11 ) Referring to fig. 4, fig. 4 is a schematic diagram of a right-handed circularly polarized light transmission spectrum in a right-handed duplex chiral long period fiber bragg grating operating at a dispersion turning point according to an embodiment of the present invention, and fig. 4 shows a core mold (LP 01 ) Respectively with cladding mode (LP 02 ，LP 0,11 ) Coupling is performed in which the cladding mode LP 02 Not working at the dispersion turning point, cladding mode LP 0,11 Operating at the dispersion turning point. As can be seen from fig. 4, the mode coupling bandwidth at the dispersion turning point is significantly improved compared to the mode coupling not at the dispersion turning point. Therefore, broadband mode coupling can be realized based on the dispersion turning characteristic of the double-helix chiral long-period fiber grating.
S2, introducing chirp into the grating period range to obtain the double-helix chirped chiral long-period fiber grating.
In general, in order to achieve broadband transmission, chirped long-period fiber gratings need to have a considerable chirp period variation to achieve a wide range of wavelength resonances. In this case, it is necessary to increase the grating length to increase the effective coupling length at different resonant wavelength positions in the spectrum; for example, a chirp period variation of 41 μm is required to achieve broadband transmission with a 3-dB bandwidth of 100nm, and a chirped grating length as high as 41.5cm is required. The grating length is too large, so that a plurality of inconveniences are caused in practical application, the packaging becomes a great challenge due to the too long grating length, and in addition, the longer grating is more easily influenced by external factors, so that the spectrum quality is reduced, and the application is quite unfavorable. In addition, for the chiral long-period fiber grating working at the non-dispersion turning point, mode coupling occurs between the fundamental mode of the fiber core and a plurality of cladding modes in a wide resonance wavelength range, so that the conversion efficiency and the mode purity of the circularly polarized mode can be greatly influenced, and the spectral performance of the fiber grating is limited.
Specifically, the double-helix chiral long-period fiber grating in step S1 realizes ultra-wideband circular polarization mode conversion with a 3-dB bandwidth of about 190nm, however, under such bandwidth, the extinction ratio of the spectrum resonance peak is not flat, i.e., there is a large difference in extinction ratio at different wavelength positions within the broadband operating wavelength, as shown in fig. 4, the extinction ratio can reach 60dB at the center of the resonance peak, and is only 3dB at the edge. The extinction ratio of the resonance peak has a great influence on the mode purity of the converted circular polarization mode, so that in order to obtain ultra-wideband and flat circularly polarized light beams, chirp is introduced into the double-helix chiral long-period fiber grating working at the dispersion turning point in the step S1.
Referring to fig. 5 a-5 b, fig. 5 a-5 b are schematic structural diagrams of two kinds of double-helix chirped chiral long period fiber gratings according to an embodiment of the present invention, wherein fig. 5a is a right-handed double-helix chirped chiral long period fiber grating, and fig. 5b is a left-handed double-helix chirped chiral long period fiber grating.
Specifically, after the chirp is introduced into the double-helix chiral long-period fiber grating period, the grating period is not constant any more, but varies with the axial direction of the fiber, as shown in fig. 5a and 5 b. For the double-helix chirped chiral long-period fiber grating with the length of L, the grating can be divided into M grating sections, and each grating section can be regarded as a double-helix chiral long-period fiber grating with a uniform period; the length of each grating segment is determined by the coupling strength of the grating segment, the stronger the coupling strength is, the shorter the length of the grating segment is, the weaker the coupling strength is, and the longer the length of the grating segment is; each grating section works at a dispersion turning point, and the grating period of each grating section is positioned near the dispersion turning point of the double-helix chiral long-period fiber grating. The number of grating segments depends on the different system accuracy requirements, e.g. M may be taken as 100.
Furthermore, by designing grating parameters (including grating period and length of each grating segment) of each grating segment, namely the double-helix chiral long-period fiber grating, the fiber grating works at the dispersion turning point of the high-radial-order cladding mode, and can effectively generate ultra-wideband circular polarization mode coupling.
S3, acquiring the grating period of each grating section in the double-helix chirped chiral long-period fiber grating according to the grating period range, wherein the grating period changes along with the position of the fiber shaft.
Specifically, the period of each grating segment is:
Λ＝Λ 0 +cz (3)
wherein, lambda 0 The initial period of the chirp period is represented by z, the axial position of the optical fiber is represented by z, the value of z ranges from 0 to L, c=delta lambda/L, c represents the chirp coefficient, and delta lambda represents the total period variation of the chirped grating.
It can be understood that the period of each grating segment is located near the dispersion turning point of the double-helix chiral long-period fiber grating, the grating period of the grating segment located at the center is equal to the period corresponding to the dispersion turning point of the double-helix chiral long-period fiber grating, the grating period of the grating segment located at the starting end is close to the smaller period in the grating period range, and the grating period of the grating segment located at the tail end is close to the larger period in the grating period range.
S4, establishing a target coupling equation under interaction between a right-handed circularly polarized fiber core mode and a left-handed circularly polarized cladding mode in the double-helix chirped chiral long-period fiber grating in a local coordinate system. The method specifically comprises the following steps:
s41, establishing a circular polarization mode coupling equation of the first coordinate system, the second coordinate system polarization fiber core mode and the cladding mode in the local coordinate system.
Specifically, similar to the double-helix chiral long-period fiber grating, the double-helix chirped chiral long-period fiber grating converts the core fundamental mode LP 01 Coupled to cladding mode LP 0n At the dispersion turning point of (n.gtoreq.2), the second phase matching condition is satisfied:
λ res ＝(n eff,01 -n eff,0n )Λ(z) (4)
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, z represents the fiber axis position, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
Chiral long period fiber grating (similar in left-hand direction) with core and cladding radius distribution of a=4.15 μm, b=62.5 μm, and refractive index of core and cladding n respectively for right-hand direction formed by twisting commercial panda fiber 1 =1.452 and n 2 Panda polarization maintaining fiber beat length l=1.444 b Is 2.5mm, and thus the dielectric constant has an anisotropic disturbance difference Deltaε x -Δε y Can be obtained from the following relationship:
wherein B is the birefringence of the panda fiber.
Calculated anisotropy disturbance difference delta epsilon of dielectric constant x -Δε y 1.8X10 -3 。
Based on the above, taking panda fiber with right-hand spiral structure and high twist rate as an example, a linear coupling mode equation of a first coordinate system x, a second coordinate system y polarization fiber core mode and a cladding mode is directly established in a local coordinate system, and then the linear polarization mode is converted into a circular polarization mode by using mode conversion, so that the coupling equation of the circular polarization mode is as follows:
where both κ and κ' represent coupling coefficients, τ (τ=2π/P) represents the spin ratio, P represents the fiber pitch,indicating the amplitude of the right-handed circularly polarized core layer,/->Indicating the amplitude of the right-handed circularly polarized core layer,/->Represents the amplitude of the left-hand circularly polarized core and cladding, +.>Indicating the amplitude, beta, of the right-handed circularly polarized core and cladding co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of> The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
S42, simplifying the circular polarization mode coupling equation based on the mutual coupling action between the right-handed circular polarization fiber core mode and the left-handed circular polarization cladding mode and a second phase matching condition satisfied by the double-helix chirped chiral long-period fiber grating for coupling the fiber core fundamental mode LP01 to the high-order cladding mode LP0n, so as to obtain the target coupling equation.
Specifically, for all coupling modes, β co Greater than beta cl For the right-handed structure, τ (z) is a positive value (corresponding to the case shown in fig. 5 a), so the second phase matching condition can be satisfied only when the following relationship is satisfied:
β co -τ(z)＝β cl +τ(z) (8)
in theoretical research, only the strong coupling between the right-handed circularly polarized (RCP) core mode and the left-handed circularly polarized (LCP) cladding mode is considered, and other modes with low coupling strength are not considered, so the coupling effect between the right-handed circularly polarized (RCP) core mode and the left-handed circularly polarized (LCP) cladding mode and the second phase matching condition are combined, and the formula (6) is simplified, so that a target coupling equation representing the coupling between the RCP core mode and the LCP cladding mode is obtained:
wherein,
where κ denotes the coupling coefficient, τ (τ=2π/P) denotes the turn ratio, P denotes the fiber pitch,indicating the amplitude of the right-handed circularly polarized core and cladding, +.>Indicating the amplitudes of the left-hand circularly polarized core and cladding; beta co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of> The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
S5, calculating the length of each grating segment according to the amplitude relation between the output end and the input end of the grating segment and the target coupling equation.
Specifically, by dividing the periodic grating, the transmission characteristic of the whole chirped grating can be calculated in a simulation manner by a transmission matrix method. For a double-helix chirped chiral long-period fiber grating, each grating segment can be described by a 2×2 matrix, and the amplitude relationship between the output end and the input end can be expressed as:
wherein,
wherein A is co (z M+1 ) Representing the amplitude of the output end core mould, A cl (z M+1 ) Representing the output end cladding mode amplitude, F i Matrix element representing the ith grating segment, A co (z 1 ) =1 represents initial conditions of core die, a cl (z 1 ) =0 denotes the cladding mode initial condition, a ij Two mode coupling coefficients in a matrix element representing the ith grating segment, k representing the coupling strength, σ representing the imaginary part of the coupling strength, z i+1 Representing the length of the i+1st segment grating, z i The i-th segment grating length is represented, i represents the grating number.
The final chirped grating amplitude can be obtained by putting the amplitude relationship into a target coupling equation (formula 9), so that the chirped grating transmission spectrum (i.e. a coupling spectrogram) can be calculated. Furthermore, the coupling strength of each grating segment can be obtained according to the chirped grating transmission spectrum, and the length of the grating segment is obtained.
S6, manufacturing the all-fiber circular polarizer according to the grating period and the length.
Specifically, after grating parameters are obtained, high-speed variable rate torsion is performed on the polarization maintaining fiber in a molten state (panda type polarization maintaining fiber is taken as an example, other types of polarization maintaining fibers are similar), and after torsion, the fiber forms a chirped spiral path with gradually changed period, so that a double-spiral chirped chiral long-period fiber grating is formed, and the double-spiral chirped chiral long-period fiber grating is the all-fiber circular polarizer. The twisting speed of the polarization maintaining fiber for fusion twisting is determined by the grating period of each grating section, and the moving speed of the polarization maintaining fiber is determined by the length of each grating section.
Referring to fig. 6, fig. 6 is a schematic structural diagram of a dual-spiral chirped chiral long-period fiber grating obtained by melt-twisting a polarization maintaining fiber according to an embodiment of the present invention. In fig. 6, by twisting the polarization maintaining fiber, a double-helix chirped chiral long-period fiber grating having a period Λ gradually varying with the length of the fiber is formed. The fiber grating is provided with a plurality of grating segments, each grating segment works near a dispersion turning point, the grating segment positioned at the center works at the dispersion turning point, and the grating period of each grating segment gradually increases along with the increase of the length. The length of each grating segment decreases with increasing coupling strength in the segment grating segment, the shorter the length of the segment grating segment, the smaller the coupling strength, and the longer the length of the segment grating segment.
In another embodiment, by twisting the polarization maintaining fiber, a double-helix chirped chiral long-period fiber grating is formed with period Λ gradually changing with the length of the fiber. The fiber grating is provided with a plurality of grating segments, each grating segment works near a dispersion turning point, the grating segment positioned at the center works at the dispersion turning point, and the grating period of each grating segment gradually decreases along with the increase of the length.
Further, according to the second phase matching condition, it is known that in the double-helix chirped chiral long-period fiber grating, each grating segment corresponds to a different resonant wavelength, and the resonant peak of the final transmission spectrum of the chirped chiral long-period fiber grating can be regarded as being obtained by overlapping the resonant peaks of different wavelength positions of each grating segment, so that broadband transmission can be realized.
Referring to fig. 7, fig. 7 is a schematic diagram of axial refractive index modulation of a dual-spiral chirped chiral long-period fiber grating according to an embodiment of the present invention. The refractive index modulation diagram in fig. 7 is a projection of the refractive index modulation of the double-helix chirped chiral long-period fiber grating on a plane, and it can be seen that the refractive index of the grating varies periodically, and the size of each period varies according to formula (3) along the length direction of the fiber due to the chirped structure design of the grating period.
Referring to fig. 8, fig. 8 is a transmission spectrum diagram of a dual-spiral chirped chiral long-period fiber grating according to an embodiment of the present invention. The transmission spectrum in FIG. 8 is that operating at LP 0,11 Near the modal dispersion inflection pointCompared with the spectrum diagram of fig. 4, the chirped chiral long-period fiber grating in fig. 8 has better flat filtering property.
In the manufacturing method of the embodiment, the grating period range is obtained when the double-helix chiral long-period fiber grating works at the dispersion turning point, so that the full-fiber circular polarizer with the ultra-wideband circular polarization filtering characteristic can be realized, and the chirp is introduced into the double-helix chiral long-period fiber grating, so that the full-fiber circular polarizer with the flat filtering characteristic can be realized, and the full-fiber circular polarizer with flat working bandwidth, wider bandwidth, small volume, low cost and easy manufacturing is manufactured. Therefore, the method realizes the manufacture of the ultra-wideband flat all-fiber circular polarizer, the bandwidth and the flatness of the circular polarizer are obviously improved at the same time, and the all-fiber can be realized by using the circular polarizer to perform light field regulation and control, so that the performance of all-optical communication is improved to a great extent, and the manufacture cost is saved.
Example two
On the basis of the first embodiment, this embodiment provides an ultra-wideband flat all-fiber circular polarizer, which is manufactured by the manufacturing method described in the first embodiment, and the structure of the all-fiber circular polarizer is shown in fig. 6.
Specifically, the all-fiber round polarizer is a double-spiral chirped chiral long-period fiber grating, and a plurality of double-spiral chiral long-period fiber gratings of the double-spiral chirped chiral long-period fiber grating are sequentially connected to form the all-fiber round polarizer; wherein, the grating period of the double-helix chiral long period fiber grating is positioned in the corresponding grating period range when the fiber grating works at the dispersion turning point; the grating period of the double-helix chirped chiral long-period fiber grating changes along with the position of the fiber shaft.
In a specific embodiment, the grating period of each section of the double-helix chiral long-period fiber grating gradually increases with the increase of the position of the fiber axis, or the grating period of each section of the double-helix chiral long-period fiber grating gradually decreases with the increase of the position of the fiber axis. The length of each section of the double-helix chiral long-period fiber grating is reduced along with the increase of the coupling strength of the section of grating.
Further, the double-helix chirped chiral long-period fiber grating may be a right-hand double-helix chirped chiral long-period fiber grating or a left-hand double-helix chirped chiral long-period fiber grating.
Specifically, the second phase matching condition, the circular polarization coupling equation and the amplitude relationship between the output end and the input end of each section of the double-spiral chiral long-period fiber grating satisfied by the all-fiber circular polarizer are referred to in embodiment one, and the description of this embodiment is omitted.
The all-fiber circular polarizer of the embodiment realizes ultra-wideband circular polarization filtering characteristics by utilizing the dispersion turning characteristics, realizes flat filtering characteristics by utilizing the chirp effect, has flat and wide working bandwidth and small volume, and improves the performance of all-optical communication to a great extent.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (8)
1. The manufacturing method of the ultra-wideband flat all-fiber circular polarizer is characterized by comprising the following steps:
calculating a grating period range of the double-helix chiral long-period fiber grating when the double-helix chiral long-period fiber grating works at a dispersion turning point according to a first phase matching condition which is met by the double-helix chiral long-period fiber grating to couple a fiber core fundamental mode to a high-order cladding mode;
introducing chirp into the double-helix chiral long-period fiber grating to obtain the double-helix chirped chiral long-period fiber grating;
acquiring a grating period of each grating section in the double-helix chirped chiral long-period fiber grating according to the grating period range, wherein the grating period changes along with the position of a fiber shaft;
establishing a target coupling equation under the interaction between a right-handed circularly polarized fiber core mode and a left-handed circularly polarized cladding mode in the double-helix chirped chiral long-period fiber grating in a local coordinate system;
according to the amplitude relation between the output end and the input end of the grating segment, the length of each grating segment is calculated by combining the target coupling equation;
and manufacturing the all-fiber circular polarizer according to the grating period and the length.
2. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 1, wherein the first phase matching condition is:
λ res ＝(n eff,01 -n eff,0n )Λ
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
3. The method of manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 1, wherein the grating period of each grating segment is:
Λ＝Λ 0 +cz
wherein, lambda 0 The initial period of the chirp period is represented by z, the axial position of the optical fiber is represented by z, the value of z ranges from 0 to L, c=delta lambda/L, c represents the chirp coefficient, and delta lambda represents the total period variation of the chirped grating.
4. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 1, wherein establishing a target coupling equation between a right-handed circularly polarized core mode and a left-handed circularly polarized cladding mode in the double-helix chirped chiral long period fiber grating in a local coordinate system comprises:
establishing a circular polarization mode coupling equation of the first coordinate system, the second coordinate system polarization fiber core mode and the cladding mode in the local coordinate system;
based on the mutual coupling effect between the right-handed circularly polarized fiber core mode and the left-handed circularly polarized cladding mode, and the fiber core fundamental mode LP of the double-helix chirped chiral long-period fiber grating 01 Coupled to higher order cladding modes LP 0n And simplifying the circular polarization mode coupling equation to obtain the target coupling equation under the satisfied second phase matching condition.
5. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 4, wherein the circular polarization mode coupling equation is:
where both κ and κ' represent coupling coefficients, τ (τ=2π/P) represents the spin ratio, P represents the fiber pitch,indicating the amplitude of the right-handed circularly polarized core layer,/->Indicating the amplitude of the right-handed circularly polarized core layer,/->Represents the amplitude of the left-hand circularly polarized core and cladding, +.>Indicating the amplitude, beta, of the right-handed circularly polarized core and cladding co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of>The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
6. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 4, wherein the second phase matching condition is:
λ res ＝(n eff,01 -n eff,0n )Λ(z)
wherein lambda is res Represents the resonant wavelength, Λ represents the grating period, z represents the fiber axis position, n eff,01 Representation of LP 01 Effective refractive index of core fundamental mode, n eff,0n Representation of LP 0n Effective refractive index of cladding mode.
7. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 1 or 4, wherein the target coupling equation is:
wherein, kappaRepresents the coupling coefficient, τ (τ=2pi/P) represents the spin ratio, P represents the fiber pitch,indicating the amplitude of the right-handed circularly polarized core and cladding, +.>Indicating the amplitudes of the left-hand circularly polarized core and cladding; beta co Representation of the core mode HE in an ideal isotropic fiber 11 Propagation constant of>The normalized electric field distribution of the different modes is shown, the superscript x or y indicates the polarization direction, ε, of the principal transverse component of the mode 0 Represents the isotropic part of the dielectric constant distribution, Δε x Anisotropic perturbation of the dielectric constant distribution in x-polarization mode, Δε y The anisotropic disturbance part representing the dielectric constant distribution in the y polarization mode, j representing complex number, ω representing the angular frequency of the light wave, s representing the integration area.
8. The method for manufacturing an ultra-wideband flat all-fiber circular polarizer according to claim 1, wherein the amplitude relationship is:
wherein A is co (z M+1 ) Representing the amplitude of the output end core mould, A cl (z M+1 ) Representing the output end cladding mode amplitude, F i Matrix element representing the ith grating segment, A co (z 1 ) =1 represents initial conditions of core die, a cl (z 1 ) =0 denotes the cladding mode initial condition, a ij Two mode coupling coefficients in a matrix element representing the ith grating segment, k representing the coupling strength, σ representing the imaginary part of the coupling strength, z i+1 Representing the length of the i+1st segment grating, z i The i-th segment grating length is represented, i represents the grating number.
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| CN101625441A (en) * | 2009-07-07 | 2010-01-13 | 中国科学技术大学 | All-fiber circuit polarizer |
| CN112068240A (en) * | 2020-09-07 | 2020-12-11 | 桂林电子科技大学 | Long-period chirped fiber grating and preparation method thereof |
| CN217766906U (en) * | 2022-01-27 | 2022-11-08 | 西安邮电大学 | Ultra-wideband flat all-fiber circular polarizer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112068240A (en) * | 2020-09-07 | 2020-12-11 | 桂林电子科技大学 | Long-period chirped fiber grating and preparation method thereof |
| CN217766906U (en) * | 2022-01-27 | 2022-11-08 | 西安邮电大学 | Ultra-wideband flat all-fiber circular polarizer |
Non-Patent Citations (2)
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| 全光纤型圆偏振起偏器的工作原理及理论分析;杨利;李成;苏觉;钱景仁;;中国科学技术大学学报(第10期);全文 * |
| 双螺旋圆单偏振光纤的偏振滤波特性研究;肖悦娱;高玮;颜锦奎;彭蕾;;中国激光(第01期);全文 * |
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