CN102944918B - Faraday rotation mirror structure - Google Patents

Faraday rotation mirror structure Download PDF

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Publication number
CN102944918B
CN102944918B CN 201210447348 CN201210447348A CN102944918B CN 102944918 B CN102944918 B CN 102944918B CN 201210447348 CN201210447348 CN 201210447348 CN 201210447348 A CN201210447348 A CN 201210447348A CN 102944918 B CN102944918 B CN 102944918B
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lens
light
optical fiber
reflective
collimation lens
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CN102944918A (en
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万助军
万琼
钟瑞
莫槟诚
刘德明
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Abstract

The invention discloses a faraday rotation mirror structure, which comprises an optical fiber, a collimating lens, a faraday rotation device, a reflective lens and a magnetic ring, wherein the optical fiber, the collimating lens, the faraday rotation device, the reflective lens and the magnetic ring are arranged coaxially, the end surface of the optical fiber is arranged at the focus of the collimating lens, the rear focal surface of the collimating lens is coincident with the front focal surface of the reflective lens, the rear end surface of the reflective lens is plated with a high-reflection membrane, a reflective surface is arranged at the rear focal surface of the reflective lens, the magnetic ring is sleeved at the outer part of the faraday rotation device, can generate a fixed electromagnetic field after the two ends of the magnetic ring are powered on, the optical fiber is used for receiving the light from the outer part, the light can be emitted to the inclined surface of the collimating lens through the end face, the collimating lens is used for collimating the light from the optical fiber, and the faraday rotation device is used for realizing that the parallel light from the collimating lens can deflect in a light polarization state under the action of the electromagnetic field generated by the magnetic ring. The faraday rotation mirror structure disclosed by the invention can avoid the debugging on a reflective light path, and is directly and mechanically assembled.

Description

A kind of faraday rotation mirror structure
Technical field
The invention belongs to sensory field of optic fibre, more specifically, relate to a kind of faraday rotation mirror structure.
Background technology
In recent years, sensor is towards sensitive, accurate, strong adaptability, small and exquisite and intelligentized future development.In this course, Fibre Optical Sensor gains great popularity.Fibre Optical Sensor mainly is comprised of optical fiber and photo-detector.Its basic functional principle is by the process of the light from light source optical fiber, in transmitting procedure, is subject to external disturbance (as vibration, pressure, temperature, electric field, magnetic field or acoustic vibration etc.), cause light optical property (as intensity, wavelength, frequency, phase place, polarization state etc.) change, be called modulated flashlight, these modulated flashlights are admitted to photo-detector, after demodulation, obtain measured parameter.Yet birefringent phenomenon very likely occurs while propagating in single-mode fiber in light signal, causes the change of light signal polarization state, causes error.For avoiding the problems referred to above, introduce faraday rotation mirror, eliminate the variation of the polarization state that light signal causes because of birefringence, keep the light signal polarization state constant.
Fig. 1 is the faraday rotation mirror structural section view of available technology adopting, and this faraday rotation mirror 11 comprises optical fiber 12, C-Lens 13, Faraday rotator 14, catoptron 15 and magnet 16.Optical fiber 12 is single-mode fibers, fiber end face (is generally oblique 8 °, the increase return loss) be positioned at the focus place of C-Lens 13, flashlight is from optical fiber 12 inputs, be converted to parallel rays by C-Lens 13 collimations, this parallel rays departs from primary optical axis and certain deflection angle is arranged, after Faraday rotator 14, under definite magnetic field, the polarized state of light ψ that rotates to an angle, impinge perpendicularly on catoptron 15, and reflected light An Yuan returns on road and again passes through Faraday rotator 14, C-Lens 13, from optical fiber 12 outputs, now polarized state of light rotates 2 ψ.But therefore use the deviation of polarization state in faraday rotation mirror 11 compensated optical fiber sensor-based systems, thereby realize system stability work.Based on above-mentioned principle of work, need to guarantee that the minute surface of catoptron is mutually vertical with the parallel rays of collimation, need accurate optics debugging, so greatly increased the complexity of manufacture craft, thus installation time that need to be longer.
Summary of the invention
For the defect of prior art, the object of the present invention is to provide a kind of faraday rotation mirror structure, can remove the debugging of reflected light path from, directly carry out the machinery assembling.
For achieving the above object, the invention provides a kind of faraday rotation mirror structure, the optical fiber that comprises coaxial setting, collimation lens, Faraday rotator, reflective lens and magnet ring, the end face of optical fiber is arranged at the focus place of collimation lens, the back focal plane of collimation lens and the front focal plane of reflective lens overlap, the rear end face of reflective lens is coated with highly reflecting films, and reflecting surface is arranged at the back focal plane of reflective lens, magnet ring is the outside that is sheathed on Faraday rotator, and can after the energising of two ends, produce changeless electromagnetic field, optical fiber is for receiving from outside light, and by its end face, be transmitted on the inclined-plane of light collimation lens, collimation lens is for collimating to the light from optical fiber, and the parallel rays after collimation is transmitted into to Faraday rotator, realize light polarization state deflection angle ψ under the electromagnetic field effect that Faraday rotator produces at magnet ring for the parallel rays that makes self-focus lens, and by the light emission after polarization state deflection to reflective lens, reflective lens will be for turning back to Faraday rotator from the former road of the light of Faraday rotator, Faraday rotator is also realized light polarization state deflection angle ψ again from the light of reflective lens for making under the electromagnetic field effect of magnet ring generation, and the light emission after the polarization state polarization is arrived to collimation lens, on the back focal plane of collimation lens, height r and the angle θ of the parallel rays after the collimation lens collimation are as follows:
Figure BDA00002383855800021
The angle that wherein α is optical fiber and vertical axis, for the angle of collimation lens and vertical axis, n ffor the fiber core refractive index of optical fiber, n cfor the refractive index of collimation lens, the focal length that f is collimation lens and
Figure BDA00002383855800023
the spherical radius of the rear end face that wherein R is collimation lens, reflective lens receives that to turn back to the relation of light of Faraday rotator from the light of Faraday rotator and reflective lens as follows:
r 2=-r 1
θ 2=-θ 1
R wherein 1and θ 1respectively height and the angle of the light of reflective lens front focal plane place's incident, r 2and θ 2respectively height and the angle that reflects back into the light at reflective lens front focal plane place.
Collimation lens is the C-Lens lens.
The C-Lens lens that reflective lens is rear end face plating highly reflecting films.
Collimation lens is also for will be from the former road of the light of Faraday rotator emission back into optical fibers, optical fiber also for future self-focus lens light emission to outside.
The above technical scheme of conceiving by the present invention, compared with prior art, the present invention has following beneficial effect: faraday rotation mirror structure of the present invention is by arranging the angle of fiber end face and collimation lens end face, the parallel rays that guarantees collimation is coaxial with collimation lens, use the reflective lens replacement catoptron that rear end face is coated with highly reflecting films instead, parallel rays is injected from the reflective lens optical axis, original optical path returns, can remove the debugging of reflected light path from, directly carry out the machinery assembling, thereby improve the efficiency of assembling of device, more be applicable to batch production, can be widely used in optical fiber communication and optical fiber sensing system.
The accompanying drawing explanation
Fig. 1 is the cross sectional view of faraday rotation mirror structure of the prior art.
Fig. 2 is the cross sectional view of faraday rotation mirror structure of the present invention.
Fig. 3 is the schematic diagram that light passes through light polarization state variation after each element of faraday rotation mirror.
Fig. 4 is the light path schematic diagram of collimation lens in the present invention.
Fig. 5 is the light path schematic diagram of reflective lens in the present invention.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.
As shown in Figure 2, faraday rotation mirror structure of the present invention comprises optical fiber 111, collimation lens 112, Faraday rotator 113, reflective lens 114 and the magnet ring 115 of coaxial setting.
The end face of optical fiber 111 is arranged at the focus place of collimation lens 112.
The front focal plane of the back focal plane of collimation lens 112 and reflective lens 114 overlaps.
The rear end face of reflective lens 114 is coated with highly reflecting films, and reflecting surface is arranged at the back focal plane of this reflective lens 114.In the present embodiment, collimation lens 112 is the C-Lens lens, and reflective lens 114 is the C-Lens lens of rear end face plating highly reflecting films.
Magnet ring 115 is the outsides that are sheathed on Faraday rotator 113, and can after the energising of two ends, produce changeless electromagnetic field.
Optical fiber 111 is for receiving from outside light, and by its end face, is transmitted on the inclined-plane of light collimation lens 112.
Collimation lens 112 collimates for the light to from optical fiber 111, and the parallel rays after collimation is transmitted into to Faraday rotator 113.
Realize light polarization state deflection angle ψ (being to take 45 ° as example in diagram) under the electromagnetic field effect that Faraday rotator 113 produces at magnet ring 115 for the parallel rays that makes self-focus lens 112, and by the light emission after polarization state deflection to reflective lens 114.
Reflective lens 114 will be for turning back to Faraday rotator 113 from the former road of the light of Faraday rotator 113.
Faraday rotator 113 is also realized polarization state deflection angle ψ again from the light of reflective lens 114 for making under the electromagnetic field effect of magnet ring 115 generations, and the light emission after the polarization state polarization is arrived to collimation lens 112.Because the optical direction of Faraday effect is decided by the externally-applied magnetic field direction, irrelevant with the direction of propagation of light, now polarized state of light rotates 2 ψ (being 90 ° in this example)
Collimation lens 112 will be also for launching back into optical fibers 111 from the former road of the light of Faraday rotator 113.
Optical fiber 111 also for future self-focus lens 112 light emission to outside.
Structure of the present invention has guaranteed that the parallel rays of collimation is coaxial with collimation lens, has removed the debugging of reflected light path from, realizes the direct mechanical assembling.The change of light by each element rear polarizer state of faraday rotation mirror of the present invention, with reference to figure 3, it should be noted that in this figure, arrow only means the lightray propagation direction.
As shown in Figure 4, on the back focal plane of collimation lens, height r and the angle θ of the parallel rays after collimation are as follows:
Figure BDA00002383855800051
The angle that wherein α is optical fiber and vertical axis, for the angle of collimation lens and vertical axis, n ffor the fiber core refractive index of optical fiber, n cfor the refractive index of collimation lens, the focal length that f is collimation lens and
Figure BDA00002383855800053
the spherical radius of the rear end face that wherein R is collimation lens.
From above formula, can see, when α and angle meet
Figure BDA00002383855800055
can, by the eliminating from axle of collimated ray, guarantee that the parallel rays of collimation is coaxial with collimation lens.
In the present embodiment, the material of collimation lens is the SF11 shaped material, and its refractive index is n c=1.7447, optical fiber adopts SMF-28 type optical fiber, and its fiber core refractive index is n f=1.4682, the optical fiber head angle of optical fiber is 8 ° usually, by above formula, can obtain angle
Figure BDA00002383855800056
be 5 °, can not affect like this return loss of collimating apparatus, and guarantee that the parallel rays of collimation is coaxial with collimation lens, and the light drift angle also reduces a lot.
As shown in Figure 5, light is from the front focal plane incident of reflective lens, and the plane of reflection is positioned at back focal plane, i.e. 2f system, and the transmission matrix that calculates reflective lens according to optical matrix is: - 1 0 0 - 1 .
According to above-mentioned transmission matrix, the relation of reflection ray and incident ray (particularly, the light that reflective lens receives from Faraday rotator is incident ray, and the light that reflective lens turns back to Faraday rotator is reflection ray) is as follows:
r 2=-r 1
θ 2=-θ 1
R wherein 1and θ 1respectively height and the angle of the light of reflective lens front focal plane place's incident, r 2and θ 2respectively height and the angle that reflects back into the light at reflective lens front focal plane place.
From above formula, can illustrate, reflected light is inevitable parallel with incident light, if light is incident on the lens axis, reflection ray will overlap fully with incident ray, and therefore not light requirement road debugging fully, directly carry out the machinery assembling and get final product.
On the basis of above-mentioned theory knowledge, the faraday rotation mirror structure that the present invention proposes, suitably design the angle of fiber end face and collimation lens end face, the parallel rays that can guarantee collimation is coaxial with collimation lens, uses the reflective lens replacement catoptron that rear end face is coated with highly reflecting films instead, and parallel rays is injected from the reflective lens optical axis, and no matter how incident angle changes, but reflection ray all original optical path returns, and can remove the debugging of reflected light path from, directly carry out the machinery assembling.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.

Claims (4)

1. a faraday rotation mirror structure, is characterized in that,
The optical fiber, collimation lens, Faraday rotator, reflective lens and the magnet ring that comprise coaxial setting;
The end face of described optical fiber is arranged at the focus place of described collimation lens;
The back focal plane of described collimation lens and the front focal plane of described reflective lens overlap;
The rear end face of described reflective lens is coated with highly reflecting films, and the reflecting surface of described reflective lens is arranged at the back focal plane of described reflective lens;
Described magnet ring is the outside that is sheathed on described Faraday rotator, and can after the energising of two ends, produce changeless electromagnetic field;
Described optical fiber is used for receiving from outside light, and by its end face, is transmitted on the inclined-plane of described collimation lens;
Described collimation lens is used for the light from optical fiber is collimated, and the parallel rays after collimation is transmitted into to Faraday rotator;
Faraday rotator is realized light polarization state deflection angle ψ from the parallel rays of described collimation lens for making under the electromagnetic field effect of described magnet ring generation, and the light emission after polarization state deflection is arrived to described reflective lens;
Described reflective lens will be for turning back to described Faraday rotator from the former road of the light of described Faraday rotator;
Described Faraday rotator is also realized polarization state deflection angle ψ again from the light of described reflective lens for making under the electromagnetic field effect of described magnet ring generation, and the light emission after the polarization state polarization is arrived to described collimation lens;
Height r and the angle θ of the parallel rays after described collimation lens collimation are as follows:
Figure FDA0000396885260000011
Figure FDA0000396885260000012
The angle that wherein α is described optical fiber and vertical axis,
Figure FDA0000396885260000021
for the angle of described collimation lens and vertical axis, n ffor the fiber core refractive index of described optical fiber, n cfor the refractive index of described collimation lens, the focal length that f is collimation lens and
Figure FDA0000396885260000022
the spherical radius of the rear end face that wherein R is described collimation lens;
Described reflective lens receives that to turn back to the relation of light of described Faraday rotator from the light of described Faraday rotator and described reflective lens as follows:
r 2=-r 1
θ 2=-θ 1
R wherein 1and θ 1respectively height and the angle of the light of described reflective lens front focal plane place's incident, r 2and θ 2respectively height and the angle that reflects back into the light at described reflective lens front focal plane place.
2. faraday rotation mirror structure according to claim 1, is characterized in that, described collimation lens is the C-Lens lens.
3. faraday rotation mirror structure according to claim 1, is characterized in that, the C-Lens lens that described reflective lens is rear end face plating highly reflecting films.
4. faraday rotation mirror structure according to claim 1, is characterized in that,
Described collimation lens will be also for launching back described optical fiber from the former road of the light of described Faraday rotator;
Described optical fiber is also outside for arriving from the light emission of described collimation lens.
CN 201210447348 2012-11-10 2012-11-10 Faraday rotation mirror structure Expired - Fee Related CN102944918B (en)

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CN103412371B (en) * 2013-07-29 2015-07-22 华中科技大学 Faraday rotary mirror capable of simultaneously carrying out polarization state conversion on multiple paths of optical signals
CN106646928A (en) * 2016-10-28 2017-05-10 京东方科技集团股份有限公司 Anti-dazzling device and control method thereof
CN106772916A (en) * 2016-12-14 2017-05-31 上海伟钊光学科技股份有限公司 Miniature Faraday speculum
CN106707414B (en) * 2016-12-26 2024-01-19 上海毫米星光光学有限公司 Optical fiber isolator
CN106940387B (en) * 2017-04-10 2023-10-27 三峡大学 Michelson interference type optical fiber acceleration sensor
CN107121876B (en) * 2017-05-26 2022-08-19 中国科学院西安光学精密机械研究所 Folding-axis mirror system capable of being positioned
CN107193137A (en) * 2017-07-24 2017-09-22 上海伟钊光学科技股份有限公司 A kind of fibre optic isolater
CN111830646A (en) * 2020-05-12 2020-10-27 上海交通大学 Optical fiber coupling packaging structure, coupling packaging method and coupling array

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