CN108919427B - Wavelength switch system based on electrode discharge and graphene coated fiber grating - Google Patents
Wavelength switch system based on electrode discharge and graphene coated fiber grating Download PDFInfo
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- CN108919427B CN108919427B CN201810816694.4A CN201810816694A CN108919427B CN 108919427 B CN108919427 B CN 108919427B CN 201810816694 A CN201810816694 A CN 201810816694A CN 108919427 B CN108919427 B CN 108919427B
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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
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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
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
- G02B6/29317—Light guides of the optical fibre type
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Abstract
The invention provides a wavelength switch system based on electrode discharge and graphene coated fiber bragg grating, which is characterized by comprising a light source, a fiber isolator, a fiber circulator, a fiber bragg grating sensor, an electrode driver and a spectrum analyzer; the optical fiber circulator is connected with the optical fiber isolator at one end and connected with the optical fiber grating sensor and the spectrum analyzer at the other end, the optical fiber grating sensor is at least connected with two Bragg optical fiber gratings with different wavelengths in series, and the surface of a grating area of each Bragg optical fiber grating is coated with 10 layers of graphene; wherein, the electrode driver controls the electrode to discharge to the grating region of the Bragg fiber grating: the electrode driver control electrode is selected according to the required wavelength range to discharge the grating regions of other Bragg fiber gratings except the wavelength range so as to turn off the Bragg fiber gratings in other wavelength ranges.
Description
The application is filed on 2016, 04, 28 and 201610274685.8, and is named as a divisional application of a wavelength switch control method based on electrode discharge and graphene coated fiber gratings.
Technical Field
The invention relates to the technical field of optical fiber communication, in particular to a wavelength switch system based on electrode discharge and graphene coated optical fiber gratings.
Background
The FBG sensor has the advantages of high sensitivity, small volume, easiness in optical fiber coupling, no electromagnetic interference and the like, and is widely applied to the fields of aerospace, petrochemical industry, ship shipping, civil industry, electric power, medical science and the like.
Since the first fiber grating in the world was made by k.o.hill et al using the standing wave interference method, the research on the writing technique of the fiber grating has been rapidly developed, such as the phase mask method, the holographic interference method, the wave division front interference method, the on-line grating method, the focused ion beam writing method, and the direct writing method. The most mature and widely applied fiber grating writing method at present is ultraviolet exposure writing based on a phase mask method, the fiber grating written by adopting the traditional ultraviolet exposure method has the advantages that the refractive index change only occurs in the fiber core of the optical fiber with photosensitivity, and the refractive index is periodically distributed along the axial direction.
In the FBG manufacturing process, firstly, the common germanium-doped optical fiber is subjected to hydrogen loading treatment to improve the photosensitivity of the optical fiber, and then, an optical fiber coating automatic stripping machine is used for removing a coating layer of the hydrogen-loaded optical fiber so as to facilitate the writing of the grating. After a common optical fiber is placed in high-pressure (107Pa) hydrogen for a period of time, hydrogen molecules gradually diffuse into a cladding and a core of the optical fiber, and when ultraviolet light with specific wavelength (generally 248nm or 193nm) irradiates the hydrogen-loaded optical fiber, the hydrogen molecules in the irradiated part of the core immediately react with germanium to form Ge-OH and Ge-H bonds, so that the refractive index of the part is permanently increased. After the writing process is finished, residual hydrogen molecules in the grating have diffusion movement, unstable Ge-OH bonds exist after reaction, and the bonds are degraded and reduced due to the increase of the temperature, so that the reflectivity of the grating is reduced.
Therefore, there is a need for a system and method that can output light of different center wavelengths at the output.
Disclosure of Invention
The invention aims to provide a wavelength switch system based on electrode discharge and graphene coated fiber bragg grating, which comprises a light source, a fiber isolator, a fiber circulator, a fiber bragg grating sensor, an electrode driver and a spectrum analyzer; the optical fiber circulator is connected with the optical fiber isolator at one end and connected with the optical fiber grating sensor and the spectrum analyzer at the other end, the optical fiber grating sensor is at least connected with two Bragg optical fiber gratings with different wavelengths in series, and the surface of a grating area of each Bragg optical fiber grating is coated with 10 layers of graphene; wherein, the electrode driver controls the electrode to discharge to the grating region of the Bragg fiber grating:
the electrode driver is selected according to the required wavelength range to control the electrode to discharge the grid regions of the Bragg fiber gratings except the wavelength range so as to close the Bragg fiber gratings in other wavelength ranges,
the electrodes are arranged at the central position of each Bragg fiber grating, and the electrode driver controls the electrodes to discharge the central points of the grid regions of the Bragg fiber gratings.
Preferably, the electrode discharge power is a fixed value of 110 mw.
Preferably, the frequency of discharging the center point of the grating region of the fiber bragg grating by the electrode is 10 Hz.
Preferably, the time for discharging the central point of the grid region of the Bragg fiber grating by the electrode is 5-10 s.
Preferably, the light source is a broadband light source or a multiband output light source.
Preferably, the grating region length of the Bragg fiber grating is 10mm, and the intensity is 10 dB.
Preferably, the electrode driver employs an optical fiber coating automatic stripper.
Preferably, the fiber bragg grating holder is made of copper with good thermal conductivity, and a contact area with the fiber bragg grating is coated with thermally conductive silicone.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:
FIG. 1 schematically illustrates a schematic structural view of a wavelength switching device based on electrode discharge and graphene coated fiber gratings according to the present invention;
FIG. 2 is a schematic diagram showing a scanning mode of an electrode scanning raster region according to the present invention;
FIG. 3 shows the reflection spectrum of the discharge at different positions of the electrode scan gate;
FIG. 4 shows FBG reflection spectra when the left side grating region is discharged at different positions;
fig. 5 shows the FBG spectrum when the gate center is discharged compared to the undischarged FBG spectrum.
Detailed Description
The wavelength switch device based on electrode discharge and graphene coated fiber bragg grating comprises a broadband light source or multiband output light source, a fiber isolator, a fiber circulator, a fiber bragg grating string (FBG) and a spectrum analyzer. Light emitted by the broadband light source or the multiband output light source enters the fiber bragg grating sensor after passing through the fiber isolator and the fiber circulator, and the fiber bragg grating sensor is provided with at least two FBGs (fiber bragg gratings) connected in series with different wavelengths. An arc discharge electrode is arranged at the central position of each FBG, the other end of the optical fiber circulator is connected to a spectrum analyzer (OSA) for real-time monitoring, and the spectrum of the electrode under discharge at different positions is observed through the spectrum analyzer. The fiber Bragg grating string is made by writing a plurality of Bragg gratings with different central wavelengths on one fiber by femtosecond laser, wherein the length of each grating region is 10mm, and the intensity is 10 dB. The surface of the grid region of the fiber grating is coated with 10 layers of graphene, and the length of the graphene is 30 mm.
Fig. 1 schematically shows a structural diagram of a wavelength switching device based on electrode discharge and graphene-coated fiber grating according to an embodiment of the present invention. As shown in fig. 1, a wavelength switching device 100 based on electrode discharge and graphene-coated fiber grating includes: ASE light source 101, fiber isolator 102, fiber circulator 103, first FBG104, second FBG105, third FBG106, electrode driver 110, and spectrum analyzer 111. The ASE light source 101, the optical fiber isolator 102, and the optical fiber circulator 103 are sequentially connected, one end of the optical fiber circulator 103 is connected to the optical fiber isolator 102, and the other end is respectively connected to the first FBG104, the second FBG105, the third FBG106, and the spectrum analyzer 111. In this embodiment, an optical fiber coating automatic stripping machine 3SAEFPUII is used as the electrode driver 110. The electrode driver 110 can set parameters such as the moving direction and speed of the electrodes, and the discharge power and time of the electrodes through the controller. The ASE light source in the embodiment is self-developed, the output power is larger than 13dBm, and the bandwidth area of the C + L wave band is 1525nm-1610 nm; the clamp of the fiber Bragg grating is made of red copper with good thermal conductivity, and a contact area of the clamp and the fiber Bragg grating is coated with heat-conducting silica gel to strengthen the heat conduction of the grating area and the clamp. Each segment of FBG is respectively fixed at two ends thereof through two fiber bragg grating clamps.
In the experiment, the electrode discharge power is a fixed value of 110mw, and the fiber bragg grating grid region is respectively subjected to scanning discharge and fixed point discharge experiments by setting discharge device parameters. Multiple experiments prove that when the electrode performs discharge scanning on the whole grid region from left to right along the axial direction of the optical fiber at the speed of 0.1mm/s (the direction a shown in fig. 2), the change of the FBG spectrum in the scanning process is symmetrical about the center of the grid region, as shown in fig. 3, and fig. 3 shows the reflection spectrum when the electrode scans different positions of the grid region for discharging. As the electrode starts scanning discharge from z-5 mm, the reflectivity of the FBG gradually decreases; when the position where z is 0mm is scanned, the peak intensity of the FBG reflection spectrum reaches the lowest, and the reflectivity gradually increases after passing through the middle point of the grid region; when z 5mm is scanned, the reflection peak is the same as the reflection peak at z-5 mm. To facilitate data analysis, spectrograms were recorded every 1mm, starting at-5 mm, and so on. Fig. 4 shows the reflection spectra of the electrode observed at 5 different positions of the left grating region, and it can be seen from the spectrum chart that the FBG reflection spectrum bandwidth is broadened and red-shifted by the electrode discharge, the peak reflection intensity is gradually reduced, and the spectrum shape gradually appears irregular and multi-peak. When z is 0mm, i.e. the electrode is at the midpoint of the gate, there is a significant deviation of the spectrum from the original spectrum and a significant wavelength resonance away from the center wavelength.
In order to analyze the influence of the electrode discharge at the central position of the grid region on the spectrum, relevant parameters of the electrode are set so as to carry out a fixed-point discharge experiment on the central position of the grid region. Fig. 5 is a comparison of FBG spectra when the center of the gate is discharged and when it is not discharged, it can be seen that the peak reduction of the transmission spectrum disappears when the discharge is continued, the peak power shows a significant switching value variation characteristic, and the phenomenon has repeatability. That is, the control electrode of the electrode driver is used to continuously discharge at the midpoint of the FBG grating region, and the peak of the reflection spectrum of the FBG grating disappears, so that the spectrum analyzer cannot detect the reflection spectrum of the corresponding FBG grating, which corresponds to the FBG of this wavelength being in the "off" state. Similarly, when a plurality of FBGs are connected in series in the wavelength switching device based on electrode discharge and graphene coated fiber grating according to the present invention, the switching of FBGs of different wavelengths can be controlled by discharging the electrode to the center of the FBG grating region, so that light of different wavelengths can be obtained in one fiber grating system. Therefore, the electrode driver can be selected according to the required wavelength range to control the electrode to discharge the middle points of the grid regions of the Bragg fiber gratings except the wavelength range, so that the Bragg fiber gratings in other wavelength ranges are turned off, and the light with the wavelength in the range can be obtained at the output end.
It is known from the mode coupling theory that the central wavelength of the grating is shifted by the change of the effective refractive index and the period of the grating. When the electrode discharges, the high energy gathered by the electrode ionizes the air nearby to generate thermal plasma, a large amount of heat is released along with the increase of the density of the thermal plasma, and then an uneven temperature field is formed nearby the electrode, and when the temperature field is close to the position of the gate region, the refractive index of the fiber core of the fiber grating is induced to change.
The temperature change can cause a thermal expansion effect and a thermo-optic effect, wherein the thermal-optic effect causes the radius of a fiber core and a cladding of the optical fiber to change, so that the effective refractive index of the grating is changed; thermal expansion effects cause the material dimensions to change, causing the grating period to change. But the thermal expansion coefficient caused by the thermal expansion effect is two orders of magnitude smaller than the refractive index temperature coefficient caused by the thermo-optical effect. Only temperature-induced changes in the refractive index of the fiber need be considered and the effects of other effects ignored. The refractive index profile at each position of the grating region changes, and the refractive index profile n (z) along the axis can be expressed as
n(z)＝n0+n(z)， (3)
Wherein n is0For the effective refractive index of the initial grating,nand (z) is the spatial modulation degree of the grating refractive index by temperature. The wavelength λ (z) reflected at each position of the grating region can be expressed as
λ(z)＝2n(z)Λ0＝2[n0+n(z)]Λ0＝2n0Λ0[1+Topt(z)]， (4)
Where n is the effective index of refraction of the grating, Λ0Defining the optical temperature parameter as T for the grating periodopt(z)＝n(z)/n0The refractive index modulation due to temperature change is shown.
The non-uniformly distributed temperature field induces the refractive index of the grating to change, and finally the grating area generates chirp. Specifying the amount of broadening of the bandwidth of the chirp spectrum to be the maximum resonance wavelength lambdamaxWith minimum resonance wavelength lambdaminDifference of delta lambdabwCan be represented as
Δλbw＝λmax-λmin＝2n0Λ0ΔTopt， (5)
In the formula,. DELTA.Topt＝Tmax-TminRepresenting the maximum temperature gradient of the grating region. As shown in the formula (5), the broadening amount of the FBG reflection spectrum bandwidth is in direct proportion to the maximum temperature gradient.
When the electrode reaches the center of the gate region, the difference between the peak optical power of the FBG reflection spectrum and the original state reaches the maximum, and at this time, the FBG transmission spectrum shows the characteristic of having more prominent peak, as shown in fig. 4. The reason for analyzing the optical grating is that when the electrode discharges, the high energy gathered by the electrode ionizes the air nearby to generate thermal plasma, a large amount of heat is released along with the increase of the density of the thermal plasma, and then an uneven temperature field is formed nearby the electrode, when the temperature field is close to the position of the grating region, the refractive index of the fiber core of the optical fiber grating is induced to change, so that the transmittance of the grating is increased, and when the uneven temperature field is located at the center of the grating region, the transmittance of the grating tends to be saturated and reaches the maximum, and the harmonic wave at the edge of the peak optical power of the reflection spectrum is caused by chirp.
The specific method for controlling the output end to output light with different wavelengths based on the wavelength switching device of the invention, which is based on electrode discharge and graphene coated fiber bragg grating, is as follows:
1. a wavelength switch system based on electrode discharge and graphene coated fiber bragg grating is built:
the wavelength switch system comprises a light source, an optical fiber isolator, an optical fiber circulator, an optical fiber grating sensor, an electrode driver and a spectrum analyzer; the optical fiber circulator is connected with the optical fiber isolator at one end and connected with the optical fiber grating sensor and the spectrum analyzer at the other end, and the optical fiber grating sensor is at least connected with two Bragg optical fiber gratings with different wavelengths in series;
2. determining the required wavelength output, and controlling the electrode to discharge the grid region of the Bragg fiber grating by the electrode driver:
the electrode driver control electrode is selected according to the required wavelength range to discharge the grating regions of other Bragg fiber gratings except the wavelength range so as to turn off the Bragg fiber gratings in other wavelength ranges.
The electrodes are arranged at the central position of each Bragg fiber grating, and the electrode driver controls the electrodes to discharge the central points of the grid regions of the Bragg fiber gratings.
The fiber grating inscribed by the femtosecond laser adopted in the invention can overcome the defect that the depth of the transmission spectrum of the electrode discharge grating is reduced. Electrode discharge is carried out to anneal the fiber bragg grating inscribed by the ultraviolet light, so that unreacted hydrogen molecules remained in the hydrogen-carrying fiber can be removed; on the other hand, some unstable Ge-OH and Ge-H bonds in the fiber core after the grating is written can be destroyed, so that the refractive index modulation of the grating is changed, and the reflectivity of the grating is changed. The axially non-uniform temperature field distribution produced by the electrode discharge causes grating chirp. The reflectivity of the grating is reduced through electrode discharge, and the depth of the grating transmission spectrum is reduced.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims (8)
1. A wavelength switch system based on electrode discharge and graphene coated fiber bragg grating is characterized by comprising a light source, a fiber isolator, a fiber circulator, a fiber bragg grating sensor, an electrode driver and a spectrum analyzer; the optical fiber circulator is connected with the optical fiber isolator at one end and connected with the optical fiber grating sensor and the spectrum analyzer at the other end, the optical fiber grating sensor is at least connected with two Bragg optical fiber gratings with different wavelengths in series, and the surface of a grating area of each Bragg optical fiber grating is coated with 10 layers of graphene; wherein, the electrode driver controls the electrode to discharge to the grating region of the Bragg fiber grating:
selecting an electrode driver according to the required wavelength range, controlling the electrode to discharge the grid region of the Bragg fiber grating outside the required wavelength range so as to close the Bragg fiber grating outside the required wavelength range,
the electrode is arranged at the central position of each Bragg fiber grating, and the electrode driver controls the electrode to discharge the central point of the grid region of each Bragg fiber grating.
2. The wavelength switching system according to claim 1, wherein said electrode discharge power is a fixed value of 110 mw.
3. The wavelength switching system of claim 2 wherein said electrode discharges the center point of the grating region of the fiber bragg grating at a frequency of 10 Hz.
4. The wavelength switching system of claim 2, wherein the time for the electrode to discharge to the center point of the grating region of the fiber bragg grating is 5 to 10 seconds.
5. The wavelength switching system of claim 1, wherein the light source is a broadband light source or a multiband output light source.
6. The wavelength switching system according to claim 3, wherein said fiber Bragg grating has a grating region length of 10mm and an intensity of 10 dB.
7. The wavelength switching system of claim 1, wherein said electrode driver employs an optical fiber coating automatic stripper.
8. The wavelength switching system according to claim 1, wherein the fiber bragg grating holder is made of copper with good thermal conductivity, and a contact area with the fiber bragg grating is coated with a thermally conductive silicone.
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| CN103956640A (en) * | 2014-05-20 | 2014-07-30 | 天津理工大学 | Wavelength switchable fiber laser based on graphene and core shift structure |
| CN105261921A (en) * | 2015-11-18 | 2016-01-20 | 北京工业大学 | Short resonant cavity all-fiber narrow line-width single frequency laser |
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| US20040247239A1 (en) * | 2001-03-12 | 2004-12-09 | Louay Eldada | Hitless errorless trimmable dynamic optical add/drop multiplexer devices |
| KR100412324B1 (en) * | 2002-01-28 | 2003-12-31 | 주식회사 아이세스 | Multi-type FBG sensor system |
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| CN105261921A (en) * | 2015-11-18 | 2016-01-20 | 北京工业大学 | Short resonant cavity all-fiber narrow line-width single frequency laser |
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