Investigation Of Fiber Based Functional Devices For High-speed Optical Communication Systems

With the overwhelming developments of cloud computing,streaming media and mobile networks,there are increasing data traffic demands.As the cornerstone of data communication,optical fiber communication network keeps a rapid development over decades,provides guarantees for building an information based society.In the optical communication system,the developments of dense wavelength division multiplexing,polarization division multiplexing and advanced modulation techniques have largely increase the transmission spectra efficiency.As one of the key modules in the optical fiber communication system,all-fiber based devices with the low insertion loss,high compatibility and cost-efficient features are attracting attentions from researchers and internet service providers.However,with the increasingly system complexity,how to design novel all-fiber based devices with new structure and unique features become one of the ultimate challenges in future optical communication networks.Aiming at the optical signal processing,optical performance monitoring,signal multicasting and switching in the high speed optical communication system,this dissertation designed,fabricated and tested multiple all-fiber based structures to provide different function.The major research contents and innovative achievements are summarized as following.(1)Based on the electrical arc discharges method,we developed a universal fabrication platform for fiber based structures.By calling the application program interface of the specialty fiber fusion splicer,we wrote computer software to control the electrodes arc discharges,motor movements and cameral monitoring procedures,achieved taper,residual stress relaxation and periodical process for conventional single mode fiber and specialty fiber,successfully implemented fiber based Mach-Zehnder interferometer with high performance,long period grating,and other functional structures.To a further step,we investigated the relationship between optical spectra shifts and temperature/strain variations.Establishing the basis for the all-fiber devices successfully applied in the real optical communication system.(2)For the high speed signal processing in the optical communication system,we designed a software-designed thermos-optic second-order optical differentiator based on linearly chirped fiber Bragg grating and programmable heating array.By secondly developing of the programmable hearing array in the commercial heat printer,we build a controllable hardware and software platform,successifully implement tunable temperature field.Based on the thermo-optic effect of fiber,we inserted programmable temperature field into the linearly chirped fiber Bragg grating at different position with dissimilar widths,successfully build the transmission function of the second order differentiator in frequency domain.We demonstrated great wavelength and bandwidth tunability of the device in experiment.Compared with the theoretical output waveform,experimental results show less deviation.In addition,we also proposed multiple different structure for wavelength division multiplexing transmission system,it can realize paralleled differentiation for high speed signal in multiple wavelength channels.(3)For the performance monitoring issues in the high speed optical communication system,we proposed and designed an all-fiber structured in-band optical signal to noise ratio monitoring technique with programmable control.Based on the narrow filtering method,we used linearly chirped fiber Bragg gratings and the programmable heating array to realize the optical signal to noise ratio monitor with a tunable ultra-narrow optical filter.In the wavelength division multiplexing coherent optical transmission system,we experimentally proved the monitor has large linear working range,great wavelength tunability and insensitive to chromatic dispersion/ polarization mode dispersion.(4)Towards optical signal switching problems in the future spatial division multiplexing networks,we proposed and designed an inter-core signal multicasting and switching device.Based on the mode coupling theory of long period grating,we inscribed large-bandwidth long period grating into the multicore fiber with electrical arc discharge stress relaxation method,realized 1:3 inter-core signal multicasting at C band.By constructing a spatial division multiplexing coherent optical communication system with 6 wavelengths and 1.344Tb/s transmission capacity,we experimentally demonstrated the multicasting performances.Furthermore,by directional bending the long period grating group in multicore fiber,we achieved transmission spectra shift and loss control,then realized the reconfigurable inter-core signal switching device,the maximum switching extinction ratio is 39 dB.Compared to the optical back-to-back transmission,only a negligible penalty was observed,which indicated the inter-core signal switching is effectively achieved in broadband wavelength range.With the aforementioned research contents,novel all-fiber based devices are expected to apply in the high-speed optical communication system.