CN101237283A - Directly modulated or externally modulated laser optical transmission system with feed forward noise cancellation - Google Patents
Directly modulated or externally modulated laser optical transmission system with feed forward noise cancellation Download PDFInfo
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- CN101237283A CN101237283A CNA2007103071530A CN200710307153A CN101237283A CN 101237283 A CN101237283 A CN 101237283A CN A2007103071530 A CNA2007103071530 A CN A2007103071530A CN 200710307153 A CN200710307153 A CN 200710307153A CN 101237283 A CN101237283 A CN 101237283A
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- laser
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/58—Compensation for non-linear transmitter output
Abstract
The invention provides an optical transmitter for generating a modulated optical signal for transmission over a fiber optic link to a remote receiver including a laser; a modulator for externally modulating the optical output signal with a RF signal to produce an optical signal including a modulated information-containing component; and a phase modulator coupled either to the output of the modulator or directly to the output of the laser for canceling the noise signals generated in the laser.
Description
Technical field
The present invention relates to a kind of optical transmission system that is used for analog signal, and more particularly, relate to the solid-state laser of a kind of direct modulation or external modulation.In addition, the present invention relates to eliminate by the many noises that may originate the white noise component (white noise) that produces or produce such as the Brownian movement of charge carrier (its and frequency change on the contrary, and so are commonly referred to " 1/f " noise) for example in the semiconductor laser by the bias current or the fluctuation in the thermal environment of laser.
Background technology
Be considered in this technology known being used for the analog intensity of direct modulated luminescence diode of the signal of telecommunication (LED) or semiconductor laser and on optical fiber, transmit for example straightforward procedure of analog signal such as voice and video signal.Have significantly less bandwidth requirement although the advantage of this type of analogue transmission technology is to compare with Digital Transmission such as for example digit pulse code modulated or simulation or pulse frequency modulated, use Modulation and Amplitude Modulation usually the noise and the distortion characteristic of reflector to be proposed comparatively strict requirement.
Owing to these reasons, under the situation that is applied to adopt short transmission link, use direct modulation technique in conjunction with the 1310nm laser with scattered optical fiber link of penetrating.For being applied to metropolitan area and long-distance optical fiber transmission link, the link low-loss requires to use the 1550nm laser of external modulation, crosses very long distance (100km) and high-frequency (surpassing 900MHz) usually.The limiting factor of this type of link may be the conversion from the residual phase noise of laser, and described residual phase noise converts amplitude noise to via the scattering that exists in the optical fiber link.Therefore the present invention is absorbed in the problem of the simple and low-cost system that is provided for the noise removing that is associated with the phase noise of laser, makes simulated optical output can be used for metropolitan area and long-reach optics network, in particular for the analogue transmission of broadband RF signal.
The direct current-modulation of laser becomes known for the digit optical transmission system, for example dense wave division multipurpose (DWDM) system." DWDM Networks, Devices, and Technology " (IEEEPress, 2003, the 154 pages) referring to (for example) Kartalopoulos.
Except to the desired low noise figure of 1550nm simulated optical transmission system, described system also is necessary for highly linear.In the specific simulating emitter intrinsic distortion to stop linear electrical modulation signal be optical signalling by linear transformation, but cause described distorted signals.These influences are harmful especially for the multichannel video transmission, and described multichannel video transmission requires fabulous linearity in case channel is interfering with each other.The simulated optical system of highly linearization is widely used in commercial analogue system, for example broadcasts TV transmission, CATV, interactive TV and visual telephone transmission.
To the linearizing research of optics and other non-linear reflector for some time, but proposed solution has shortcoming in practice.The bandwidth that major applications discussed above had is excessive for many actual embodiments.Be used for the complicated system component of linearizing feed-forward technique needs, for example luminous power combiner and a plurality of light source.The quasi-optics feed-forward technique suffers similar complexity problem, and the part that need mate fabulously in addition.Yet as discussed below, the forward direction technology that is used for the phase noise elimination is the practical technique that can use many exploitation good technical to implement.
As mentioned above, the known external modulator that in optical transmission system, uses in the prior art.The 5th, 699, No. 179 United States Patent (USP) is described a kind of external modulation and feedforward linearized simulated optical reflector that optical fiber brings out compound secondary (CSO) distortion component that be used to reduce.
Before the present invention, use the purpose of the phase noise component that the phase-modulator be coupled to direct (electric current) modulated laser produces with the various noise sources that are used for eliminating by the semiconductor structure of laser as yet.It should be noted that semiconductor laser represents noise in its amplitude (being commonly referred to relative intensity noise) and its phase place.These noise characteristics are irrelevant with optical maser wavelength basically, but noise can be sentenced the different modes appearance at different wave length in the single mode fibers transmission.The main internal mechanism that causes phase place and amplitude noise is the spontaneous emission in the active region of laser.Because the photon of spontaneous emission does not have given phase relation with those photons that produce via stimulated emission, thereby the amplitude of gained light field and phase place all are affected.Spontaneous emission process is well-known, and has been shown as by the Brownian motion process description, and wherein noise spectrum is constant (white noise) basically in frequency of operation.In the laser outside, for example environmental impacts such as microphone effect, temperature fluctuation and bias current noise also can produce phase noise in light field.These incidents cause the light phase noise usually, and it represents the noise spectrum with " 1/f " correlation.The present invention manage by feedforward eliminate minimize from the proper phase noise of semiconductor laser and no matter the driving mechanism of noise how.
Summary of the invention
1. goal of the invention
The object of the present invention is to provide a kind of improvement optical transmission system that uses direct modulated laser.
Another object of the present invention is to compensate the noise of the laser that is used for the simulated optical transmission system.
A further object of the present invention is to provide a kind of 1550nm of being used for simulated optical transmission system to improve the outside Mach Zender modulator that phase noise reduces.
Another purpose of the present invention is to provide a kind of and is applicable to that long distance dispersion optical fiber media and use have the highly linear simulated optical transmission system of the direct modulated laser of phase-correcting circuit.
Another purpose of the present invention is to provide a kind of and is used at the phase-shift circuit of the simulated optical transmission system reduction that is applicable to long distance dispersion optical fiber media from the residual phase noise of laser.
The present invention also aims to provide the phase noise compensation process in the simulated optical transmission system of a kind of broadband.
2. inventive features
In brief and put it briefly, the invention provides and a kind ofly be used to produce optical modulation for via the optical launcher that disperses the optical fiber link transmission to remote receiver, it has: input is used to receive the input of broadband analog radio-frequency signal; Semiconductor laser, it is used to produce the optical signalling with the phase noise that is associated; And noise canceller circuit, it comprise optical phase modulator with the phase noise that is used for reducing optical launcher output and and then reduce that the receiver end place of optical fiber link presents because the distorted signals that the phase modulated noise component causes.
On the other hand, the invention provides a kind ofly for via the optical transmission system that disperses optical fiber link to use, it comprises: the optical launcher with analog signal input; Semiconductor laser; Modulation circuit is used for directly modulating described laser; And the phase deviation circuit, be used for the optical phase modulation product that is associated with external modulator at the optical signalling noise removing that produces by semiconductor laser.
On the other hand, the present invention further provides the direct modulation technique of a kind of low cost, it preferably includes the circuit that is used to control optical phase modulator, and described optical phase modulator is used to reduce the phase noise component that laser produces.
In another aspect of this invention, a kind of noise canceller circuit that is used for reducing in analog signal transmission phase noise is provided, it will split into two paths from the output optical signalling of semiconductor laser, and one leads to phase-modulator and another leads to frequency discriminator.On amplitude and phase place, adjust frequency or the phase place dependence of described phase modulated erasure signal with the phase noise of coupling laser generation.The phase place of described signal by described path one in delay or phase adjustment element synchronous.Then main and secondary signal only has amplitude-modulated single optical signalling with generation by the optical phase modulator reorganization.Therefore, phase-modulator is modulated main signal from semiconductor laser in the mode that minimizes the gained phase noise, thereby makes analog signal be suitable for via disperseing the optical fiber link transmission.
According to this disclosure (comprise following be described in detail in) and, be understood by those skilled in the art that extra purpose of the present invention, advantage and novel feature by putting into practice the present invention.When hereinafter describing when of the present invention, should understand the present invention and be not limited to this referring to preferred embodiment.Can access additional application, modification and the embodiment in other field of those skilled in the art will realize that of this paper teaching, described additional application, modification and embodiment belong in the scope of the invention that discloses in this article and advocate, and the present invention can have remarkable effectiveness with respect to it.
Description of drawings
In conjunction with the drawings referring to following detailed description, will understand and more fully understand these and other feature of the present invention and advantage better, wherein:
Fig. 1 (a) is the height simplified block diagram of external modulation optical transmission system well known in the prior art;
Fig. 1 (b) is the height simplified block diagram of direct modulated optical transmission system well known in the prior art;
Fig. 2 is the height simplified block diagram according to optical transmission system of the present invention.
Statement novel feature of the present invention and characteristic in appended claims.Yet, can be in conjunction with the drawings referring to the detailed description of specific embodiment is come the best the present invention of understanding itself and further feature and advantage.
Embodiment
Now will describe details of the present invention, comprise its exemplary aspect and embodiment.Referring to the accompanying drawings and the description below, same reference numerals is used to discern identical or intimate element, and wishes the principal character with the graphic mode explanation one exemplary embodiment of highly simplifying.In addition, do not wish that accompanying drawing describes each feature of practical embodiments or the relative size of institute's elements depicted, and accompanying drawing is not drawn in proportion.
Fig. 1 (a) is as the 5th, 699, the block diagram of the prior art optical launcher that utilizes external modulator that No. 179 United States Patent (USP)s represent.Described reflector (usually with 10 show) via fiber path 30 to receiver 60 transmitting optics signals.Reflector 10 comprises semiconductor laser 12, and it produces continuous wave (CW) output.The representative instance of this type of laser is distributed Feedback (DFB) laser and/or Fabry-Perot laser, and it is with 1, and the wavelength of 550nm produces output beam.Unmodulated optics signal from laser is coupled to modulator 16 by optical fiber 14.Modulator 16 can be an above modulator in single modulator, cascade MZ modulator or for example feedforward linearized circuit of for example Mach-Zehnder modulator.Modulator 16 also receives broadband RF signal, for example Modulation and Amplitude Modulation residual sideband (AM-SDB) cable TV (CATV) or vision signal via terminal 18 and circuit 20.In addition, when using feedforward linearized circuit, provide the signal that depolarizes to modulator 16 via terminal 22 and circuit 24.The described signal that depolarizes is used at modulator 16 the optics input of error correction modulator (not shown) being depolarized.
What carry video data is coupled to amplifier 28 through optical modulation by optical fiber link 26.Amplifier 28 is erbium doped optic fibre amplifier (EDFA) normally.Optical signalling through amplifying is coupled to the optical fiber transmission line 30 towards receiver 60.Described optical fiber transmission line 30 can be the long-distance link of several kms of extend past.In the case, can provide for example EDFA 28 line amplifiers such as grade with spacing distance therein along described circuit, so that described signal is boosted to required level.At receiver 60 places, also can provide the amplifier optical signalling that (not shown) imports into to boost.Then the signal through boosting is applied to photoelectric detector and at receiver 60 places its demodulation is made as the signal of telecommunication, the described signal of telecommunication is represented the original video or the data-signal at circuit 50 places.
Fig. 1 (b) is the block diagram of prior art optical launcher that utilizes the direct current-modulation of laser.The broadband RF analog signal is applied directly to laser 12.Optical modulation from laser 12 is coupled to amplifier 28, for example EDFA by optical fiber link 26.Optical signalling through amplifying is coupled to the optical fiber transmission line 30 towards receiver 60.At the receiver place, convert optical signalling to the signal of telecommunication, the described signal of telecommunication is represented the original video or the data-signal at circuit 50 places.
Fig. 2 is the height simplified block diagram according to optical transmission system 100 of the present invention.Show analog rf signal input source 101 (broadband signal that for example comprises a plurality of channels) and predistortion circuits 105 among the figure.Come rightly the RF signal that is applied to laser 102 to be carried out predistortion by using predistortion circuit 105, as known in the state of the art, to be used to revise the nonlinear response of the RF signal that is applied to laser with the signal that influences the remote receiver place of compensate for laser.The output of predistortion circuit 105 is applied to laser 102 to come it is modulated.The modulation of the laser 102 among the present invention can be AM-VSB modulator or quadrature amplitude modulation device.The optical signalling output 110 of laser is split into two parts: a part is applied to phase-modulator 111; Another part is applied to frequency discriminator circuit 115.
Employed edge-emission semiconductor laser distributed feedback laser (DFB) preferably in Fig. 2 system, but can use Fabry-Perto (FP) laser equally.Distributed Feedback Laser is an optimization approach, because its optics output mainly is included in the single zlasing mode, and the optical energy of FP laser is dispersed in the middle of many patterns.
In a preferred embodiment, described laser is that the laser optical output wavelength is at 1530 outside cavity gas lasers that arrive in the 1570nm scope.In addition, broadband analog signal input has greater than the bandwidth of an octave and comprises that a plurality of different information carry channel.
The output of frequency discriminating 115 is applied to circuit for signal conditioning 103, and described circuit 103 is made up of the tandem sequence circuit of the output RF signal of frequency discriminator being carried out the phase ETTHER-OR operation.The RF signal is applied to attenuator 116 adjusting the amplitude of described signal rightly, matches with the amplitude of the phase deviation component introduced with the phase noise feature of laser 102.
The output of attenuator then is connected to phase deviation circuit 117.Circuit 117 is proofreaied and correct the time lag that the described signal with being applied to modulator 111 of the signal output that is applied to circuit element 115,116,117 is compared.In the video transmission frequency band of being paid close attention to (is 50MHz-1000MHz for traditional C ATV system), the phase noise of semiconductor laser is " in vain ", i.e. the spectral power density of noise and frequency-independent.In the case, the phasing path has constant (can adjust) gain with needs, and it postpones just in time to mate with the delay of predominating path.Needing an aspect of explanation is frequency discriminator, and specifically the optics in the phasing path is to the electricity transfer process.When photodiode detects optical signalling, observe the phenomenon that is called shot noise.This noise is to produce with the statistic processes that produces electron-hole pair by absorb photon in photodiode.This noise is inevitable for all practical purposes.Therefore, shot noise will constitute lower limit to attainable phase noise amount of cancellation.
Then the output with phase deviation circuit 117 is applied to phase-modulator 111, with so that with phasing be incorporated in the optical signalling with so that proofread and correct or noise that compensation is produced.
The pectrum noise density of the photoelectric current that produces from photodiode is given as
<i
n 2>＝2eI
p
Wherein e is electron charge and I
pIt is the DC photoelectric current.The those skilled in the art will recognize such fact immediately: noise power has linear dependence to the optical power that is received, and improved along with the increase of institute's received power by the signal to noise ratio of the process of shot noise domination.This represent propose the invention in basic design tradeoff.The more power that is switched in the phasing path will be that cost is improved final noise removing with the optics power output of reflector.
The output of modulator 111 is coupled to amplifier 113 via optical fiber 112, and described amplifier 113 then is connected to optical fiber or link 114.At far-end, optical fiber or link 114 are connected to receiver, and described receiver is converted to the RF signal with the optical signalling that is received.
Under the situation that does not break away from the spirit and scope of the present invention, it will be apparent to those skilled in the art that many changes and modification.For instance, although in the context of TV signal modulated laser or light-emitting diode, be described and illustrate, can eliminate for example inherent distortion of other non-linear device such as amplifier by this technology to a great extent.The precision adjustment of the relative phase of the signal in the main and secondary path is in the illustrated embodiment in secondary path, but this also can be in having the predominating path of rough adjustment.Secondary path is preferred, because this type of delay in the predominating path may have inappropriate impedance to this path.
The various aspects of technology of the present invention and device can be implemented in digital circuit or computer hardware, firmware, software or its combination.Circuit of the present invention can be implemented in computer product (it visibly is implemented in the machine-readable storage device for programmable processor and carries out) or go up and implement at the software that is positioned at network node or website place (its can be automatically or download to as required computer product).Aforementioned techniques can be carried out by the gate array of (for example) single central processing unit, multiprocessor, one or more digital signal processors, gate or hard-wired logic, and described device is used to carry out a sequence signal or instruction repertorie to carry out function of the present invention by output is operated and produced to the input data.Described method can advantageously be implemented in one or more computer programs that can carry out on programmable system, and described programmable system comprises that at least one is through programmable processor, at least one input/output device and at least one output device of coupling to receive data and instruction from data-storage system and to transmit data and instruction to data-storage system.Each computer program can be optionally implemented with advanced procedures or object oriented programming languages or with compilation or machine language; And under any circumstance, described language can be compiling or interpreter language.For instance, Shi Yi processor comprises general purpose microprocessor and special microprocessor.In general, processor will receive instruction and data from read-only memory and/or random access memory.The storage device that is suitable for visibly implementing computer program instructions and data comprises and the nonvolatile memory of form of ownership comprises: semiconductor device, for example EPROM, EEPROM and flash memory device for instance; Disk, for example internal hard drive and removable dish; Magneto optical disk; And CD-ROM dish.Any aforementioned means can be replenished or is incorporated among the ASIC by specially designed application-specific integrated circuit (ASIC) (ASIC).
To understand, each in the said elements or both or both more than also can effectively be applied to the structure of other type different with the above-mentioned type together.
Although, do not wish that it is limited to the details of being showed, because can under the situation that breaks away from spirit of the present invention never in any form, make various modifications and structural change with the present invention explanation and be described as in optical transmission system, implementing.
Do not doing under the situation about further analyzing, aforementioned content will represent main points of the present invention so comprehensively, make other people under the situation of the feature that is not omitted in the intrinsic propesties that constitutes the general or particular aspects of the present invention on the prior art position fully, to adjust being used for various application it easily, and therefore this type of is adjusted and should and wish to be included in the equivalence meaning and scope of appended claims by using current knowledge.
Claims (7)
1. one kind is used to produce through optical modulation to be transferred to the optical launcher of remote receiver via optical fiber link, and it comprises:
Laser, it is used to produce the base band optical signalling of the noise expansion that comprises on the frequency spectrum;
Modulator, it is used for analog rf signal described laser being carried out direct Modulation and Amplitude Modulation, comprises with generation and containing through the component of amplitude modulation information and the optical signalling of phase-modulated component; And
Phase-modulator, its output that is coupled to described laser is to be used to eliminate the phase noise that is associated with described optical signalling.
2. reflector according to claim 1, wherein said laser is a semiconductor laser, and described phase-modulator is eliminated the noise component(s) in the output signal of described laser.
3. reflector according to claim 1, wherein said phase-modulator increase the SBS threshold value of the optical signalling of described remote receiver place reception.
4. reflector according to claim 1, it further comprises the frequency discriminator circuit, described circuit has the input of the described output that is connected to described laser and is coupled to photodiode output, so that the described phase noise in the described optical signalling is converted to the modulation signal that is applied to described phase-modulator,, eliminates effective phase noise so that taking place.
5. reflector according to claim 1, the wavelength of the light output of wherein said laser arrives in the 1570nm scope 1530.
6. reflector according to claim 1, wherein broadband analog signal input has greater than the bandwidth of an octave and comprises that a plurality of different information carry channel.
7. reflector according to claim 1, it further comprises predistortion circuit, and it is used to revise the nonlinear response with the signal at the described remote receiver of the influence that compensates described laser place of the described RF signal that is applied to described laser.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11/701,742 US7881621B2 (en) | 2006-03-02 | 2007-02-02 | Optical transmission system with directly modulated laser and feed forward noise cancellation |
| US11/701,742 | 2007-02-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101237283A true CN101237283A (en) | 2008-08-06 |
| CN101237283B CN101237283B (en) | 2016-02-24 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN200710307153.0A Expired - Fee Related CN101237283B (en) | 2007-02-02 | 2007-12-27 | There is directly modulation or the externally modulated laser optical transmission system of feed-forward noise elimination |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP5512090B2 (en) |
| KR (1) | KR20080072520A (en) |
| CN (1) | CN101237283B (en) |
| TW (1) | TW200835182A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103575408A (en) * | 2013-10-29 | 2014-02-12 | 桂林电子科技大学 | Coherent light detection system and method for optical fiber delay line phase control |
| CN112393692A (en) * | 2019-08-14 | 2021-02-23 | Oppo广东移动通信有限公司 | Laser projection module, image acquisition module, depth camera and electronic equipment |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5424939B2 (en) * | 2010-03-01 | 2014-02-26 | 日本電信電話株式会社 | Optical phase noise suppression circuit, phase fluctuation detection circuit, and phase fluctuation detection method |
| JP6232334B2 (en) * | 2014-04-17 | 2017-11-15 | 日本電信電話株式会社 | Laser phase noise reduction device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060210282A1 (en) * | 2005-03-15 | 2006-09-21 | John Iannelli | Directly modulated laser optical transmission system with phase modulation |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8602017D0 (en) * | 1986-01-28 | 1986-03-05 | British Telecomm | Reducing fluctuations in radiation beam characteristic |
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2007
- 2007-12-10 TW TW096147089A patent/TW200835182A/en unknown
- 2007-12-27 KR KR1020070139064A patent/KR20080072520A/en not_active Application Discontinuation
- 2007-12-27 CN CN200710307153.0A patent/CN101237283B/en not_active Expired - Fee Related
-
2008
- 2008-02-01 JP JP2008051203A patent/JP5512090B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060210282A1 (en) * | 2005-03-15 | 2006-09-21 | John Iannelli | Directly modulated laser optical transmission system with phase modulation |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103575408A (en) * | 2013-10-29 | 2014-02-12 | 桂林电子科技大学 | Coherent light detection system and method for optical fiber delay line phase control |
| CN103575408B (en) * | 2013-10-29 | 2017-04-12 | 桂林电子科技大学 | Coherent light detection system and method for optical fiber delay line phase control |
| CN112393692A (en) * | 2019-08-14 | 2021-02-23 | Oppo广东移动通信有限公司 | Laser projection module, image acquisition module, depth camera and electronic equipment |
Also Published As
| Publication number | Publication date |
|---|---|
| TW200835182A (en) | 2008-08-16 |
| KR20080072520A (en) | 2008-08-06 |
| CN101237283B (en) | 2016-02-24 |
| JP2008193709A (en) | 2008-08-21 |
| JP5512090B2 (en) | 2014-06-04 |
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