CN113376730B - Cascade long-period grating filter with adjustable wavelength and bandwidth and manufacturing method thereof - Google Patents
Cascade long-period grating filter with adjustable wavelength and bandwidth and manufacturing method thereof Download PDFInfo
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- CN113376730B CN113376730B CN202110394687.1A CN202110394687A CN113376730B CN 113376730 B CN113376730 B CN 113376730B CN 202110394687 A CN202110394687 A CN 202110394687A CN 113376730 B CN113376730 B CN 113376730B
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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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
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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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
- G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
- G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
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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
- G02B6/29304—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 operating by diffraction, e.g. grating
Abstract
The invention discloses a cascade long-period grating filter with adjustable wavelength and bandwidth and a manufacturing method thereof, wherein the filter comprises 8 long-period grating cascades with different periods, 4 of the 8 long-period grating cascades are high-frequency wavelength filtering period gratings, the other 4 of the 8 long-period grating cascades are low-frequency wavelength filtering period gratings, a supporting frame used for fixing a cascade filter grating group, and two accurately controllable graphite heating platforms. The manufacturing method comprises the steps of optical fiber pretreatment, long-period grating drawing, long-period grating etching and filter assembly. The invention can realize the widening or reduction of the width of the filter bandwidth of the filter by adjusting the temperature of the two precisely controllable graphite heating platforms. If the temperature of the two heating platforms is adjusted at the same time, the position of the central wavelength of the filter can be changed. The filter is of an all-fiber structure, is highly adaptive to fiber sensing, fiber lasers and the like, and can adjust filtering parameters in different use environments. The filter is convenient to manufacture, low in cost, flexible to adjust and high in stability.
Description
Technical Field
The invention relates to a cascade long-period grating filter and a manufacturing method thereof, in particular to a cascade long-period grating filter with adjustable wavelength and bandwidth and a manufacturing method thereof, belonging to the technical field of fiber grating filters.
Background
The optical fiber type filter is an optical filter device with wavelength selective reflection or transmission to input optical signals, and has wide application prospect and high application value in the application fields of optical fiber sensing, optical fiber communication, optical signal processing and the like. The performance of the optical fiber type filter directly determines the quality of the optical index of the optical fiber system. The sensitivity, resolution and measurement range of the optical fiber sensor are limited by the influence of parameters such as bandwidth, insertion loss, extinction ratio and the like of the optical fiber filter. The extinction ratio, wavelength and power stability, line width and slope efficiency of the laser source output are closely related to the fiber filter and the capability of optical signal processing, for example, the differentiation effect of the optical time domain differentiator and the shaping effect of the pulse shaping are all dependent on the extinction ratio of the filter. The existing optical filter and different filtering systems have the advantages that after production and forming, the central wavelength and the filtering bandwidth width of filtering are fixed, and are difficult to change, different requirements can be generated on the central wavelength and the filtering bandwidth of the filter when different conditions are met or experimental conditions are improved, the problems can be solved only by purchasing or manufacturing the corresponding filter, the inconvenience is avoided, and the research cost is also increased. The long-period fiber grating as a novel passive optical device has the advantages of low insertion loss, compact size, no backward reflection and the like, and is easily connected with an optical fiber type optical device to form an all-optical fiber structure. The all-fiber structure has the advantages of simple structure, small volume, light weight and the like, is more flexible and convenient in practical application, is easy to realize higher conversion efficiency and high power output, and has excellent heat dissipation performance. A new idea is provided for designing and producing the filter meeting the requirements of the center wavelength and the filter bandwidth of different filters.
Disclosure of Invention
The invention aims to provide a cascade long-period grating filter with adjustable wavelength and bandwidth and a manufacturing method thereof, and solve the problem that the filtering wavelength and the filtering bandwidth in the filter in the prior art can not be changed.
In order to solve the technical problem, the invention adopts the technical scheme.
A cascade long-period grating filter with adjustable wavelength and bandwidth comprises a high-frequency filtering group and a low-frequency filtering group which have the same structure; the high-frequency filtering group comprises more than one high-frequency long-period grating group, a first support frame and a first temperature control platform which are cascaded; the low-frequency filtering group comprises more than 1 group of low-frequency long-period grating groups, a second supporting frame and a second temperature control platform; each high-frequency long-period grating group and each low-frequency long-period grating group are cascaded and etched on the same optical fiber; each high-frequency long-period grating group and each low-frequency long-period grating group are composed of first to Nth long-period gratings which are closely connected, and N is more than or equal to 1; the upper surface of the first temperature control platform is provided with a heat preservation and insulation device, and the first support frame is a stainless steel hollow annular frame and fixedly arranged around the first temperature control platform; each high-frequency long-period grating group is solidified in the first support frame and is tightly attached to the heating platform of the first temperature control platform; the distance between the long-period gratings in each high-frequency long-period grating group and each low-frequency long-period grating group is greater than or equal to the period of the previous long-period grating; the period of each long period grating in the low-frequency filtering group is larger than that of each long period grating in each high-frequency filtering group.
Further, the high-frequency filtering group comprises a first high-frequency long-period grating group, a second high-frequency long-period grating group and a third high-frequency long-period grating group, wherein the first high-frequency long-period grating group comprises 2 closely cascaded long-period gratings, the periods of the 2 long-period gratings in the first high-frequency long-period grating group are the same, and the interval is 1 period; the second high-frequency long-period grating group comprises 2 closely cascaded long-period gratings, the periods of the 2 long-period gratings in the second high-frequency long-period grating group are the same, and the interval is 1 period; the low-frequency filtering group comprises a first low-frequency long-period grating group, a second low-frequency long-period grating group and a third low-frequency long-period grating group, wherein the first low-frequency long-period grating group comprises 2 closely cascaded long-period gratings, and the periods of the 2 long-period gratings in the first low-frequency long-period grating group are the same and are spaced by 1 period; the second high-low frequency long period grating group comprises 2 closely cascaded long period gratings, and the periods of the 2 long period gratings in the second low frequency long period grating group are the same and are spaced by 1 period.
Furthermore, the first temperature control platform, the second temperature control platform and the third temperature control platform use a graphite temperature control platform with the upper heating limit of 400 ℃, and the drift temperature after thermal stabilization is less than 1 ℃; the period range of the long-period grating in the first high-frequency long-period grating group is 180-200 mu m; the period range of the long period grating in the second high-frequency long period grating group is 220-240 mu m; the period range of the long period grating in the first low-frequency long period grating group is 270-290 mu m; the period range of the long period grating in the second low-frequency long period grating group is 310-330 μm; the high-frequency long-period grating groups and the low-frequency long-period grating groups are respectively cured on the tops of the first support frame and the second support frame by ultraviolet curing glue; the ultraviolet curing adhesive resists high temperature of 300 ℃.
The invention adopts the technical scheme II that:
a method for manufacturing a cascade long-period grating filter with adjustable wavelength and bandwidth comprises the following steps:
step 1: optical fiber pretreatment: before etching, stripping a coating layer on the surface of the single-mode optical fiber, reserving more than 20cm of tail fibers on the left side and the right side respectively, fastening and fixing the single-mode optical fiber to be etched by using an optical fiber clamp, and applying axial tension;
step 2: drawing a long-period grating: drawing a long-period grating with a single period, and drawing according to the required period length;
and step 3: etching the long-period grating: the method comprises the following steps:
step 3-1: monitoring with online monitoring equipment, and using CO with working wavelength of 1064 μm 2 Etching the center of the long-period grating by the infrared laser workstation, and stopping when the sinking reaches 15 dB;
step 3-2: keeping the pre-tensioned state of the optical fiber, keeping a distance of one period of the previous long-period grating at intervals, continuously drawing another long-period grating which is closely cascaded with the previous long-period grating, and finishing etching according to the step 3;
step 3-3: judging whether all the long-period gratings are manufactured or not, if so, turning to the step 6, and otherwise, turning to the step 4;
and 4, step 4: assembling the filter: closely attaching long-period gratings in the first to second high-frequency long-period grating groups to a heating plate of the first temperature control platform, and curing and packaging the long-period gratings in the first support frame through ultraviolet curing adhesive; and closely attaching the first to second low-frequency long-period grating groups to the heating plate of the second temperature control platform, and curing and packaging the grating groups in the second support frame through ultraviolet curing adhesive.
Furthermore, the period ranges of 2 long-period gratings in the first high-frequency long-period grating group are all 180-200 μm, 120 periods are etched, and the distance between the grating periods is one grating period; the period ranges of 2 long period gratings in the second high-frequency long period grating group are all 220-240 mu m, 120 periods are written, and the distance between every two grating periods is one grating period; the period ranges of 2 long period gratings in the first low-frequency long period grating group are 270-290 mu m, 120 periods are written, and the distance between every two grating periods is one grating period; the period range of 2 long period gratings in the second low-frequency long period grating group is 310-330 μm, 120 periods are written, and the distance between every two grating periods is one grating period.
Further, the CO is 2 The etching speed of the laser workstation is 8mm/s, the laser frequency is 7kHz, the model of the single-mode optical fiber is HI1060, and the working wave band is 980nm-1600 nm.
The technical effect obtained by adopting the technical scheme is as follows:
1. the core components for filtering are all of an all-fiber structure, the filtering parameters are adjusted through temperature change, and the all-fiber structure has extremely strong anti-electromagnetic interference characteristics and extremely high adaptability with other optical fiber devices.
2. The invention adopts a mode of cascading two groups of 8 long-period gratings, fully utilizes the filtering characteristic and the temperature change characteristic of the grating, and realizes the adjustment of the central wavelength and the bandwidth of the filtering.
3. The invention forms the cascade long period grating group by the band elimination characteristic of the long period grating, so that the adjustable filtering is carried out in a wider range near a 1 mu m wave band, the adjustable range width of the central wavelength reaches 19.5nm, and the adjustable range width of the filtering bandwidth reaches 13.4 nm.
4. The invention adopts the precisely controllable graphite heating platform to control the temperature of the cascade long-period grating group, correspondingly changes the central wavelength and the bandwidth of the filter, and the change precision can reach 0.07 nm.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a spectrum diagram of the narrowest bandwidth of the filter in the filter of embodiment 1 of the present invention.
Fig. 3 is a spectrum diagram of the widest bandwidth of the filter of the embodiment 1 of the present invention.
Fig. 4 is a diagram showing a relationship between a filter bandwidth and a temperature according to embodiment 1 of the present invention.
FIG. 5 is a graph showing the relationship between the central wavelength of the filter and the temperature in example 1 of the present invention.
FIG. 6 is a graph showing the linearity of the wavelength with temperature in example 1 of the present invention.
Wherein, good meaning is listed: 1-a first support frame, 2-a second support frame, 3-a high-frequency filtering group, 4-a low-frequency filtering group, 5-a first temperature control platform, 6-a second temperature control platform, 7-ultraviolet curing glue, 8-a single-mode fiber, 301-a first high-frequency long-period grating group, 302-a second high-frequency long-period grating group, 401-a first low-frequency long-period grating group, and 402-a second low-frequency long-period grating group.
Detailed Description
The following examples serve to illustrate the invention.
Example 1
A cascade long-period grating filter with adjustable wavelength and bandwidth comprises a high-frequency filtering group 3 and a low-frequency filtering group 4 which have the same structure; the high-frequency filtering group 3 comprises more than one high-frequency long-period grating group, a first support frame 1 and a first temperature control platform 5 which are cascaded; the low-frequency filtering group 4 comprises more than 1 group of low-frequency long-period grating groups, a second supporting frame 2 and a second temperature control platform 6; each high-frequency long-period grating group and each low-frequency long-period grating group are cascaded and etched on the same single-mode optical fiber 8; each high-frequency long-period grating group and each low-frequency long-period grating group are composed of first to Nth long-period gratings which are closely connected, and N is more than or equal to 1; the upper surface of the first temperature control platform 5 is provided with a heat preservation and insulation device, and the first support frame 1 is a stainless steel hollow annular frame and fixedly arranged around the first temperature control platform 5; each high-frequency long-period grating group is arranged in the first support frame 1 and is tightly attached to the heating platform of the first temperature control platform 5; the distance between the long-period gratings in each high-frequency long-period grating group and each low-frequency long-period grating group is greater than or equal to the period of the previous long-period grating; the period of each long period grating in the low frequency filtering group 4 is greater than that of each long period grating in each high frequency filtering group 3.
The high-frequency filtering group 3 comprises first to second high-frequency long- period grating groups 301 and 302, the first high-frequency long-period grating group 301 comprises 2 closely cascaded long-period gratings, and the periods of the 2 long-period gratings in the first high-frequency long-period grating group 301 are the same and are 1 period at intervals; the second high-frequency long-period grating group 302 comprises 2 closely cascaded long-period gratings, and the periods of the 2 long-period gratings in the second high-frequency long-period grating group 302 are the same and are spaced by 1 period; the low-frequency filtering group 4 comprises first to second low-frequency long-period grating groups 401-402, the first low-frequency long-period grating group 401 comprises 2 closely cascaded long-period gratings, the periods of the 2 long-period gratings in the first low-frequency long-period grating group 401 are the same, and the interval is 1 period; the second high-low frequency long period grating group 402 includes 2 closely cascaded long period gratings, and the periods of the 2 long period gratings in the second low frequency long period grating group 402 are the same, and the interval is 1 period.
The first to second temperature control platforms 5, 6 use graphite temperature control platforms with the upper heating limit of 400 ℃, and the drift temperature after thermal stabilization is less than 1 ℃; the period range of the long period grating in the first high-frequency long period grating group 301 is 180 μm to 200 μm; the period range of the long period grating in the second high-frequency long period grating group 302 is 220 μm to 240 μm; the period range of the long period grating in the first low-frequency long period grating group 401 is 270 μm to 290 μm; the period range of the long period grating in the second low-frequency long period grating group 402 is 310 μm to 330 μm; the high-frequency long-period grating groups and the low-frequency long-period grating groups are respectively cured on the tops of the first and second support frames 1 and 2 by ultraviolet curing glue; the ultraviolet curing adhesive resists high temperature of 300 ℃.
The all-fiber filter based on the long-period grating enters the cladding from the fiber core LP01 mode and is coupled with the cladding LP0m mode to form the depressed loss of a transmission spectrum at different wavelengths. The cascade long-period fiber grating can be regarded as two long-period fiber gratings with different periods, and is a long-period fiber grating combination separated by the cascade fiber with the length of d. When the parameters of the cascaded long-period grating are the same, after light passes through the first long-period grating, the fiber core mold is partially coupled to the cladding mold, the cladding mold and the residual fiber core mold are respectively transmitted along the cladding and the fiber core, and at the cascaded long-period grating, the cladding mold is coupled back to the fiber core to form the fiber core mold and is interfered with the fiber core mold which is not coupled by the previous long-period grating.
Phase matching conditions of the long-period grating:
in the formula: lambda [ alpha ] m The central wavelength of the loss peak after the m-order cladding mode is coupled with the fiber core fundamental mode;
is the effective refractive index of the fundamental core mode;
is the effective refractive index of the m-order cladding mode; Λ is the period of the corresponding long period grating. By r is j And t j Respectively representing the cladding mode transmission amplitude and the fundamental mode transmission amplitude of the uniform long-period fiber grating:
in the formula: l is j Is the length of the j-th section of the grating; delta m For the coupling coefficient, it is defined as follows:
the transmission amplitude r of the cladding mode and the transmission amplitude of the fundamental core mode of the cascaded long-period grating group can be expressed as:
the transmission rate T of the cascaded long period grating is:
in the embodiment, the single-mode fiber 8 is in a HI1060 type, the working wavelength band is from 980nm to 1600nm, and 8 closely cascaded long-period gratings are etched on the single-mode fiber 8 in total. The first to second temperature control platforms 5, 6 are used with a temperature control range of room temperature to 400 ℃, and when only the filter wavelength is changed, the two temperature control platforms set the same temperature, and when the filter bandwidth is required to be changed, the temperatures of the two platforms need to be set respectively.
First, the temperature of the heating platform is set to 20 ℃, and after the temperature is stabilized, the central wavelength of the whole filter is stabilized at 1046.08nm, and the filter bandwidth is 10.25nm, namely 3dB of the central wavelength. When the central wavelength of the filter needs to be changed, the temperature of the temperature control platform is changed, the filtering frequency of each liter of high-frequency grating group and low-frequency grating group with the first degree can be reduced by 20GHz, and the corresponding wavelength can be increased by about 0.07 nm. The accurate control of the central wavelength of the filter can be realized by accurately controlling the temperature.
The required filter center wavelength and bandwidth are determined by adjusting the filter bandwidth. Different temperatures are set for the first graphite temperature control platform 5 to the second graphite temperature control platform 6, so that the filtering wavelengths of the high-frequency filtering group 3 and the low-frequency filtering group 4 are relatively displaced, the 3dB bandwidth is 10.25nm under the isothermal condition, if the bandwidth of 8nm is to be obtained, the temperature difference between the first graphite temperature control platform 5 and the second graphite temperature control platform 6 is kept at about 32 ℃, and if the bandwidth of 10nm is to be obtained, the temperature difference between the first graphite temperature control platform 5 and the second graphite temperature control platform 6 is kept at about 25 ℃.
Heating the first graphite temperature control platform 5 to the second graphite temperature control platform 6, wherein the filtering center wavelength increases along with the increase of the temperature, after the temperature is completely stabilized, the whole filtering wavelength shifts correspondingly, only the temperature of the first graphite temperature control platform 5 is increased, or only the temperature of the second graphite temperature control platform 6 is reduced, or the temperature of the first graphite temperature control platform 5 is increased and the temperature of the second graphite temperature control platform 6 is reduced, so that the filtering bandwidth can be correspondingly reduced; only the temperature of the first graphite temperature control platform 5 is reduced, or only the temperature of the second graphite temperature control platform 6 is increased, or the temperature of the first graphite temperature control platform 5 is reduced and the temperature of the second graphite temperature control platform 6 is increased at the same time, so that the filtering bandwidth can be correspondingly increased.
According to the embodiment, the band stop frequency of the long-period grating is changed through the accurate control of the temperature, so that the change of the integral central wavelength of the filter is reflected, the adjustment range of the filter bandwidth of 13.4nm can be provided, the central wavelength is from 1045.45nm to 1064.95nm, the adjustable range can reach 19.5nm, and the change accuracy of the wavelength can reach 0.07 nm.
Example 2
A method for manufacturing a cascade long-period grating filter with adjustable wavelength and bandwidth comprises the following steps:
step 1: optical fiber pretreatment: before etching, a coating layer on the surface of the single-mode optical fiber 8 is stripped, the left and right tail fibers are respectively reserved for more than 20cm, the single-mode optical fiber 8 to be etched is fastened and fixed by an optical fiber clamp, and axial tension is applied;
step 2: drawing a long-period grating: drawing a long-period grating with a single period, and drawing according to the required period length;
and step 3: etching the long-period grating: the method comprises the following steps:
step 3-1: monitoring with online monitoring equipment, and using CO with working wavelength of 1064 μm 2 Etching the center of the long-period grating by the infrared laser workstation, and stopping when the sinking reaches 15 dB;
step 3-2: keeping the pre-tensioned state of the optical fiber, keeping a distance of one period of the previous long-period grating at intervals, continuously drawing another long-period grating which is closely cascaded with the previous long-period grating, and finishing etching according to the step 3;
step 3-3: judging whether the manufacture of all long-period gratings is finished, if so, turning to the step 6, otherwise, turning to the step 4;
and 4, step 4: assembling the filter: closely attaching long-period gratings in the first to second high-frequency long- period grating groups 301 and 302 to a heating plate of the first temperature control platform 5, curing the long-period gratings through high-temperature-resistant ultraviolet curing adhesive, and packaging the long-period gratings in the first support frame 1; the first to second low-frequency long- period grating groups 301 and 302 are closely attached to the heating plate of the second temperature control platform 6, cured by high-temperature-resistant ultraviolet curing adhesive, and encapsulated in the second support frame 2.
The period range of 2 long period gratings in the first high-frequency long period grating group 301 is 180-200 μm, 120 periods are written, and the distance between every two grating periods is one grating period; the period ranges of 2 long period gratings in the second high-frequency long period grating group 302 are all 220 μm to 240 μm, 120 periods are written, and the interval is one grating period; the period ranges of the 2 long-period gratings in the first low-frequency long-period grating group 401 are 270-290 μm, 120 periods are written, and the distance between the two periods is one grating period; the 2 long-period gratings in the second low-frequency long-period grating group 402 have a period range of 310 μm to 330 μm, 120 periods are written, and a grating period is arranged between the periods.
The CO is 2 The etching speed of the laser workstation is 8mm/s, the laser frequency is 7kHz, the model of the single-mode optical fiber is HI1060, and the working wave band is from 980nm to 1600 nm.
Claims (5)
1. A cascade long-period grating filter with adjustable center wavelength and bandwidth is characterized in that: the light transmitted in the fiber core couples partial modes into a cladding layer through a long-period grating to generate a cladding mode, the cladding mode and a fiber core mode are transmitted along the optical fiber together, when the cladding mode returns to the fiber core, the light is coupled with the fiber core mode transmitted in the fiber core, the coupled wavelength components generate loss and are not transmitted continuously, the wavelength components which are not coupled are transmitted continuously along the fiber core, and the non-transmitted light components are eliminated through high-frequency and low-frequency long-period grating groups, so that the function of band-pass filtering is realized, and the high-frequency and low-frequency long-period grating groups comprise a high-frequency filtering group (3) and a low-frequency filtering group (4) which have the same structure; the high-frequency filtering group (3) comprises more than one high-frequency long-period grating group, a first support frame (1) and a first temperature control platform (5) which are cascaded; the low-frequency filtering group (4) comprises more than 1 low-frequency long-period grating group, a second supporting frame (2) and a second temperature control platform (6); each high-frequency long period grating group and each low-frequency long period grating group are cascaded and etchedEtched on the same single mode fiber (8); each high-frequency long period grating group and each low-frequency long period grating group are respectively a first grating group, a second grating group and a third grating group which are closely connectedNLong period grating composition; the first temperature control platform (5) is tightly attached to the heating platform; the distance between the long-period gratings in each high-frequency long-period grating group and each low-frequency long-period grating group is greater than or equal to the period of the previous long-period grating; the period of each long period grating in the low-frequency filtering group is larger than that of each long period grating in each high-frequency filtering group.
2. The cascaded long-period grating filter with adjustable center wavelength and bandwidth of claim 1, wherein: the first temperature control platform, the second temperature control platform (5) and the second temperature control platform (6) use a graphite temperature control platform with the upper heating limit of 400 ℃, and the drift temperature after thermal stabilization is less than 1 ℃; when the parameters of the cascaded long-period grating structures are the same, after light passes through the first long-period grating, the fiber core mold is partially coupled to the cladding mold, the cladding mold and the residual fiber core mold are respectively transmitted along the fiber core of the cladding, and at the second cascaded long-period grating, the cladding mold is coupled back to the fiber core to form the fiber core mold and is interfered with the fiber core mold which is not coupled before; the first high-frequency long-period grating group comprises 2 closely cascaded long-period gratings with the interval of 1 period, and the period range of the long-period gratings is 180-200 mu m; the second high-frequency long-period grating group comprises 2 closely cascaded long-period gratings with the interval of 1 period, and the period range of the long-period gratings is 220-240 mu m; the first low-frequency long-period grating group comprises 2 closely cascaded long-period gratings with the interval of 1 period, and the period range of the long-period gratings is 270-290 mu m; the second low-frequency long-period grating group comprises 2 closely cascaded long-period gratings with the interval of 1 period, and the period range of the long-period gratings is 310-330 μm; the high-frequency long-period grating groups and the low-frequency long-period grating groups are respectively cured on the tops of the first support frame (1) and the second support frame (2) by ultraviolet curing glue; the ultraviolet curing adhesive resists high temperature of 300 ℃.
3. A method for manufacturing a cascaded long period grating filter with adjustable wavelength and bandwidth according to claim 1, wherein: the method comprises the following steps:
step 1: optical fiber pretreatment: before etching, a coating layer on the surface of the single-mode optical fiber (8) is stripped, the left and right tail fibers are respectively reserved for more than 20cm, the single-mode optical fiber (8) to be etched is fastened and fixed by an optical fiber clamp, and axial tension is applied;
step 2: drawing a long-period grating: drawing a long-period grating with a single period, and drawing according to the required period length;
and step 3: etching the long-period grating: the method comprises the following steps:
step 3-1: monitoring with online monitoring equipment, and using CO with working wavelength of 1064 μm 2 Etching the center of the long-period grating by the infrared laser workstation, and stopping when the sinking reaches 15 dB;
step 3-2: keeping the pre-tensioned state of the optical fiber, keeping a distance of one period of the previous long-period grating at intervals, continuously drawing another long-period grating which is closely cascaded with the previous long-period grating, and finishing etching according to the step 3;
step 3-3: judging whether the manufacture of all long-period gratings is finished, if so, turning to the step 4, and otherwise, re-performing the step 3;
and 4, step 4: assembling the filter: the long-period gratings in the first high-frequency long-period grating group, the second high-frequency long-period grating group and a heating plate of the first temperature control platform (5) are tightly attached, and are cured and packaged in the first supporting frame (1) through ultraviolet curing glue; and (3) closely attaching the first to second low-frequency long-period grating groups to the heating plate of the second temperature control platform (6), and curing and packaging the grating groups in the second supporting frame (2) through ultraviolet curing adhesive.
4. The method of claim 3, wherein the wavelength and bandwidth tunable cascaded long period grating filter is characterized in that: the period ranges of 2 long period gratings in the first high-frequency long period grating group (301) are all 180-200 mu m, 120 periods are written, and the distance between the periods is one grating period; the period ranges of 2 long period gratings in the second high-frequency long period grating group (302) are all 220-240 mu m, 120 periods are written, and the distance between the periods is one grating period; the period ranges of 2 long-period gratings in the first low-frequency long-period grating group (401) are 270-290 mu m, 120 periods are written, and the distance between the periods is one grating period; the period range of 2 long period gratings in the second low-frequency long period grating group (402) is 310-330 μm, 120 periods are written, and the distance between every two grating periods is one grating period.
5. The method of claim 3 or 4, wherein the wavelength and bandwidth of the cascade long period grating filter are adjustable, and the method comprises the following steps: the CO is 2 The etching speed of the laser workstation is 8mm/s, the laser frequency is 7kHz, the type of the single-mode optical fiber 8 is HI1060, and the working wave band is 980nm-1600 nm.
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| EP0897124A1 (en) * | 1997-08-12 | 1999-02-17 | Photonics Research Ontario | Design of complex optical fiber filters using long-period gratings |
| CN105137591A (en) * | 2014-04-03 | 2015-12-09 | 骆飞 | Fiber bragg grating superstructure tuning method and device |
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| US20030215185A1 (en) * | 1999-12-06 | 2003-11-20 | Cidra Corporation, | Large diameter optical waveguide having long period grating therein |
| EP1243949A1 (en) * | 2001-03-14 | 2002-09-25 | Alcatel | Optical filter device, method for tuning and communication system |
| CN105022114B (en) * | 2015-07-27 | 2018-06-26 | 江苏大学 | A kind of mode filter of cascade connection type long-period fiber grating |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP0897124A1 (en) * | 1997-08-12 | 1999-02-17 | Photonics Research Ontario | Design of complex optical fiber filters using long-period gratings |
| CN105137591A (en) * | 2014-04-03 | 2015-12-09 | 骆飞 | Fiber bragg grating superstructure tuning method and device |
Non-Patent Citations (3)
| Title |
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| Highly tunable microwave and millimeter wave filtering using photonic technology;Joe Seregelyi.et.al;《Optical Engineering》;20150531;全文 * |
| Tunable WDM filters based on cascaded long-period fiber gratings;Dong, Xinyong.et.al;《Asia-Pacific Optical Communications, 2004》;20050110;全文 * |
| 一种通道数可变的光纤光栅梳状滤波器;董新永.et.al;《光子学报》;20100228;全文 * |
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