CN101604048B - All-fiber filter based on thin-core fibers - Google Patents
All-fiber filter based on thin-core fibers Download PDFInfo
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- CN101604048B CN101604048B CN2009101007651A CN200910100765A CN101604048B CN 101604048 B CN101604048 B CN 101604048B CN 2009101007651 A CN2009101007651 A CN 2009101007651A CN 200910100765 A CN200910100765 A CN 200910100765A CN 101604048 B CN101604048 B CN 101604048B
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Abstract
The invention relates to an all-fiber filter based on thin-core fibers. The conventional fiber grating filter has poor temperature stability, and is not suitable for the operation under extreme working conditions. The all-fiber filter comprises a packing box, a single-mode fiber component is arranged by passing through the packing box, and two ends of the single-mode fiber component are connected with a ring flange respectively. The single-mode fiber component comprises three sections of single-mode fibers which are connected in series, wherein the single-mode fibers at two ends adopt standard single-mode fibers, the middle section of the single-mode fibers adopts thin-core single-mode fibers, the three sections of the single-mode fibers are coaxially arranged, and two ends of the thin-core single-mode fibers are fused with one end of the two sections of the standard single-mode fibers respectively. The filter is simple to manufacture, and has good temperature stability and response characteristic to the external refractive index change.
Description
Technical field
The invention belongs to the optical fiber technology field, relate to a kind of all-fiber filter based on thin-core fibers.
Background technology
Optical fibre device is because advantages such as little, the light weight of volume, simple in structure, anti-electromagnetic interference (EMI) have obtained application widely in fields such as communication, sensings.Especially the wave filter of full fiber type, its performance direct relation is the transmission quality of Networks of Fiber Communications till now.Wherein, fiber grating is now at the wave filter of using the most ripe a kind of optical-fiber type, and it is divided into two kinds: a kind of be called Fiber Bragg Grating FBG (Fiber BraggGrating, FBG), it is a kind of reflection-type BPF. of arrowband; Another kind is called LPFG, and (Long Period Fiber Grating, LPG), it is a kind of transmission-type rejection filter.Though these two kinds of wave filter structures are relatively simple, rejection ratio is also than higher, and temperature stability is not fine; Especially LPFG; More responsive to temperature, temperature-responsive is approximately 0.1～0.3nm/ ℃, and this has influenced it greatly as stability of filter.In addition, fiber grating will begin to degenerate in greater than 300 ℃ environment, does not therefore utilize it under extreme condition of work, to move.
No matter the optical fibre device of non-optical grating construction is as wave filter or Application in Sensing, is superior to grating class device on its thermal stability and the manufacture difficulty mostly, has attracted many scholars' sight in recent years in the world, becomes the focus of research.The direction of many researchs is exactly the design of optical fiber internal interference appearance, utilizes its interference pattern to realize the application of filtering or sensing detection.The design philosophy that this type device is general all is to utilize special construction in the optical fiber to excite the higher order mode of transmission light, and the light that causes different mode is in that to have different optical path later on through same fiber lengths poor.But some design proposal often has complicated step in manufacturing process, such as connecing a bit of multimode optical fiber, or utilizes means such as heating to make technology such as fiber end face place fibre core expansion, has all increased the manufacture difficulty of device; Some needs special material, and such as using some extraordinary doubly clad optical fibers, photonic crystal fiber etc., cost are quite high; Having is exactly the non-constant of physical strength of some structures again, such as draw awl to realize the structure that higher order mode excites through optical fiber, does not almost have practical value.
Summary of the invention
The object of the invention just provides a kind of new mode filter based on different core diameter single-mode fused fiber splice structures; This wave filter utilizes the optical fiber core diameter mismatch at fused fiber splice place; Cause that higher order mode excites; Thereby the Mach-Zehnder interferometer in the optical fiber that forms, the spectrum of its transmission has good bandreject filtering characteristic.
The present invention includes enclosure, the single-mode fiber assembly passes the enclosure setting, and the two ends of single-mode fiber assembly are connected with ring flange respectively.Described single-mode fiber assembly comprises three section single-mould fibers of series connection; Wherein the single-mode fiber at two ends adopts standard single-mode fiber (Corning SMF28, core diameter 6.06 μ m), and the interlude single-mode fiber adopts thin core single-mode fiber (Nufern 460-HP; Core diameter 3.30 μ m; Cutoff wavelength 450nm), the coaxial setting of three section single-mould fibers, the two ends of thin core single-mode fiber respectively with an end welding of two segment standard single-mode fibers.
Principle of work of the present invention: light is single mode transport in first section single-mould fiber, only has the basic mode of sandwich layer transmission.Behind the one section thin-core fibers of light in the middle of importing into, because fibre core varies in size, cause light single mode transport again, the pattern of even a plurality of high-orders is excited out.Since different patterns when in optical fiber, transmit effective refractive index be different, therefore, can have optical path difference during another section single-mould fiber of the light of different mode arrival, will produce interference then, the form of Here it is Mach-Zehnder interferometer.Its interference pattern has promptly been represented the filtering characteristic of wave filter, and the rejection ratio of filtering is directly related with the interference contrast.Through being various patterns under the different core diameters radially to be distributed to simulate obtain: at first, the mode field diameter of the single-mode fiber basic mode of different core diameters is different, and this provides necessary condition for exciting of higher order mode.Secondly, the inferior higher order mode of idol does not have power transfer at sandwich layer.At last; For the optical fiber of thin core, the energy relative standard single-mode fiber of the sandwich layer part that odd order modes comprises is a lot of less, therefore; Interior basic mode of sandwich layer and high-order mode energy are approaching when interfering; Therefore interfere good contrast, because higher order mode covering energy loss is few, the insertion loss of this wave filter is also very little in addition.
Wave filter of the present invention is made very simple, need comprise a whole set of writing system of laser instrument unlike the grating that kind, only needs two kinds of single-mode fibers of a unjacketed optical fiber welder and different core diameters.The present invention utilizes the Mach-Zehnder interferometer in the optical fiber that the mutual welding of the optical fiber of different core diameters realizes, the interference pattern of the transmission-type of this interferometer demonstrates low Insertion Loss, high rejection ratio (＞30dB) filtering characteristic.Relate generally to the manufacturing technology of this wave filter, good temperature stability and the response characteristic of variations in refractive index to external world.
Description of drawings
Fig. 1 is the structural representation of median filter of the present invention;
Fig. 2 is the filter transmission spectrum;
Fig. 3 is that wave filter is to the temperature-responsive spectral line;
Fig. 4 is a wave filter refractive index response spectral line to external world.
Embodiment
As shown in Figure 1, the thin-core fibers wave filter comprises enclosure 3, and the single-mode fiber assembly passes enclosure 3 and is provided with, and the two ends of single-mode fiber assembly are connected with ring flange 1 respectively.Described single-mode fiber assembly comprises three section single-mould fibers of series connection; Wherein the single-mode fiber at two ends adopts standard single-mode fiber 2 (Corning SMF28, core diameter 6.06 μ m), and the interlude single-mode fiber adopts thin core single-mode fiber 4 (Nufern 460-HP; Core diameter 3.30 μ m; Cutoff wavelength 450nm), the coaxial setting of three section single-mould fibers, the two ends of thin core single-mode fiber 4 respectively with an end welding of two segment standard single-mode fibers 2.This wave filter links to each other with spectrometer with wideband light source respectively with other wire jumpers prolongations through ring flange, and it is exactly that light source light spectrum is through the transmission spectrum behind the filter filtering that spectrometer obtains.
Because transmission length different in thin-core fibers can be brought different interference patterns, this wave filter has inserted three sections thin-core fibers of different length respectively in the process of making, see Fig. 2, and wherein (a) is for inserting 2cm, (b) for inserting 4cm, (c) for inserting 6cm.The length of thin core single-mode fiber and the number of the stopband in the special spectrum scope are directly proportional, and also have influence on the bandwidth of stopband simultaneously, and thin-core fibers is long more, and the bandwidth of rejection of same wavelength location is more little.The length that this design only needs to change thin-core fibers changes bandwidth.The thin-core fibers structure of different length possibly the filtering peak occur at same position; Among Fig. 2 (a) and (c) at the filtering peak of long wave position almost at same position; Therefore, if a certain specific band filtering is not had special bandwidth requirement again, the structure of selecting the thin-core fibers about 2cm to insert; The filter filtering characteristic that obtains like this is simple, and cost is relatively low.
A very important index of wave filter during temperature-responsive is directly connected to the stability of its work.The present invention uses a programmable temperature control furnace to test the temperature stability that inserts the wave filter sample of 2cm thin-core fibers.As can beappreciated from fig. 3, the position of interference peaks centre wavelength is along with the rising of temperature is drifted about to the long wave direction, and both present a good linear relationship.Calculate the slope of this straight line, obtain the temperature-responsive sensitivity of wave filter, be 15pm/ ℃, the temperature stability that this wave filter is described is goodish.
In addition, because the effective refractive index of the higher order mode that excites transmission receives the influence of extraneous refractive index, so this wave filter utilizes the drift of its centre wavelength also to can be used as sensing applications.This wave filter has carried out the test of refractive index to the sucrose solution of variable concentrations, and (mass percent is respectively: (1.381,5.123,8.425,11.817,14.821,18.033,21.136,24.242,26.901,29.577,32.432,35.065; Corresponding refractive index is 1.3346,1.3400,1.3448,1.3500,1.3547,1.3599,1.3651,1.3704,1.3750,1.3798,1.3850,1.3899); Can see; Its to external world variations in refractive index be quite responsive; Sensitivity reaches 135.5/ unit refractive index, sees Fig. 4.And within a large range, the drift of variations in refractive index and centre wavelength is a linear relationship, and therefore this wave filter has the very big potentiality as Application in Sensing.
Claims (1)
1. the all-fiber filter based on thin-core fibers comprises enclosure, it is characterized in that: the single-mode fiber assembly passes the enclosure setting, and the two ends of single-mode fiber assembly are connected with ring flange respectively; Described single-mode fiber assembly comprises three section single-mould fibers of series connection; Wherein the single-mode fiber at two ends adopts standard single-mode fiber; The interlude single-mode fiber adopts thin core single-mode fiber; The coaxial setting of three section single-mould fibers, the two ends of thin core single-mode fiber respectively with an end welding of two segment standard single-mode fibers; Described standard single-mode fiber adopts the Corning SMF28 single-mode fiber of core diameter 6.06 μ m, and described thin core single-mode fiber adopts the Nufern 460-HP single-mode fiber of core diameter 3.30 μ m, cutoff wavelength 450nm.
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| CN2009101007651A CN101604048B (en) | 2009-07-21 | 2009-07-21 | All-fiber filter based on thin-core fibers |
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| CN2009101007651A CN101604048B (en) | 2009-07-21 | 2009-07-21 | All-fiber filter based on thin-core fibers |
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Families Citing this family (11)
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| CN103196520A (en) * | 2012-01-06 | 2013-07-10 | 中国计量学院 | Transmission-type optical fiber liquid level sensor with irregular core structure |
| CN102967388A (en) * | 2012-11-01 | 2013-03-13 | 上海大学 | Intrinsic F-P microcavity high-sensitivity temperature sensor based on micro-sized conical fiber probe and manufacture method thereof |
| CN103823125A (en) * | 2014-03-10 | 2014-05-28 | 天津理工大学 | Fine-core optical core and magnetic fluid-based electric field sensor |
| CN106154421B (en) * | 2015-04-10 | 2019-11-22 | 福州高意通讯有限公司 | A kind of production method of all -fiber etalon or filter |
| CN106291410B (en) * | 2015-10-13 | 2018-11-23 | 北京信息科技大学 | A kind of Measurement Method for Magnetic Field based on thin-core fibers Mach-Zehnder interferometer |
| CN105698858B (en) * | 2016-02-04 | 2018-03-09 | 华中科技大学 | A kind of fibre optical sensor for the curvature and temperature simultaneously measuring for differentiating bending direction |
| CN108168729B (en) * | 2018-01-30 | 2024-02-13 | 中国海洋大学 | Two-point seawater temperature sensor based on cascade connection of fine core optical fiber and standard single mode optical fiber |
| WO2020118807A1 (en) * | 2018-12-10 | 2020-06-18 | 中国科学院上海微系统与信息技术研究所 | Temperature-insensitive mach-zehnder interferometer |
| CN109283616B (en) * | 2018-12-10 | 2023-09-12 | 中国科学院上海微系统与信息技术研究所 | Temperature insensitive Mach-Zehnder interferometer |
| CN110579726A (en) * | 2019-10-15 | 2019-12-17 | 哈尔滨理工大学 | Spr-based high-sensitivity magnetic field sensing device |
| US20230152514A1 (en) * | 2020-04-20 | 2023-05-18 | Sumitomo Electric Industries, Ltd. | Gain flattening filter, and method for manufacturing gain flattening filter |
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| CN201464669U (en) * | 2009-07-21 | 2010-05-12 | 浙江大学 | Interference type fine-core optical fiber wave filter |
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