Study On High Power Double-clad Fiber Amplifier With Gain Flattening

In the current of the communication network, both the development oflong-distance,large-capacity DWDM tramsmission technology and theimplementation of Optical fiber Cable Television (CATV) network, FTTH are inorder to meet users requirement of network bandwidth. It means that the skeletonpart of the communicaiton network must allow more channels. Because the channelspacing is a fixed vaule,to increace the number of channel needs larger bandwidth,and will make the signal power higher in optical fiber. The combination of Er/Ybco-doped double-clad fiber amplifier and fiber loop mirror can solve the problemsthat the output power of fiber amplifer is lower and the gain bandwidth is not enoughbecause of gain spectral unflatness. The reason that the Er/Yb co-doped double-cladfiber amplifier use high power semiconductor laser as pumping source make the costlower. With the high output power and gain flattening in the optical communicationwavelength of1550nm, high power double-clad fiber amplifier with gain flatteningcan meet the demand of the amplifier which is needed by fiber communicationstechnology. So it has important applications.The parameters of the Er/Yb co-doped double-clad fiber amplifier and gainflattening filter based on fiber loop mirror are simulated and optimized byoptisystem and matlab. On that basis, the experimental system with high power andgain flattening is eatablished. Under the precondition of the flatness within±1.3dB,10mW signal power and7.6A pump current, the maximum output power of1.104Wis obtained.;0.3mW signal power and7.6A pump current, the gain of32.9dB is alsoobtained. From two sides of theory and experiment, the work is done as follows:Firstly,in the basis of introducing the different kinds of optical amplifier, thebackground and important significance of high power fiber amplifier with gainflattening is expounded. The technology of Er/Yb co-doped double-clad fiber amplifier, gain flattening and the energy transfer relationship of Er/Yb co-dopedsystem are introduced. The theoretical model of amplifier based on rate equationsand power propagation and the stucture and filter principle of gain flattening filterbased on fiber loop mirror are given.Secondly, based on the amplifier theoretical model, simulation of the amplifierparameters is made by optical design softwareoptisystem. The effect of theparameters such as active fiber length,pump power and input signal power onforward pumping amplifier output performance and gain is analyzed. Theoptimization of fiber loop mirror is carried on by matlab. The length ofhigh-birefrigence fiber and the state of polarization controller indiffernt complexityfiber loop mirror are detailed studied. Then calculate the total output gain spectrumof the cascade system of amplifier and fiber loop mirror, making the simulationsystem gain spectrum flattening.Finally, according to the optimization parameters, Er/Yb co-doped double-cladfiber amplifier with the forward pumping is established; Design and bulid a gainflattening filter based on fiber loop mirror according to tested ASE spectra of theamplifier, and test the performance of the system with fiber amplifier and fiber loopmirror.Analyze the impact of pump power and input signal power on amplificationsystem performance from the experimental point. Noteworthy phenomennon foundin experiment is described and the cause of the phenomennon is analyzed.