Studies On Optical Amplification Technology Of Bidirectional Optical Fiber Communication System With Reflective Modulation

Optical fiber communication's influence and scope of it's potential has greatly surpassed it's original expectations with its low loss,huge communication capacity,and with it's strong resistance to electromagnetic interference in it's dedicated transmission channels.Coherent optical communication technology has become a popular technology due to its high sensitivity,longer relay distance,and greater communication capacity.Traditional coherent optical communication systems require a closed-loop frequency tracking system so that the phase of local oscillator(LO)can be tracked with the carrier phase of the signal.However,the complexity of stabilizing the phase shift of the locked carrier makes its application in practice more difficult.In the research of the reflectionmodulated bidirectional coherent optical communication system,avoids the requirements of traditional closed-loop frequency tracking systems and it shows great development potential in practical engineering applications.Based on the reflection-modulated bidirectional coherent optical communication system,the application of optical amplifiers is mainly studied.In the system,the modulated signal and the carrier are transmitted in the same fiber.The backscattered noise caused by this single-fiber bidirectional method increases the complexity of the system.For the amplifier implementation in this system,not only the noise such as spontaneous emission,double Rayleigh backscatter,but the effect of carrier backscattered noise need to be accounted as well.After considering the main noise effects such as amplified spontaneous emission and backscattered noise,the research shows that,the backscattered noise will be amplified when a bidirectional erbium-doped fiber amplifier or distributed Raman fiber amplifier is applied to the system,which makes the system application value greatly reduced.Based on a deep analysis of the system's optical amplification technology,t the combination of unidirectional optical amplification of erbium-doped fiber amplifier or discrete Raman fiber amplifier for this system is used in this thesis,and it has been deeply discussed from theory,simulation,and experiment.The gain and noise figure of the amplifier are analyzed,and its performance in the system is also analyzed to demonstrate its applicability.In addition,considering the problem of the pumping efficiency of the discrete Raman amplifier,this thesis also studies a two-way amplified discrete Raman amplifier,which uses the fiber Bragg grating to reflect the pump light to achieve two amplifications of the signal light.The simulation results prove its unique advantages in improving pump efficiency,and the performance of the system is improved as well.Due to the influence of the backscattered noise,the transmission distance of the system is limited,and its application may also be limited to local area networks and metropolitan area networks.However,the system's special reflection modulation method can play a role in secure communication.