The Research Of Detection And Manipulation Technology Of Polarization Information In The Optical Fiber Link

With the rapid development of optical fiber communication and optical fiber sensing technology,the influence of polarization effect in optical fiber links appears gradually.It is a double-edged sword: on the good side,the external physical fields can be obtained by measuring the polarization information of the optical fiber link,and the transmission capacity of the communication system can be improved through polarization multiplexing technology;on the bad side,any scene that requires coherent detection needs two beams of coherent light with the same polarization direction,any polarization mismatch will deteriorate the signal-to-noise ratio,and even cause the failure of coherent detection.By improving the detection and control technology of polarization information,this thesis mainly studies the suppression technology of polarization signal fading in polarization-sensitive optical fiber sensing system(POFS)and the suppression technology of carrier fading caused by the random walk of the polarization state(SOP)of delivered local oscillator(LO)in self-coherent optical fiber communication system.The purposes of this paper are to improve the stability and reliability of the POFS system and stabilize the SOP of delivered LO to provide technical support for the use of the self-coherent optical fiber communication system in short-range scenes.The main innovations and works of this thesis are listed below:(1)For the suppression of polarization signal fading in the forward POFS system,a PMF-based fading-free solution is proposed.Firstly,three cases of signal fading in SMF-based POFS system are simulated and analyzed based on the wave plate model,and then,for the most sensitive case,a PMF-based implementation scheme is designed to completely suppress the fading phenomenon in the forward POFS system.(2)For the suppression of polarization signal fading in the POTDR system,Firstly,a rotating coordinate system model is introduced to describe the procedure of polarization detection in the POTDR,which reveals the relationship of the system response with respect to the initial SOP and the direction of the polarizer.On this basis,a 45° aligned dual-polarizer structure is proposed for the suppression of signal fading in POTDR.For the ease of practical application,an integrated space optics scheme is designed and fabricated independently.Experimental results show that the possibility of signal fading occurrence is reduced from 35.5% in a traditional POTDR down to 6.5% using the proposed scheme Then,to further suppress the signal fading in POTDR,two schemes of multi-dimensional polarization modulation and demodulation are proposed.Combined with the latest understanding of the polarization signal fading phenomenon in the POTDR,using the optical fiber wave plate model,the simulation results show that the proposed scheme can suppress the signal fading well.(3)For the reset problem of the silicon-based polarization controller,firstly,based on the continuous rotation and polarization rotation characteristics of the half-wave plate model(HWP),it is proposed to use a rotatable HWP to continuously stabilize the SOP of arbitrary incident light in a state with equal energy of X and Y polarization components.At the same time,it is proved that the PS-DC-PS-DC structure can form an equivalent continuously rotatable HWP.Then,to simplify the structure of the polarization controller,it is proposed that the same SOP stabilization goal can be realized by designing a suitable algorithm on the PS-DC structure.At the same time,it is pointed out that these two schemes can be used to stabilize the arbitrary SOP to the TE state once the 3-d B energy loss is allowed.Finally,it is proposed that through the DC-PS-DC structure,the arbitrary SOP can be continuously stabilized to the TE polarization state without losing extra energy.(4)A bidirectional self-coherent transmission structure(coherent Bi Di)for next-generation data center interconnection is proposed.First of all,the advantages and practical challenges are discussed.Then,to continuously stabilize the X and Y components of delivered LO,a silicon-based automatic polarization controller(APC)with a PS-DC structure is designed and implemented.A polarization tracking speed of up to hundreds of rad/s is achieved without affecting the performance of the communication system.On this basis,A successful real-time demonstration with 600-Gb/s DP-64 QAM using low-cost uncooled DFB lasers with linewidths of up to 1.5 MHz is conducted.Finally,a detailed experimental parametric study of the proposed system is presented in which various system parameters are swept,such as the laser linewidth,mismatch length,reach,and laser power.