Impact of apodisation functions on group delay and reflectivity ripple of chirped fiber Bragg gratings

With the rapid development of fiber communicationsystem,fiber Bragg gratings (FBG) especially linear-chirped FBGis widely appliedtothe fiber compensationby its character of linear delay[1-2].However ,the per-formance is degraded because of reflectivity an…     

Research on the characteristics of a twisted high birefringence fiber grating

In recent years ,the demand of the project survey grewincreasingly,sothetorsionsensor has obtainedextensiveattention.But the related studies about optical fiber tor-sionsensor are veryfewinthe domestic andforeign[1-3].Inthe traditional torsion sensor we p…     

Novel method to optimize the distributed pump powers in a kilowatt ytterbium-doped double-clad fiber laser

High-power ytterbium-doped fiber laser has attractedmuch attention recently in commercial and military ap-plications due to its high efficiency,compactness andhigh beam quality.In kilowatt power domain,the heatdissipation will play an i mportant role and …     

Flat-top silica-based arrayed waveguide grating with 40-channels

A wavelength multiplexer or demultiplexer plays ani mportant role in all wavelength division multiplexing( WDM) system.Silica-basedarrayed waveguide gratings(AWGs) offer attractive featuresinthis area due to theadvantage of large output channels and lowlo…     

A new type photonic crystal fiber with high birefringence

Highperformancepolarization maintainingfibers (PMFs)havepotentialforanumberofapplicationssuchashighbitratecommunicationsystem,PMfibre loopsforgyroscopesandsoon.Theindex guidingPCFs arecharacterizedbyaseriesofholesrunningthroughou thelengthofthefiberarrangedinamicroscalestructurearoundahighindexcore.Thisoffersanewpossibilityto createhighbirefringenceintheindex guidingPCFs,be causethestack and drawprocessallowstheformationoftherequiredsymmetricorasymmetricmicrostructure andtheindexcontrasto…     

Threshold level and gain of forward stimulated Brillouin scattering in a forward pumped s-band discrete DCF fibers Raman amplifier

Recently,with fast developing of extra-capacity of fi-ber communication experi mental systems ,dense wave-length division multiplexing (DWDM) technology hasbeen adopted widely[1-3].Now,1300 nmband and 1550nmband have been connected with each other to be a…     

Supercontinuum generation in a Bragg fiber：a novel proposal

Nonlinear optical effects such as self-phase modula-tion,four-wave mixing,cross-phase modulation,sti mula-ted Raman scattering,together with appropriate tempo-ral dispersion profileinan optical fiber couldsignificant-ly broaden ( >100 nm) the spectrumof a…     

L-band tunable erbium doped fiber ring laser using fiber loop mirror filters

We present a novel and efficient L-band wavelength-tunable Er^3＋ doped fiber laser of ring structure. In the cavity two segments of Er^3＋ doped fiber and a fiber Bragg grating are used to improve pump efficiency. Tunable filters based on fiber loop mirrors are also applied inside the cavity to act as both a wavelength selector and a line-width compressor. Using these techniques, a tunable laser with tuning range up to 42 nm, output power larger than 1 mW, power uniformity controlled within 1.75 dB and side mode suppression ratio about 40 dB is achieved.     

Coupling constant of triple-clad long-period fiber grating

Because of its high sensitivity to external refractiveindex,the long-period fiber grating(LPFG) has beenused as chemical sensor1-3.Now the multi-clad LPFGwiththe fil ms coated on cladding area of the fiber grat-ing has drawn much attention[4].It cani mpro…     

New modulator for the optical signal in a fiber

Generally,there are two kinds of modulator used inthefiber system.Oneis electro-optic modulator based onthe change of guided modes in plane waveguides .Theother oneis electro-absorbingsemiconductor diode mod-ulator with internal structure si milar to the …     

Demodulated method of optical fiber stokes temperature sensors

The optical fiber temperature sensoris one of the dis-tributed measurement apparatus applied to the smartstructures of civil and military engineering.In the dis-tributedfiber Ramantemperature sensor ,the anti-Stokesand Stokes scattering radiation is sensi…     

Theoretical analysis of radiation-balanced double clad fiber laser

Recently,double clad fiber lasers with an output ofkilo-watt power have been reported[1].Thermal prob-lems such as thermal stressinducedfracture,decreasingof quantumefficiency andthermal lens effect are seriousinthis kind of high powerfiberlaser[2].In1995 ,fluores-cence cooling in Yb doped ZBLANP(ZrF4-BaF2-LaF3-AlF3-NaF-PbF2) glass was realizedfor thefirst ti me[3].Consequently,a section of Yb doped ZBLANP glass fi-ber laser was cooled from298 Kto 282 Kin the vacu-um[4].According t…     

Modeling laser-diode-pumped Tm3+-doped fiber amplifiers

A theoretical model is developed for the laser-diode-pumped Tm³⁺-doped fiber amplifier, and a set of ordinary differential equations (ODEs) governing the dynamics of dual-wavelength pumping scheme (1.4μ+1.56μ) based on the rate equations and propagation equations was established. The relationship between the spectra gain and pump power was described and analyzed by numerically solving the ODEs. Spectral gain as a function of longitudinal position along the fiber was given to optimize the fiber length; spectral gain per unit length, and fractional inversion were used to explain the gain shift property of TDFA. The theoretical results agree well with the experimental data. Received 28 March Supported by China Scholarship Council, Natural Science Foundation of Shandong Province of China (grant no. Y2003G01 and Y2002G06), Research Fund for the Doctoral Program of Higher Education of China (grant no. 2002022048     

High-power superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber

A new type of high-power broadband superfluorescent source of Yb^3＋ -doped double-cladding photonic crystal fiber is reported experimentally, which is pumped at 976 nm by a high-power laser diode with the end-coupling method. We have obtained a smooth broadband output of superfluorescence The maximum output power is 1.649 W with a slope efficiency of 56.7%. The 3 dB bandwidth is 22.4 nm To the best of our knowledge, this is the first report about SFS with such high output power of 1.649 W.     

Experimental and theoretical analysis of fiber Bragg gratings under Transverse Force to a Small Grating Section

Fiber Bragg grating (FBG) technology has been de-veloped rapidlyinrecent years ,and has beenextensivelystudied in today′s optical communication and sensingsystems . Because of the linearity between the Braggwavelength and outside environmental parameters ,theaxial strain response of FBGhas been fullyinvestigatedand usedin measurement for strain,pressure,andther-mal expansion coefficient etc . By contrast ,fewstudieshave been carried out onthe transverseload response ofFBG[1-3].Gafsi and …     

Reconstruction of strain distribution in fiber Bragg gratings with differential evolution algorithm

Differential evolution algorithm is used to solve the inverse problem of strain distribution in fiber Bragg grating （FBG）. Linear and nonlinear strain profiles are reconstructed based on the reflection spectra. An approximate solution could be obtained within only 50 rounds of evolutions. Numerical examples show good agreements between target strain profiles and reconstructed ones. Online performance analysis illuminates the efficiency and practicality of differential evolution algorithm in solving the inverse problem of FBG.     

Linearity optimization of edge filter demodulators in FBGs

A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBG .By using a logarithm amplifier and an extraction operation, the linear range of optimized edge filter demodulators has been broadened effectively, and the requirement of optical filter＇s linear range has been reduced. Theoretical analyses and the simulation results indi-cated that the linear range of optimized edge fdter demodulator＇s covers the whole transition region of the edge filter, while a strict linearity of the optical filter is not necessary.     

Analysis of fiber lens with gradient index based on thin lens equivalence

Optical communication components have been devel-oped currentlytowards the direction of micromation andintegration. The problem which li mits the componentperformancesis howto couple the function slugs to theinput-output fiber effectively,as appeared in a…     

Principles and realizations of FBG wavelength tuning with elastic beams

FiberBragggrating(FBG)isasignificanttechnology thatisusedtodesignkeydevicesorcomponentsinthesystemsoffibercommunicationandfibersensing[1], suchastunablefiberlasers[2],WDW/DM[3],WADM[4],tunablefiberfilter[5],fiberdispersioncom pensation[6],gainflattingofEDFA[7],FBG typeinter ferometer[8]andfibergratingsensors[9,10].OneofthekeyresearchissuesonFBGdevicesistomakethetun ingwavelengthdeviceswhichhavegoodcharacteristics ofwidetunablewavelengthrange,stableoutput,goodmultiplexingcapability. …