Realize optoisolated method and device thereof in Experiments of Optics and the optical fiber telecommunications system
Technical field
The present invention relates to realize in a kind of Experiments of Optics and the optical fiber telecommunications system optoisolated method and device thereof, be used to prevent that the light beam that light source sends from returning light source again behind a certain optical element end face reflection, can be applicable to belong to laser, technical field of optical fiber communication in Experiments of Optics and the optical fiber telecommunications system.
Background technology
In systems such as Experiments of Optics and optical fiber communication, the light beam that luminescent device sends can be caused influences such as light source video stretching, noise increase, power shakiness, performance degradation by the end face reflection of a certain optical element of downstream light path and back light source again.In order to protect luminescent devices such as laser instrument, image intensifer, eliminate the reflecting light of not expecting, guarantee system stable operation, often need in the light path of light source output terminal back, place a kind of optical device that allows the light one-way transmission, be referred to as optoisolator usually.
Optoisolator can be divided into two classes by polarization characteristic, i.e. polarization relationship type and polarization independent type.Existing polarization relationship type optoisolator is mainly formed (referring to Fig. 1) by the polarizer, Faraday polarization apparatus and analyzer, the direction of shaking the thoroughly angle at 45 of shake the thoroughly direction and the polarizer of analyzer, and Faraday polarization apparatus places between the two.Incident light becomes linearly polarized light after by the polarizer, through thoroughly the shake direction rotation 45 ° of its plane of polarization behind the Faraday polarization apparatus to analyzer, just in time is parallel to the direction of shaking thoroughly of analyzer, thereby can passes through analyzer smoothly again; Emergent light is reverse through analyzer and Faraday polarization apparatus by the end face part of optical element in the light path of downstream reflection back, because the Faraday effect of Faraday polarization apparatus, the reflected light plane of polarization is vertical with the polarizer direction of shaking thoroughly along continuing 45 ° of rotations with the direction of the identical rotation direction of incident light polarization face, thereby make light beam can't oppositely pass through the polarizer, realize isolation effect.Because Faraday polarization apparatus is relevant with the temperature of plane polarization light wavelength and this device environment of living in to the angle of linearly polarized light rotation, therefore, this type of optoisolator can only be realized above-mentioned functions usually in less relatively temperature range.
Polarization independent type optical isolator mainly contains two kinds of displacement type and wedge shapes.Its ultimate principle is, between two GRIN Lens, place a polarizing beam splitter, two orthogonal polarization components (being o light and the e light in the uniaxial crystal) of incident beam are made apart, the light beam that forward passes through synthesizes a branch of light again at another polarizing beam splitter place behind Faraday polarization apparatus, and can not synthesize a branch of light again behind the light beam that oppositely passes through process polarizing beam splitter and the Faraday polarization apparatus, thereby realize isolation effect.Yet, have only when two reverse cross polarization light components in the space separately more greatly apart from the time, just can play buffer action, this makes and to need large-size as the crystal of polarizing beam splitter and faraday rotator or birefringent wedge crystal, thereby causes the volume of device big, cost is high.
Summary of the invention
The technical matters that solves
For fear of the deficiencies in the prior art part, the present invention proposes to realize in a kind of Experiments of Optics and the optical fiber telecommunications system optoisolated method and device thereof, overcome the existing narrower deficiency of isolator operating temperature range, satisfy the requirement of device miniaturization simultaneously, this optoisolator can be realized the function of logical light of forward and reverse isolation in a wider temperature range, and realizes satisfying the requirement of device miniaturization.
Technical scheme
Realize optoisolated method in a kind of Experiments of Optics and the optical fiber telecommunications system, it is characterized in that step is as follows:
Step 1: with forward entrance laser beam P
0Be converted into the monochromatic circularly polarized light P of forward
1Described forward is the incident direction of initial light;
Step 2: in magnetic field environment, with the monochromatic circularly polarized light P of forward
1Vertical irradiation target bit B behind vertical irradiation and the transmission target bit A, the monochromatic circularly polarized light P of forward under the action of a magnetic field
1One way phase shift from target bit A to target bit B is the integral multiple of π;
Step 3: with the monochromatic circularly polarized light P of forward
1Repeatedly turn back between target bit B and target bit A, the transmitted light beam of turning back at target bit B repeatedly superposes in target bit B rear end light path becomes the monochromatic circularly polarized light P of forward
2, in the target bit B corresponding multiple beam constructive interference that obtains and turn back; The monochromatic circularly polarized light P of described forward
2With the monochromatic circularly polarized light P of forward
1The polarization direction identical, realize the logical light function of forward;
Step 4: with reflection lasering beam P '
0Be converted into and the monochromatic circularly polarized light P of forward
2The reverse monochromatic circularly polarized light P that the polarization direction is opposite
3
Step 5: in magnetic field environment, with reverse monochromatic circularly polarized light P
3Vertical irradiation target bit A behind reverse vertical irradiation and the transmission target bit B, this reverse monochromatic circularly polarized light P under the action of a magnetic field
3One way phase shift from target bit B to target bit A is the odd-multiple of pi/2; The described opposite direction of initial light incident direction that is reversed;
Step 6: with reverse monochromatic circularly polarized light P
3Between target bit A and target bit B, repeatedly turn back, offset the destructive interference of formation multiple beam in target bit A rear end light path stack back, realize the reverse isolation function at the transmitted light beam that target bit A turns back.
A kind of isolation device of realizing said method is characterized in that comprising forward polarization state Control Component 1, barrier assembly 2 and the negative polarization state Control Component of establishing along the optical axis order 3; First linear polarizer 11 and first quarter-wave plate 12 of described forward polarization state Control Component 1 for establishing, and the direction of shaking the thoroughly angle at 45 of the quick shaft direction of first quarter-wave plate 12 and first linear polarizer 11 along the optical axis order; First high reflectance reflecting body 22, Faraday polarization apparatus 21 and the second high reflectance reflecting body 23 of described barrier assembly 2 for establishing along the optical axis order, place axial magnetic field 27; The placement that is parallel to each other of the described first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 constitutes the Fabry-Perot etalon structure; Faraday polarization apparatus 21 is positioned at described Fabry-Perot etalon; Second linear polarizer 31 and second quarter-wave plate 32 of described negative polarization state Control Component 3 for establishing along the optical axis order, the quick shaft direction of second quarter-wave plate 32 is parallel with the quick shaft direction of first quarter-wave plate 12, and the direction of shaking thoroughly of second linear polarizer 31 is vertical with the direction of shaking thoroughly of first linear polarizer 11.
Described barrier assembly 2 comprises Faraday polarization apparatus 21, the first high reflectance reflecting body 22, the second high reflectance reflecting body 23, anti-reflection film 24, micro-displacement apparatus 25, permanent magnet 26 and supporter 41; At the two ends of supporter 41 fixed permanent magnet 26 and micro-displacement apparatus 25, the centre of permanent magnet 26 is a Faraday polarization apparatus 21, and the both sides of Faraday polarization apparatus (21) are the first high reflectance reflecting body 22 and anti-reflection film 24; Micro-displacement apparatus 25 and anti-reflection film 24 close ends are provided with the second high reflectance reflecting body 23; Faraday polarization apparatus 21, the first high reflectance reflecting body 22, the second high reflectance reflecting body 23 and anti-reflection film 24 are same optical axis.
When the quick shaft direction of the quick shaft direction of described second quarter-wave plate 32 and first quarter-wave plate 12 was vertical, the direction of shaking thoroughly of second linear polarizer 31 was parallel with the direction of shaking thoroughly of first linear polarizer 11.
The described first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 are catoptron or reflectance coating, and reflectivity is more than 80%, preferred 92%.
Described Faraday polarization apparatus 21 is made of the magneto-optic memory technique of the parallel polishing of both ends of the surface that produces Faraday effect, and described magneto-optic memory technique is that faraday's anglec of rotation that the magneto-optical crystal of yttrium iron garnet YIG, terbium gallium garnet TGG, contour Fil moral constant or magneto-optic thin film, requirement produce is 15 °~75 °.
Described axial magnetic field 27 is one to be applied to the permanent magnet 26 on the Faraday polarization apparatus 21; Described permanent magnet 26 is neodymium iron boron Nd-Fe-B or SmCo Sm-Co.
Described anti-reflection film 24 is monofilm or assembly of thin films.
Described micro-displacement apparatus 25 is piezoelectric chip PZT.
Faraday's anglec of rotation of described Faraday polarization apparatus (21) is 45 °.
Principle of work of the present invention: after first linear polarizer is passed in the forward entrance monochromatic light incident that laser instrument sends, become the monochromatic linearly polarized light of forward; Shake thoroughly behind first quarter-wave plate at direction angle at 45 through quick shaft direction and first linear polarizer again, become forward monochrome circularly polarized light; Then normal incidence is to containing in Fabry-Perot etalon Faraday polarization apparatus, that be made of the first high reflectance reflecting body and the second high reflectance reflecting body.The refractive index of the monochromatic circularly polarized light of described forward in Faraday polarization apparatus is N
1This Fabry-Perot etalon chamber length is a desired value, can make the monochromatic circularly polarized light of described forward is the integral multiple of π by the first high reflectance reflecting body through the one way phase shift of Faraday polarization apparatus to the second high reflectance reflecting body, form the multiple beam constructive interference, then this Fabry-Perot etalon has the largest light intensity transmitance to the monochromatic circularly polarized light of forward, and the monochromatic circularly polarized light of forward passes through this Fabry-Perot etalon with high permeability.Afterwards, the monochromatic circularly polarized light of forward becomes and the consistent linearly polarized light of initial incident forward monochrome plane polarization light polarization direction after by perpendicular second quarter-wave plate of quick shaft direction and first quarter-wave plate, and pass outgoing behind the direction of shaking second linear polarizer consistent, thereby realize the logical light function of forward of optoisolator with this plane polarization light polarization direction.
Emergent light is returned along original optical path is reverse by reflecting body end face part reflection back in the light path of downstream, is converted into behind second linear polarizer and second quarter-wave plate and the opposite reverse monochromatic circularly polarized light in the monochromatic circularly polarized light polarization direction of forward; Then normal incidence is in the described Fabry-Perot etalon that contains Faraday polarization apparatus.Faraday polarization apparatus has different refractive indexes to the light of different rotation directions, and the refractive index of reverse monochromatic circularly polarized light in Faraday polarization apparatus is N
2Therefore, under the length of the above-mentioned suitable chamber of Fabry-Perot etalon, reverse monochromatic circularly polarized light is the odd-multiple of pi/2 by the second high reflectance reflecting body through the one way phase shift of Faraday polarization apparatus to the first high reflectance reflecting body, can form the multiple beam destructive interference, this Fabry-Perot etalon has the minimum intensity of light transmitance to reverse monochromatic circularly polarized light, and reverse monochromatic circularly polarized light passes through this Fabry-Perot etalon with low transmission, thereby realizes the reverse isolation function of optoisolator.
Beneficial effect
Realize optoisolated method and device thereof in Experiments of Optics that the present invention proposes and the optical fiber telecommunications system, beneficial effect is: utilize compression and the filter action to spectrum of the nonreciprocal effect of the left and right sides rounding polarized light characteristic that refractive index is different in the Faraday magneto-optical material, Faraday effect and Fabry-Perot etalon, the Faraday magneto-optical material is placed in the Fabry-Perot etalon, realization has high permeability and the circularly polarized light of another opposite rotation direction is had the effect of low transmission the circularly polarized light of a certain rotation direction, reaches optoisolated purpose.Utilize this method to realize that optoisolated advantage is:
1, the present invention utilizes Faraday effect to control the effect of the phase differential realization light isolation of generation pi/2 between the circularly polarized light of opposite rotation direction, therefore but do not need faraday's rotation angle strict and steady on 45 °, promptly, the small size variation of faraday's rotation angle is the serious performance of deterioration optoisolator not, effectively reduce requirement like this, therefore can be used for being operated in the system of big temperature difference environment Faraday magneto-optical material temperature stability;
2, only utilize single-stage to isolate the requirement that just can realize the above isolation of 40-65dB;
3, light does not produce transversal displacement, can realize miniaturization of devices.
Description of drawings
Fig. 1 is existing polarization relationship type optoisolator principle of work synoptic diagram;
Fig. 2 is the optical principle synoptic diagram of isolation method of the present invention;
Fig. 3 realizes optical isolator structural representation of the present invention;
Fig. 4 utilizes isolation method of the present invention to realize optoisolated apparatus structure synoptic diagram;
Fig. 5 is the transmittance curve comparison diagram of different rotation direction circularly polarized lights when utilizing isolation method of the present invention to realize isolation; Solid line be under the different condition light positive to by the time transmittance curve; Dotted line be under the corresponding conditions light oppositely by the time transmittance curve;
Fig. 6 utilizes isolation method of the present invention to realize that isolation time strong reflection rate R and faraday's rotation angle θ are to isolation influence curve comparison diagram.
Among the figure, 1-forward polarization state Control Component, 11-first linear polarizer, 12-first quarter-wave plate; The 2-barrier assembly, 21-Faraday polarization apparatus, the 22-first high reflectance reflecting body, the 23-second high reflectance reflecting body, 24-anti-reflection film, 25-micro-displacement apparatus, 26-permanent magnet, 27-axial magnetic field; 3-negative polarization state Control Component, 31-second linear polarizer, 32-second quarter-wave plate; The 41-supporter, 42-first optical fiber collimator, 43-incident optical, 44-second optical fiber collimator, 45-outgoing optical fiber, 46-sleeve, 47-laser instrument, 48-reflecting body.
Embodiment
Now in conjunction with the embodiments, accompanying drawing is further described the present invention:
See also Fig. 4, present embodiment is applied to comprise laser instrument 47, first linear polarizer 11, first quarter-wave plate 12, Faraday polarization apparatus 21, the first high reflectance reflecting body 22, anti-reflection film 24, permanent magnet 26, the second high reflectance reflecting body 23, micro-displacement apparatus 25, supporter 41, second quarter-wave plate 32, second linear polarizer 31 and reflecting body 48 in the Experiments of Optics system that resolution element builds.Faraday polarization apparatus 21 places the inside of permanent magnet 26, its magneto-optic memory technique is selected yttrium iron garnet crystal (YIG) for use, its on forward entrance light direction end face, be coated with reflectivity be 92% reflectance coating as the first high reflectance reflecting body 22, it is coated with anti-reflection film 24 on forward emergent light direction end face; The second high reflectance reflecting body 23 is positioned at after the Faraday polarization apparatus 21, links with micro-displacement apparatus 25, and constitutes Fabry-Perot etalons, Faraday polarization apparatus 21 parallel this etalons that are positioned at the first high reflectance reflecting body 22; Micro-displacement apparatus 25, Faraday polarization apparatus 21 and permanent magnet 26 overall fixed are on supporter 41.First linear polarizer 11 and first quarter-wave plate 12 are parallel successively to be positioned at before the described Fabry-Perot etalon, and the quick shaft direction angle at 45 of shake the thoroughly direction and first quarter-wave plate 12 of first linear polarizer 11; Second quarter-wave plate 32 and second linear polarizer 31 are parallel successively to be positioned at after the described Fabry-Perot etalon, and the quick shaft direction of second quarter-wave plate 32 is vertical with the quick shaft direction of first quarter-wave plate 12, and the direction of shaking thoroughly of second linear polarizer 31 is parallel with the direction of shaking thoroughly of first linear polarizer 11.Anti-reflection film 24 reduces the monofilm or the assembly of thin films of reflection, enhancing transmission for making incident light at the interface.Permanent magnet 26 is the permanent magnet of a hollow drum NdFeB material, and it is parallel to even axial magnetic field optical direction, that the magnetic field positive dirction is identical with the forward entrance light direction for Faraday polarization apparatus 21 provides.Micro-displacement apparatus 25 is piezoelectric chip (PZT), can make by its adjustment to contain Fabry-Perot etalon Faraday polarization apparatus 21, that constitute by the first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 to have an optimum chamber long, to obtain the optimal isolation degree.
The course of work of present embodiment is: in coordinate system as shown in Figure 4, the forward entrance light that laser instrument 47 sends is to be converted into the forward linearly polarized light that the polarization direction is x-y plane one or three quadrant angle bisectors behind first linear polarizer 11 of x-y plane one or three quadrant angle bisectors to the direction of shaking thoroughly along z axle positive dirction vertical incidence, again through too fast axle for be converted into forward right-circularly polarized light (this rotation direction goes into to define in face of described) behind axial first quarter-wave plate 12 of y when light is observed.The refractive index of described forward right-circularly polarized light in Faraday polarization apparatus 21 is n
-, its light intensity transmitance of passing through behind the Fabry-Perot etalon that contains Faraday polarization apparatus 21 that is made of the first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 is
In the formula, R is the light intensity reflectivity of the first high reflectance reflecting body 22 and the second high reflectance reflecting body 23, φ
-For described forward right-circularly polarized light by of the one way phase shift of the first high reflectance reflecting body 22 through Faraday polarization apparatus 21 to second high reflectance reflecting bodys 23.By moving the micro-displacement apparatus 25 that links with the second high reflectance reflecting body 23, adjust φ
-Be the integral multiple of π, make the forward right-circularly polarized light form the complete constructive interference of multiple beam in the Fabry-Perot etalon that contains Faraday polarization apparatus 21, this moment, light intensity transmitance T was a maximal value, realized the purpose of the logical light of forward.The forward right-circularly polarized light is converted into the forward linearly polarized light that the polarization direction is x-y plane one or three quadrant angle bisectors again after too fast axle is for axial second quarter-wave plate 32 of x, be similarly lossless ejaculation behind second linear polarizer 31 of x-y plane one or three quadrant angle bisectors through the direction of shaking thoroughly, become the forward emergent light.
Described forward emergent light is returned along z axle negative direction by the end face part of reflecting body 48 in the light path of downstream reflection back, reverse vertical incident is converted into the reverse linearly polarized light that the polarization direction is x-y plane one or three quadrant angle bisectors after passing second linear polarizer 31 that the direction of shaking is x-y plane one or three quadrant angle bisectors, is to be converted into the reverse right-circularly polarized light opposite with forward right-hand circular polarization light polarization direction when described backlight is observed (this rotation direction in face of definition) behind second quarter-wave plate 32 of x axle through quick shaft direction again.The refractive index of described reverse right-circularly polarized light in Faraday polarization apparatus 21 is n
+, its light intensity transmitance of passing through behind the Fabry-Perot etalon that contains Faraday polarization apparatus 21 that is made of the first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 is
In the formula, φ
+For described reverse right-circularly polarized light by of the one way phase shift of the second high reflectance reflecting body 23 through Faraday polarization apparatus 21 to first high reflectance reflecting bodys 22.Because the refractive index difference of the 21 pairs of different rotation direction circularly polarized lights of Faraday polarization apparatus in the Fabry-Perot etalon, i.e. n
-With n
+Unequal, so forward right-circularly polarized light and reverse right-circularly polarized light have different one way phase shifts after by same Faraday polarization apparatus 21, its difference is
In the formula, L is the logical light length of Faraday magneto-optical material, and V is the Fil moral constant of Faraday magneto-optical material, and θ is faraday's rotation angle, and B is the magnetic field that is applied on the Faraday polarization apparatus 21.By regulating the size control faraday rotation angle θ of magnetic field B, can adjust the one way phase shift difference of different rotation direction circularly polarized lights, when θ=45 °, described one way phase shift difference Δ φ=pi/2, this moment is as forward right-circularly polarized light one way phase shift φ
-Be the integral multiple of π, form the multiple beam constructive interference, when having the largest light intensity transmitance, the one way phase shift φ of reverse right-circularly polarized light
+Be the odd-multiple of pi/2, form the multiple beam destructive interference, have the minimum intensity of light transmitance, realize the purpose of reverse isolation.
The effect of described Faraday polarization apparatus 21 is to make the phase differential that produces pi/2 between the circularly polarized light of opposite rotation direction,, makes forward right-circularly polarized light one way phase shift φ that is
-For the integral multiple of π forms complete constructive interference, reverse right-circularly polarized light one way phase shift φ
+For the odd-multiple of pi/2 forms complete destructive interference; Faraday's rotation angle θ of the generation of its generation is as the criterion so that different rotation direction circularly polarized lights can effectively be separated the transmittance curve spike of Fabry-Perot etalon, usually be limited between 15 °-75 °, then isolation effect is good more near 45 ° more, and optimal value is 45 ° (referring to Fig. 6 and Fig. 7).
The light intensity reflectivity R of the described first high reflectance reflecting body 22 and the second high reflectance reflecting body 23 is limited in more than 80% usually, bigger R helps the increase of isolation, but the requirement to later stage device assembling and mechanical stability is higher, otherwise, less R is unfavorable for the realization of high-isolation, but can reduce the requirement to later stage device assembling and mechanical stability; Preferred 92% (referring to Fig. 6 and the Fig. 7) of light intensity reflectivity R.