Analysis And Design Of Bidirectional Erbium-doped Fiber Amplifier

Single-fiber two-way transmission can not only improve system capacity,but also save 50% of transmission fiber,which is very beneficial for reducing costs.In an improved reflective synchronous homodyne coherent receiving system mentioned in this thesis,there is an optical carrier at the same time.The modulated and reflected optical signal is transmitted in a single optical fiber link.To compensate for the round-trip transmission loss of the laser power,the unidirectional amplified optical amplifier is required to be modified to meet the requirements of the system.Optical amplifiers that provide gain at the same time,erbium-doped fiber amplifiers(EDFAs)have been widely used in various high-capacity transmission applications for the past ten years,Therefore,the analysis and design of bidirectional erbium-doped fiber amplifier(Bidirectional Erbium Doped Fiber Amplifier,Bi-EDFA)based on EDFA theory and structural model are carried out in this thesis.Optical isolators are added to the EDFA,which can reduce the discrete distribution of reflections in the optical fiber links,but it allows light to be transmitted only in one direction.If the optical isolator is not added,the maximum allowable gain of the bidirectional EDFA will be seriously limit.Even though discrete reflections can be reduced to some extent by careful processing of all the connection points in the fiber link,one of the characteristics of the Rayleigh backscattered fiber itself cannot be eliminated.There will be various beat noises in the channel.If the reflection is strong enough,self-oscillation is also possible,which may accelerate the deterioration of the entire transmission system.This thesis fully considered these factors in the design.When analyzing the gain and noise characteristics of Bi-EDFA,classical rate equations,propagation equation theory,and numerical simulation methods are used.After discussing the structure of a Bi-EDFA structure composed of a single erbium-doped fiber and a fiber-type circulator,an improved Bi-EDFA scheme design is given,but this single-fiber bi-directional amplification model amplifier can Conventional unidirectional amplifiers behave differently because of the presence of opposite forward and backward light in a single Erbium-doped fiber.This will inevitably affect the amplifier's gain,noise figure and other operating parameters and pump power,fiber length,and pumping.The relationship between the mode and otherstructural parameters.This thesis through the design of simulation experiments,and for these operating parameters using Optisystem7.0 optical communication simulation software to build a simulation model,obtained a number of related characteristics of Bi-EDFA,the results show that,under the premise of equal wavelengths of the forward and reverse light,always get Consistent forward and reverse gains,the size of which is determined by the total input power.In Bi-EDFA,simultaneous amplification of forward and backward light is performed,with more complex noise characteristics.In the case of one-way pumping,the forward noise figure is better than The reverse noise figure,Finally,the gain and noise performance of the improved Bi-EDFA are evaluated,Under the condition of satisfying the system gain requirement,there is lower noise index.