CN201926824U - Polarization mode simulation and dispersion compensation device and optical wavelength division multiplexing communication device thereof - Google Patents
Polarization mode simulation and dispersion compensation device and optical wavelength division multiplexing communication device thereof Download PDFInfo
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- CN201926824U CN201926824U CN2010202282777U CN201020228277U CN201926824U CN 201926824 U CN201926824 U CN 201926824U CN 2010202282777 U CN2010202282777 U CN 2010202282777U CN 201020228277 U CN201020228277 U CN 201020228277U CN 201926824 U CN201926824 U CN 201926824U
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Abstract
The utility model relates to a polarization mode simulation and dispersion compensation device and an optical wavelength division multiplexing communication device thereof, which belong to the technical field of optical polarization devices and application thereof. An optical device comprises a group of differential group delay units, a group of adjustable optical polarization rotators and a controller, wherein the differential group delay units are arranged at intervals along a light transmission direction; the adjustable optical polarization rotators perform different polarization rotation; each adjustable optical polarization rotator is arranged in a gap between two differential group delay units respectively; and the controller is used for communicating with the adjustable optical polarization rotators, and is connected with each adjustable optical polarization rotator respectively. Due to the adoption of a plurality of adjustable optical polarization rotators, the device has different discrete polarization rotation states for generating and analyzing the polarization states of a beam of light under different applications.
Description
Background technology
The utility model belongs to optical information processing and optical information transmission technique field, particularly polarization mode emulation device and polarization mode dispersion compensator spare.
Background technology
Utilize that optical device or system record the optical characteristics, parameter etc. of light many-sided application can be arranged.For example, this optical measurement can be used for the performance and the condition of work of decision device or system.Light polarization information is an important parameter of optical signalling in various optical systems, device, the application.The polarisation of light information of two polarization state quadratures, Optical Signal To Noise Ratio, differential group delay etc. all are very important parameters in the optical application.In optical fiber telecommunications system, polarization mode dispersion (PMD) can influence the normal performance and the performance of optical device or system greatly, and the speed of communication system transmits is fast more, this influence just strong more (for example, from 10Gbps to 40Gbps, 100Gbps even higher).Polarization mode dispersion will cause that mainly two main polarized components of a light signal propagate so expanded the bit width of signal with different speed.The result causes it can increase the generation of the bit error rate (BER) and service disruption.Different with other system defect (chromatic dispersion for example, polarization mode dispersion to the influence of system be at random and also vertiginous in time, therefore reducing polarization mode dispersion also becomes very difficult.
Summary of the invention
The purpose of this utility model provides a kind of polarization mode emulation and dispersion compensation device and optical wavelength-division multiplex communicator thereof, by adopting a plurality of tunable optical polarization rotators, this tunable optical polarization rotator has different discrete polarization rotation attitudes, is used for producing and analyzing a branch of polarization state of light under different application.
The utility model proposes a kind of polarization mode emulation and dispersion compensator device, it is characterized in that, comprise with the lower part:
One group differential group delay (DGD) unit, each Differential Group Delay unit is spaced along the direction of propagation of light;
One group of tunable optical polarization rotator that produces different polarization rotations, each tunable optical polarization rotator is placed on respectively in two spaces between the differential group delay unit;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each tunable optical polarization rotator respectively.
The birefringence effect of light is realized in above-mentioned each DGD unit, and this effect is introduced Differential Group Delay to restrainting between the orthogonal polarisation state through DGD unit input light two.Each DGD unit is discrete each other, is placed on respectively by light inlet to receive on the light path of incident light.The rotatable polarization state between DGD unit and next DGD unit of each tunable optical polarization rotator.This tunable optical polarization rotator comprises a continuously adjustable optical rotator at least, realize rotation polarization state continuously with continuously adjustable control signal, reach the target polarization state of light, and discrete tunable optical polarization rotator produces the discrete polarization rotation of two or more differences with corresponding discrete control signal.Entire device also comprises a controlled module can communicate by letter with the tunable optical polarization rotator, realizes the control of each tunable optical polarization rotator.This control module is adjustable can produce different continuously adjustable control signal value, realize controlling continuous tunable optical polarization rotator, and produce a discrete value and regulate each independent discrete tunable optical polarization rotator for each discrete control signal, produce corresponding one or two or more polarizations rotation attitude.This discrete attitude tunable optical polarization rotator can be adjusted to the binary states polarization rotator, and each can change by its polarisation of light anglec of rotation, realizes by first rotation angle with reciprocal second rotation angle of first rotation angle.
The birefringence effect of light is realized in above-mentioned each Differential Group Delay (DGD) unit, and this effect is introduced Differential Group Delay to restrainting between the orthogonal polarisation state through DGD unit input light two.The DGD unit piece is discrete each other to be arranged in the light path, and the tunable optical polarization rotator is arranged in respectively between the DGD unit.Each tunable optical polarization rotator is rotatable polarization state between DGD unit and next DGD unit.The control signal of each tunable optical polarization state spinner response produces three different polarization rotations, control module and tunable optical polarization rotator are controlled each light polarization spinner separately, and one that produces in three different polarization rotation attitudes by DGD unit and tunable optical polarization rotator produces single order or high-order polarization mode dispersion.
The utility model also proposes a kind of optical wavelength-division multiplex (WDM) communicator, it is characterized in that, comprises with the lower part:
A WDM demodulation multiplexer of from different signal paths and WDM wavelength, isolating the WDM signal;
One group of optical receiver is positioned at different signal path positions separately;
Wherein, each optical receiver contains a polarization mode dispersion compensator, and this polarization mode dispersion compensator comprises:
One group of Differential Group Delay (DGD) unit, each DGD unit is spaced along the direction of propagation of light;
One group of tunable optical polarization rotator, each tunable optical polarization rotator are placed between two DGD unit;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each tunable optical polarization rotator respectively.
Above-mentioned Wave division multiplexer/demultiplexer is used for isolating different wavelength-division multiplex signals from different signal paths; Optical receiver in the unlike signal path, corresponding, each optical receiver receives one road wavelength-division-multiplexed optical signal of specific wavelength, and extracts data from the optical wavelength division multiplexed signal that receives.Each optical receiver comprises a polarization mode dispersion (PMD) compensator, it comprises Differential Group Delay (DGD) unit late, crossed polarized light to the light by the DGD unit produces birefringence, the DGD unit is discrete each other to be arranged in the light path, adjustable light polarization spinner is arranged in the space, DGD unit accordingly, an adjustable light polarization spinner, between two DGD unit, rotate polarization state of light, the control signal of each tunable optical polarization rotator correspondence produces three different polarization rotations, control module and adjustable light polarization spinner are controlled each light polarization spinner separately, and one that the light by the DGD unit is produced in three different polarization rotation attitudes by Differential Group Delay device and adjustable polarization rotator produces single order or high-order polarization mode dispersion.The tunable optical polarization rotator can be subdued the polarization mode dispersion of the wavelength-division multiplex signals of reception.
The utility model also proposes a kind of polarization mode emulation and dispersion compensation device, it is characterized in that, comprises following a few part:
One in order to accept the input port of light;
One group of Differential Group Delay unit, each differential group delay unit is spaced along the direction of propagation of the light that input port is accepted;
One group in order to produce the discrete attitude tunable optical polarization rotator of two or more different polarization state directions, and each tunable optical polarization rotator is placed on respectively between two differential group delay;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each discrete attitude tunable optical polarization rotator respectively.
Characteristics of the present utility model:
The utility model is by adopting a plurality of tunable optical polarization rotators, and this tunable optical polarization rotator has different discrete polarization rotation attitudes, can be used for producing and analyzing a branch of polarization state of light under different application.
Description of drawings
Fig. 1 has shown a kind of optical device that typically can be used for PMD compensation and PMD emulation of the present utility model, and this device is that utilization has the polarization rotator of 3 discrete polarization states and the birefringent material of different Differential Group Delays is constructed.
What Fig. 2 showed is a kind of polarization rotator that three kinds of discrete polarization states are typically arranged of mentioning among Fig. 1.
What Fig. 3 showed is the optical device that another kind of the present utility model typically can be used for PMD compensation and PMD emulation, and this device is constructed with the birefringent material with different differential group delay based on the polarization rotator with two discrete polarization states.
Fig. 4 of the present utility modelly a kind ofly is used for the optical device that compensates PMD and carry out PMD emulation based on the mixed polarized spinner that has two discrete polarization states and three discrete polarization states and the Differential Group Delay device that has a distinct group time delay.
What Fig. 5 showed is a kind of typically have at least the PMD compensation of a continuous adjustable polarization rotator and the optical device of emulation of the present utility model.Polarization rotator has different polarization states in this device, and the Differential Group Delay device has different group delays.
What Fig. 6 showed is the function of second order PMD for differential group delay, and this image is based on that the optical device of the Differential Group Delay device of the polarization rotator that has three discrete polarization states among Fig. 5 and distinct group time delay draws.What Fig. 7-A and Fig. 7-B showed also is the function of second order PMD about differential group delay, be based on continuous adjustable polarization rotator respectively and have that the device of the polarization rotator of two discrete polarization states draws, the DGD unit in this device has different group delays.
The example that is based on the optimized PMD emulation of polarization state on the device shown in Figure 5 basis that Fig. 8 shows.
The PMD tolerance limit test that Fig. 9 A device shown is used for being, the i.e. tolerance limit of PMD in optical fiber communication passage.
Fig. 9 B and 9C show be about the bit error rate (BER) of Fig. 9 A device respectively with the relation of differential group delay and PMD.
What Figure 10 showed is wavelength-division multiplex (WDM) device that uses Fig. 1-5 and device shown in Figure 2 to be used for estimating and judging PMD.
What Figure 11 A and 11B showed is two optical WDM communicators of the present utility model, and these two devices can utilize backfeed loop that PMD is provided compensation based on the device shown in Fig. 1-5.
What Figure 12 and 13 showed is two optical communication apparatus that typically have PMD detection and compensation of the present utility model.
Embodiment
The utility model is disclosed to be optics PMD compensation and PMD analog device, and these devices use has discrete polarization state polarization rotator, as the bifurcation polarization rotator, and three state polarization spinner, bifurcation and ternary polarization rotator combination; The utility model has also been described PMD compensation and the analog device that a kind of use has discrete polarization state and at least one continuous adjustable polarization state spinner.The polarization rotator that has discrete polarization state can make light produce two kinds or the discrete polarization rotation attitude of more kinds of difference under the effect of its control signal.For example, a three state polarization spinner can make light produce three kinds of different polarization rotation attitudes under different control signal effects.Employed polarization rotator (as 2 attitudes, three state polarization spinner) all is the single order, second order and the high-order PMD use that produce in conjunction with the substandard multistage birefringence of different Differential Group Delays in described PMD compensation and the emulation device.Therefore, can effectively utilize above-mentioned PMD compensation and emulator to carry out compensation and the emulation of PMD.
The device 100 that Fig. 1 shows is of the present utility model a kind of based on the PMD compensation of three state polarization spinner and the optical device of emulation, and device 100 comprises a plurality of different DGD unit 110 and tunable optical polarization rotator 120 two parts.Each DGD unit 110 is by birefringent material structure, when light can produce birefringence during by this material, makes light pass through the polarization state that the Differential Group Delay parts can the individual quadrature of companys of generation like this.Each DGD (Differential Group Delay) part arranges successively along the direction of light ray propagation.Other is placed on tunable optical polarization rotator 120 minutes in the slit of per two DGD unit, and the light of previous DGD unit outgoing will enter a back DGD unit through the modulation of tunable optical polarization rotator.Thereby each tunable optical polarization rotator produces three kinds of different polarization states (being the three state polarization spinner) by a control signal control.Control module 130 will control these 3 different polarization rotation attitudes of polarization rotator and light by DGD unit 110 and tunable optical polarization rotator after single order and the more generation of high-order PMD.This device can be used to reduce the PMD of light signal in the wavelength-division multiplex system, therefore can be used as a PMD compensating device, and this device can also be used to produce the various simulated effects of PMD.
The DGD unit 110 of different length can produce different Differential Group Delays, as shown in Figure 1, the DGD unit of making by birefringent material of the same race 110 along the light ray propagation direction from left to right length successively decrease, this length also can from left to right increase progressively equally.In some implementation methods, the length of DGD unit 110 can be according to parameter 2 or 2
mThe ratio increasing or decreasing, wherein m is an integer.Can produce fixing DGD numerical value by disposing these DGD unit.
In addition, DGD unit 110 also can produce variable Differential Group Delay down by the effect of a control signal.For example, for electrooptical material, can make DGD unit 110 produce variable Differential Group Delay parameter by changing control voltage.Other technologies also can be used for producing may command DGD unit 110.For example, optical fiber squeezer can be coupled in the polarization maintaining optical fibre optical fiber is pushed, this optical fiber promptly can be used as adjustable DGD unit 110; Cascade multistage birefringence in the time of also can passing through the light ray propagation different length in addition, and the birefringent elements of adjoining with the coupling of tunable optical spinner forms DGD unit 110.Because light its polarization state when propagating can change owing to the effect of spinner, then light its Differential Group Delay parameter when propagating also can change.In some implementation methods, above-mentioned tunable optical polarization rotator also can be polarized switch and replace, polarization state of light conversion between two states that this switch receives control, first kind of state is that the fast and slow axis direction was constant after light passed through birefringent elements, and second kind of state is that the fast and slow axis direction was exchanged after light passed through birefringent elements.When the polarization state switch was transferred to first kind of state, the Differential Group Delay of the birefringent elements that two pictures adjoin mutually increased, when being transferred to second kind of state, this time minimizing of postponing a meeting or conference.In some implementation methods, the tunable optical polarization rotator can make together with polarization switch and be used for being connected adjacent birefringent elements to form variable DGD unit 110.These typical DGD unit 110 implementation methods have a detailed description (patentee is Yao Xiaotian) in United States Patent (USP) NO5978125 and NO7227686, also open in the lump as reference of the present invention simultaneously.
What Fig. 2 showed is the realization of a kind of typical 3 attitude tunable optical polarization rotators 120 (as Fig. 1) of the present utility model.Each tunable optical polarization rotator in this method comprises two bifurcation polarization rotators of putting along light path 210,220.Each bifurcation spinner 210 or 220 can rotate to second rotation attitude that the reverse anglec of rotation is identical from first anglec of rotation with polarization state of light.Above-mentioned two spinners are put together to use and can be produced three kinds of different polarization rotation attitudes.Control module 130 can be used for controlling this two bifurcation polarization rotators 210 and 220, and total like this polarization anglec of rotation is the twice of the anglec of rotation first time.This is first polarization state that ternary tunable optical polarization rotator 120 can reach.Control module can also make first bifurcation spinner 210 produce the polarization rotation of a certain angle, second spinner then produces the rotation of a reverse equal angular, must the anglec of rotation be the comprehensive of these two rotations like this, because this twice rotation size equidirectional is opposite, so comprehensively be 0.This is second polarization state that ternary tunable optical polarization rotator 120 can reach.If all along the reverse certain angle of deflection, then the total angle of polarization then is the twice of above-mentioned second polarizer deflection angle to two bifurcation spinners 210 and 220, this is the 3rd polarization state of ternary tunable optical polarization rotator 120.
In some implementation methods, bifurcation polarization rotator 210 and 220 can be with the influence of magneto-optical rotator to avoid mechanical movable part to bring.These utilize the spinner that does not need moving device of magneto-optic or other method can improve the performance of device.For example, the bifurcation magneto-optical rotator can have following characteristics: when (1) was added on the magneto-optical rotator when the positive voltage greater than saturation voltage, spinner can make+22.5 ° of SOP rotations; (2) when the negative voltage greater than saturation voltage is added on the spinner, then the SOP rotation is-22.5 °.Other polarization rotator also can reach above-mentioned effect as liquid crystal polarized spinner and Solid Double refracting crystal spinner under the control of appropriate signal.
Lift a special case, suppose that the bifurcation spinner anglec of rotation first time is+22.5 °, the anglec of rotation is-22.5 ° for the second time, and then must the polarization rotation have following three kinds of possibilities: (1) total anglec of rotation all is+22.5 ° for+45 ° two bifurcation spinner rotation angle; (2) total polarization angle is 0 °, and first spinner rotation angle is+22.5 °, and second is-22.5 °;
(3) total deflection angle is-45 °, and two spinner rotation angle all are-22.5 °.This is sandwiched adjacent DGD unit to spinner just can form a simple PMD source.When the SOP anglec of rotation be+45 ° the time, the Differential Group Delay of the optical axis of these two crystal can be maximum; When the SOP anglec of rotation was-45 °, then this Differential Group Delay reached minimum; When the SOP anglec of rotation is 0+ °, then have between two optical axis of crystal+45 ° differential seat angle, thereby produce second order PMD, therefore, when being 0, the polarization anglec of rotation can cause the PMD effect of PMD compensation and emulation device generation high-order.
The unit number that the value of PMD equals the birefringence portion material adds 1 or can be expressed as 3
N(N is the right number of spinner), for example during N=6, the value of PMD is 729.The value of DGD (under the single order PMD situation) then is 2N., and for example during N=6, the value of DGD is 64.Utilize the value of the PMD that above-mentioned formula draws to be 3N, the maximal value of DGD then is half because the scope of DGD value be-DGDmax/2 is to+DGDmax/2.
In Fig. 2, two the bifurcation polarization rotators 210 and 220 that constitute ternary tunable optical polarization rotator 120 can be chosen in that the different time is activated so that of short duration loss minimum.
What Fig. 3 showed is a kind of optical device 300 that is used for PMD compensation and emulation based on the bifurcation polarization rotator of the present utility model.Device 300 is similar with the structure of device 100, has just replaced three state polarization spinner in shown in Figure 2 with a bifurcation polarization rotator.The unit number that this device PMD value equals the birefringence portion material adds 1 or can be expressed as 2N, and this PMD value than device shown in Figure 1 is little, under both DGD unit 110 the same number of situations.Polarization rotator shown in Figure 3 is more cheap than ternary spinner, because only use a bifurcation spinner in the system.
Fig. 4 shows is of the present utility modelly a kind ofly to mix and have the PMD compensation of birefringent material structure of distinct group time delay and an optical device of emulation based on bifurcation and three state polarization spinner.The quantity of bifurcation polarization rotator 210 and ternary tunable optical polarization rotator 120 and relative position can be decided according to special demand and application.
Above-mentioned PMD compensation and emulation device based on spinner with discrete polarization state and DGD unit 110 provides condition to realizing various specific PMD values.In some applications, except specific PMD value, it may also need from a specific PMD value to can be adjustable continuously another specific PMD value.Use one or more continuous adjustable polarization rotators to replace the continuous variation that the spinner that only has discrete attitude can provide the PMD value, the polarization rotator that has discrete attitude with those uses is compared, and has increased the quantity of PMD value.
Like this one is used the equipment of one or more continuous adjustable polarization rotator also can comprise some DGD unit, thereby can to light by the DGD unit after the variation of birefringence and difference group delay probe into, these continuous adjustable polarization rotators between adjacent DGD unit can be rotated the polarization direction from previous DGD unit emergent light.Spinner with discrete polarization rotation attitude is contained in the continuous adjustable polarization rotator.The polarization rotator of each discrete attitude can produce 2 or more polarization rotation attitude under the effect of control signal.And its polarization rotation under control signal (as voltage) effect of adjustable polarization rotator can change in a scope continuously.The polarization rotator that a kind of control model will be controlled each discrete attitude respectively separately has the polarization rotator that different polarization is rotated attitude with generation.This control model also can be used in the control of continuous adjustable polarization rotator.
The of the present utility model a kind of typical PMD that Fig. 5 shows compensates and simulate optical device 500, comprises the DGD unit of a continuous adjustable polarization rotator 510, the tunable optical polarization rotator 120 or 210 of specific discrete attitude, different Differential Group Delays.In this device, continuous adjustable polarization rotator 510 is placed on device to begin between part first and second the DGD unit, and device 120 or 210 then is placed on continuous adjustable spinner back.In other device, continuous adjustable polarization rotator also can be placed on other positions of device.
Also can comprise in above-mentioned each device: one receives input light and controls the input polarization controller of importing polarization state of light, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator; One in order to survey the photo-detector through the output light of differential group delay unit and tunable optical polarization rotator, is connected to the output terminal of each tunable optical polarization rotator; Error monitoring device in order to the bit error rate of measuring light detector output is connected the output terminal of photo-detector; Feedback controller in order to the bit error rate that reduces output light is connected the input end of photo-detector.
Also can comprise in perhaps above-mentioned each device: one receives input light and controls the input polarization controller of importing polarization state of light, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator; One in order to survey the photo-detector through the output light of differential group delay unit and tunable optical polarization rotator, and the output terminal with each tunable optical polarization rotator links to each other respectively; A feedback controller that extracts radio spectrum maximal value or minimum value is connected the output terminal of photo-detector.
Fig. 1-5 has introduced some some researchs about PMD.Some is relevant with optical wavelength for the PMD that device that Fig. 1-5 is introduced produces, and some and optical wavelength it doesn't matter.PMD value that the wavelength that is produced by device shown in Fig. 1-5 relies on or state can make PMD compensation and emulation complexity, thereby make it have at wavelength-division multiplex and other that application becomes difficult in system of different wave length light wave.Therefore, need device under the situation that does not rely on optical wavelength, can compensate and emulation to PMD.
What Fig. 6 showed is by second order PMD (SOPMD) that utilizes three state polarization spinner shown in Figure 1 to produce and the relation between the DGD.Second order PMD value is distributed in each zone of this figure.The second order PMD value that this device produces lacks continuous variation with respect to the DGD value, can also find that the second order PMD value of this device generation has only minority not rely on the optical wavelength value.
It should be noted that if device shown in Figure 5 only at the continuously adjustable polarization rotator of input end, all uses the bifurcation spinner in other parts, can realize that then all PMD values that produce during this period are all irrelevant with optical source wavelength.Fig. 7 A and 7B show is relation between this device SOPMD (second order PMD) and the DGD.What Fig. 7 A showed is the variation of DGD value SOPMD when 0-100ps changes.Compare with the PMD-DGD figure of Fig. 6, only all use the device of bifurcation spinner that quasi-continuous PMD numerical value can be provided with continuously adjustable polarization rotator in other parts at input end.
DGD unit by a series of given bifurcation polarization rotators and fixed value and regulate continuous adjustable polarization rotator continuously and can obtain PMD-DGD curve shown in 7B.This PMD-DGD figure is continuous in some zones, and therefore this quasi-continuous PMD curve makes device shown in Figure 5 have advantage in PMD compensation and emulation.
Device shown in Fig. 1-5 can be realized compensating and simulated effect to reach the PMD that needs in different optical devices or system, and concrete example can be with reference to device shown in Figure 1 100, and the device shown in Fig. 2-5 also can be realized needed function.
Shown in Figure 8 is the PMD emulation device of optimizing according to device shown in Fig. 1-5 100 800.In the light path of device 800, be to have used Polarization Controller (PC) 810 in the front, DGD unit of the device 100 shown in Fig. 1 or Fig. 2-5, be used for light beam of accepting to import 801 and the polarization state of controlling this input beam, and to produce output beam be 802.Input polarizer 820 is placed in the light path DGD unit and adjustablely revolves before the inclined to one side device and after the Polarization Controller (PC) 810, be used for measuring the input polarisation of light that is received from Polarization Controller 810.In addition, an output analyzer 830 is placed on DGD and the adjustable inclined to one side device back of revolving is used for measuring from DGD and adjustable output polarization state of light of revolving inclined to one side device.Control module 840 one of is measured below the control at least according to input polarization and output polarization by central processing unit and circuit interface: (1) input polarization controller; (2) tunable optical is revolved inclined to one side device.
When carrying out the experiment of the PMD upper limit of a communication system with device shown in Figure 8 800, require the SOP of input to be consistent with the maximum PMD effect in PMD source.Device shown in Figure 8 can be used for realizing the Automatic Optimal of polarization state when PMD obtains different value.Device shown in Figure 8 specifically can produce different PMD values by the ternary spinner with computer or microprocessor control.All device 100 issuable PMD values can be listed in the table.The user can select different PMD values from table, on the other hand, also the statistical distribution that can obtain single order and second order PMD by device shown in Figure 8 is used corresponding function by writing corresponding program, and for example Maxwellian distributes.The PMD value can obtain by the statistics that characteristics in the form distribute.
In Another application, device shown in Figure 8 can be used for the optimization of DGD for-45 polarization states when spending.This device has a Polarization Controller (PC) and Polarization Detection device at input end.The Polarization Detection device can be a polarizer or a polarization beam apparatus, and its direction is consistent with the birefringent material optical axis direction in the PMD generator.Processor receives the information of detecting device and according to resulting signal controlling PC.For example, processor can indicate PC to align with the birefringent material optical axis angle by programmed control.
In addition, device shown in Figure 8 can be used for the polarization optimization of PMD value when the poorest.The parameter that PMD changed when the detecting device that can place some other types at output terminal detected degree of polarization (DOP) and other light by this device.Processor can be adjusted SOP according to the numerical value of polarization degree by indication Polarization Controller PC after receiving the signal of second detecting device.Processor also can be controlled the generation of different value PMD.For example, processor can detect second Polarization Detection device to such an extent that DOP minimizes by programmed control Polarization Controller PC.Other parameter values that processor can also obtain numerical value and the detecting device 1,2 of DOP compare to observe the influence of PMD.
Fig. 9 A shows is to be used for the device of the PMD upper limit that can tolerate in the measuring fiber communication system.Device 800 shown in Figure 8 is herein as the PMD source, and light source TX910 is used for producing and the collimation input beam incides in the instrument 100 it, and optical receiver RX920 is placed in the bottom of instrument 100 and output analyzer 830.Error rate tester 930 is used for measuring the bit error rate of 920 output signals.Device shown in Fig. 9 A is the instrument at the worst DGD or PMD influence.Along with the DGD or the constantly rising of PMD value of device 100, the data that RX920 received feed back to and detect its bit error rate in the error rate tester 930.The corresponding relation of the bit error rate and DGD and PMD numerical value is respectively shown in Figure 94 B, 94C.The upper limit of DGD, PMD promptly is defined as pairing DGD, PMD value when the bit error rate surpasses user's preset threshold.
Device shown in Fig. 9 A also can be used as the PMD compensator.Device 800 shown in Figure 8 can be used as a pattern receiver on detector 920 tops herein.Device 800 input ends receive a light signal, and being optically coupled in the optical fiber that this optical signals light source 910 is sent produces.The processor of device 800 receive polarization detector 830 detect DOP, PMD information, indication PC810 adjusts input SOP, the DOP value of the light signal that detects by detector 830 can reach maximum like this.When the corresponding PMD value of DOP reaches maximum, think that PMD can be compensated.In order to reach optimum PMD compensation, when PC810 adjusted the SOP input, the PMD value also can change.It is relevant that can optimum PMD compensation and optimum PMD setting and DOP get maximal value.
The wdm system that is to use PMD compensator 800 that Figure 10 shows, device 800 is measured and compensating device based on being used for link PMD shown in shown in Figure 1 or Fig. 2-5.In this system, a plurality of optical sender TXs1010 produce the wdm optical signal of different wave length.Wavelength division multiplexer MUX 1020 connects wdm optical signal to optical fiber link 1040, receives output signal at receiving end.At receiving end, WDM demodulation multiplexer (DeMux) 1030 is divided into WDM signal separately along different propagated with the WDM signal of the different wave length that receives.In each light path, device 800 provides the dispersion compensation of each WDM signal, and signal can be detected to do other processing in the downstream.
In the PMD of device 800 compensation model, as Fig. 8, when the PMD compensation was optimum, corresponding single order, second order PMD value can think approaching with optical fiber link 1040.When specifically, the worthwhile PC810 adjustment of processor change PMD SOP value makes the DOP value maximum.The value of single order, second order PMD is relevant with the maximum DOP value that the PMD source produces, and its value is considered to approximate with the PMD value of the joints of optical fibre 1040.
What Figure 11 A and 11B showed is two wdm systems that provide PMD to compensate, and PMD compensating device 1101 is mainly finished based on the device shown in Fig. 1, Fig. 2-5.Shown in Figure 11 A, the upstream that PC810 is placed on device 100 is used for controlling the polarization state that receives light signal, and the polarization state monitor is coupled to survey in the output of device 1 and connects and the PMD information in PMD source.The parameter of PMD effects as DOP, feeds back in the microcontroller circuit 840.The SOP value that circuit 840 control Polarization Controller PC810 adjust the light that is input to device 100 makes parameter reach maximum or minimum.If DOP is as parameter, when PMD appropriately compensated, it is maximum that its value can reach.Receiver RX1110 is used for accepting the output signal of detecting polarization monitor 830.
PMD compensator shown in Figure 11 B utilizes the bit error rate as feedback information.In this device, PMD compensator 1102 comprises PC810, device 100, receiver RX1110 and based on the processor of the feedback signal of circuit 840 and receptacle RX1110.Detector among the receiver RX1110 is converted into electric signal with light signal.This signal is relevant with the bit error rate (BER) that detector circuit receives.BER information via microcontroller circuit 840 is handled, and PC310 adjusts the SOP value and makes the BER minimum.When BER hour, PMD has obtained compensation effectively.
Among Figure 11 B, the PMD compensation realizes by way of compensation by the radio-frequency information that the WDM signal that receives carries.In this structure, optical sender RXs1010 is added to the RF signal on the WDM signal.Detector in the receiver RX1010 is converted into electric signal with light signal, and signal is analyzed at the spectrum under the characteristic frequency.RF information on these frequencies changes with the PMD influence that the PMD source and the joints of optical fibre cause jointly.The RF information feedback that records is in microprocessor, and circuit 840 indication PC810 adjust input SOP makes the RF signal reach maximum or minimum value.
Above-mentioned technology can be used for constructing the optimum PMD of polarization source by using above-mentioned polarization rotator spare, uses different combined method and implementation method.For example, high precision and high duplication PMD can obtain by the ternary spinner of high duplication.A kind of like this device can produce 729 PMD states altogether, does not rely on DGD, 192 kinds of second order PMD (SOPMD) that do not rely on optical source wavelength comprising 64 kinds, and remaining all is the PMD that relies on wavelength.Can select the PMD of free position, high duplication, self-defined time interval or the like.This instrument can produce your needed PMD at 1ms or less time.Can quicken the experiment of PMD restriction like this and when PMD changes suddenly, the reaction time of PMD compensator.On the other hand, this instrument can also be imported polarization state of light by automatic optimization, when the single order under carrying out worst case, 2 rank PMD restriction test.Condition of uncertainty when the polarization optimization can reduce test, and reduce the test duration.These characteristics are helpful for PMD upper limit test experiments.This device also can be used for the PMD value optimized arbitrarily and with the PMD compensation of the PMD value of choosing.Compensation is by detecting output terminal to such an extent that the maximization of DOP value is finished.PMD and DOP value all can be presented on the lcd screen.By adjust the value of PMD when DOP is maximum, the user can find out the influence of PMD value to the PMD compensation intuitively.When selecting optimization PMD pattern, equipment can experience all PMD states and seek maximum DOP value.The maximum PMD state of DOP value will be chosen as optimum state and be used for the PMD compensation.
With reference to Figure 10,11A, 11B, such device can be used for the PMD value of measuring optical fiber connector because the PMD value under the optimization therewith the time PMD of the joints of optical fibre close.Therefore, for the PMD value of photometry fiber connector, can realize with the PMD source that optimization is crossed.The optimized PMD of the last demonstration of LCD is the PMD value of this connector.At the PMD of specific ROADM Network Transmission state, in this case, transmitting terminal need use LASER Light Source, and receiving terminal uses polarization optimization PMD source to carry out the PMD compensation.Optimization PMD value later is the PMD value of Optical Fiber Transmission.Based on the information of PMD, it can determine whether this round can carry out the 40G transmission and whether need to carry out the PMD compensation.In concrete device, can before the PMD source, place image intensifer (for example Erbium-Doped Fiber Amplifier (EDFA) EDFA) to strengthen light signal.
Also can be used to the loss situation of measuring system based on the device of Fig. 1-5.In a problematic spread fiber system, often be difficult to determine the reason of its problem.No matter be problem of the problem of PMD, the problem of chromatic dispersion (CD), signal to noise ratio (snr) or the like.Can decision problem whether be caused by the PMD compensation by PMD.If the PMD compensation has solved the problem of transmission, PMD shows it is the reason place of problem so, if the PMD compensation is not dealt with problems, then it may be not the reason that has problems just.By such judgement, could determine whether Optical Fiber Transmission needs to carry out the PMD compensation.
The Another application in PMD source is to carry out PMD emulation, and control PMD source can obtain the variation that the statistical distribution of PMD is come PMD in the analog optical fiber system.
In addition, the Polarization Control unit realization that also can use the same method.Inner Polarization Controller can be realized a lot of Polarization Control functions, comprises that special SOP produces, disturbs partially, polarization state tracking etc.Therefore, this instrument can satisfy the requirement of all polarization analyses, control.
Polarization optimization can realize by using the PMD source in the utility model.For example, in the experiment of DGD numerical range, input SOP can be by detecting to such an extent that the SOP signal is optimized as the DGD feedback information.In PMD scope test, input SOP can detect to such an extent that the DOP value realizes by minimizing, and this DOP value is the feedback of signal attenuation information that DGD and SOPMD signal are caused.In the PMD compensation, the SOP of input can realize optimization by above-mentioned DOP value is got maximal value.
What Figure 12,13 showed is the typical optical communications device that two assembling devices have above-mentioned PMD detecting device and PMD compensator.
Fiber optic communications devices 1200 its optical source wavelengths shown in Figure 12 are adjustable to survey the PMD value of WDM passage under the different wave length.This adjustable channel sources can produce any wavelength line polarized light in the WDM passage.The test light signal directly arrives fiber device 1200 by WDM multiplexer 1020, Optical Fiber Transmission device 1040.Like this, the PMD of this test signal light can reflect the PMD of this device.This light source comprises a light source 1212, tunable optical filter 1214.In the device, image intensifer 1216 can be used to amplify the transmitting optical signal through behind the wave filter, and an optical polarizer 1218 can guarantee that the linearly polarized light of test light signal enters WDM multiplexer 1020 with making a return journey.
The receiving end of device has optical coupler 1220, and it is positioned at the upstream of WDM demodulation multiplexer 1030, is used for decomposing to come out with comprising the part optical signals 1222 of surveying light signal in 1030 light signals of being accepted.Tunable optical filter 1230 is used for accepting photodetector signal 1222, and light detecting signal 1232 after the generation filtering.Tunable optical filter 1230 be tuned to identical adjustable light wave-filter 1214 wavelength-division multiplex wavelength.Filtered light detecting signal will enter in the PMD equipment 1201, and this equipment can be described in Fig. 1-5 a kind of in the equipment.Each wavelength that adjustable filter 1214,1230 can be adjusted to the WDM passage is measured the PMD characteristic of each passage, and the PMD characteristic of WDM passage can be measured in the different time like this.
Fiber optic communications devices 1300 shown in Figure 13 has tunable optical filter at receiving end, therefore selects the WMD channel wavelength can produce corresponding light detecting signal arbitrarily.At the device receiving end, photo-coupler 1220 is positioned at WDM demodulation multiplexer upstream, and detectable signal 1222 is separated in the signal 1030 from the WDM passage.Adjustable filter 1220 is used for light detecting signal 1222 filtering are comprised the detectable signal that selects the WDM passage with generation.Regulate wave filter 1230, the PMD characteristic of WDM passage can be measured in the different time.In this design, the WDM channel signal is used for carrying out PMD and measures, and the tunable ASE light signal 1210 among Figure 12 is removed.
This device is designed among Figure 12 and Figure 13, uses a single PMD instrument 1201 to be connected with the monitoring passage of appointment, uses adjustable light wave-filter 1230 to monitor the PMD of all channels, so that select WDM channel sometime.These designs all are based on shares identical PMD instrument 1201 monitoring PMD on all WDM channels, so PMD instrument 1201 needn't be connected to each multifunctional optical WDM path downstream from WDM DeMUX 1030.
Although foregoing has comprised many details; but these should not be interpreted as having limited the scope of protection of the present utility model; but having specifically described the specific function of utility model, those described some functions also can be combined in the single part and realize.Opposite, the various functions of describing in a certain single part also can realize in each several part or any suitable built-up section respectively.And though above-mentioned functions acts on some built-up section, in some cases, functions one or more in the built-up section can be deleted from built-up section, and described combination may directly change the change form of recombinant or recombinant into.
Minority embodiment has only been described at present.Yet, based on described in claims and the described content of instructions, can embodiment and other embodiment that describe be out of shape, revise and improve.
Claims (23)
1. polarization mode emulation and dispersion compensation device is characterized in that, comprise with the lower part:
One group differential group delay unit, each Differential Group Delay unit is spaced along the direction of propagation of light;
One group of tunable optical polarization rotator that produces different polarization rotations, each tunable optical polarization rotator is placed on respectively in two spaces between the differential group delay unit, each tunable optical polarization rotator is subjected to the control of external control signal, produces three kinds of different polarization rotations;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each tunable optical polarization rotator respectively.
2. device as claimed in claim 1, it is characterized in that: described each tunable optical polarization rotator is formed by the tunable optical polarization rotator of two bifurcations, the tunable optical polarization rotator of these two bifurcations is placed along the optical propagation direction series connection, and second rotation angle is opposite with the first rotation angle direction in the tunable optical polarization rotator of each bifurcation.
3. device as claimed in claim 2 is characterized in that: the light polarization spinner of described each bifurcation is made up of the magneto-optic polarization rotator.
4. device as claimed in claim 2 is characterized in that: the light polarization spinner of described each bifurcation, and its first anglec of rotation is+22.5 °, second anglec of rotation is-22.5 °.
5. device as claimed in claim 1 is characterized in that: it is 2 times or 2m times that the length of described differential group delay unit differs, and wherein m is an integer.
6. device as claimed in claim 1 is characterized in that: also comprise:
One receives input light and controls the input polarization controller of importing polarization state of light, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator;
The input polarizer of the input polarization state of light of a measurement behind the input polarization controller is placed on before described one group of differential group delay unit and the tunable optical polarization rotator, after the input polarization controller;
The output analyzer of the polarization state of light of a measurement behind differential group delay unit and tunable optical polarization rotator is placed on after described one group of differential group delay unit and the tunable optical polarization rotator.
7. device as claimed in claim 1 is characterized in that: also comprise
One that be used for receiving input light and control input polarization state of light and control the reception input light of one of input polarization controller or tunable optical polarization rotator and the input polarization controller of control input polarization state of light according to measured input polarization and output polarization attitude, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator;
Measurement is placed between differential group delay unit and tunable optical polarization rotator and the input polarization controller from the input polarizer of the polarization state of light of input polarization controller;
The output analyzer of the polarization state of light of a measurement behind differential group delay unit and tunable optical polarization rotator is placed on the back of described one group of differential group delay unit and tunable optical polarization rotator.
8. device as claimed in claim 7 is characterized in that: also comprise:
One in order to survey the photo-detector through the output light of differential group delay unit and tunable optical polarization rotator, is connected the output terminal of described one group of tunable optical polarization rotator;
Error monitoring device in order to the bit error rate of measuring light detector output is connected the output terminal of photo-detector;
The feedback signal that the bit error rate that basis measures from the detector output control module provides, and according to feedback signal to one of input polarization controller and light polarization spinner or all control feedback controller with the bit error rate that reduces detector output, be connected between photo-detector and input polarization controller or the light polarization spinner, or all connect with it.
9. device as claimed in claim 1 is characterized in that: also comprise:
One receives input light and controls the input polarization controller of importing polarization state of light, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator;
One in order to survey the photo-detector through the output light of differential group delay unit and tunable optical polarization rotator, with described
The output terminal of one group of tunable optical polarization rotator links to each other;
A processing is exported from the detection of photo-detector, to extract by input beam by the entrained spectral information of radiofrequency signal, and control control module and then one of control input polarization controller and light polarization spinner or whole, the radiofrequency signal that produces a maximum or minimum power is connected the output terminal of photo-detector to reduce the feedback controller of the bit error rate of exporting light.
10. an optical wavelength-division multiplex communicator is characterized in that, comprises with the lower part:
A WDM demodulation multiplexer of from different signal paths and WDM wavelength, isolating the WDM signal;
One group of optical receiver is positioned at different signal path positions separately;
Wherein, each optical receiver contains a polarization mode dispersion compensator, and this polarization mode dispersion compensator comprises:
One group of Differential Group Delay unit, each differential group delay unit is spaced along the direction of propagation of light;
One group of tunable optical polarization rotator, each tunable optical polarization rotator are placed between two differential group delay unit;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each tunable optical polarization rotator respectively.
11. device as claimed in claim 10, it is characterized in that, each tunable optical polarization rotator is made up of the tunable optical polarization rotator of two bifurcations, the tunable optical polarization rotator of these two bifurcations is placed along optical propagation direction, and the tunable optical polarization rotator of each bifurcation has first anglec of rotation and second anglec of rotation opposite with first anglec of rotation.
12. device as claimed in claim 11 is characterized in that,
The light polarization spinner of each bifurcation is made up of the magneto-optic polarization rotator.
13. device as claimed in claim 11 is characterized in that,
First anglec of rotation of the light polarization spinner of each bifurcation is+22.5 °, and second anglec of rotation is-22.5 °.
14. device as claimed in claim 10 is characterized in that, it is 2 times or 2m times that the length of each differential group delay unit differs, and wherein m is an integer.
15. device as claimed in claim 10 is characterized in that, each optical receiver also comprises:
One receives input light and controls the input polarization controller of importing polarization state of light, is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator;
The input polarizer of the input polarization state of light of a measurement behind the input polarization controller is placed on the front of described one group of differential group delay unit and tunable optical polarization rotator, the back of input polarization controller;
The output analyzer of the polarization state of light of a measurement behind differential group delay unit and tunable optical polarization rotator is placed on the downstream of one group of differential group delay unit and tunable optical polarization rotator.
16. device as claimed in claim 10 is characterized in that, each optical receiver also comprises:
A photo-detector of surveying the light of output analyzer links to each other with the output terminal of output analyzer;
The bit error rate detector of the bit error rate of a measuring light detector output links to each other with the output terminal of photo-detector;
Basis from detector measurement to bit error rate control input polarization controller and one of adjustable Polarization Controller or all, to reduce the feedback controller of the error code of exporting light, be connected between photo-detector and input polarization controller or the tunable optical polarization rotator, or photo-detector is connected with adjustable polarization rotator simultaneously with the input polarization controller.
17. device as claimed in claim 10 is characterized in that, each optical receiver also comprises:
One receives input light with control input light, and control the input polarization controller of the polarization state of one of input polarization controller and tunable optical polarization rotator at least according to the input and output polarization state that measures, be connected the front of one group of differential group delay unit and tunable optical polarization rotator;
The output analyzer of the polarization state of light of a measurement behind differential group delay unit and tunable optical polarization rotator is connected the back of one group of differential group delay unit and tunable optical polarization rotator.
18. device as claimed in claim 10 is characterized in that, each optical receiver also comprises:
One receives input light and controls the input polarization controller of importing polarization state of light, is connected the front of one group of differential group delay unit and tunable optical polarization rotator;
A photo-detector of surveying the light of differential group delay unit and the output of tunable optical polarization rotator is connected to the output terminal of each tunable optical polarization rotator;
The bit error rate detector of the bit error rate of measuring light detector output is connected the output terminal of photo-detector;
One provides feedback signal based on the detector output error rate that measures to control section, and control input polarization controller and tunable optical polarization direction spinner at least according to feedback signal and one of use feedback controller with the bit error rate that reduces output light, be connected the output terminal of photo-detector.
19. polarization mode emulation and dispersion compensation device is characterized in that, comprise following a few part:
One in order to accept the input port of light;
One group of Differential Group Delay unit, each differential group delay unit is spaced along the direction of propagation of the light that input port is accepted;
One group in order to produce the discrete attitude tunable optical polarization rotator of two or more different polarization state directions, and each tunable optical polarization rotator is placed on respectively between two differential group delay;
Controller in order to communicate with the tunable optical polarization rotator links to each other with each discrete attitude tunable optical polarization rotator respectively.
20. device as claimed in claim 19 is characterized in that, described discrete attitude tunable optical polarization rotator is adjustable bifurcation polarization state spinner.
21. device as claimed in claim 20 is characterized in that, first anglec of rotation is+22.5 ° in the light polarization spinner of described each bifurcation, and the second opposite anglec of rotation is-22.5 °.
22. device as claimed in claim 19 is characterized in that, described discrete attitude tunable optical polarization rotator comprises:
Adjustable three state polarization attitude spinner and adjustable bifurcation polarization state spinner.
23. device as claimed in claim 22 is characterized in that, described each adjustable three state polarization attitude spinner comprises two bifurcation polarization state spinners arranging along optical propagation direction, produces three different anglecs of rotation so that it merges.
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