CN1839570A - Combined wavefornt sensor and data detector for a free space optical communications system with adaptive optics - Google Patents
Combined wavefornt sensor and data detector for a free space optical communications system with adaptive optics Download PDFInfo
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- CN1839570A CN1839570A CNA2003801053218A CN200380105321A CN1839570A CN 1839570 A CN1839570 A CN 1839570A CN A2003801053218 A CNA2003801053218 A CN A2003801053218A CN 200380105321 A CN200380105321 A CN 200380105321A CN 1839570 A CN1839570 A CN 1839570A
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Abstract
In an adaptive optics module, wavefront sensing and data detection are implemented in a single device (420). For example, an optical-to-electrical converter (427) converts a data-encoded optical beam to an intermediate electrical signal, which contains both the data encoded in the beam and also wavefront information about the beam. The data and wavefront information are later separated, for example by frequency filtering (428).
Description
Technical field
The present invention relates to the free space optical communication field.More particularly, the present invention relates to use adaptive optics (for example comprising inclination (tip/tilt) correction) as enhancing to free space optical communication chain path.
Background technology
Along with latest development, be concerned about day by day free space optical communication is used for various application.For example, present most telecommunication infrastructure are with the basis that is transmitted as of the light signal by optical fiber.Though the use of optical fiber has increased the capacity and the efficient of transfer of data, be not many situations of best solution but still there be laying of new optical fiber.Thereby, be concerned about to enlarge telecommunication infrastructure by free space transmitting optical signal through atmosphere.
Free space optical communication chain path also can be advantageously utilised in the application outside the telecommunication infrastructure.Compare with other communication technology, free space optical communication chain path can have higher mobility and less size, better directivity (for example more being difficult to intercepting) is set up faster and is dismantled, and/or is suitable for one or two transceiver all in the advantage of situation about moving.Thereby free space optical communication chain path can be used in many different situations, is included in airbornely, carrier-borne, uses under space and/or the land situation.
But in many these potential application, there is the problem of optical distortion in free space optical communication.For example, precision, reliability and the efficient of the change meeting appreciable impact free-space optical communication system of atmospheric conditions.Wind, heat wave, artificial pollutant and other influence can produce the distortion that continues variation.The quality that this can reduce the light signal that can obtain at receiver again causes the total quality of communication channel and the reduction of efficient.
Adaptive optics can compensate these distortion, thereby improves the performance of free space optical communication chain path.But the present free space optical communication chain path with adaptive optics ability generally uses independently detector to carry out data snooping and wavefront detects.The light beam of input is generally separated by optical splitter, and a part is drawn towards data detector, and another part is drawn towards Wavefront sensor.But this requires the mutual exactly registration of data detector and Wavefront sensor.The use of two separate detectors and the registration that causes have thus required to increase the cost and the complexity of whole system, and have reduced the reliability of system.
Thereby for ADAPTIVE OPTICS SYSTEMS, the needs of eliminating two separate detectors should be favourable.
Summary of the invention
The present invention realizes together wherein that by providing wavefront detects and the adaptive optics module of data snooping, has overcome the restriction of prior art.In one embodiment, such equipment comprises the optical-electrical converter that couples with separation module.The signal of telecommunication in the middle of optical-electrical converter converts data-encoded light beam to, the middle signal of telecommunication both had been included in coded data in the light beam, comprised the wavefront information about light beam again.Separation module produces the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication.The wavefront signal of telecommunication comprises wavefront information, and datagram number comprises data.
In one approach, wavefront information and data in the middle signal of telecommunication with frequency separation.For example, wavefront information can be positioned at the low frequency of frequency that is positioned at than data.Separation module is by using tuning circuit/filter or electric dividing network, according to frequency separation wavefront information and data.
In one embodiment, optical-electrical converter comprises a plurality of detector elements.A sub-aperture part of each detector element receiving beam, and the signal of telecommunication in the middle of converting thereof into.The middle signal of telecommunication is combined so that carry out data snooping, and coverlet is stayed alone reason so that carry out the wavefront detection.
In a special embodiment, the adaptive optics module uses the deformable curvature speculum to compensate distortion.For example, the deformable curvature speculum can be the sandwich with resistance material of electrode section pattern.By electrode section is used different voltage, make the sandwich distortion.Wavefront/the data pick-up of combination comprises a segmented detector, and the deformable curvature speculum is imaged onto on the segmented detector.In one embodiment, each section in the detector is corresponding to one of electrode section on the deformable curvature speculum.The film speculum of the focal plane between deformable curvature speculum and segmented detector vibrates with chattering frequency, thereby the focus shake is introduced in the optical system.Dividing network receives the middle signal of telecommunication from segmented detector, and according to frequency wavefront information (it is positioned at around the chattering frequency) and data (it is positioned under the frequency of chattering frequency) is separated.
Others of the present invention comprise the adaptive optics module, the system of transceiver and FSO communication link and use the said equipment, and corresponding to above-mentioned whole method.
Description of drawings
In conjunction with the accompanying drawings, according to following detailed description of the present invention and additional claim, other advantage of the present invention and feature will become apparent, wherein:
Fig. 1 graphic extension is suitable for free-space optical communication system of the present invention.
Fig. 2 graphic extension is fit to another free-space optical communication system of the present invention.
Fig. 3 graphic extension is fit to another free-space optical communication system of the present invention.
Fig. 4 graphic extension is according to adaptive optics module of the present invention.
Fig. 5 is the power spectrum that the graphic extension wavefront information is separated with data frequency.
Fig. 6 is the circuit diagram of an example of separation module.
Fig. 7 is the circuit diagram of another example of separation module.
A kind of realization of the adaptive optics module of Fig. 8 graphic extension Fig. 4.
Fig. 9 A-9C is the circuit diagram of different dividing network.
Embodiment
The example of free space optical (FSO) communication system of adaptive optics is used in Fig. 1-graphic extension.FSO communication system among Fig. 1 is used to by FSO data link 150, and data are sent to land receiver 120 from airborne reflector 110, and receiver 120 can be that fix or mobile.For convenience's sake, term " transceiver " will be used to indicate the only module 110 of emission, the module 120 that receives only, and the module of not only launching but also receiving.
Each transceiver 110,120 comprises the telescope (telescope) that points to another transceiver.Transmitter-telescope 110 generally comprises the assembly of following the tracks of receiving telescope 120 and light beam 150 being guided into receiving telescope 120.Receiving telescope 120 generally comprises follows transmitter-telescope 110, and receives the assembly from the light beam 150 of transmitter-telescope 110.The example that can be used for the assembly of these purposes comprises steering reflection mirror, mechanical gimbals, follower and control loop, automatic focus and zoom capabilities.
FSO communication link 150 can because of the time become distortion (aberration) and suffer damage.For example, for many application, the influence of atmosphere is the main source of distortion.The density of atmosphere generally changes along with time and space, for turbulent area (cell), generally with about 1kHz or less than the rate variation of 1kHz.The distortion that as a result of causes can cause injurious effects, for example causes dispersing of beam drift, at the blinker pattern of receiver 120 and the wavefront of degeneration.
In the example of Fig. 1, these distortion are positioned at the adaptive optics module (adaptive optics module) 125 of receiver 120 and partly or completely proofread and correct.Adaptive optics module 125 is proofreaied and correct the wavefront (wavefront) of input (incoming) light, and this is convenient to again dispose light beam at receiver.General wavefront (usually after proofreading and correct) by directly measuring input beam 150 is determined the wavefront correction that adaptive optics module 125 applies, though also can use other method before estimation distortion or the incoming wave.The level of the correction that ADAPTIVE OPTICS SYSTEMS applies is commonly called the grade (order) of ADAPTIVE OPTICS SYSTEMS.For example, term first order adaptive optics will be used to indicate correct tilt and/or rudimentary distortion (for example piston (piston)), rather than correction defocuses or the ADAPTIVE OPTICS SYSTEMS of senior distortion.Term advanced, adaptive optics will be used to indicate to proofread and correct and defocus and/or the ADAPTIVE OPTICS SYSTEMS of senior distortion.
Fig. 2 graphic extension utilizes another FSO communication system of adaptive optics.In this example, the FSO communication system is used in the urban environment, and reflector 210 and receiver 220 are positioned on the roof of two buildings.Fig. 2 represents the building of differing heights, automobile, and road, tree and an architectural chimney, they produce different atmospheric conditions.Rain, mist, cigarette etc. reduce radiative intensity.The heat wave that produces with building that causes such as the sun, except the normal atmosphere distortion that causes by meteorological condition, the air-conditioning discharging, heat exchangers, automobile exhausts etc. produce the distortion along optical link 250.In used in the rural area, constantly landform and the vegetation that changes can influence along the distortion of optical link 250.
In Fig. 2, each transceiver 210,220 comprises adaptive optics module 215,225, so that alleviate otherwise can be to the atmospheric conditions that have a negative impact that transmit and receive of data encoded light ripple.In reflector 210, the wavefront of adaptive optics 215 precorrection output (outgoing) light.This precorrection is reduced in the beam drift and the blinker pattern of receiver 220, thereby increases the quantity at the light of receiver 220 incidents, also improves the wavefront quality of the light beam that receives.At receiver 220, adaptive optics 225 is proofreaied and correct the distortion that receives in the wavefront, thereby improves picture quality and/or collection efficiency at receiver.
At receiver 220,, determine the wavefront correction that adaptive optics module 225 applies according to the wavefront of input beam 250.The detecting light beam 260 of anti-spread (counter-propagating) is used to be positioned at the adaptive optics module 215 of reflector 210.Detecting light beam 260 is along almost identical with initial data-encoded light beam 250 light path backpropagation.It can have the wavelength identical or different with incipient beam of light 250.The distortion that detecting light beam 260 experience fundamental sum incipient beam of light 250 is identical, the precorrection that adaptive optics module 215 applies is based on the wavefront of detecting light beam 260.In a comparable manner, the detecting light beam of co-propagate (not shown among Fig. 2) can be used as the basis of the wavefront of proofreading and correct incipient beam of light 250 at receiver 225, rather than uses incipient beam of light 250 own.
Both-end at Fig. 2 connects in the corrective system, and two adaptive optics modules 215,225 are reciprocation undesirably under certain conditions.In alleviating a kind of method of this influence, the feature propagation distance can be defined as z0=π σ
2/ λ, wherein σ is the width of projecting beam (being assumed to Gauss's projecting beam in this example), λ is a wavelength.For example, with regard to the wavelength of 4 centimetres width of light beam and 1.55 microns, the feature propagation distance is near 3 kilometers.For the link range less than the feature propagation distance, phase information can propagate into receiver 220 from reflector 210, produces the feedback path by these two adaptive optics modules 215,225, and may cause unsteadiness in the adaptive optics module.Size by utilizing zoom optics for example to reduce to launch light beam can reduce this influence.On the other hand, the residual quantity focus between reflector 210 and the reflector 220 can be used to guarantee the not significantly underfill of aperture of receiving telescope.Under the link range greater than the feature propagation distance, the phase change that is positioned at reflector 210 is converted into the amplitude variations that is positioned at receiver 220 usually, and data signal strength becomes square distance ground to descend simultaneously.Thereby under these longer link range, the phase instability problem is little.
The second kind of influence that takes place under the link range that is shorter than the feature propagation distance is that pupil (pupil) illumination may become inhomogeneous.A kind of means to save the situation is to adjust the focus of transmitter-telescope 210, so that the pupil illumination of expansion incipient beam of light 250.
Communication link 150,250 among Fig. 1 and 2 is expressed as unidirectional.Two independently one-way system can be used to produce a bilateral system.More economical is, for example by data source (for example modulated laser or fiber-fed) and data sink (for example photodetector or output optical fibre) both be set at each transceiver 210,220, and share many identical optics of telescope devices, comprise the adaptive optics correction, the reflector of each position and receiver can be combined into individual unit.
For example, in Fig. 2, light beam 260 is the data available coding also.Subsequently, the transfer of data for from 210 to 220, transceiver 210 is reflectors, and light beam 250 is incipient beam of light of digital coding, and light beam 260 is detecting light beams, and transceiver 220 is receivers.In the opposite direction, transceiver 220 is reflectors, and light beam 260 is digital coding incipient beam of light, and light beam 250 is detecting light beams, and transceiver 210 is receivers.Note 250,260 two purposes of each light beam.It is a digital coding incipient beam of light on the direction, and the detecting light beam on the other direction.Four light beams are used in a kind of standby realization: two data coded beams and two detecting light beams, all four light beams are all at two transceivers, 210,220 shared identical optics of telescope devices.
Another FSO communication system of adaptive optics is used in Fig. 3 graphic extension.This example is used modulation back (retro) reflector 330.Reflector 310 is transferred to rear reflector 330 to light beam 350A.To light beam, rear reflector 330 is near the light beam 350B reflected back of the digital coding origin 310 digital coding in the modulation of rear reflector 330.In one implementation, identical telescope 310 receives Returning beam 350B.But in many application, rear reflector 330 sizes are limited, and the diffraction limited spot size of Returning beam 350B is significantly greater than the size of telescopic aperture.Thereby, one independently telescope 320 can be used as receiver, as shown in Figure 3.On the other hand, rear reflector 330 can be by not being that backward reflector is replaced.The adaptive optics module can be used in any one or these two telescopes (and being used in the rear reflector) thus precorrection or post-equalization light beam 350, communication link can be unidirectional or two-way.
Fig. 1-3 is example just.Other application will be tangible.In addition, the selection of wavelength, data rate, link range, telescope design, data source and light source, data sink and other design alternative will be depended on application.FSO communication link itself can be according to application and marked change.In one application, two transceivers all are ground-based transceiver, and link is mainly along the surface of the earth.Example comprises the link in urban environment, the rural environment or crosses over the link of water body.In other is used, link can be ground-to-air or air to surface (for example between ground station and the aircraft) link, perhaps air to air (for example between the aircraft) link.The FSO communication system also can be unidirectional or two-way, and utilizes single-termination or both-end to connect adaptive optics and proofread and correct.Principle described herein is applicable to these situations.
Proved data rate and distance by experiment, but according to application, the various combination of data rate and distance may be suitable up to 100Gbps and 27km.Use 1.55 the wavelength in the micron wave length scope is preferred for telecommunications at present, but also can use other wavelength, under some atmospheric conditions or ground in the application of other type or even preferred.For example, 1.3 micron wave length scopes show under single wavelength mode well.Term such as " optics " or " light " is not intended to be confined to any one certain wavelengths scope.They also are not intended to be confined to the visible-range of electromagnetic spectrum.
The source of any number can be used to data-encoded light beam.For example, the optical fiber of transmission digital coding optics signal can directly be couple to transmitter-telescope.If data-signal is the signal of telecommunication, can carry out the electrical-optical conversion so.For example, electric data can be used to inner modulation laser diode (perhaps other light source).On the other hand, can be modulated by electric data external through for example Mach-Zender modulator from the light beam of laser (perhaps other light source).If data-signal is an optical signalling, but have incompatible wavelength with current system, can carry out wavelength conversion so, for example from 1.3 micron wave length range conversions to 1.55 micron wave length scopes.Wavelength conversion can be finished by Optical devices (for example based on nonlinear optical phenomena) or by light-electrical-optical device.
At receiver, can handle or retransmit the light beam of reception according to many different modes.For example, some input light can directly be couple in the output optical fibre.On the other hand, it can convert electric form to by photodetector or other electro-optic detector.As last example, it can be exaggerated and be couple in another FSO communication link so that further transmission.
Itself also can have the complicated of varying level the adaptive optics module.In simple the application, the slant correction that only has or do not have focus may be just enough.In requiring higher application, can realize the correction of senior distortion.Simple first order adaptive optics is proofreaied and correct, and for example slant correction can be realized or increase by other assembly such as steering reflection mirror, allows the adaptive optics module proofread and correct senior distortion.
The optics of telescope device also can change.Can use refraction, reflection or Mixed Design.In some application (for example short-range applications), telescope may be optional.On the other hand, the collection optics except that telescope is suitable.The U.S. Patent application No.09/892913 that submits to June 16 calendar year 2001 at J.Elon Graves and Malcolm J.Northcott, described other example of the FSO communication system of using adaptive optics in " Atmospheric Optical Data Transmission System ", this patent application is drawn at this and is reference.
Fig. 4 graphic extension is according to adaptive optics module of the present invention.This system comprises telescope 410 (by lens among Fig. 4 418 expression), variable phase equipment 424 and serve as Wavefront sensor and the equipment of data detector 420.Variable phase equipment 424 and wavefront/data pick-up 420 are arranged in telescopical light path, and wavefront/data pick-up 420 is in the downstream of variable phase equipment 424.This system also comprises the data source 440 of launching.In this example, this system also comprises beam steering mechanism 416, for example inclined mirror.
On receive direction, system is collecting wavefront/data pick-up 420 from the light 451 of remote source (for example from transmitter-telescope).Variable phase equipment 424 and wavefront/data pick-up 420 form the adaptive optics loop of compensation along the distortion of FSO communication link.Variable phase equipment 424 is introduced the adjustable phase of the influence of the undesirable distortion of compensation, thereby reduces the residual distortion in the wavefront.The example of variable phase equipment 424 comprises deformable mirror, liquid crystal apparatus, the MEMS speculum, sound-optical, heat-light, magnetic-light and electrical-optical modulator, eidophor (eidophors) and light are write photoactivation (optically written optically active) material.The actual amount of distortion or residual distortion is measured in the wavefront test section of wavefront/data pick-up 420, and control module 422 sends to variable phase equipment 424 to control signal corresponding.Like this, can be about the wavefront of distortion correction input beam, partly obtain better pictures quality and/or collection efficiency at the data snooping of wavefront/data pick-up 420.
On transmit direction, source 440 produces light beam, and this light beam will be by being launched with the identical FSO communication link of light beam that receives.From the light beam in source 440 by 424 precorrection of variable phase equipment.This has increased the quantity that is incident on the energy on the receiving telescope, and can reduce scintillation effect.Notice that receiving beam is identical with the major part of the light path of emission beam propagation.Thereby identical adaptive optics is proofreaied and correct and both can be used to receiving beam is carried out post-equalization, can launch light beam again with being used to and carry out precorrection.
In close loop maneuver, adaptive optics is preferably with apparently higher than the speed along the rate of change of the distortion of light path, for example preferably with the rate correction wavefront of fast about 10 times or higher multiple.If distortion is caused by atmospheric conditions that mainly variable phase equipment 424 is preferably adjusted with about 10kHz or bigger speed so, because the turbulent flow microcell in the atmosphere is with about 1kHz or littler rate variation.
Wavefront/the data pick-up 420 of explanation combination now, transducer 420 comprises the electro-optic detector 427 that couples with separation module 428.The example of electro-optic detector 427 comprises photodetector and coherent detection device (for example mixing the optical local oscillator that is detected subsequently with input beam).Electro-optic detector 427 converts input beam to electric form.The signal of telecommunication in the middle of the resulting signal of telecommunication will be called as.This centre signal of telecommunication both had been included in coded data on the light beam, comprised the wavefront information relevant with the wavefront of light beam again.The signals of telecommunication in the middle of separation module 428 receives, and produce the wavefront signal of telecommunication that comprises wavefront information and comprise the datagram number of data.Control module 422 is according to wavefront signal of telecommunication control variable phase equipment 424.Datagram number can be processed so that restore data.
Structure shown in Fig. 4 is before the composite wave/example of data pick-up 420.Also can use other design.In an alternative, input beam comprises the incipient beam of light that comprises information and the co-propagate detecting light beam of different wave length.Before the composite wave/and data pick-up 420 comprises multilayer or complex detector, it comprises the different detector layers to the different wave length sensitivity.For example, top layer can comprise the detector element to the detecting light beam wavelength sensitive, and bottom can comprise the detector element to the wavelength sensitive of incipient beam of light.Thereby the signal of telecommunication from top layer comprises wavefront information, comprises data from the signal of telecommunication of bottom.
Return the object lesson shown in Fig. 4, in one approach, in the middle signal of telecommunication according to frequency separation wavefront information and data.Fig. 5 represents that wherein wavefront information takies lower frequency band, the middle signal of telecommunication of the frequency band that data occupancy is higher.Separation module 428 is subsequently according to frequency separation wavefront information and data.
Situation shown in Fig. 5 is not rare.For example, the distortion that atmospheric oscillation causes generally has the bandwidth in 1～10kHz scope, and is common (for example, the 150MHz of OC3, the 1GHz of Gigabit Ethernet etc.) greater than the data rate of 1MHz.Attention is in Fig. 5, and data do not have the DC component.Many communication protocols cause (perhaps even require) zero DC component.For example, can utilize NRZ, or its modification is encoded to data with 8B/10B coding.
Can utilize the whole bag of tricks to realize the frequency separation of data and wavefront information.For example, can use tuning circuit/frequency filter.Fig. 6 is the circuit diagram of an example.Here, optical-electrical converter 427 is realized as photodiode or the similar device that produces the circuit that is proportional to incident intensity.The middle signal of telecommunication of input 610 is divided into two components at the junction point.Amplifier circuit 620 plays high pass filter, and the high-frequency data part of the signal of telecommunication stops wavefront information in the middle of selecting.Similarly, amplifier circuit 630 plays low pass filter, selects the low frequency wavefront information, block data.
Fig. 7 is based on the block diagram of another example of auto-gain circuit.In this example, 710 pairs of middle signals of telecommunication of variable gain parts (block) are used time-varying gain, so that the amplitude equalization of signal (equalize).In order to estimate zero passage more accurately, this is desirable.720 pairs of output signal samplings of automatic gain control module, and adjust gain in view of the above.If auto-gain circuit is enough fast, time-varying gain variation that the compensated wave front signal is caused so.Thereby, can retrieve the wavefront information signal from the time-varying gain that auto-gain circuit applies, can be from the signal restore data of amplitude equalization.
The specific implementation of the adaptive optics module of Fig. 8 graphic extension Fig. 4.This system comprises the telescope 810 with adaptive optics module.Light 851 from long-range light source enters this system by inclined mirror 816.
In one embodiment, receiving telescope 810 is designed to be arranged vertically.Inclined mirror 816 can be around two vertical axis pivoted, and one of described two vertical axis are on the telescopical vertical axis of picture capstan head (turret), on another horizontal line in the plane of speculum, so that realize tilt adjustments.As an alternative, telescope 810 can rotate around its vertical axis, thereby a rotating shaft of speculum 816 can be eliminated.Other alternative can be used to telescopical rough sensing or aiming, for example uses other inclined mirror or the less amount of object lens translation.
Referring to Fig. 8, from inclined mirror 816, rays pass through lens 818, to principal plane OIP, the clear picture of long-range light source ground is present on the principal plane lens 818, but is not corrected light focusing.Light arrives deformable mirror 824 by collimating lens 819 subsequently.Deformable mirror 824 dynamically is shaped, so that proofread and correct the distortion in the wavefront.According to the wavefront measurement that wavefront/data pick-up 820 carries out, control deformable mirror 824.Adjust element by inserting conjugation (conjugate), can adjust the conjugation of deformable mirror 824 at OIP.The example that conjugation is adjusted element comprises insertable lens, zoom lens or second deformable mirror.
Can use various types of Wavefront sensors and deformable mirror.In this example, the zones of different that deformable mirror 824 is based on piezoelectric applies different voltage, thereby causes the deformable curvature speculum that is out of shape.Submit to January 25 calendar year 2001 at J.Elon Graves and Malcolm J.Northcott, and the U.S. Patent No. 6464364 " Deformable Curvature Mirror " of issuing on October 15th, 2002; J.Elon Graves and MalcolmJ.Northcott submitted to January 25 calendar year 2001, and the U.S. Patent No. 6568647 " Mounting Apparatus for Deformable Mirror " of issuing on May 27th, 2003; Reach J.Elon Graves and Malcolm J.Northcott described and represented this deformable mirror in the U.S. Patent application No.09/892913 in June 16 calendar year 2001 " Atmospheric Optical Data Transmission System " other details.All these draw at this and are reference.
In the example of Fig. 8, the Wavefront sensor of equipment 820 partly is based on the wavefront curvature sensor of mydriasis image.Submit on May 26th, 2000 at J.Elon Graves and Malcolm J.Northcott, and the U.S. Patent No. 6452145 " Methodand Apparatus for Wavefront Sensing " of issuing on September 17th, 2002; Reach J.Elon Graves and MalcolmJ.Northcott described and represented this wavefront curvature sensor in the U.S. Patent application No.09/892913 in June 16 calendar year 2001 " Atmospheric Optical Data Transmission System " other details.All these draw at this and are reference.
To lens 825, lens 825 focus on vibrating membrane speculum 832 to image to light again from the surface reflection of deformable mirror 824.Rays pass through lens 834 reflexes on the segmented detector 827 from vibrating membrane speculum 832.When film speculum 832 does not vibrate, that is, when its when being straight, deformable mirror 824 is imaged onto on the detector 827.But when film speculum 832 vibration, it is crooked between etat lacunaire and raised position, makes the alternately positive ground of image and being defocused on the detector 827 negatively.Wavefront information is extracted by separation module 828, is transmitted to control module 822 subsequently, so that determine the curvature of wavefront.
Software in the control module 822 obtains wave-front curvature, and corresponding control signal is provided for deformable mirror 824.Specifically, the variable focus shake that causes of film speculum 832 causes the signal component under the chattering frequency.The size of this component is proportional to the wave-front curvature in the pupil, and is proportional to the borderline wavefront radial skew of pupil.By utilizing the relevant Neumann boundary condition of shape with extra focusedimage, find the solution the Poisson equation about intensity, obtain or recover wavefront.Can adopt iterative data Algorithm for Reduction or other nonlinear fitting technology to compensate the non-linear of measurement result in the open cycle system.
In this realization, detector 827 is by segmentation.Pupil is divided into sub-aperture, and the sub-aperture of each of light beam part drops on independently on the detector stage.Each detector stage produces an independently signal of telecommunication.Thereby, from segmented detector 827 to separation module 828 the middle signal of telecommunication actual comprise by represent across the slash of 828 lines from segmented detector 827 to separation module a plurality of in the middle of the signal of telecommunication.The signal of telecommunication provides the information relevant with whole wavefront in the middle of each, by handling the middle signal of telecommunication that separates, carries out wavefront and determines.For data snooping, segmented detector 827 plays light bucket (light bucket) in essence.By the signal of built-up section or all middle signal of telecommunication and treatment combination, restore data.
For example, if light beam is divided into N sub-aperture, detector 827 can have the N section that produces N the middle signal of telecommunication.But each middle signal of telecommunication of separation module 828 low-pass filters, thus N the independently wavefront signal of telecommunication produced, and the individual independently wavefront signal of telecommunication of described N is handled by control module 822 subsequently.Simultaneously, separation module 828 high pass filtered signals, thereby and the combined result generation individual data signal of telecommunication.
An advantage of detection and data snooping is simple in structure and firm before the composite wave.The number of detector is reduced usually, does not need registration independently wave front detector and data detector.Provide under the serious turbulent-flow conditions of the light in the telescope pupil in a plurality of light paths, it is obvious that another advantage becomes.This can cause several " mirage phantom " in the picture plane.Owing to guide the cause of the adaptive optics module in two centre positions between the mirage phantom into, perhaps owing to cause the adaptive optics module to switch (snap) between image from the transmission of the energy of another mirage phantom of mirage phantom, mirage phantom can cause being couple to the loss of monomode fiber.Though when being couple to monomode fiber, mirage phantom can cause losing (dropout), but the optical power level in the pupil is unaffected to a great extent.Thereby the Wavefront sensor of combination and data detector generally will provide more sane performance under serious turbulent-flow conditions.
Fig. 9 A-9C is the circuit diagram that the difference of separation module 828 realizes.In Fig. 9 A, separation module 828 is realized as electric dividing network 910.Dividing network 910 is divided into high fdrequency component (being data-signal) and low frequency component (being wavefront signals) in exporting from N of segmented detector 82 each.In this example, the middle signal of telecommunication of each input is separated individually, obtain the signal of telecommunication before N the dateout signal of telecommunication and N the output wave.
An embodiment of Fig. 9 B graphic extension frequency division net (crossover) network 910.In this example, the capacitor block low frequency component, inductor stops high fdrequency component.In addition, N data-signal is added, thereby forms single " compound " datagram number.Be to amplify after the dividing network 910.An amplifier 920 is used to compound data-signal, and separating amplifier 930 is used to each in N the wavefront signals.
Fig. 9 C is similar to Fig. 9 B, except amplifying before separating.Before data and wavefront information were separated, amplifier 940 amplified N the centre signal of telecommunication.Other frequency division embodiment is possible, for example based on being used for the transformer coupled of high fdrequency component, directional coupler or transmission line coupling; The frequency division embodiment that separates with resistance that is used for low frequency component or inductance.
Comprise many details though describe in detail, but they limitation of the scope of the invention be should not be understood that, and different example of the present invention and aspect just illustrated.Will be appreciated that scope of the present invention comprises top other embodiment that does not describe in detail.
For example, in some cases, the optics of telescope device is opposite with being positioned at, variable phase equipment 424,824 can and the outmost element of optics group preferably.Variable phase equipment 424,824 also can be realized as more than one equipment.For example, separate equipment can be used to input beam is carried out post-equalization and output beam is carried out precorrection.On the other hand, possible input beam and output beam are used public correction together, and other equipment provides increment (or difference) to proofread and correct simultaneously.With the situation of satellite communication under, such structure is favourable, light beam can have " predicted point " to a certain degree, with the compensation satellite motion.Also can make Wavefront sensor before proofreading and correct, measure distortion, rather than after correction, measure residual distortion according to the optical correction of open loop approach application self-adapting.
Change as another kind, control module 422,822 information and wavefront information from other system or transducer capable of being combined are so that improve performance.Example comprises that use calculates advance angle about the orbital elements prime information of satellite, perhaps uses rotation speed sensor on the moveable platform to improve the bandwidth of steering correction.Reflector also can be received as from external system, comprises the information of control module.Such information can comprise about the management information of communication link or about the state information of reflector, for example wavelength is preferentially selected, power stage, and predicted point requires or the polarization requirement.
In some cases, the use of relevant (for example QPSK) data snooping can enlarge markedly sensitivity.In one approach, optical local oscillator mixes with input light in pupil plane.Utilize detector array, for example photodiode array is surveyed resulting modulation.In this case, on each detector the optical distortion difference with the phase place of mobile data recovered signal, thereby before each pupil plane signal was combined, application phase was proofreaied and correct.If use the Phase Tracking signal combiner, the relative phase of each restoring signal provides directly measuring of atmosphere phase distortion on the corresponding pupil zone so.The coherent detection of wavefront is created under the condition of given similar accurate compensation equipment, but enough certainties of measurement of proofreading and correct are used in open loop.
As another example, can realize difference in functionality described above according to different physical form.According to concrete application, function can be realized as hardware, firmware, software and/or their combination.In superincumbent many descriptions, different functions are realized as special circuit, so that utilize low energy consumption and high-speed advantage.In other is used, identical functions can be realized as generally digital signal processor or even general processor on the software that moves.Also can use various combinations.For example, some operation may be quite common, can standard package, the form of software or circuit design exists.These can realize combined with the customization of residue function.
Similarly, " the coupling " between the module also can be taked different forms.Special circuit can pass through hardwired, by shared bus, perhaps couples mutually by visit common register or memory cell.Can realize that software " couples " by any-mode, thereby in (perhaps between software and hardware, in this case) transmission information between the component software.Term " couples " intention and comprises all these, is not limited to two hardwireds between the assembly and forever connects.
Under the situation that does not break away from the spirit and scope of the present invention that in additional claim, define, here significantly various other modifications are to one skilled in the art made in the structure of disclosed method and apparatus of the present invention, operation and details aspect, change and change.So scope of the present invention should be determined by additional claim and their legal equivalents.In addition, any element, assembly or method step do not plan to be offered to the public, no matter whether exemplified described element, assembly and method step in the claims clearly.
Claims (44)
1, a kind of equipment that is used for wavefront detection and data snooping, described equipment comprises:
Reception utilizes the light beam of digital coding, and the optical-electrical converter of the signal of telecommunication in the middle of the Beam Transformation one-tenth, the described middle signal of telecommunication comprises described data, and comprises the wavefront information relevant with the wavefront of light beam; With
Couple with optical-electrical converter, produce the separation module of the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication, the wavefront signal of telecommunication comprises wavefront information, and datagram number comprises described data.
2, according to the described equipment of claim 1, wherein optical-electrical converter comprises a photodiode.
3, according to the described equipment of claim 1, wherein optical-electrical converter comprises a coherent detection device.
4, according to the described equipment of claim 1, wherein in the middle signal of telecommunication, wavefront information and data are separated on frequency; Separation module is according to frequency separation wavefront information and data.
5, according to the described equipment of claim 4, wherein wavefront information is positioned at the low frequency of frequency that is positioned at than data.
6, according to the described equipment of claim 4, wherein wavefront information is positioned at the frequency less than 1MHz, and data are positioned at the frequency greater than 1MHz.
7,, wherein in the middle signal of telecommunication, utilize zero DC component that data are encoded according to the described equipment of claim 4.
8, according to the described equipment of claim 4, wherein, produce wavefront information by the light path of dithered beam under chattering frequency, wavefront information is arranged in the frequency band around the chattering frequency.
9, according to the described equipment of claim 4, wherein separation module comprises:
The splitter that the middle signal of telecommunication is divided at least two components;
Coupled to receive one of component, so that produce the first frequency filter of the wavefront signal of telecommunication; With
Coupled receiving another component, so that produce the second frequency filter of datagram number.
10, according to the described equipment of claim 4, wherein separation module comprises:
The middle signal of telecommunication is applied the variable gain parts of time-varying gain; With
Couple with the variable gain parts, be used to regulate time-varying gain, so that the automatic gain control module of the amplitude equalization of the middle signal of telecommunication, wherein the Jun Heng middle signal of telecommunication comprises described data, and time-varying gain comprises wavefront information.
11, according to the described equipment of claim 1, wherein:
Optical-electrical converter comprises the sub-aperture part of receiving beam and the sub-aperture part of light beam is converted to the optical-electrical converter of a plurality of detector parts of the middle signal of telecommunication; With
Separation module produces the wavefront signal of telecommunication according to middle the signal of telecommunication that separates, and according to the middle signal of telecommunication generation datagram of combination number.
12, according to the described equipment of claim 11, wherein separation module according to the middle signal of telecommunication with produce datagram number.
13, according to the described equipment of claim 11, wherein in the middle signal of telecommunication, wavefront information and data are separated on frequency; Separation module frequency separation wavefront information and data.
14, according to the described equipment of claim 11, wherein separation module comprises:
Receive the middle signal of telecommunication and separate wavefront information and the dividing network of data.
15, according to the described equipment of claim 11, wherein separation module comprises:
An amplifier that is used for the middle signal of telecommunication of each separation; With
An amplifier of the middle signal of telecommunication that is used to make up.
16, a kind of adaptive optics module that is used for wavefront correction and transfer of data, described adaptive optics module comprises:
Reception utilizes the light beam of digital coding, and produce the composite wave of the wavefront signal of telecommunication and datagram number according to light beam before/data pick-up, the wavefront signal of telecommunication comprises the wavefront information relevant with the wavefront of light beam, and datagram number comprises described data; With
Couple with the wavefront/data pick-up of combination, and be arranged in the variable phase equipment of the light path of light beam, the described variable phase device responds wavefront signal of telecommunication is introduced adjustable phase in light path.
17, according to the described adaptive optics module of claim 16, wherein Zu He wavefront/data pick-up comprises:
Receiving beam and Beam Transformation become in the middle of the optical-electrical converter of the signal of telecommunication, described in the middle of the signal of telecommunication comprise described data and wavefront information; With
Couple with optical-electrical converter, produce the separation module of the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication.
18, according to the described adaptive optics module of claim 16, also comprise:
Produce the reflector of the data-encoded light beam of anti-spread, wherein reflector is positioned, and makes the data-encoded light beam of variable phase equipment precorrection anti-spread.
19, according to the described adaptive optics module of claim 16, wherein variable phase equipment comprises a deformable mirror.
20, according to the described adaptive optics module of claim 19, wherein deformable mirror is the deformable curvature speculum.
21, according to the described adaptive optics module of claim 20, wherein the deformable curvature speculum comprises:
First and second parallel-plates of resistance material, described first and second flaggies stack, described first plate has outer surface and the imaging plane that is positioned on the described first plate outer surface, described second plate has outer surface, the pattern of electrode section is positioned on the described second plate outer surface, each described electrode section has it is applied variable voltage, so that make the absolute electrode terminal of deformable curvature speculum distortion selectively.
22, according to the described adaptive optics module of claim 16, wherein wavefront information comprises wave-front curvature.
23, according to the described adaptive optics module of claim 16, wherein optical-electrical converter receives and defocuses pupil image.
24, according to the described adaptive optics module of claim 23, also comprise:
Be positioned at the oscillating mirror of optical-electrical converter upstream, described oscillating mirror is introduced in pupil image and is defocused.
25, according to the described adaptive optics module of claim 16, also comprise the optics of telescope device of collecting light beam.
26, according to the described adaptive optics module of claim 16, wherein adjustable phase is only proofreaied and correct the distortion that grade is equal to or less than inclination.
27, according to the described adaptive optics module of claim 16, wherein adjustable phase is proofreaied and correct at least one distortion that grade is equal to or higher than focusing.
28, according to the described adaptive optics module of claim 16, wherein:
Light beam comprises with the incipient beam of light of digital coding and the detecting light beam of anti-spread; With
Wavefront/the data detector of combination comprises:
To first detector layer of the wavelength sensitive of incipient beam of light, be used for incipient beam of light is converted to datagram number; With
To the wavelength sensitive of detecting light beam, and second detector layer overlapping with first detector layer, be used for detecting light beam is converted to the wavefront signal of telecommunication.
29, a kind of FSO transceiver comprises:
Collect optics of telescope device with the light beam of digital coding;
Be arranged in the deformable curvature speculum of the light path of light beam, the deformable curvature speculum is used to respond the wavefront signal of telecommunication, introduces adjustable phase in light path; With
Be arranged in the equipment that is used for wavefront detection and data snooping in the light path downstream of deformable curvature speculum, described equipment comprises:
The optical-electrical converter of the signal of telecommunication in the middle of the Beam Transformation one-tenth, the described middle signal of telecommunication comprises described data, and comprises the wavefront information relevant with the wave-front curvature of light beam; With
Couple with optical-electrical converter, produce the separation module of the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication, the wavefront signal of telecommunication comprises wavefront information, and datagram number comprises described data.
30, according to the described FSO transceiver of claim 29, wherein optical-electrical converter receives and defocuses pupil image.
31, according to the described FSO transceiver of claim 30, wherein
The equipment that is used for wavefront detection and data snooping also comprises the oscillating mirror that is positioned at the optical-electrical converter upstream, and described oscillating mirror is introduced in pupil image under chattering frequency and defocused;
Wavefront information is arranged in the frequency band around the chattering frequency, and data are positioned at the high frequency of frequency band that is positioned at than wavefront information; With
Separation module is according to frequency separation wavefront information and data.
32, according to the described FSO transceiver of claim 29, wherein:
The deformable curvature speculum comprises the first and second parallel-plate faces of resistance material, described first and second flaggies stack, described first plate has outer surface and the imaging plane that is positioned on the described first plate outer surface, described second plate has outer surface, the pattern of electrode section is positioned on the described second plate outer surface, each described electrode section has it is applied variable voltage, so that make the absolute electrode terminal of deformable curvature speculum distortion selectively;
Optical-electrical converter receives the out-of-focus image of deformable curvature speculum, and optical-electrical converter comprises the sub-aperture part of receiving beam, and the sub-aperture part of light beam is converted to a plurality of detector parts of the middle signal of telecommunication; With
Separation module produces the wavefront signal of telecommunication according to middle the signal of telecommunication that separates, according to the middle signal of telecommunication generation datagram of combination number.
33, according to the described FSO transceiver of claim 29, also comprise:
Produce the reflector of the data-encoded light beam of anti-spread, wherein reflector is positioned, and makes the data-encoded light beam of deformable curvature speculum precorrection anti-spread.
34, the method for a kind of wavefront detection and data snooping comprises:
Reception utilizes the light beam of digital coding;
Beam Transformation is become the middle signal of telecommunication, and the described middle signal of telecommunication comprises described data, and comprises the wavefront information relevant with the wavefront of light beam; With
Produce the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication, the wavefront signal of telecommunication comprises wavefront information, and datagram number comprises described data.
35, according to the described method of claim 34, wherein:
In the middle signal of telecommunication, wavefront information and data are separated on frequency;
The step that produces the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication comprises according to frequency separation wavefront information and data.
36, according to the described method of claim 35, wherein the light path by dithered beam under chattering frequency produces wavefront information, and wavefront information is arranged in the frequency band around the chattering frequency.
37, according to the described method of claim 34, wherein:
Become Beam Transformation the step of the middle signal of telecommunication to comprise the sub-aperture part of light beam is converted to the middle signal of telecommunication; With
The step that produces the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication comprises:
According to middle the signal of telecommunication generation wavefront signal of telecommunication that separates and
According to middle the signal of telecommunication generation datagram of combination number.
38, the method for a kind of wavefront correction and data transmission comprises:
Reception utilizes the light beam of digital coding;
Beam Transformation is become the middle signal of telecommunication, and the described middle signal of telecommunication comprises described data, and comprises the wavefront information relevant with the wavefront of light beam;
Produce the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication, the wavefront signal of telecommunication comprises wavefront information, and datagram number comprises described data; With
Phase place in the light path of response wavefront signal of telecommunication adjustment light beam.
39, according to the described method of claim 38, also comprise:
Produce the data-encoded light beam of anti-spread, wherein the data-encoded light beam of the adjustment phase precorrection anti-spread of light path.
40, according to the described method of claim 38, the step of wherein adjusting the phase place of light path comprises the curvature of the wavefront of adjusting light beam.
41, according to the described method of claim 38, wherein wavefront information comprises wave-front curvature.
42, a kind of FSO data transmission method comprises:
Collect light beam with digital coding;
Beam Transformation is become the middle signal of telecommunication, and the described middle signal of telecommunication comprises described data, and comprises the wavefront information relevant with the wave-front curvature of light beam;
Produce the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication, the wavefront signal of telecommunication comprises wavefront information, datagram number comprise described data and
Phase place in the light path of response wavefront signal of telecommunication adjustment light beam.
43, according to the described method of claim 42, wherein:
Become Beam Transformation the step of the middle signal of telecommunication to comprise:
With the light path of chattering frequency dithered beam, thus produce the mydriasis image and
The mydriasis image transitions is become the middle signal of telecommunication;
Wavefront information is arranged in the frequency band around the chattering frequency, and data are positioned at the high frequency of frequency band that is positioned at than wavefront information; With
The step that produces the wavefront signal of telecommunication and datagram number according to the middle signal of telecommunication comprises according to frequency separation wavefront information and data.
44, according to the described method of claim 42, also comprise:
Produce the data-encoded light beam of anti-spread, wherein the data-encoded light beam of the adjustment phase precorrection anti-spread of light path.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41962402P | 2002-10-17 | 2002-10-17 | |
| US60/419,624 | 2002-10-17 | ||
| US60/419,878 | 2002-10-18 | ||
| US60/688,575 | 2003-10-16 |
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| CN1839570A true CN1839570A (en) | 2006-09-27 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101982948A (en) * | 2010-11-08 | 2011-03-02 | 北京邮电大学 | FSO (free space optic) dynamic networking method based on back scattering estimation |
| CN102017471A (en) * | 2008-04-29 | 2011-04-13 | 空中客车营运有限公司 | Optical free space data transmission |
| CN104570321A (en) * | 2014-12-30 | 2015-04-29 | 中国科学院长春光学精密机械与物理研究所 | Meter-scale vehicle-mounted adaptive optical imaging telescope |
-
2003
- 2003-10-17 CN CNA2003801053218A patent/CN1839570A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102017471A (en) * | 2008-04-29 | 2011-04-13 | 空中客车营运有限公司 | Optical free space data transmission |
| CN101982948A (en) * | 2010-11-08 | 2011-03-02 | 北京邮电大学 | FSO (free space optic) dynamic networking method based on back scattering estimation |
| CN104570321A (en) * | 2014-12-30 | 2015-04-29 | 中国科学院长春光学精密机械与物理研究所 | Meter-scale vehicle-mounted adaptive optical imaging telescope |
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