CN103969851A - Magnetic-control tunable filter based on inclined micro-structure fiber Bragg grating - Google Patents

Abstract

A magnetic-control tunable filter based on inclined micro-structure fiber Bragg grating comprises a light source, a single-mode fiber, a spectroanalysis instrument, the inclined micro-structure fiber Bragg grating filled with magnetic fluid and a magnetic field generation and tuning device, wherein the light source is connected with one end of the inclined micro-structure fiber Bragg grating through the single-mode fiber, and the other end of the inclined micro-structure fiber Bragg grating is connected to the spectroanalysis instrument through the single-mode fiber. As the refractive rate of the magnetic fluid injected into a micro-structure optical fiber air hole is sensitive to the magnetic field, the intensity of the magnetic field generated by the magnetic field generation and tuning device is adjusted, the refractive rate of the magnetic fluid inside the optical fiber is changed due to the change of the magnetic field, the effective refractive rate of a micro-structure cladding mode changes, the resonant wavelength of the fiber Bragg grating is changed, and the magnetic-control tunable filter capable of changing along with the externally added magnetic field is obtained. The magnetic-control tunable filter is simple in manufacturing process, low in production cost and high in sensitivity.

Description

Magnetic control tunable optic filter based on inclination microstructure optical fiber grating

Technical field

The invention belongs to technical field of optical fiber communication, relate to the selective filling of a kind of optical fiber filter and photonic crystal fiber, be specifically related to a kind of magnetic control tunable optic filter based on inclination microstructure optical fiber grating.

Background technology

Fiber grating is a kind of passive filtering device that the refractive index generation axial cyclic modulation of fiber core is formed by certain method.Because fiber grating has, volume is little, splice loss, splice attenuation is little, be entirely compatible with the advantages such as optical fiber, therefore in optical fiber communication and sensory field, is widely used.

Photonic crystal fiber (Photonic Crystal Fibers, PCF) microstructured optical fibers (the Micro-Structured Fibers that is otherwise known as, MSF), cause in recent years extensive concern, on its xsect, there is more complicated index distribution, conventionally the pore that contains different spread patterns, the yardstick of these pores and optical wavelength are roughly in same magnitude and run through the whole length of device, the fiber cores district that light wave can be limited in low-refraction propagates, by fill different liquid in photonic crystal fiber airport, the transport property of tuned light photonic crystal fiber flexibly.

Along with the fast development of Fibre Optical Communication Technology and optical fiber sensing technology, wavelength-division multiplex (WDM) technology is applied even more extensively, and optical fiber filter is one of Primary Component in optical WDM communication system and sensor-based system.Tunable optic filter can be used as demultiplexing, signal demodulation of WDM etc., is bringing into play extremely important effect.The method that realizes optical fiber filtering has a lot, after a lot of optical fiber filters in the past complete, just cannot change its transport property again, such as the optical fiber filter of the Sagnac based on high birefringence optical fiber, has limited its range of application, does not have a dirigibility.But need in actual applications to select suitable detecting band according to actual conditions, have the shortcoming that Production Time and cost are higher.Thereby, thering is at present the favor that passband position is tunable, the tunable optical fiber filter of channel spacing is just being subject to researcher, this is also in engineering reality, to be badly in need of the key issue of solution.

The present invention writes on fibre core by oblique raster and mixes on the microstructured optical fibers of germanium, and in conjunction with the tunable refractive index characteristic of magnetic fluid, obtains that passband position is adjustable, tuning range is large, multichannel magnetic control tunable optic filter.

Summary of the invention

The present invention seeks to solve the problems such as the wavelength tuning speed that general turnable fiber filter exists is slow, tuning range is narrow, linearity of tuning degree is poor, channel is few, provide a kind of to need to select suitable oblique raster cycle and angle of inclination just can control flexibly its filtering wave band, i.e. the adjustable magnetic control tunable optic filter based on inclination microstructure optical fiber grating of wavelength.

Technical solution of the present invention:

Magnetic control tunable optic filter based on inclination microstructure optical fiber grating, comprises light source, single-mode fiber, spectroanalysis instrument, is filled with the inclination microstructure optical fiber grating of magnetic fluid and magnetic field produces and tuner; Described light source is connected with inclination microstructure optical fiber grating one end by single-mode fiber, and the inclination microstructure optical fiber grating other end is connected on spectroanalysis instrument by single-mode fiber.

Described inclination microstructure optical fiber grating is with phase-mask method, at fibre core, to mix the oblique raster of writing system on the microstructured optical fibers of germanium; Inclination microstructure optical fiber grating is filled magnetic fluid in the airport of microstructured optical fibers, and filling magnetic fluid part is corresponding with the position of oblique raster, and is greater than the length of scribed fiber grating, to guarantee that magnetic fluid covers whole fiber grating region;

Described magnetic field produces and tuner, is the electromagnet apparatus that inclination microstructure optical fiber grating both sides arrange, electromagnet apparatus and adjustable voltage equipment connection, and the magnetic field of variation provides by the voltage of regulation voltage equipment.

Described inclination microstructure optical fiber grating, is placed on that magnetic field produces and the center of tuner.

The tilt principle of work of microstructure optical fiber grating of the present invention:

When light enters inclination microstructure optical fiber grating from single-mode fiber, when oblique raster core mode harmonic peak and cladding mode resonant phase-matching condition meet, can show that the expression formula of basic mode resonance wavelength and cladding mode resonant wavelength is respectively formula (1) and formula (2):

${\mathrm{\λ}}_{\mathrm{Bragg}}={2n}_{\mathrm{eff}}^{\mathrm{co}}\frac{{\mathrm{\Λ}}_g}{\cos \mathrm{\ξ}}---\left(1\right)$

${\mathrm{\λ}}_{\mathrm{cl},i}=(n_{\mathrm{eff}}^{\mathrm{co}}+n_{\mathrm{eff},i}^{\mathrm{cl}})\frac{{\mathrm{\Λ}}_g}{\cos \mathrm{\ξ}}---\left(2\right)$

In formula, λ _braggand λ _{cl, i}be respectively the resonance wavelength at core mode harmonic peak and cladding mode resonant peak, i rank, for fibre core effective index of fundamental mode, Λ g is the cycle along fibre core direction grid, be the effective refractive index of i rank cladding mode, ξ is the pitch angle of oblique raster grid face.

According to phase matching relation, grating resonance wavelength was determined jointly by effective index of fundamental mode and the grating cycle of the microstructured optical fibers after Filled Dielectrics.When environment temperature keeps stable, the grating cycle remains unchanged, and can be expressed as:

$\frac{{\mathrm{d\λ}}_{\mathrm{Bragg}}}{{\mathrm{dn}}_{\mathrm{mat}}}=2\frac{{\mathrm{\Λ}}_t}{\cos \mathrm{\ξ}}\frac{{\mathrm{dn}}_{\mathrm{eff}}^{\mathrm{co}}}{{\mathrm{dn}}_{\mathrm{mat}}}---\left(3\right)$

N wherein _matfor the refractive index of filled media, by formula (3), known that the impact of the refractive index of filled media on optical fiber effective index of fundamental mode is the deciding factor that determines refraction index changing core mode harmonic peak.

Because fibre core is too little, the transmission mode in optical fiber can not be limited in the middle of silica core completely, and portion of energy will be diffused into surrounding air hole.When the refractive index of filled media and quartz approach, the overlapping coefficient of optical fiber basic mode and medium increases, and the variation of the medium refraction index of filling can change the position of harmonic peak like this.Because the refractive index that pours into magnetic fluid in microstructured optical fibers airport is to residing magnetic-field-sensitive, when light process microstructured optical fibers, the size of the magnetic field intensity that the generation of adjusting magnetic field and tuner produce, the variation in magnetic field has changed the refractive index of magnetic fluid in optical fiber, the effective refractive index of microstructured optical fibers effective index of fundamental mode and cladding mode is changed, basic mode resonance wavelength and cladding mode resonant wavelength drift about, change the resonance wavelength of slant optical fiber grating, thereby obtained the magnetic control tunable optic filter changing with externally-applied magnetic field.

Advantage of the present invention and beneficial effect:

The present invention is by inclination microstructure optical fiber grating, on microstructured optical fibers, write oblique raster processed, then in its airport, fill magnetic fluid, magnetic control tunable optic filter provided by the invention has that passband position is tunable, tuning range is large and multi channel advantage.Its manufacture craft is simple, production cost is low and highly sensitive.

Accompanying drawing explanation

Fig. 1 is the structural representation of the magnetic control tunable optic filter based on inclination microstructure optical fiber grating in the present invention;

Fig. 2 is the structural representation that is filled with the inclination microstructure optical fiber grating of magnetic fluid in the present invention;

In figure: 1. light source, 2. single-mode fiber, 3. spectroanalysis instrument, 4. inclination microstructure optical fiber grating, 5. magnetic field produces and tuner, 6. magnetic fluid, 7. oblique raster, 8. microstructured optical fibers airport, 9. mixes the microstructured optical fibers fibre core of germanium.

Embodiment

For objects and advantages of the present invention are described better, below in conjunction with accompanying drawing and example, the invention will be further described.

Embodiment 1

As shown in Figure 1, the magnetic control tunable optic filter based on inclination microstructure optical fiber grating provided by the invention, comprises that light source 1, single-mode fiber 2, spectroanalysis instrument 3, the inclination microstructure optical fiber grating 4 that is filled with magnetic fluid and magnetic field produce and tuner 5; Described light source 1 is connected with inclination microstructure optical fiber grating 4 one end by single-mode fiber 2, and inclination microstructure optical fiber grating 4 other ends are connected on spectroanalysis instrument 3 by single-mode fiber 2.

Described inclination microstructure optical fiber grating 4 as shown in Figure 2, is with phase-mask method, at fibre core, to mix the oblique raster 7 of writing system on the microstructured optical fibers of germanium; In the airport 8 of inclination microstructure optical fiber grating, fill magnetic fluid 6, filling magnetic fluid 6 parts are corresponding with the position of oblique raster, are greater than the length of scribed oblique raster 7, to guarantee that magnetic fluid 6 covers whole oblique raster 7 regions;

Described magnetic field produces and tuner 5, is the electromagnet apparatus arranging in inclination microstructure optical fiber grating 4 both sides, electromagnet apparatus and adjustable voltage equipment connection, and the magnetic field of variation provides by the voltage of regulation voltage equipment.

Described inclination microstructure optical fiber grating 4, is placed on that magnetic field produces and the center of tuner 5.

Because the refractive index that pours into magnetic fluid 6 in microstructured optical fibers airport 8 is to residing magnetic-field-sensitive, when light process microstructured optical fibers, by changing the voltage of regulation voltage equipment, regulate magnetic field to produce and the size of the magnetic field intensity that tuner 5 produces changes, the variation in magnetic field has changed the refractive index of magnetic fluid 6 in optical fiber, the effective refractive index of microstructured optical fibers basic mode and the effective refractive index of cladding mode are changed, harmonic peak wavelength drifts about, changed the resonance wavelength of slant optical fiber grating, thereby obtain the magnetic control tunable optic filter changing with externally-applied magnetic field.

Due to the change at pitch angle, the phase condition of oblique raster 7 fibre core guided modes and cladding mode coupling also can change, and, when writing oblique raster, can realize the pattern conversion (position at peak and intensity) of luminous energy by controlling pitch angle.The angle of inclination of oblique raster 7 planes and the depth of modulation of refractive index have determined the bandwidth at coupling efficiency and cladding mode resonant peak simultaneously, and exposure also can make the resonance peak intensity of grating and the change of resonant wavelength.Therefore by controlling pitch angle and uv-exposure amount, can control wavelength location and the stiffness of coupling at this cladding mode resonant peak, thereby expand its different range of application to realize the filtering demand of dynamic range.By after the suitable parameter of adjustment oblique raster 7 and the size of external magnetic field, just can realize that passband position is tunable, tuning range large, multichannel, this magnetic control tunable optic filter possesses in working range that sensitivity is very high, advantages of simple structure and simple.

The service band of the light source of the present embodiment is 600-1700nm, with phase-mask method, at fibre core, mix the oblique raster of writing system on the shaddock type microstructured optical fibers of germanium, the core diameter of this shaddock type microstructured optical fibers is 12 μ m, mixing the refractive index of germanium fibre core at 1550nm wavelength place is 1.4572, fibre core is around the inner cladding that a circle consists of pure quartz, inner cladding diameter is 36 μ m, refractive index at 1550nm wavelength place is 1.444, have six shaddock type airports that size is identical, the area of each airport is 300 μ m ², angle of inclination is 1.44 °.In its transmission spectrum, the scope at cladding mode resonant peak is at 1552.8nm-1561.54nm, and total corresponding 7 harmonic peak wavelength, have 7 channels.Magnetic fluid is water base Fe ₃o ₄, its density is 1.2g/mL.Method by low pressure suction is filled into the magnetic fluid solution configuring in the covering airport of the microstructured optical fibers of TFBG, light source 1 is connected with inclination microstructure optical fiber grating 4 one end by single-mode fiber 2, and inclination microstructure optical fiber grating 4 other ends are connected on spectroanalysis instrument 3 by single-mode fiber 2.Populated inclination microstructure optical fiber grating is placed on to the center of magnetic field generation and tuner 5.And with commercial teslameter, the actual value in added magnetic field is demarcated, on spectroanalysis instrument 3, monitor the variation of transmission spectrum.When magnetic field becomes large, these 7 harmonic peak wavelength location there will be blue shift, and drift value can reduce with the increase in magnetic field, and the scope of its tunable wave length can reach 20nm.And in the scope of certain external magnetic field, the drift value of harmonic peak wavelength and the size of external magnetic field have good linear relationship.The tunable optic filter of this case study on implementation belongs to bandpass filter, and tuning range is large, and tuned speed is fast.Thereby obtain with externally-applied magnetic field change realize that passband position is tunable, tuning range greatly, multi channel magnetic control tunable optic filter.

Claims (5)

1. the magnetic control tunable optic filter based on inclination microstructure optical fiber grating, the inclination microstructure optical fiber grating and the magnetic field that comprise light source, single-mode fiber, spectroanalysis instrument, are filled with magnetic fluid produce and tuner; Described light source is connected with inclination microstructure optical fiber grating one end by single-mode fiber, and the inclination microstructure optical fiber grating other end is connected on spectroanalysis instrument by single-mode fiber.

2. magnetic control tunable optic filter according to claim 1, is characterized in that: described inclination microstructure optical fiber grating is with phase-mask method, at fibre core, to mix the oblique raster of writing system on the microstructured optical fibers of germanium.

3. magnetic control tunable optic filter according to claim 1 and 2, it is characterized in that: in the airport of described microstructured optical fibers, fill magnetic fluid, fill magnetic fluid part corresponding with the position of oblique raster, be greater than the length of scribed slant optical fiber grating, to guarantee that magnetic fluid covers whole fiber grating region.

4. magnetic control tunable optic filter according to claim 1, it is characterized in that: described magnetic field produces and tuner, it is the electromagnet apparatus that inclination microstructure optical fiber grating both sides arrange, electromagnet apparatus and adjustable voltage equipment connection, the magnetic field of variation provides by the voltage of regulation voltage equipment.

5. magnetic control tunable optic filter according to claim 1 and 2, is characterized in that: described inclination microstructure optical fiber grating, is placed on that magnetic field produces and the center of tuner.