Design And Experimental Study Of Gain Flatness Erbium-doped Fiber Amplification

With the development of the information age,information interaction has become more and more important.Traditional electronic communication methods have long since departed from the mainstream of the times.Instead,optical transmission methods with faster transmission rates and lower transmission error rates are used.Fiber-optic communication,which is unique in the communication market,has become the hottest transmission method.However,with the development of optical fiber communication,people find that the signal gradually decreases with the increase of the transmission distance,and even the signal cut-off distortion occurs.Signal amplification during transmission is imminent.Scholars have successively studied different types of optical amplifiers.The earliest amplifiers were amplified by converting optical signals into electrical signals.The photoelectric conversion itself has the problem of conversion efficiency,and it is impossible to achieve 100% conversion.It puts tremendous pressure on communication costs.All-optical amplifiers have emerged in response to the needs of the times.They directly amplify light through a combination of optics.One of the most important optical amplifiers is Erbium-doped Fiber Amplifier(EDFA),which is currently the most studied by scholars.The erbium ions are doped in the fiber,and the signal light is amplified by the excited erbium ions in the fiber to compensate for various losses during transmission.However,with the popularity of dense wavelength division multiplexing systems,it is required that the signal light of all wavelengths propagating in the optical fiber has the same gain multiple after passing through the amplifier.Due to the unequal optical amplification of different wavelengths,the fluctuation of the gain spectrum is caused by the unevenness of the EDFA system.In the case of long-distance transmission,a single amplifier cannot completely solve theloss problem.When the signal light passes a certain distance,it must be amplified again.If the gain spectrum will have similar fluctuations after each amplification,this will further aggravate the instability of the final output spectrum.The superposition of the gain difference at different wavelengths will cause the power between the channels to be different,which will cause the power saturation of the wavelength channel corresponding to the gain spectrum peak to induce a nonlinear effect.This may cause distortion in the wavelength channel corresponding to the gain spectrum trough to increase the bit error rate during transmission.In order to solve this situation,the gain equalization problem needs to be solved.The main research direction of this thesis is to reduce the unevenness of the erbium-doped fiber amplifier while reducing the loss of gain,without introducing additional noise,and reducing the experimental cost when possible.The work of the thesis is mainly carried out from the following parts:Firstly,in the macrostructure analysis of the various components and design requirements of the EDFA system,the working principle of the erbium-doped fiber amplifier is analyzed in the microstructure and the performance characteristics are discussed.Secondly,the OptiSystem simulation software was used to simulate the effects of structural factors such as signal source,pump source and erbium-doped fiber length on the erbium-doped fiber amplifier.The best structural parameters were determined by analyzing the simulation results.Based on the previous work experience,a gain flattening idea was proposed to upgrade the traditional single-stage amplifying optical path to a single-pumped bipolar amplifying optical path,and further reduce the flatness based on the thin film filter.Finally,the best structural parameters and gain flat optimization ideas obtained from the research and analysis were merged into the actual optical path and tested to verify that the designed erbium-doped fiber amplifier meets the design requirements.