10353

9552

كارشناسي ارشد

الكترونيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

1394

نه، 89ص.: مصور، جدول، نمودار

1396/10/03

كتابنامه

برق و كامپيوتر

مهندسي برق و كامپيوتر

ID9552

به فارسي و انگليسي

106 Linewidth Measurement of Narrow Linewidth Laser Narges Shahriari Kalemasihi n shahriari@ec iut ac ir Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan Iran Degree M Sc Language FarsiSupervisor Asghar Gholami gholami@cc iut ac irAbstract The light of laser source is not completely single frequency and has limited linewidth Lasers linewidthmight be up to several hundreds of GHz Today with the development of laser systems construction and useof narrow linewidth lasers are rapidly developing Therefore introduction of methods of precisemeasurements of frequency spectrum and noise characteristics of these lasers seems to be an important need Recently lasers with linewidth less than 100 kHz are commercialized One of the challenges that facemanufacturers is accurate linewidth measurement of such lasers Optical spectrum analyzer has the accuracyof a few tens of megahertz Therefore for narrow linewidth laser another measurement methods based onelectrical devices electrical spectrum analyzer ESA are replaced To measure the linewidth of the narrowlinewidth lasers due to limited bandwidth of ESA measurement methods based on interference areemployed The main idea of this method is based on the conversion of phase or frequency fluctuations intointensity changes in an interferometer such as Mach Zehnder or Michelson In general the source of laserfrequency noise can be considered white noise Lorentzian and 1 f noise Gaussian Many applicationssuch as coherent communications systems is limited by the white component of the frequency noise Becausethe phase or frequency fluctuation resulting from 1 f noise are very small and by using the frequency trackingcircuits and PLL circuits could be compensated Therefore measuring the spectrum broadening caused bywhite noise Lorentzian linewidth as a result of random changes in phase laser beam is in important todesign data transfer systems In this report various methods of the linewidth measuring of the narrow linewidth laser have beenstudied Then according to the existing facilities a modified delayed self homodyne interferometer DSHOI using a phase modulator and delay fiber length less than the coherence length of the laser in a Mach Zehnder

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