CN1264291C - Polarization mould disporsion compensation system - Google Patents
Polarization mould disporsion compensation system Download PDFInfo
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- CN1264291C CN1264291C CNB031501206A CN03150120A CN1264291C CN 1264291 C CN1264291 C CN 1264291C CN B031501206 A CNB031501206 A CN B031501206A CN 03150120 A CN03150120 A CN 03150120A CN 1264291 C CN1264291 C CN 1264291C
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- 230000010287 polarization Effects 0.000 title claims abstract description 83
- 239000013078 crystal Substances 0.000 claims abstract description 60
- 239000013307 optical fiber Substances 0.000 claims abstract description 50
- 230000003287 optical effect Effects 0.000 claims abstract description 36
- 239000000835 fiber Substances 0.000 claims abstract description 16
- 238000004891 communication Methods 0.000 claims abstract description 6
- 239000006185 dispersion Substances 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 9
- 229910009372 YVO4 Inorganic materials 0.000 claims description 8
- 238000000034 method Methods 0.000 abstract description 15
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000010276 construction Methods 0.000 abstract 1
- 230000005540 biological transmission Effects 0.000 description 5
- 239000004973 liquid crystal related substance Substances 0.000 description 5
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- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
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Abstract
The present invention discloses a polarization mould color dispersing compensation system which belongs to the field of optical fiber communication. The system comprises a coupler, a polarization controller, an optical collimator, a changeable optical delay line, a detector, a computer and a control system, wherein the optical collimator and the changeable optical delay line are concentrically placed on one line by an optical axis. After the coupler, the detector and the computer are connected in series, the computer is respectively connected with the polarization controller and the changeable optical delay line to form a feedback control circuit. The coupler, the polarization controller and the optical collimator are the devices with tail fiber to be helpful for being connected with an optical fiber system. The polarization controller is controlled by a DC servo motor to be convenient for rapidly and automatically controlling a polarization state. The changeable optical delay line uses a plurality of sections of birefringent crystals and PRs to be arranged and fixed according to a certain type. No movable component exists in the operating process, and thus, the present invention has the advantages of simple structure, stable performance and little outside environment influence. The feedback control circuit composed of the computer, the detector, etc., is used for feeding the system PMD direction information back to the control circuit of the polarization controller. Thus, the polarization controller generates a polarization state opposite to the system PMD direction for mutual cancellation. Thus, the purpose of polarization mould color dispersing compensation is obtained. The device has simple assembly, convenient adjustment and no movable component, and thus, the device has the advantages of easy manufacture, portability and easy construction in order to obtain reduced cost and wide applying space.
Description
Technical field
The invention belongs to fiber optic communication field, particularly a kind of Polarization Mode Dispersion Compensation Systems.
Background technology
Polarization mode dispersion is a major reason that causes signal broadening in high speed, the high-capacity optical fiber communication system.In desirable fiber optic transmission system, optical fiber is the circle symmetrical structure.And in real system, optical fiber is not desirable round symmetrical structure, thereby causes random birefringence owing to influences such as the reason of making and temperature, vibration, stress.When a branch of light signal transmits in such optical fiber, light signal will produce division, thereby cause pulse stretching, and the phenomenon of this pulse stretching is called polarization mode dispersion (being called for short PMD).When analyzing in the transmission system PMD, usually optical fiber is thought to exist the birefringent medium of two orthogonal polarisation state, the transmission speed difference of light signal on the pairwise orthogonal polarization state, thus cause signal broadening.During characterization system PMD, usually with propagation velocity in the orthogonal polarisation state faster the polarization state direction be defined as the direction of PMD, the group delay difference that signal transmits on the pairwise orthogonal polarization state is called differential group delay (being called for short DGD).PMD is having a strong impact on signal transmission quality, is especially adopting in the early stage system of optical cable transmission rate greater than 10Gbps of laying, because the signal broadening that PMD causes will make signal differentiate, therefore must compensate.
Because the Unpredictability of optical fiber random birefringence has determined the PMD compensation to be necessary for the mode of dynamic self-adapting.For this reason, people have designed many compensation methodes and device.Except that the electronic compensating method, these methods based on adopting variable or the fixed light delay line adds Polarization Controller, add the method for feedback control circuit substantially, artificial generation and the PMD equal and opposite in direction in the system, the PMD that direction is opposite, both cancel out each other, and reach the purpose that reduces the PMD of system.But, at document (1) .D.Sobiski, D.Pikula, etal, " Fast first-orderPMD compensation with low insertion loss for 10Gbit/s system ", and Electron.Lett., Vol.37, No.1, pp 46～48, and 4
ThJan.2001; (2) Hok Yong Pua, etal, " Anadaptive first-order polarization-mode dispersion compensation systemaided by polarization scrambling:theory and demonstration ", J.ofLightwave Technol., Vol.18, No.6, pp832～841, Jun.2000; (3) .FredHeismann, etal, " Automatic compensation of first-order polarization modedispersion in a 10Gb/s transmission system; in Proc.ECOC ' 98 (Madrid); pp529～5301 and patent WO 02/35743; propose in 2002/5/2 based on the method for birefringence fiber and the method for interferometer, bucking-out system is not that length is long, is exactly that device is very high to environmental requirement.And as patent WO01/61385, employing polarization splitting prism that proposes in 2001/8/21 and common GRIN Lens are as the method for Polarization Controller and collimater, and the ray machine part is too much, is unfavorable for the system integration.At document (4) S.Lee, etal, " Adjustable compensation of polarization mode dispersion using ahigh-birefringence nonlinearly chirped fiber Bragg grating ", IEEEPhoton.Technol.Lett., Vol.11, No.10, pp1277 ~ 1279, the method of the employing high birefringence nonlinearly chirped fiber grating that proposes among the Oct.1999, complex manufacturing technology costs an arm and a leg.Document (5) D.Sandel, etal, " 10-Gb/s PMD compensation using deformed-helicalferroelectric liquid crystals ", in Proc.ECOC ' 98 (Madrid), pp555 ~ 556 and patent US 6,417,948 B1,2002/7/9, the middle proposition " adopted the method for liquid crystal as Polarization Controller ", but it is restricted its reaction speed owing to the intrinsic property of liquid crystal.Patent US 2002/0118455A1, in 2002/8/29 " method that the high birefringence material of employing geometric ratio length compensates ", when not having PMD in the optical fiber, but produced certain additional PMD by the PMD compensator, and WO 01/10811 A2, though cause birefringece crystal or liquid crystal to have produced PMD be zero state by powering up in 2002/2/7, driving voltage is higher or higher to environmental requirement usually.For making the PMD compensator can really be applicable to optical fiber telecommunications system, be necessary to design a kind of simple in structure, stable performance, volume is little, easily and system, coupled, is swift in response, power consumption is little, the PMD bucking-out system that realizes and can dynamically control easily on the engineering.
Summary of the invention
The purpose of this invention is to provide easy and system, coupled, be swift in response, power consumption is little, a kind of Polarization Mode Dispersion Compensation Systems that realizes and can dynamically control easily on the engineering, this system comprises a coupler, a Polarization Controller, a pair of optical collimator, one section variable light delay line and feedback control circuit, it is characterized in that: described optical collimator, variable light delay line are put point-blank with one heart with optical axis, and described variable light delay line is between described a pair of optical collimator; The detector 5 of described feedback control circuit and computer 6 are connected with coupler 1, computer 6 more respectively with Polarization Controller 2, variable light delay line 4 connects, light beam from the optical fiber outgoing of the applied optical fiber telecommunications system of Polarization Mode Dispersion Compensation Systems, at first enter coupler 1, light beam by coupler 1 outgoing is divided into two bundles, wherein a branch ofly enter detector 5 as control signal, handle by computer 6, obtain the size and Orientation of described optical fiber telecommunications system PMD, another bundle enters Polarization Controller 2, enters optical collimator 3 from the light beam of Polarization Controller 2 outgoing; Computer 6 feeds back to the control circuit of Polarization Controller 2 with the directional information of described optical fiber telecommunications system PMD, and Polarization Controller 2 is produced and the opposite polarization states of optical fiber telecommunications system PMD direction; Computer 6 feeds back to the control circuit of variable light delay line 4 with the size information of described optical fiber telecommunications system PMD, the DGD value of variable light delay line 4 is equated with DGD in the described optical fiber telecommunications system, thereby reach the purpose of compensated fiber communication system PMD.
Described coupler, Polarization Controller and optical collimator are the magnetic tape trailer fiber device, help being connected with fibre system; Its Polarization Controller is DC servo motor control, is convenient to fast automatic control polarization state.
Described variable light delay line comprises n+1 section birefringece crystal and n the polarization rotator PR based on magneto optical effect, and described crystal and PR are spaced, and arrangement mode is for to be followed successively by the longest crystal from front to back, PR, and vice-minister's crystal, PR is up to the shortest crystal; Its n+1 section birefringece crystal comprises that the crystal that n length is doubled and redoubled adds the crystal of shortest length in a n birefringece crystal with other; This PR is made of hot-wire coil and its inner magneto-optical crystal; By the size and Orientation of electric current in the control hot-wire coil, can control size and Orientation by the magnetic field of magneto-optical crystal, make the fast axle or the slow axis coincidence of front and back two crystal in the variable light delay line, thereby control adding, subtracting of two crystal DGD values; Wherein n is a natural number.
Described birefringece crystal is YVO4, and fast axle or slow axis angle are 45 degree between two-phase vincial faces body, and PR can make linearly polarized light polarization state rotation ± 45 degree.
Described n requires the maximum DGD value of compensation and optical fiber telecommunications system to allow remaining DGD value to determine according to optical fiber telecommunications system, wherein establish the maximum DGD=x of optical fiber telecommunications system, optical fiber telecommunications system allows remaining maximum DGD=y, then require bucking-out system resolution smaller or equal to 2y, therefore require the DGD value that smallest crystals produces in the optical delay line to be less than or equal to y, thereby the minimum value of n is by computing formula 2
N-1+ 1 〉=x/2y determines, determines the material and the length of birefringece crystal thus.
Beneficial effect of the present invention: 1. the variable light delay line adopts plurality of sections crystal and PR to fix by the ad hoc fashion arrangement, does not have movable part in the operating process, and is therefore simple in structure, stable performance, and it is little to be affected by the external environment; 2. coupler, Polarization Controller and optical collimator are the magnetic tape trailer fiber device, help being connected with fibre system; Its Polarization Controller is DC servo motor control, is convenient to fast automatic control polarization state.3. computer feeds back to the Polarization Controller control circuit with the directional information of the PMD of optical fiber telecommunications system, and Polarization Controller 2 is produced and the opposite polarization state of optical fiber telecommunications system PMD direction.4. realize the dynamic control of PMD compensation on the engineering easily, when 5. system does not have PMD, can not produce extra PMD.
Description of drawings
Fig. 1 is the Polarization Mode Dispersion Compensation Systems schematic diagram.
Embodiment
The present invention is to provide easy and system, coupled, be swift in response, power consumption is little, a kind of Polarization Mode Dispersion Compensation Systems that realizes and can dynamically control easily on the engineering.The optical collimator 3 of this system and by comprising that variable light delay line 4 that n+1 section birefringece crystal and n the polarization rotator PR based on magneto optical effect forms puts point-blank (n for the maximum DGD value that requires compensation according to optical fiber telecommunications system and certain definite natural number of DGD value of the permission remnants of system) with one heart with optical axis.The mode that is spaced of above-mentioned crystal and PR is for to be followed successively by the longest crystal from front to back, PR, and vice-minister's crystal, PR is until the shortest crystal.Feedback control circuit comprises that detector 5 and computer 6 connect with coupler 1, computer is connected (as shown in Figure 1) with Polarization Controller 2, variable light delay line 4 respectively again, be used for the directional information of PMD is fed back to Polarization Controller 2 control circuits, Polarization Controller 2 is produced and the opposite polarization state of optical fiber telecommunications system PMD direction; The size information of described optical fiber telecommunications system PMD is fed back to the control circuit of variable light delay line 4, the DGD value of variable light delay line 4 is equated with DGD in the described optical fiber telecommunications system.Above-mentioned coupler 1, Polarization Controller 2 and optical collimator 3 are the magnetic tape trailer fiber device, help being connected with fibre system; Its Polarization Controller 2 is convenient to fast automatic control polarization state for DC servo motor control.Can further be illustrated by following operation principle the present invention:
1) from the light beam of the optical fiber outgoing of the applied optical fiber telecommunications system of Polarization Mode Dispersion Compensation Systems, at first enter coupler 1, light beam by coupler 1 outgoing is divided into two bundles, wherein a branch ofly enter detector 5 as control signal, handle by computer 6, obtain the size and Orientation of the PMD of described optical fiber telecommunications system.2) computer feeds back to Polarization Controller 2 control circuits with the directional information of described optical fiber telecommunications system PMD, and Polarization Controller 2 is produced and the opposite polarization state of described optical fiber telecommunications system PMD direction.3) light beam enters collimater 3 from Polarization Controller 2, makes light beam become collimated light beam and penetrates.These collimater 3 operating distances should be greater than the length of variable light delay line 4.4) light beam enters variable light delay line 4 after collimater 3 outgoing, and computer 6 feeds back to the control circuit of variable light delay line 4 with the size information of described optical fiber telecommunications system PMD, and the DGD value of variable light delay line 4 is equated with DGD in the described optical fiber telecommunications system.5) variable light delay line 4 is by comprising what n+1 section birefringece crystal and n formed based on the polarization rotator of magneto optical effect.Fast axle or slow axis angle are 45 degree between two-phase vincial faces body, PR can make linearly polarized light polarization state rotation ± 45 degree, when PR spends linearly polarized light polarization state rotation+45, the fast axle of preceding faceted crystal overlaps with the slow axis of back faceted crystal, the DGD value of optical delay line is subtracted each other for the DGD value of independent two crystal, otherwise, when PR spends linearly polarized light polarization state rotation-45, the fast axle of preceding faceted crystal overlaps with the fast axle of back faceted crystal, and the DGD value of optical delay line is the DGD value addition of two crystal.By control crystal length or select suitable birefringece crystal material, can produce optical delay line with different resolution, by the hop count of control birefringece crystal, can produce abundant DGD state and enough big DGD value, therefore can satisfy the requirement of different occasions.N is certain natural number that allows remaining DGD value to determine according to maximum DGD value and system in the optical fiber telecommunications system, is determined by the remaining DGD value that system allows.Computing formula is as follows: establish maximum DGD=x in certain optical fiber telecommunications system, system allows maximum DGD=y, then require bucking-out system resolution (to go into principle by 4 houses 5 smaller or equal to 2y, the remaining DGD that half of compensator resolution allows for communication system), therefore require the DGD value that smallest crystals produces in the optical delay line to be less than or equal to y, determine the material and the length of birefringece crystal thus; Bucking-out system need produce N 〉=x/2y kind DGD value, and promptly 2
N-1+ 1 〉=x/2y, the minimum value of definite n thus.6) the light beam collimater 3 that enters the magnetic tape trailer fibre after optical delay line 4 outgoing connects and enters optical fiber telecommunications system.This invention does not have movable part owing to just adopt plurality of sections birefringece crystal and PR fixing by the ad hoc fashion arrangement in the operating process, therefore simple in structure, stable performance, and it is little to be affected by the external environment.Because the high birefringence crystal can produce very big DGD value in very short length, therefore under the condition that produces same DGD, its volume is relatively very little, and for example, its length of delay line that a kind of maximum can produce the DGD of 45ps only is 150mm.Because coupler, Polarization Controller 2, collimater all adopt the device of magnetic tape trailer fibre, so the ray machine part is few, it is little to be affected by the external environment, easy and optical fiber telecommunications system coupling.The method that adopts the variation of controlling magneto-optical crystal polarization angle of rotation to obtain different DGD values in the delay line is compared with the method that modes such as adopting machinery or liquid crystal are adjusted the DGD value, and speed is faster, and stable.In this delay line because minimum birefringent material in the general delay line is increased to two, and between two minimum birefringent materials, increased a PR, thereby solved the situation that does not have the DGD=0 state in the general bucking-out system, the PMD in therefore can the increase system based on birefringent material.In the automatically controlled part, Polarization Controller 2 driving voltage 12V, electric current is 0.65A, and each PR drive current is 50mA, and driving voltage is 2.5V under the 2KHz, so power consumption is little.Therefore whole system also is self adaptation and dynamic for by PMD in the feedback signal self compensating system.
Exemplify a calculated examples: be made as compensation DGD value at 45ps with interior optical fiber telecommunications system, the DGD of system's permission is 0.75ps.Calculate, for meeting the demands, the DGD≤0.75ps that needs the minimum length birefringece crystal to produce needs 30 kinds of DGD states, at least according to 2
N-1+ 1 〉=30, obtain n 〉=5.85, get n=6, promptly birefringece crystal is 7 sections, polarization rotator is 6.The PMD of this system value is bigger, and resolution requirement is not high, chooses the high birefringence crystal, as YVO4.The DGD value that 1mmYVO4 produces is 0.72ps, so its resolution can reach 1.44ps, and this result of calculation shows, from front to back according to 32mmYVO4, PR, 16mmYVO4, PR, 8mm YVO4, PR, 4mm YVO4, PR, 2mm YVO4, PR, 1mm YVO4, PR, the optical delay line that 1mm YVO4 arranges satisfies system requirements, can produce 0,1.44,2.88,4.32,, 46.08ps is totally 33 kinds of states, remaining DGD≤0.72ps.It is fast that magneto-optical crystal is chosen response speed, the magneto-optic thin film that saturation magnetic field is little etc., and coil adopts little enamelled wire or the other materials of inductance, to increase system response time and to reduce power consumption.Coupler adopts the coupler of suitable splitting ratio, can be advisable by the noise annihilation with the loss and the detector received signal that reduce light signal as far as possible.
Claims (4)
1. Polarization Mode Dispersion Compensation Systems, this system comprises a coupler, a Polarization Controller, a pair of optical collimator, one section variable light delay line and feedback control circuit, it is characterized in that: described a pair of optical collimator, variable light delay line are put point-blank with one heart with optical axis, and described variable light delay line is between described a pair of optical collimator; Detector of described feedback control circuit (5) and computer (6) are connected with coupler (1), computer (6) more respectively and Polarization Controller (2), variable light delay line (4) connects, light beam from the optical fiber outgoing of the applied optical fiber telecommunications system of Polarization Mode Dispersion Compensation Systems, at first enter coupler (1), light beam by coupler (1) outgoing is divided into two bundles, wherein a branch ofly enter detector (5) as control signal, handle by computer (6), obtain the size and Orientation of the PMD of described optical fiber telecommunications system, another bundle enters Polarization Controller (2), enters optical collimator from the light beam of Polarization Controller (2) outgoing; Computer (6) feeds back to the control circuit of Polarization Controller (2) with the directional information of the PMD of described optical fiber telecommunications system, and Polarization Controller (2) is produced and the opposite polarization state of described optical fiber telecommunications system PMD direction; Computer (6) feeds back to variable light delay line (4) with the size information of the PMD of described optical fiber telecommunications system, and the DGD value of variable light delay line (4) is equated with DGD in the described optical fiber telecommunications system, thereby reaches the purpose of compensated fiber communication system PMD.
2. a kind of Polarization Mode Dispersion Compensation Systems according to claim 1, it is characterized in that: described variable light delay line comprises n+1 section birefringece crystal and n the polarization rotator PR based on magneto optical effect, described crystal and PR are spaced, arrangement mode is for being followed successively by the longest crystal from front to back, PR, vice-minister's crystal, PR is until the shortest crystal; Its n+1 section birefringece crystal comprises that the crystal that n length is doubled and redoubled adds the crystal of shortest length in a n birefringece crystal with other; This PR is made of hot-wire coil and its inner magneto-optical crystal; By the size and Orientation of electric current in the control hot-wire coil, can control size and Orientation by the magnetic field of magneto-optical crystal, make the fast axle or the slow axis coincidence of front and back two crystal in the variable light delay line, thereby control adding, subtracting of two crystal DGD values; Wherein n is a natural number.
3. a kind of Polarization Mode Dispersion Compensation Systems according to claim 2, it is characterized in that: described birefringece crystal is YVO4, fast axle or slow axis angle are 45 degree between two-phase vincial faces body, PR can make linearly polarized light polarization state rotation ± 45 degree, by the hop count of control birefringece crystal, Polarization Mode Dispersion Compensation Systems can produce enough big DGD value.
4. a kind of Polarization Mode Dispersion Compensation Systems according to claim 2, it is characterized in that: described n requires the maximum DGD value of compensation and optical fiber telecommunications system to allow remaining DGD value to determine according to optical fiber telecommunications system, wherein establish the maximum DGD=x of optical fiber telecommunications system, optical fiber telecommunications system allows remaining maximum DGD=y, then require bucking-out system resolution smaller or equal to 2y, therefore require the DGD value that smallest crystals produces in the optical delay line to be less than or equal to y, thereby the minimum value of n is by computing formula 2
N-1+ 1 〉=x/2y determines, determines the material and the length of birefringece crystal thus.
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| CNB031501206A CN1264291C (en) | 2003-07-18 | 2003-07-18 | Polarization mould disporsion compensation system |
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| CNB031501206A CN1264291C (en) | 2003-07-18 | 2003-07-18 | Polarization mould disporsion compensation system |
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| CN1264291C true CN1264291C (en) | 2006-07-12 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1333285C (en) * | 2005-03-25 | 2007-08-22 | 清华大学 | Polarization controller and use thereof |
| CN101834673B (en) * | 2010-05-13 | 2013-09-04 | 武汉邮电科学研究院 | Polarization mode dispersion compensation method |
| CN102044835B (en) * | 2010-12-09 | 2012-07-25 | 中国电子科技集团公司第四十四研究所 | Narrow-pulse polarization controller |
| CN102170312B (en) * | 2011-04-26 | 2013-10-30 | 聊城大学 | Self-adaptive polarization mode optical dispersion compensation method |
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