Theoretical Research On The Gain Saturation Characteristics And Wavelength Conversion Technology Of Semiconductor Optical Amplifier

Optical fiber communications is one of the drivers to enable broadband services for the end-users of nowadays telecommunication networks,which will then also be able to spread over larger geographic areas.Optical fiber is thereby used as transmission medium since it offers several advantages compared to the copper wires such as the traditional twisted pair cable,such as the small diameter,light weight,and abundant raw materials,which is beneficial to resource utilization.The advantage of optical telecommunication eases the daily life though it is so far not really transparent to the mankind since it is hidden in the core networks and therefore not touchable.To support the growing internet traffic and multimedia communication services,future optical acess networks will possess ultra-high transmission speeds and superlarge capacity.At present,the optical access networks are facing some problems,such as opaque optical networks,low spectral efficiency,and severe bandwidth shortage.In order to solve this series of problems,this paper proposes to provide a transparent optical network scheme for wavelength conversion by using easily integrated semiconductor optical amplifiers.Then the high-order modulation scheme is used to replace the traditional direct modulation to improve the spectral efficiency.The coherent detection techniques is used to receive higher-order modulated signals and provide a feasible solution for '?-to-the-user',thus alleviating the current serious bandwidth shortage problem.The main research achievements are summarized as follows:Firstly,an iterative algorithm-based steady-state model is established.The analysis is carried out for In P-In Ga As P uniformly buried semiconductor optical amplifier,and its parameters such as carrier concentration,amplified spontaneous radiation noise,and excited radiation are updated in real-time,and finally the gain and noise index of the device under certain bias current and input power are obtained by this steady-state model.Secondly,semiconductor optical amplifiers are used to realize fast wavelength conversion.Based on the theoretical model of semiconductor optical amplifier,the theory of four-wave mixing in wavelength conversion is further developed,and the theoretical verification experiment of all-optical wavelength conversion is carried out at 10 Gb/s transmission rate for a certain channel to realize wavelength conversion.Then,a 4×10 Gb/s bidirectional transmission system is further built to observe its BER and eye diagram under multiple channels.Thirdly,the differential phase shift keying(DPSK)high-order modulation coherent detection is implemented.By comparing the advantages and disadvantages of several modulation formats through theoretical analysis.Then,the balanced detection and coherent detection schemes are compared at 40 Gb/s transmission rate using DPSK modulation and demodulation schemes to further verify the advantages of coherent detection in terms of BER,receiver sensitivity.