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Study On The In-line Fiber Optical Modulator Based On Graphene And Mach-zehnder Interferometer

Posted on:2018-12-24Degree:MasterType:Thesis
Country:ChinaCandidate:C GaoFull Text:PDF
GTID:2348330533461135Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Optical modulator plays a key role in optical fiber communication system.To increase the information transmission speed and the capacity in optical fiber communication system,we should improve the modulation speed and modulation bandwidth of optical modulator.Based on optical and electrical properties of graphene,two kinds of optical modulation structure including graphene-covered Mach-Zehnder interferometer(MZI)all optical modulation structure and graphene-covered Mach-Zehnder interferometer(MZI)electro-optic modulation structure are studied in this thesis.This thesis has the following contents:(1)Based on the band structure of graphene,the all optical modulation property and electro-optic modulation property are analyzed in this dissertation.And the theoretical analysis shows that the incoherent optical modulation is mainly resulted from the carrier-phonon process of graphene,which provides the theory basis for fabricating the graphene-covered Mach-Zehnder interferometer(MZI)modulator in the essay.(2)The process of incoherent optical modulation of graphene covered inline fiber MZI is firstly investigated.The inline MZI is fabricated by splicing D-shaped fiber and single mode fibers with a lateral offset.Single layer graphene is then transferred and covered on the D-shaped fiber.The incoherent optical modulation of graphene is studied by the modulation of refractive index through external laser.With a backward pump-probe setup,we find that incoherent optical modulation occurs independent of the wavelength difference between pump and probe laser.Further,the modulation depth of probe light is found to be decreasing with the increase of the pump wavelength in an exponential trend when the pump power is fixed.The modulation depth of probe light is obviously increasing with the increase of pump power,also in an exponential trend.The experimental results are beneficial in understanding the incoherent optical modulation process in graphene,which can be utilized for fabricating phase/intensity modulators.(3)Graphene-covered MZI electro-optic modulation structure is fabricated by MZI based on D-shaped,copper foil electrode,and then a graphene sheet is transferred to D-shaped fiber.Due to the refractive index of graphene can be modulated by external electric field,it prove that Fermi level can be modulated in graphene.Experimental results show that the modulation depth of probe interference spectrum increases as the voltage increases.And with the decreasing of voltage,the modulation depth of probe light is decreased too.We also study the relationship between the voltage and modulation depth of different probe wavelengths.What is more,this trend is approximately the same to every probe wavelength.This electro-optic modulation structure has adventages of excellent compatibility,compact structure and so on.
Keywords/Search Tags:Optical Modulator, Graphene, Mach-Zehnder Interferometer, Incoherent Optical Modulation, Electro-optic Modulation
PDF Full Text Request
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