2012 Vol. 41, No. 8
2012, 41(8): 1965-1970.
The brightness temperatures of IR spectral radiation of cirrus atmosphere with different cirrus altitude were computed by a combined atmospheric radiative transfer (CART) model. The effects of cirrus altitude on brightness temperature spectra of different IR bands and on the retrieval of optical thickness and effective size of cirrus were analyzed. The results show that the variation of IR brightness temperature with cirrus altitude in the atmospheric window region is consistent with the atmospheric temperature profile below the tropopause. The slope of the brightness temperature from 790 cm-1 to 960 cm-1 bands increases with the altitude of cirrus clouds. Variation of brightness temperature difference between 900 cm-1 and 1 231 cm-1 bands to cirrus altitude is sensitive to thin cirrus and small effective size. Variation of brightness temperature difference between 900 cm-1and 1 559 cm-1 bands to cirrus altitude is basically not dependent on effective size and optical thickness for thick cirrus. Thus, the effects of cirrus altitude on the remote sensing of optical quantitation of cirrus parameters should be considered.
2012, 41(8): 1971-1978.
Dual-band quantum well infrared photodetectors(QWIP) have been proved to be a kind of important third-generation infrared photodetectors. However, there are few systematic calculations and optimization design on the structure of its active regions and coupling grating. Based on envelope function approximation, transfer-matrix method(TMM) and classical grating theory, a MWIR-LWIR dual-band QWIP was designed, and detailed calculations on the structural parameters of multi-period active regions and 2-D coupling grating was presented. Lattice matched GaAs/AlGaAs MQW and strained InGaAs/GaAs/AlGaAs mini-band SLs were adopted as LWIR and MWIR active regions respectively, and the corresponding peak absorption wavelengths were 8.5 m and 4.5 m. Moreover, the type of electron transition was designed as B-QB to decrease the dark current and increase the detectivity. Besides, through optimized design, the dual-band incident IR radiations of LWIR and MWIR can be coupled effectively by a 2-D diffraction grating with single period.
2012, 41(8): 1979-1984.
IR images of airplane generated by simulation are very important data source for IR based air target identification. To improve the simulations validity and real time performance, amendments on the existing IR simulation algorithms were proposed in this paper, a simulation platform was also built. First, IR radiation characteristics of the whole aircraft was analyzed comprehensively. IR calculation models of aircraft components such as engine, plum, and skin were established based on the blackbody radiation theory. Amendment on the calculation methods of skin temperature and aircraft velocity on IR model were proposed. Then the simulation platform was built based on OpenSceneGraph(OSG) in VS2005 C++, this system can dynamically change the aircrafts IR performance and generate the IR images of the aircraft in real time. Simulation result demonstrates that the proposed IR model can provide more accurate data sources for the IR based air target identification than existing models. Besides, the single target simulation can be updated up to 100 frames per-second which is sufficient for real-time simulation.
2012, 41(8): 1985-1989.
Aiming at the difficulties of charactering the optical inhomogeneity of opaque Ge-Sb-Se chalcogenide glasses(internal stripes, cracks, bubbles, uniformity, etc.), a new method was proposed which used the transmission image, line spread function and modulation transfer function(MTF), and the corresponding detection device was also established. On this basis, we studied the internal defects and optical inhomogeneity of the self-made Ge28Sb12Se60(mol%)chalcogenide glass and analyzed the influence of sample flatness and parallelism influence on the test results. The results show the near infrared imaging can clearly detect the stripes distribution and defects in the sample, the line spread function and MTF can characterize the inhomogeneity features semi-quantitatively. The experimental and theoretical average of MTF is with a difference of less than 10% when the surface aperature of samples is less than 1.
2012, 41(8): 1990-1994.
A real-time data acquisition and processing technique of long linear infrared detectors which was realized on FPGA was introduced. A method of rearrangement of parity line detectors was illustrated with FPGA. By illustrating traditional 2D linear extrapolation blind pixel detection and restoration algorithm, an improved one, which well fitted the case when several blind pixels bordered each other and reduced the detection and restoration efficiency, was proposed. Non-uniformity correction(NUC) of detectors was implemented inside FPGA by referring to the proposed data processing organization. The experiment results show that the mentioned data acquisition and processing techniques can raise data transmission efficiency to a great degree. Meanwhile, it possesses the characteristic of well real-time and can be widely applied in related area.
This investigation compared the brightness temperatures observed by infrared band of FY-3A MERSI using on-board radiometric calibration coefficients with that simulated surface observation data. The primary surface data were collected from the simultaneous observation in Qinghai Lake site in 2008, 2009 and Dunhuang site in 2010, and buoy data in Qinghai Lake site in 2008 and 2009. Seven and eighteen groups of available data from the simultaneous observation data using optical instruments and buoy data in Qinghai Lake were used. It was found that the observed brightness temperatures by medium resolution spectral imager(MERSI) sensor were basically higher than the results derived from buoy data at nighttime, and the results were opposite at daytime. To sum up, the results from both simultaneous observation and buoy data indicate that the brightness temperatures observed by MERSI sensor are 1.721.18 K, which are systematically higher than the simulated results using surface observation data, which is mainly attributed to the variations of emissivity of on-board blackbody without calibration.
2012, 41(8): 2002-2007.
Infrared detection of the ground target was greatly determined by the radiation contrast between the target and its background. The influence of emissivity of target and temperature difference on radiation contrast was briefly discussed. Factors on buildings and cement floor temperature were also analyzed. The model that computed temperature was built on the basis of finite difference method and realized by MATLAB. The target-background radiation contrast at 8-14m was calculated on the basis of the simulated temperature. It turns out that the radiation contrast of the same target and background changes significantly under different conditions. Variation trends of radiation contrast of the same target and background when observed in different azimuths are also presented.
2012, 41(8): 2008-2011.
A Resistive Trans-impedance Amplifier(RTIA) readout circuit for Uncooled Focal Plane Array (UFPA) using active resistor was proposed in this paper. By using a sub-threshold MOSFET as a 1011 and above feedback resistor, a high gain current amplifier could be realized by common source structure which consisted of two transistors. The simple three transistors could be easily integrated under pixel and it had good impedance matching with pyroelectric infrared detector. Compared with traditional RTIAs which use special high-resistance materials as feedback resistor, the novel RTIA was low cost because no additional materials and processes were needed. The circuit was successfully manufactured by 0.5 um standard CMOS process of CSMC foundry. 40 dB gain and 3 V output swing were realized by this design and the gain and bandwidth of the chip kept stable during high and low temperature tests. So it can be used for large arrays pyroelectric detectors such as Lead Zirconate Titanate(PZT) and Barium Strontium Titanate (BST), etc.
2012, 41(8): 2023-2026.
The modulation characteristics of the liquid space light modulator was discussed, and its application in the large mode area photonic crystal fiber ultrafast laser amplification system was studied. The results indicated the real time control on pulse shape was realized. The influence of pump power on the spectral and temporal shape of strongly linearly chirped square pulse after amplification was discussed. By using a spectral pulse pre-shaping of the seed pulse before the power amplifier, the square pulse with 15-ps pulse duration, 13-nm bandwidth at 1 031-nm central wavelength was obtained. The results also demonstrate the significant role of liquid space light modulator in compensating pulse distortions induced by the asymmetric gain, by a pre-optimization of the seed pulse spectrum before amplification.
2012, 41(8): 2027-2032.
The transient temperature characteristics of high power laser diode(LD) with multiple emitters were presented and discussed in this paper. The transient temperature response curves were measured by electrical temperature sensitive parameter method. Structure function method was performed to evaluate the thermal resistance constitution for multiple emitters LD. The thermal resistance network model was adopted to characterize the thermal behavior of LDs with one, two and four emitters respectively. The experiment result shows that chip level thermal resistance of multiple emitters LD decreases in proportion to the number of emitters, while the package level thermal resistance remains unchangeable. The study provides an important reference for the thermal design of multiple emitters LD.
2012, 41(8): 2125-2129.
A ring frequency shifter based on the photonic crystal fiber was proposed. Based on Brillouin frequency shift theory, the frequency shifter could achieve a narrow linewidth and high-gain laser output for the photonic crystal fiber which had high Brillouin gain and low threshold, using the frequency selecting amplification technology of fiber optic ring resonator. The experiment results show that the threshold power of stimulated Brillouin scattering(SBS) of photonic crystal fiber is 457 mW, the frequency shift of stimulated Brillouin scattering wave compared with the incident light is 9.778 GHz with linewidth less than 500 kHz, the frequency shift can be finely adjusted by temperature. The frequency shifter can be applied in the distributed fiber optic Brillouin sensor and microwave generator.
2012, 41(8): 2012-2016.
The source and control mechanism of fusion splicing loss were analyzed for the splicing between the photonic crystal fibers with different air-hole fraction and single-mode fiber. The splice loss evolution with the splicing parameters, including the fusion current, fusion time, power of discharge, were experimentally studied. With a carefully adjustment, splicing loss as low as 0.22 dB was realized both for high and low air-hole fraction photonic crystal fibers. The fibers were used in experiments of generating supercontinuum and ytterbium doped large mode area photonic crystal fiber laser amplifier was used as pump source. Supercontinuum with power as high as 7.45 W and wavelength range from 650 nm to 1 750 nm was obtained.
2012, 41(8): 2017-2022.
The change of the distribution of electron density caused by photo-ionization when hv=5 eV and hv=10 eV was studied to identify the effect of ultraviolet pre-ionization on the main discharge. Firstly, the essential processes in the mixture gas under radiation of ultraviolet was introduced. Then a simple model was established. With the model, the distributions of electron density after the radiation of ultraviolet(hv=5 eV and hv=10 eV) were obtained. The results are as follows: the effective interaction lengths on hv=5 eV and hv=10 eV are 0.15 cm and 0.5 cm respectively under the condition of P=50 kPa and I=103 W/cm2. When the light intensity is increased to 106 W/cm2, the effective interaction lengths increase only to 0.3 cm and 0.8 cm respectively, which cant affect the main discharge effectively; when P=10 kPa, the effective interaction lengths are 1.1 cm and 2.7 cm, exerting large effect on the main discharge. According to the results, the conclusions is as follows: the ultraviolet with both 5 eV and 10 eV photon energy can affect the discharge effectively when P=10 kPa, and the pre-ionization could be more effective if the atmospheric pressure is lower.
2012, 41(8): 2033-2037.
In order to study the polarization properties of photonic crystals containing magnetic single-negative materials, an (AB)3(BA)3 symmetrical structured one-dimensional photonic crystal was constructed from common material A(SiO2) and magnetic single-negative material B. Numerical calculation results indicate that at the normal incidence, there is a very sharp tunneling model at 1 907 nm of the original band. For TE wave, when the incident angle increases，the permittivity B or the geometry thickness variation of B medium decreases, blue-shifts are observed with the edge of band gap. The width of the tunneling mode is narrowed, the transmittance and the full-width half-maximum does not change, but its position blue shifts. When the above three parameters change respectively, the transmission spectra and the tunneling mode of TM wave change as same as TE waves. Only when the incident angle increases, the blue shift of long-wave edge of TM wave band is less than TE waves. It is helpful for designing high-quality filter.
2012, 41(8): 2038-2041.
An efficient method of 593 nm yellow laser with a single LD pump source and Nd:YVO4 double crystals was reported. The theory was analyzed, the experiment device was designed and the experiment result was verified. The device was composed of laser diode, optical coupling system, Nd:YVO4 crystals, plan-curved mirror, LBO and totally reflecting mirror. By using V-type resonant cavity, with incident pump source with the 5 W power and the 808.7 nm wavelength, the experiment adopts typeⅠcritical phase-matched LBO as sum-frequency crystal, and the 244 mW yellow laser at 593 nm was obtained. The optical to optical conversion efficiency was 4.9%, the laser instability was about 5%. The experiment result shows that the intra-cavity sum-frequency in V-type resonant cavity can obtain 593 nm laser, and the method has structure compact and high conversion efficiency advantages, and can be used in many sum-frequency laser.
2012, 41(8): 2042-2047.
The received waveforms of laser altimeter were composed of multiple non-Gaussian waveforms appended with noise. It was absolutely crucial for retrieving the height and category of target by extracting the statistical parameters of non-Gaussian waveforms. Based on the feature of received pulse signal, its mathematics model was described with generalized Gaussian function. Using the method of smoothing filtering and calculating initial parameters on received waveforms, and the non-linear least squares algorithm, an analyzer with extracting the statistical parameters for received waveforms was developed. In terms of the analyzer, simulated waveforms processing and statistical parameters extraction were performed well. The analyzed results show that the maximal extraction error for statistical parameters is less than 1% for the single generalized Gaussian waveforms with 15 dB signal to noise ratio (SNR). Meanwhile, with the increase of the number of generalized Gaussian components and the decrease of SNR, extraction error for statistical parameters becomes larger. The statistical parameters can be extracted effectively with waveforms analyzer, which provides data gist for retrieving the target information.
The bidirectional reflection distribution of target satellite surface with different roughness was simulated by the formula of the bidirectional reflection distribution function(BRDF) in laser tracking in the space. The component of diffuse reflection became larger and the component of specular reflection became smaller with the increase of the target surface roughness. Meanwhile, the scattering angle became larger. These benefited the random receiving direction and decreased the sensitivity of receiving direction. The varieties of BRDF of target satellite surface affected by the change of the incident angle were also simulated. The change of bidirectional reflection distribution was obtained. The receiving echo increased with the increase of the component of specular reflection, when the incident angle was small and the illumination beam axis and receiving telescope axis were coaxial. The receiving echo power decreased quickly with the increase of the incident angle. When the incident angle was larger than 34, the minimum receiving echo power computed by BRDF was lower than the one computed by the formula of lidar supposing that the target satellite surface was Lambertian reflection plate. The illuminating laser power should become 5 times the former one or the receiving aperture became 2.5 times the former one. These methods could remove the effect of the decrease of the receiving echo power.
2012, 41(8): 2053-2057.
Instead of the original wind-head laser seeker, the gyro-stabilized seeker is used in new generation laser guidance bomb widely. In order to improve the acquisition probability of seeker, based on the analysis of different working mechanism between the two kinds of seeker, the influence on target acquisition probability was studied, which caused by the trajectory deviation and attack of angle from autopilot working error in the phase of zero-command planning flight. The theory of seeker acquisition ground zone was given. The relative distance error between the nominal center of acquisition ground zone and the target position was calculated and used as the bombing range modifying method of firing table, in order to decrease the influence of trajectory deviation caused by disturbance on acquisition probability. The simulation shows that the acquisition probability can be improved with the new firing table.
2012, 41(8): 2058-2062.
Anewmicro-opticalmethodforTerahertzradiationmeasurementwaspresented,whichwas basedonopticalleverandthermalradiationdetection.Abi-materialmicrocantileverwasusedtogenerate micro-deformationcausedbyTerahertzradiantthermaleffect,andthemicro-deformationwasmeasuredby amultiplereflectionopticallevercomposedofapairofplanemirrors.ThenradiationpowerofTerahertz waveswereobtained.Micro-displacementtheoreticalresolutionofthismultiplereflectionopticallever methodcouldbelessthan1nmandameasuringsystemwassetuptoverifyit.Experimentsshowthat theoreticalresolutionofthistestsystemislessthan4nmanditsactualresolutionwaslessthan10nm. DesignsandparametersofaTerahertzdetectorbasedonthismethodweregiven.Thisapproachhadmany advantagessuchasanti-airturbulence,anti-beamcross-talk,andworkingatroomtemperature.Sothisnew methodwassuitableforrealizingminiaturizedTerahertzdetectorswiththefeaturesofuncooled,real-time, low-cost,anditwasalsoappropriateformanufacturingarraydetectorsforimagingdetection.
2012, 41(8): 2063-2067.
The multiple scattering has happened when the laser pulse of the underwater lidar by wake is
in the near-field transmission. Its coaxial optical system has a certain near-field suppression ability to the
strong scattering and can prevent saturation of the receiver system. The near-field suppression ratio of the
coaxial optical system is of great significance. The reason for that the traditional formula of photon
returned contribution was not suitable for the near-field calculation was analyzed and a new formula was
presented for underwater near-field coaxial optical system. A simple method to solve it with coordinate
transforms was presented. The near-field suppression ratio was calculated based on Monte Carlo
simulation. The relationship between near-field suppression ratio and suppression time and the relationship
between near-field suppression ratio and the laser pulse width were analyzed and calculated. The results
prove that this method can satisfy the needs of underwater coaxial optical system analysis completely.
2012, 41(8): 2068-2072.
The airborne multi-pulse LADAR target signal simulator was studied based on signal model to
evaluate the performance of laser echo signal processing algorithms and their digital hardware platform.
Firstly, the main elements of target signal model and two definition of SNR were pointed out.
Subsequently, based on the ladar equation and 1.064 um laser radiation photoelectric receiver experiment,
the signal waveform was obtained and the target signal composition was analized. The echo signal model
was further established by the analysis of air target echo pulse broadening. Then, the method to generate
echo signal according to SNR was proposed based on the RMS value standardization of echo noise
samples. Finally, the implement of target signal simulator was given based on FPGA and high-speed D/A
and USB2.0 data transmission, which could provide the echo signal and sync -signal of static and
dynamic targets with the SNR of 1-9.
2012, 41(8): 2073-2078.
Non-line-of-sightimagingisanewkindofimagingmoderecentlyproposedbyforigncountries,
whichcanlookaroundcornersandbeyondthelineofsight.Inthispaper,theconceptofnon-line-of-sight
imagingmodebasedonlaserrange-gatedimagingtechnologywasillustrated,someforeigntypical
experimentsandexperimentresultsofitwerealsopresented.Then,therange-gatedimagingset-upinthe
laboratory,employing532nmNd:YAGpulsedlaserandintensifiedchargecoupleddevice(ICCD),was
utilizedtogetnon-line-of-sightimagesthroughthereflectionofglasswindowandceramictilewall.
Experimentswerecarriedoutwithadistanceof50mand20mrespectively.Analysisoftheresultantimages
showsthatthefeasibilityofnon-line-of-sightimagingisrelatedtothereflectionpropertiesofthereflection
media,thatis,mediawithspecularreflectiontoacertainthresholdcanbeusedinnon-line-of-sightimaging.
Finally,non-line-of-sightimagingtechnologywillbeanewpromisingopticalimagingmode,showinga
potentialapplicationinurbanstreetfighting,publicsecurityreconnaissance,disasterrelief,andsoon.
2012, 41(8): 2079-2084.
Space target detection ability of visible light camera is related to the visible characteristics of
the space target, detector performance and other factors. To get the detection ability of space optical
camera on medium-orbit and low-orbit space target at the distance from 200 to 1 500 km, a mathematical
model of space target characteristics was established based on the basic theory of radiation by considering
geometry, background, and material characteristics of the space target. Furthermore, a simulation was
conducted at the spectral bands of 0.4 to 0.7 um. The theoretical calculations of detection ability on
medium-orbit and low-orbit space target by the visible light camera was got and the formula of related
optical parameters was also obtained. These conclusions can provide theoretical support for the design of
space optical camera.
2012, 41(8): 2085-2089.
The space camera defocus caused by temperature makes the focal plane outside the correct
position range. In order to auto control the focal plane and guarantee the imaging quality, the auto-
focusing system based on temperature was proposed. Firstly, the current compensation strategies of focal
plane were analyzed in detail and an improvement method was presented to resolve their shortcomings
and inadequacies. Secondly, the system structure and design and operating principle were introduced.
Finally, the system was experimented. Experimental results indicate that the defocusing amount of camera
can be controlled less than 10 um, the adjusting error of focal plane is no more than 1.3 um, and the
controlling result of temperature level satisfies the requirement of system design. The auto-focusing
system based on temperature can auto control temperature level, auto calculate defocusing amount, auto
control focal plane and satisfiy the requirement that the focal plane of camera is inside the correct
position range when camera working.
Amethodofin-orbitradiometriccalibrationbychangingintegrationtimeforspaceinfrared camerawasproposedaimingtomultiple-pointradiometriccalibrationobtainingmethod.Firstly,the responsemodelbychangingintegrationtimewasdevelopedaccordingtoresponsecharacteristicsofspace infraredcamera.Secondly,theoreticaldifferencesbetweenchangingintegrationtimeandradiancewere analyzed.Themethodofradiometriccalibrationbychangingintegrationtimeusingasingle-pointstandard wasproposedforin-orbitapplication.Finally,theerrorintroducedbythismethodwasanalyzed combiningthenonlinearityofdetector.Theexamplecalculationshowsthatthemaximumprincipleerror ofthismethodis1.5%underpropertemperatureatthesameradiantenergywhentemperatureis250to 500Kandintegrationtimeis10ms.Single-pointabsoluteradiometriccalibrationbychangingintegration timecanavoidthecomplexityofdesignandcontrolofmultiple-pointradiometriccalibrationsystem,and canbeusedforin-orbitradiometriccalibration.
2012, 41(8): 2096-2101.
Beamsplitterisacrucialpartofalargespaceopticalremotesensortosplittheimaginglight intotwobeams.Inordertosolvetheproblemofsupportingalargebeamsplitterofaspacecamera, theresearchworkonthesupportingsyructureofalargebeamsplitterwithadimensionof200mm200mm 200mmwasperformed.Thedesignofthesupportingstructureofalargecubicbeamsplitterbasedon thephilosophyofsemi-kinematicmountingandpassivethermalcompensationwaspresented.Thecontact pairconstrainswerebuilt,thenonlinearityoftheboundaryconditionwassimulatedandtheengineering analysisontheprismassemblyutilizingnonlinearfiniteelementmethodswasperformed.Theanalysis resultsindicatedthesurfacefigureprecisionofthebeamsplitter'sLightPassSurface,thusthePVvalue waslessthan73.2nmandtheRMSvaluewaslessthan12nmunderthecouplingofgravityand15℃ stationarytemperaturechange;thefirstnaturalfrequencyofthebeamsplitterassemblyreached183Hz. Thesupportingstructuredesignofthebeamsplittterisvalid,andcansatisfythedemandsonthe structuralstiffnessandthermalstabilityinthespaceenvironment.
2012, 41(8): 2102-2106.
Inordertoreducetheinfluenceofopticalwindowonimagingqualityinaerialremotesensor,theopticalwindowwasoptimizedinglassthickness.Theminimumthicknessofopticalwindowglasswascalculatedwithstrengththeory.Theconvectionheattransfercoefficientonoutersurfaceofopticalwindowglasswascalculatedwiththetheoryoflongitudinallysweepingplanmural.Basedonthethermalopticalanalysis,transientstatetemperaturefieldwasemulated,andtheopticalpathinpeaktovalleyvalue(PV)androotmeansquare(RMS)errorwerecalculatedunderthethermal-forcecouplingcondition. Thicknessoftheopticalwindow(290mm140mm)wasdeterminedas17mm.TheresultofpracticalapplicationshowsthattheMTFis0.304whenthecharacteristicsfrequencyis60lp/mmandthestableanddistinctimageisobtained.Thestudyresultshowsthatthermal/structural/opticalintegrateddesignforopticalwindowisachievedsuccessfully,anditprovidesareferencefortheopticalwindowdesign.
2012, 41(8): 2107-2111.
Areflectiontypepolarizationmaintainopticalfibertemperaturesensorwasdesigned.The
operationprinciplewasintroducedandthesensingequationwasgiven.Analysisindicatedthatthe
propagationlossvarietywasthemainfactorwhichmadesensingequationparameterschange.So,inthe
applicationfieldwheretheopticalpathstructureofsensormightbere-assembled,theparameters
calibrationwasnecessary.Basedonthecharacteristicandtherelationofsensoropticalsectionoutput
signalandthesensingequationparameters,thepropagationlosscouldbeseparatedfromthesensor
initializationparametersandasimpleandpracticalfieldcalibrationmethod,withwhichthewholesensing
equationparameterscouldbecalibratedwhenthetemperatureatthesensorprobewasgiven,was
proposedandthecalculationequationwasestablished.Anexperimentalsensorsystemwasbuiltandthe
calibrationexperimentsweremadebychangingthepropagationloss.Thedateobtainedwereanalyzed
andcomparedwithpolynomialfittingandmodelcalculation.Theresultprovesthefieldcalibration
technologyandthesensingtemperatureprecisioncanbebetterthanupanddown0.5℃beforeandaftercalibration.
Theinfluenceofphaseshiftdriftandsplittingratioonsidebandssuppressionratioofoptical
millimeterwaveandbiterrorrate(BER)ofradiooverfiber(ROF)systemaregreat.Fortheschemeof
opticalmillimeterwavegenerationwithoctupling-frequencyusingtwocascadedMach-Zehndermodulators,
withthemethodofexpandingBesselseries,anexactanalyticalsolutionforopticalmillimeterwave
affectedbyphaseshiftdriftandsplittingratiowasderived.Itfollowedthattheundesiredsidebands
suppressionratiowas35.9dBwhenthesplittingratiodeviationwas0.001andphaseshiftdriftwas1.
Theharmonicinfluencecouldbeneglectedinthiscase.Simulationresultsshowthatfor0.001splitting
ratiodeviationand1phaseshiftdrift,thepowerpenaltyvalueis0.001dBatBERof10-10inback-to-back
signaltransmission.Thepowerpenaltyvalueis0.145dBafter20kmtransmission.Thesystemperformance
isgood.
2012, 41(8): 2119-2124.
Inordertomeetthedevelopingneedsofbroadamplificationaswellasgain-flattened
operationforfiberamplifier,adouble-passstructureofbismuth-basederbium-dopedfiberamplifier(Bi-
EDFA)withtheincorporationofC-band(1530-1565nm)broadfiberBragggrating(FBG)inbetweenthe
twocascadedsegmentsofbismuth-basederbium-dopedfiber(Bi-EDF)wasdesigned,andtheamplifying
performancesofBi-EDFAwerepresentedtheoretically.Theresultsindicatethatabroadamplification
andgain-flattenedspectrumcanbeachievedwiththeaidofthesimultaneouslyobtainedhighgainofthe
C-bandandL-band(1570-1620nm)signalsduetotheirexperiencingadifferentlengthbi-directional
transmissioninBi-EDFaftertheincorporationofFBG.Againbandwidthof90cmwithaveragegain
35.7dBandgainvariationofapproximatelyupanddown2.3dBwithinthewavelengthrangefrom1530nmto1620nm
areobtainedundertheconditionsofthe1480nmbi-directionalsymmetricalpumpingwithpumppower
of200mW,thefirstandsecondBi-EDFlengthof50cmand170cm,and56-channelsignalsofC+L
bandwithintervalof2nmandeachpowerof-30dBmareinputtedsimultaneously.Meanwhile,thenoisefigureofBi-EDFAisimprovedevidently.Thetheoreticalstudieswillprovidepracticalsignificancefora
newdesignofC+L-bandBi-EDFAwithbroadandflattenedgain.
