CN1476185A - Polarization mould disporsion compensation system - Google Patents
Polarization mould disporsion compensation system Download PDFInfo
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- CN1476185A CN1476185A CNA031501206A CN03150120A CN1476185A CN 1476185 A CN1476185 A CN 1476185A CN A031501206 A CNA031501206 A CN A031501206A CN 03150120 A CN03150120 A CN 03150120A CN 1476185 A CN1476185 A CN 1476185A
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- 230000010287 polarization Effects 0.000 title claims abstract description 75
- 239000013078 crystal Substances 0.000 claims abstract description 59
- 230000003287 optical effect Effects 0.000 claims abstract description 30
- 239000000835 fiber Substances 0.000 claims abstract description 16
- 239000006185 dispersion Substances 0.000 claims abstract description 15
- 239000013307 optical fiber Substances 0.000 claims description 19
- 239000000463 material Substances 0.000 claims description 11
- 229910009372 YVO4 Inorganic materials 0.000 claims description 10
- 238000004891 communication Methods 0.000 claims description 5
- 238000000034 method Methods 0.000 description 14
- 230000005540 biological transmission Effects 0.000 description 5
- 239000004973 liquid crystal related substance Substances 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 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
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
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Abstract
The system includes placing optical collimator and variable optical retardation line on a straight line, serial-connecting coupler, detector and computer and then forming feedback control circuit by connecting the computer separately with polarization controller and the said redaration line of which coupler, polarization controller and optical collimator having tail fibre device, polarization controller is controlled by DC servo motor and the said redardation line applies birefringer crystal and PR arranged in special manner. The directional information of system PMD is fed back by feedback control circuit to polarization controller circuit to generate counter-polarization state for counterbalancing to each other to realize purpose of polarization mode dispersion compensation.
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, ppl277 ~ 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; Described feedback control circuit is by coupler, detector and computer series connection, computer connects to form with Polarization Controller, variable light delay line respectively again, be used for direction and the size information of PMD are fed back to Polarization Controller and variable light delay line control circuit respectively, the polarization state direction that Polarization Controller is produced is opposite with PMD direction in the communication system, the DGD value of delay line equates with DGD in the system, thereby reaches the purpose of bucking-out 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 its birefringece crystal comprises that crystal that n length is doubled and redoubled adds the crystal of a shortest length in addition; PR is made of hot-wire coil and its inner magneto-optical crystal.By the size and Orientation of electric current in the control coil, can control size and Orientation by the magnetic field of magneto-optical crystal, make in the delay line before and after the fast axle of two crystal overlaps with fast axle or spool overlaps soon with slow axis, thereby control adding, subtracting of two crystal DGD.
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 until the shortest crystal.Crystal can be YVO4 or other birefringent materials, and fast axle (or slow axis) angle is 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 certain natural number that system allows remaining DGD value to determine according to optical fiber telecommunications system, and described a value allows remaining DGD value to determine by system; Computing formula is as follows: establish the maximum DGD=x of certain optical fiber telecommunications system, system allows maximum DGD=y, then require bucking-out system resolution smaller or equal to 2y, the DGD value a that therefore requires smallest crystals generation in the optical delay line determines the material and the length of birefringece crystal thus smaller or equal to y; 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.
Beneficial effect of the present invention: 1. optical 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 system, and Polarization Controller 2 is produced and the opposite polarization state of system's 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 form based on the polarization rotator (PR) of magneto optical effect 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 system's PMD direction; The size information of PMD is fed back to variable light delay line control circuit, the DGD value of delay line is equated with DGD in the 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 optical fiber outgoing, at first enter coupler, wherein a branch ofly enter detector 5 as control signal, handle by computer 6, obtain the size and Orientation of the PMD of system, another bundle enters Polarization Controller 2.(2) computer feeds back to Polarization Controller 2 control circuits with the directional information of the PMD of system, and Polarization Controller 2 is produced and the opposite polarization state of system's 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 optical delay line Unit 4.(4) light beam enters variable light delay line 4 after collimater 3 outgoing, and computer 6 feeds back to variable light delay line 4 unit controls circuit with the size information of PMD, and the DGD value of delay line Unit 4 is equated with DGD in the system.(5) delay line 4 is by comprising what n+1 section birefringece crystal and n formed based on the polarization rotator (PR) of magneto optical effect.Fast axle (or slow axis) angle is 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.If the DGD=a that the shortest crystal produces in this delay line then by controlling the magnetic direction of n PR respectively, can produce 0,2a, 4a, 6a, 8a ... 2a2
N-1Totally 2
N-1+ a kind of DGD state, resolution are 2a.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, and a value 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 the DGD value a that requires smallest crystals generation in the optical delay line determines the material and the length of birefringece crystal thus smaller or equal to y; 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 DG=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 32mm YVO4, PR, 16mm YVO4, 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 (5)
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 optical collimator, variable light delay line are put point-blank with one heart with optical axis; Described feedback control circuit is by coupler, detector and computer series connection, computer connects to form with Polarization Controller, variable light delay line respectively again, be used for direction and the size information of the PMD of system are fed back to Polarization Controller and variable light delay line control circuit respectively, the polarization state direction that Polarization Controller is produced is opposite with PMD direction in the communication system, the DGD value of delay line equates with DGD in the system, thereby reaches the purpose of bucking-out system PMD.
2. according to claim 1. a kind of Polarization Mode Dispersion Compensation Systems is characterized in that: 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.
3. according to claim 1. a kind of Polarization Mode Dispersion Compensation Systems, 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, and its birefringece crystal comprises that crystal that n length is doubled and redoubled adds the crystal of a shortest length in addition; PR is made of hot-wire coil and its inner magneto-optical crystal; By the size and Orientation of electric current in the control 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 delay line, thereby control adding, subtracting of two crystal DGD values.
4. according to claim 1. a kind of Polarization Mode Dispersion Compensation Systems is characterized in that: described crystal and PR are spaced, and arrangement mode is for to be followed successively by the longest crystal from front to back, PR, vice-minister's crystal, PR is until the shortest crystal; Crystal can be YVO4 or other birefringent materials, fast axle (or slow axis) angle is 45 degree between two-phase vincial faces body, and PR can make linearly polarized light polarization state rotation ± 45 degree, by the hop count of control birefringece crystal, can produce enough big DGD, therefore can satisfy the requirement of different occasions.
5. according to claim 3. a kind of Polarization Mode Dispersion Compensation Systems is characterized in that: described n is the maximum DGD value that requires compensation according to optical fiber telecommunications system and certain natural number that system allows remaining DGD value to determine; Described a value allows remaining DGD value to determine by system; Computing formula is as follows: establish the maximum DGD=x of certain optical fiber telecommunications system, system allows maximum DGD=y, then require bucking-out system resolution smaller or equal to 2y, the DGD value a that therefore requires smallest crystals generation in the optical delay line determines the material and the length of birefringece crystal thus smaller or equal to y; 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.
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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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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1333285C (en) * | 2005-03-25 | 2007-08-22 | 清华大学 | Polarization controller and use thereof |
| CN101834673A (en) * | 2010-05-13 | 2010-09-15 | 武汉邮电科学研究院 | Polarization mode dispersion compensation method |
| CN102044835A (en) * | 2010-12-09 | 2011-05-04 | 中国电子科技集团公司第四十四研究所 | Narrow-pulse polarization controller |
| CN102170312A (en) * | 2011-04-26 | 2011-08-31 | 聊城大学 | Self-adaptive polarization mode optical dispersion compensation method |
-
2003
- 2003-07-18 CN CNB031501206A patent/CN1264291C/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1333285C (en) * | 2005-03-25 | 2007-08-22 | 清华大学 | Polarization controller and use thereof |
| CN101834673A (en) * | 2010-05-13 | 2010-09-15 | 武汉邮电科学研究院 | Polarization mode dispersion compensation method |
| CN102044835A (en) * | 2010-12-09 | 2011-05-04 | 中国电子科技集团公司第四十四研究所 | Narrow-pulse polarization controller |
| 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 |
| CN102170312A (en) * | 2011-04-26 | 2011-08-31 | 聊城大学 | Self-adaptive polarization mode optical dispersion compensation method |
| CN102170312B (en) * | 2011-04-26 | 2013-10-30 | 聊城大学 | Self-adaptive polarization mode optical dispersion compensation method |
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