Single mode and multi-mode cladding mode interference special type optical fibre and preparation method thereof
Technical field
The present invention relates to a kind of single mode and multi-mode cladding mode interference special type optical fibre, belong to the optical fiber technology field.
Background technology
It is to utilize luminous energy that some special optical waveguide structure will transmit in fiber core to be coupled in the fibre cladding waveguide to transmit that cladding mode is interfered, the coupled structure parameter determines the not phase-matching condition of same order core mode formula and cladding mode, thereby realize cladding mode interference [T.Erdogan.Journal of the Optical Society of America A, 1997,14 (8): 1760-1773].The cladding mode interference pattern can solve the key technical problem in many optical fiber communications and the sensory field of optic fibre: first, the spectral filtering effect---based on the cladding mode interference pattern, can the good fiber spectrum wave filter of obtained performance, as flat gainization in the EDFA system, the filtering of spectrum etc.; Second, the covering of Fibre Optical Sensor effect---optical fiber is responsive more for the variation (as refractive index, absorption) of external physical quantity with respect to fibre core, therefore by monitoring the variation of fibre cladding mould transport property, can be easy to more obtain to have highly sensitive Fibre Optical Sensor, as fiber optic temperature, pressure, displacement transducer etc.In sum, cladding mode is interfered has become important techniques link in the association area researchs such as optical fiber communication, sensing, so prepares single mode and multi-mode cladding mode interference special type optical fibre is necessary.
Realize that the technology that the fibre cladding mould is interfered mainly comprises fiber grating [Na Chen, Binfeng Yun, and Yiping Cui.Applied Physics Letters, 2006,88:133902 1-3], photonic crystal fiber [B.J.Eggleton, P.S.Westbrook, et al.Journal of Lightwave Technology, 2000,18 (8): 1084-1100] etc.Fiber Bragg Grating technology be booster action by writing grating in the optical fiber obtaining the phase matching of core mode and cladding mode, thereby realize that cladding mode interferes; Cladding mode interference technique based on photonic crystal fiber is by certain refractive index structures defective of design in the porous cladding structure of uniform period distribution, the dispersion characteristics of control cladding mode and core mode are to satisfy phase-matching condition, thereby realize cladding mode interference [Kunimasa Saitoh, Nikolaos John Florous, et al.Optics Express, 2006,14 (16): 7342-7352].
But, interfere the secondary processing that needs optical fiber based on the covering that optical fiber grating structure is realized, aspects such as its reliability and consistance all can have problems, and particularly can occur the problem of performance degradation when high temperature and long-time the use; Interfere based on the cladding mode that photonic crystal fiber is realized, because of its preparation technology very complicated, at present China mainly need import, particularly mode profile and with the coupled problem of conventional single-mode fiber also be that problem to be solved is arranged, so this just needs novel fibre-optic waveguide and device thereof to occur.
Summary of the invention
The objective of the invention is to provides a kind of single mode and multi-mode cladding mode interference special type optical fibre and preparation method thereof according to the cladding mode interference theory.This optical fiber have stable performance, preparation simple, use flexibly, be convenient to characteristics such as batch process, can be applicable to fiber spectrum wave filter, dispersion compensator, fibre optic compression sensor, the fibre optic temperature sensor in fields such as fiber optic telecommunications equipment and Fibre Optical Sensor, or the like.
In order to achieve the above object, design of the present invention is:
The single mode and the multi-mode cladding mode interference special type optical fibre that have proposed, this optical fiber is based on the doubly clad optical fiber structure, its basic structure as shown in Figure 1, be separated by by a low-refraction inner cladding between fibre core and the surrounding layer, core mode and cladding mode interact by evanescent wave, satisfy under the situation of phase matching at core mode and cladding mode, the luminous energy of transmitting in fibre core is transferred in the surrounding layer and is transmitted, and realizes the cladding mode interference.Because the phase-matching condition co-wavelength of modal dispersion characteristic has relation, promptly interferes wavelength, shows as the stopband filtering characteristic at this wavelength place core mode transmission spectrum.By the optimal design of fibre core and cladding structure, can realize the device such as optical fiber filtering, sensing of function admirable.
According to above-mentioned design, the present invention adopts following technical proposals:
A kind of single mode and multi-mode cladding mode interference special type optical fibre, it is made up of fibre core (1), interference inner cladding (2) and surrounding layer (3), and the material that it is characterized in that fibre core (1) is by pure quartz core doped with Ge O
2Material constitutes, and its refractive index is greater than pure quartz material; The material of interfering inner cladding (2) is the additive B by pure quartzy doping low-refraction
2O
3Or fluorine F composition, its doping content is 200~400ppm, cladding thickness is 5~10 μ m; And the material of surrounding layer (3) is pure quartz; Interfere inner cladding (2) to be clipped between fibre core (1) and the surrounding layer (3), and have than fibre core (1) and the low refractive index of surrounding layer (3);
A kind of above-mentioned single mode and the preparation method of multi-mode cladding mode interference special type optical fibre, it is characterized in that adopting vapour deposition process MCVD, on vapour deposition process MCVD bar machine, directly make pure quartzy surrounding layer (3), interfere inner cladding (2) and fibre core (1) successively in the vapour deposition mode, the clavate that contracts at last becomes preform, and then carries out wire drawing and make optical fiber.
A kind of above-mentioned single mode and the preparation method of multi-mode cladding mode interference special type optical fibre, it is characterized in that adopting the outer vapour deposition process OVD of pipe, outside pipe, directly make fibre core (1), interfere inner cladding (2) and pure quartzy surrounding layer (3) successively on the vapour deposition process OVD bar machine in the vapour deposition mode, form preform at last, and then carry out wire drawing and make optical fiber.
Compare with the cladding mode interference that fiber grating and photonic crystal fiber are realized, the present invention has its unique advantage: (1) is because cladding mode interference special type optical fibre and conventional single mode and multimode optical fiber structural similarity, its have mature preparation process, simple, production efficiency is high, with low cost, with various prefabricated rods technologies of preparing advantage such as compatibility mutually; (2) compare with fiber grating, need not the secondary processing of optical fiber, the high conformity of performance, the problem that does not exist high temperature or long-term usability to degenerate; (3) the cladding mode interference special type optical fibre is compared with photonic crystal fiber and is had more simple index distribution, therefore the optimal design by structural parameters, can realize efficient coupling more conveniently, promptly directly be coupled with conventional fiber with fusion techniques with conventional single mode and multimode optical fiber; (4) this cladding mode interference special type optical fibre uses very flexibly, simultaneously can insert length and regulate its transport property by controlling it, can also insert this special optical fiber of multistage in addition, optimizes filtering characteristic.
Description of drawings
Fig. 1 is single mode of the present invention and multi-mode cladding mode interference special type optical fibre structural representation.
Fig. 2 is the refractive index profile of optical fiber shown in Figure 1.
Among the figure: 1-fibre core, 2-interference inner cladding, 3-surrounding layer; n
Co-fiber core refractive index, n
Cl1-interference inner cladding refractive index, n
Cl2-cladding refractive index, n-ordinate refractive index, r-horizontal ordinate fiber radius, r
a-fiber core radius, r
Cl1-optical fiber inner cladding radius, r
b-fiber radius.
Embodiment
After now in conjunction with the accompanying drawings and embodiments the present invention further being described in.
Embodiment one: referring to Fig. 1, and a kind of single mode of the present invention and multi-mode cladding mode interference special type optical fibre, be made up of three parts: fibre core 1, interference inner cladding 2 and surrounding layer 3, the material of fibre core 1 is the GeO of pure quartzy doping high index of refraction
2Material is formed; Interfere the material of inner cladding 2 to be made up of the additive fluorine (F) of pure quartzy doping low-refraction, the doping of fluorine is 350ppm, and to the single-mode fiber of 125 μ m, its inner cladding thickness is 8 μ m; The material of surrounding layer 3 is made up of pure quartz, interferes inner cladding 2 to be folded between fibre core 1 and the surrounding layer 3.
Above-mentioned single mode and multi-mode cladding mode interference special type optical fibre, be to use modified chemical vapor deposition process (MCVD) MCVD, on chemical vapour deposition technique MCVD bar machine, directly make pure quartzy surrounding layer (3), interfere inner cladding (2) and fibre core (1) successively in the vapour deposition mode, the clavate that contracts at last becomes preform, and then carry out wire drawing and make the pure quartz core cladding mode interference special type optical fibre, its core diameter 8 μ m, fibre diameter 125 μ m.
The index distribution of above-mentioned optical fiber is shown in Fig. 2.