Acoustic anisotropy of piezoelectric LiNbO3 crystals and its application in integrated acousto-optical tunable filters

We use Joness matrix method and the global optimal method to investigate the propagation characteristic of surface acoustic wave（SAW） for X-cut single crystal Lithium Niobate（LiNbO3 ）. As an application, a novel integrated acousto-optical filter,which allows to minimize the dimension of AO cells and suppress side-lobes,was designed on the base of LiNbO3 crystal.     

Design of the annular binary filters with super-resolution based on the genetic algorithm

Inthe history of the development of pupil filters,to o-vercometheli mitsinresolutioni mposed by diffractionini magingsystems has hadlong beingthe ai mof manyre-searches.The spot size(Δr)and the depth of focus(DOF)are relative to the numerical aperture(NA…     

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.     

GHz band frequency hopping PLL-based frequency synthesizers

In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter（LPF）. The frequency synthesizer is designed for a frequency hopping （FH） transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator （VCO） is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz. A novel Dual-Modulus Prescaler（DMP） is designed to achieve a very low jitter and a lower power. The settling time of PLL is 80 μs while the reference frequency is 400 KHz. This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter, with a maximum VCO output frequency of 1.5 GHz, and is fabricated with a 0.18 μm mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.     

Thermo-optically tunable arrayed-waveguide-grating made of polymer/Si

Inthe future,optical communication systems will usemore exceptional optical fiber with high bandwidth.Dense wavelength division multiplexing(DWDM)isconsidered as a promising solution to the demand fortransportingterabits ofinformation viafibers[1].Arrayed…     

Generation of low jitter and discrete tunable dual-wavelength optical pulses at arbitrary repetition rates

Recently there is an increasing interest in generatingshort optical pulses with lowti ming jitter and tuneablemulti-wavelength due toitsi mportant applicationin op-tical ti me division multiplexed(OTDM),wavelength di-vision multiplexed(WDM)systems,and opt…     

Design of low-confinement-loss and highly birefringent index-guiding photonic crystal fibers

We present a systematic scheme to achieve both high birefringence and low confinement loss in index-guiding photonic crystal fibers （PCFs）, using a structurally-simple PCF with finite number of air holes in the cladding region. By increasing the size of the outermost-ring air holes in the cladding region, highly birefringent PCFs with low confinement loss can be successfully achieved. The design strategy is based on the fact that the modal birefringence of PCFs is dominated by the inner-ring air holes in PCF, which is verified by a full-vector finite element method with anisotropic perfectly matched layers. Numerical results show that modal birefringence in the order of 10-3 and confinement loss less than 0.1 dB/km can be easily realized in the proposed PCF with only four rings of air holes in the cladding region. We expect that such fibers will be much easier to be fabvicated than those with more air holes in the cladding region.     

Novel algorithm of finding good candidate pre-configuration cycles in survivable WDM mesh network

Pre-configuration Cycle (p-cycle) is a promising ap-proach for protecting working capacities in WDMnet-works because of its ability to achieve ring-like recoveryspeed while maintaining the capacity efficiency of amesh-restorable network[1].The first and t…     

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 …     

Microarray image processing by order morphology

Thetrendofmicroarrayishigh densityandmore spotswhoseareasaresmallandarealignedonthechips.Fluorochromeoneveryspotislittleandenergyof excitedfluorescenceislittle.Sothespotsofimageare small.Thedifferenthybridizationonthesamechiphasdifferentintensityofspots[1…     

Novel self-similar traffic shaping mechanism in transport networks

Withthe development of networkingtechnologies andnewservices of Internet ,there is an explosive growthtrend of Internet traffic which has created the need totransport IP packets on high-speed links .Due to highbandwidth utilization and easy realization,SDH/ WDMtechnology becomes thei mportant way to carry IPtraf-fic over the backbone network[1].In addition,the searchfor accurate mathematical models of data streams inmodern computer networks has attracted a considerableamount ofinterestinth…     

Experimental study of thermal lensing of Nd：YAG laser

Beamfocusing and higher-order wavefront distortiondue to heat dissipationinalaser gain mediumarei mpor-tant considerationsinthe design of solid-statelasers be-cause wavefront distortion can profoundly influence theperformance of a givenlaser design.Althou…     

Experimental study of thermal lensing of Nd：YAG laser

Beamfocusing and higher-order wavefront distortiondue to heat dissipationinalaser gain mediumarei mpor-tant considerationsinthe design of solid-statelasers be-cause wavefront distortion can profoundly influence theperformance of a givenlaser design.Althou…     

Influence of stress birefringence on the performance of a FBG pressure sensor

No matter designing and manufacturing a FBG pres-sure sensor ,or monitoringthe strain on material surfaceby using FBGas a pressure sensor ,the difficult technicalproblems to be solved are as follows :first ,howto effec-tively couple and propagatethe external stresstothe ax-ial direction of FBGthrough the underlay material ;sec-ond,howto make the FBGpressure sensor achieving aneffect of enhancing sensitivity;third,how to ensure alinear relationship between FBG′s reflection wavelengthand t…     

Numerical analysis of thermal distortion of the mirror in space-to-ground laser communication links

Thereis cold-heat exchange under the large tempera-ture gradient in the space environment ,andin space-to-ground laser communication links the optical reflectorson a satellite in orbit someti mes need to be placed out-side the capsule.Therefore,tremendous thermal distor-tions will occur onthe optical mirror surface,which maybring shift andspreading ofits reflectedfocus andthere-by influences the performance of space-to-ground lasercommunicationlinks . Although there are many reports on thermal…     

High stable power control of a laser diode

For a high precise sensing and measuring system,theerror of measurement resulting fromthe fluctuation ofthe light source must be considered[1-3].The main noisesources include fluctuation of current source,self-heat ,aging and theintrinsic noises of a lase…     

New design of 2-D photonic crystal waveguide couplers

Optical couplers arei mportant componentsinthe sys-temof optical signal processing,optical communicationand optical calculation.Therefore many people areinter-estedinseekingfor those couplers with uniquefunction.Photonic crystals (PC)[1-2]have drawn great…     

A novel method to improve spatial resolution of acousto-optic deflector

In mobile atmosphere laser communication,the fastand accurate beamsteeringis one of the key techniquesfor acquisition,tracking and pointing(ATP) of laser sig-nals .Compared with the normal loop-locked trackingand pointing system composed of fast steering …     

Optimization design of an electroabsorption modulator integrated with spot-size converter

In the recent years ,the electroabsorption modulator(EAM) is attractive as anexternal modulator because ofits many features ,such as low power consumption,lowdrive voltage,small size,large bandwidth,polarization-intensity and potential for monolithic integration withother components[1-3].An optical device integrated witha spot-size converter(SSC) has been paid more attentionfor its direct couplingto an optical fiber without using amicro-lens or tapered fiber[4].EAMintegrated with anSSC(EA…     

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. …