Background technology:
Fiber grating is the periodic refractive index distribution at single mode silica fibre fibre core internal production.It has the reflection characteristic of arrowband, and it is little in use to insert loss, and volume is little, and the reliability height can directly be connected with fibre system, in the optical fiber infotech, as optical fiber communication, Fibre Optical Sensor, optical fibre interference etc., is widely used.It can be used for frequency-selecting, the frequency stabilization element of semiconductor laser and fiber laser; The optical add/drop multiplexer that is used for the dense wave division multipurpose optical fiber telecommunications system; The optical fiber sensing system that is used for the wavelength sensitive type; Be used for optical-fiber type spectroanalysis instrument or the like.Owing to the peak wavelength of fiber grating reflectance spectrum can change along with the strain of temperature and optical fiber, therefore has crucial tuning characteristic.But thereby can constitute add-drop multiplexer, tunable optical fiber sensor of tunable laser source dynamic-configuration or the like.Accurately control in the application of wavelength at needs, utilize the tunable characteristic of fiber grating, cooperate feedback control technology, can realize the High Accuracy Control of fiber grating peak wavelength.Therefore the tunable characteristic of fiber grating is a focus of research and development.
Formerly in the technology, various mechanism arranged to the stress of fiber grating is tuning, as with piezoelectric ceramics (being called for short PZT) to the fiber grating stress application, to fiber grating apply lateral stress carry out tuning, linear tuning etc. based on the fiber grating of semi-girder.The characteristics of each stress mechanical tuning device are:
1. tuning with piezoelectric ceramics (Piezoelectric Transducer is called for short PZT), this mechanism appears in the wavelength tuning of single mode erbium doped fiber laser the earliest.It is to utilize piezoelectric ceramics to produce the characteristic of deformation under the making alive situation, makes the variable in distance between two sections fiber gratings that constitute fiber laser, and promptly the length of laserresonator changes, thereby makes the output wavelength difference.According to technology [1] formerly (referring to Ball G A, Morey W W.Continuously tunable single-mode erbium fiberlaser.opl.lett., 1992,17 (6): 420-422), when the PZT deformation quantity reached 90 μ m, wavelength tuning range reached 0.72nm.For the PZT of monolithic, make deformation quantity reach 90 μ m, institute's making alive is very high, and this does not meet requirement of actual application; Though the PZT deformation quantity of synusia is big, cost an arm and a leg, the actual use also is restricted.And the tuning range of PZT is too little, does not satisfy actual needs.Utilize PZT tuning to short wavelength's direction, when PZT deformation is big, usually can causes that fiber grating is crooked and make tuning inefficacy, can make the fiber grating fracture when serious the peak wavelength of fiber grating.
2. fiber grating being added lateral stress carries out tuning, formerly in the technology [2] (referring to TetsuroKomukai, Yoshiaki Miyajima and Masataka NAKAZAWA.In-Line FiberGrating-Type Optical Bandpass Filter Tuned by Applying Lateral Stress.J.Appl.Phys.Vol.34 (1995) pp.L306-L308 Part 2, No.3A, 1 March 1995) this mechanism and experimental result have been reported.It is by side direction to being encapsulated in the fiber grating stress application in the plastic casing, thereby make optical fiber generation strain.This structure is regulated sensitivity lower (the power 1.26nm of 1N), operate easy inadequately, the shortage controllability.
3. tuning based on the fiber grating linearity of semi-girder, tuning different with the tuning middle free beam of lateral stress.Formerly technology [3] is (referring to Yu Youlong, Liu Zhiguo, Dong Xiaoyi, Wang Jiang is tuning based on the light pricker linearity of raster of semi-girder, optics journal Vol.19, No.5, May, 1999) the semi-girder tunable technology proposed, it is linear that the strain and the free end external force size of its surperficial fiber grating adhered in utilization, realizes the linear tuning of its reflectance spectrum centre wavelength.But chirp phenomenon can occur in this tuning process, promptly along with the increase of applied stress, when the wavelength tuning amount increased, the bandwidth of fiber grating reflectance spectrum also was the trend of increase.This be since on the one hand all the bragg reflection wavelength of grids variation has taken place, between different on the other hand grids the different institutes of intensity of variation extremely, the latter is the principal element that causes bandwidth to increase.Particularly in optical add/drop multiplexer (OADM), the bandwidth increase of fiber grating reflectance spectrum can cause crosstalking of interchannel, makes the transmission signals distortion.
The stress mechanical tuning device of above-mentioned technology formerly, general only realization is unidirectional tuning to long wave.Because in stress is tuning, optical fiber is implemented draw ratio be easier to.Optical fiber is easy to bending when implementing compression, can not reach the purpose of axial compression strain.Yet the pulling strengrth of optical fiber so will reach bigger tuning range, will guarantee the long-term tuning dependability of fiber grating well below its compression strenght simultaneously, just must solve the not flexural deformation problem of fiber grating being implemented compression.
Summary of the invention:
When the utility model was implemented compression for overcoming in the above-mentioned technology formerly to fiber grating, the easy diastrophic problem of fiber grating placed fiber grating in one guide rail, and it both can freely be stretched, and limiting it simultaneously again can bending when compressing.For this reason, optical fiber grating tuning device of the present utility model mainly contains first transverse arm 2 and second transverse arm 4 that central axis is put side by side on same horizontal line.Between first transverse arm 2 and second transverse arm 4 with both concentricity axis be equipped with inner chamber 6 and be the guide rail 3 of isogonism equilateral triangle.Fiber grating 5 places 6 li of the inner chambers of guide rail 3, and the optical fiber at fiber grating 5 two ends is separately fixed on first transverse arm 2 and second transverse arm 4.First transverse arm 2 and second transverse arm 4 are connected with the driving mechanism 1 that can make move toward one another and reverse motions.As shown in Figure 1.
When driving mechanism 1 was made move toward one another or reverse motions, both made move toward one another or reverse motions to drive first transverse arm 2 and second transverse arm 4, then made fiber grating 5 compressions that place 6 li of guide rail 3 inner chambers or stretched, and reached tuning purpose.Because fiber grating 5 is to place 6 li of guide rail 3 inner chambers, when it is compressed, can flexural deformation.
Said can do in opposite directions or the driving mechanism 1 used driving force of reverse motions is an electromagnetic force.
The diameter D of the inscribed cylinder of the inner chamber 6 of said guide rail 3 isogonism equilateral triangles
1Outer diameter D greater than fiber grating 5
2, i.e. D
1>D
2And inscribed cylinder and equally distributed three the tangent line l of isogonism equilateral triangle
1, l
2And l
3With fiber grating 5 outer diameter D
2Tolerance fit be clearance fit.As shown in Figure 2.
The inner chamber 6 of the isogonism equilateral triangle of said guide rail 3 is to be made of the cover plate 7 of upper cover between two pipes 901 that are placed side by side that frid 8 upper groove interior diameters equate and 902, as shown in Figure 3.Or by being fixed on side by side on dull and stereotyped 10, the cover plate of upper cover 7 between two pipes 901 of equal diameters and 902 constitutes.In order to make two pipes 901 and 902 fix firmly, at their two ends fixing pipe 903 and 904 more respectively, as shown in Figure 4.Or constitute by the pipe 901,902,903 of three equal diameters, as shown in Figure 5.Or constitute by the V-shaped groove loam cake upper cover plate 7 of the slab 12 that is carved with 60 ° of angle V-shaped grooves, as shown in Figure 6.
Be described in detail the structure of the utility model tuner below.
Realize the axial compression strain of fiber grating 5, need a kind of can being limited in the fiber grating 5 of diameter in the rigid guideway 3 of rectilinear direction motion less than 0.13 millimeter.As above-mentioned, guide rail 3 is an isogonism equilateral triangle from the xsect of inner chamber 6.As shown in Figure 2, be placed in the inner chamber 6 of guide rail 3 the inscribed cylinder diameter D of inner chamber 6 by tuning fiber grating 5
1Outer diameter D greater than fiber grating 5
2, common D
1=1.0001 D
2So, equally distributed three tangent line l on the inscribed cylinder of fiber grating 5 and inner chamber 6
1, l
2And l
3Tolerance fit be clearance fit, this is in order to guarantee that fiber grating 5 is stretched or not only can but also to be unlikely crooked at 6 li free moving linearlies of inner chamber when being compressed.
Because fiber grating 5 two ends are connecting the ordinary optic fibre that is surrounded by overlay, its external diameter is 0.25 millimeter, is two times of fiber grating 5 diameters, and institute thinks and prevent that fiber grating 5 from rupturing with the junction of optical fiber that this guide rail 3 is can be fabricated.The cover plate 7 of said formation inner chamber 6 is dismountable, can cover and take down at any time.The length of inner chamber 6 is by being determined by the length of tuning fiber grating 5.
Driving mechanism 1 as shown in Figure 1 drives first transverse arm 2 and second transverse arm 4 is done in opposite directions or reverse motions, thereby the fiber grating 5 that is fixed between first transverse arm 2 and second transverse arm 4 is compressed or stretches, and reaches tuning purpose.
Guide rail 3 of the present utility model provides above-mentioned four kinds of constituted modes, can guarantee that all fiber grating 5 is in tuning process, no matter be stretched or be compressed, fiber grating 5 not only can freely stretch on straight line or compression for 6 li at guide rail 3 inner chambers, and can be crooked.
Said guide rail 3 first kind of structure as shown in Figure 3.Fiber grating 5 is limited in the stainless-steel tube (or stainless steel wire) of two equal diameters, outside surface polishing as between pipe 901,902 and the cover plate 7.Two stainless steel pipes 901,902 are fixed in the groove of the frid 8 of having processed groove.According to geometric relationship, stainless-steel tube 901,902 external diameters should be 4 times of fiber grating 5 outer diameter D 2.
Said guide rail 3 second kind of structure as shown in Figure 4.Basic structure is similar to first kind.Adopted four identical stainless-steel tubes as pipe 901,902,903 and 904, the stainless-steel tube 903,904 of both sides plays the positioning action to middle two stainless-steel tubes 901,902.Dull and stereotyped 10 is stainless steel flat plates, and it does not need to resemble needs the very high groove of requirement on machining accuracy first kind of structure.Article four, stainless-steel tube 901,902,903 and 904 sticks with glue knot and gets final product on dull and stereotyped 10.
The
guide rail 3 of said the third structure as shown in Figure 5.
Fiber grating 5 is limited in three stainless-steel tubes (or stainless steel wire) as in the middle of pipe 901,902 and 903 threes.Article three, two ends of stainless-steel tube are fixed with two
sleeve pipes 11 with stainless-steel tube of inside diameter-variable respectively.Pipe 901,902 and 903 external diameter should be
fiber grating 5 outer diameter D
2 Doubly.
The 4th kind of structure of said guide rail 3 as shown in Figure 6.Fiber grating 5 has been limited in processing between the slab 12 and cover plate 7 of smooth V-type groove.The drift angle of V-type groove is taken as 60 ° of angles.According to geometric relationship, the degree of depth of the V-type groove at 60 ° of angles should be fiber grating 5 outer diameter D
21.50015 times.
As mentioned above, the utility model produces in opposite directions or opposing motion first transverse arm 2 that makes fixed fiber grating 5 by driving mechanism 1 and second transverse arm 4, and to carry out stress tuning thereby fiber grating 5 is applied compression stress or drawing stress.The mode that driving mechanism 1 produces driving force has electromagnetic force, piezoelectricity to render a service the rotating force of (PZT), micromachine (stepper motor or servomotor) or the modes such as tension force of hot swollen shrinkage.
The driving force of driving mechanism 1 of the present utility model is to adopt electromagnetic force, as shown in Figure 7, contain the base plate 101 that is fixed in the shell 113, link to each other with the bottom of second shell fragment 112 by first shell fragment 102 respectively with first support arm 103 and second support arm 108 at the two ends of base plate 101.On base plate 101, between first support arm 103 and second support arm 108, be equipped with first solenoid 105 and second solenoid 109, first magnetic core 104 is arranged in first solenoid 105, the central axes of second magnetic core, 110, two magnetic cores 104 and 110 is arranged in second solenoid 109.One end of first magnetic core 104 and second magnetic core 110 links to each other with second support arm 108 with first support arm 103 respectively, the other end of first magnetic core 104 and second magnetic core 110, cushion 107 is arranged between two opposite ends, between first transverse arm 2 on the top board 106 of shell 113 and second transverse arm 4 is guide rail 3, first transverse arm 2 links to each other with the top of first support arm 103 and second support arm 108 respectively with second transverse arm 4, and fiber grating 5 puts into that the optical fiber at two ends is separately fixed on first transverse arm 2 and second transverse arm 4 behind 6 li of the inner chambers of guide rail 3.Said first transverse arm 2 and second transverse arm 4 are that the square hole from the top board 106 of shell 113 stretches out to guarantee that fiber grating 5 puts into that the optical fiber at two ends can be horizontally fixed on first transverse arm 2 and second transverse arm 4 behind 6 li of the inner chambers of guide rail 3.Sense of current can make first magnetic core 104, second magnetic core 110 attract mutually or repulsion mutually in first solenoid 105, second solenoid 109 by controlling, thereby drive first transverse arm 2 and second transverse arm 4 produces in opposite directions or opposing motion, correspondingly make the fiber grating 5 that is fixed on first transverse arm 2 and second transverse arm 4 be subjected to axial compression stress or tension, reach tuning purpose.Between first magnetic core 104, second magnetic core 110 elastic cord breaker 107 that is made of sponge is arranged, after preventing that first magnetic core 104, second magnetic core 110 from holding fully, fiber grating 5 curved transitions are ruptured.To guarantee guide rail 3 during assembling, cushion 107, the central lines of base plate 101.
Compare with technology formerly, the progress of the utility model tuner is:
1. the fiber grating in the utility model 5 is 6 li of inner chambers that are placed on guide rail 3, thereby guaranteed that fiber grating 5 can be not crooked in the fiber grating 5 compression-tuned processes, just do not make tuning inefficacy even fracture simultaneously yet, thereby solved the bilaterally adjustable problem of centre of homology wavelength that conventional media film bandpass filter is difficult to realize because of crooked deformation.
2. the utility model tuner is in tuning process, because three tangent line l of even distribution of the isogonism equilateral triangle inner chamber 6 of guide rail 3
1, l
2And l
3Restriction, fiber grating 5 stress everywhere is even, can not cause that fiber grating reflectance spectrum bandwidth increases, i.e. chirp phenomenon.
In the utility model tuner by the optical fiber at first transverse arm 2 and second transverse arm, 4 fixed fiber gratings, 5 two ends; the guide rail 3 protection structures that adopt above-mentioned driving mechanism 1 stretching and compression and constituted make by tuning fiber grating and can not rupture because of crooked in the joint of naked fibre and coating fibre; so be easy to safeguard; tuner is convenient to combination; loading and unloading are simple, satisfy the requirement of system's practicability.
4. guide rail 3 structures that adopt in the utility model and by the electromagnetic field driving mechanism that solenoid constitutes all be easy to processing, cost is lower, so tuner of the present utility model has good economic and practical.
5. therefore the electromagnetic field driving mechanism 1 that adopts in the utility model is easy to control added stress, so tuning recovery is good owing to control with DC current.