Experimental And Analysis To Temperature Dependent Characteristics Of L-Band EDFA Gain-tilt

Erbium-Doped Fiber Amplifier (EDFA) can amplify signals directly, which can avoid tousing "light-electric-light" amplified mode as traditional light communication system andsimplifies communication systems, and improve communication system cost, so it willachieve wide applications in fiber communication systems in future.WDM/DWDM (Wavelength Division Multiplexing/Dense WDM) system has alreadybroadened the bandwidth of optical fiber communication system, and become the majortechnology of exploitation and application. But in the long-distance, high-speed WDMsystems using EDFA is also facing some problems. For example, WDM system requiredmore bandwidth of transmission capacity, network management, so the study for L-BandEDFA application becomes more and more important. Since the different wavelengths of lightin optical fiber have different transmission loss, as the wavelength increases, the loss isreduced; the signal light will have an inclination before enter into the EDFA. In addition, thestimulated Raman scattering effect which lead to the power transfer from short wavelength tolong wavelength to produce the tilt. Therefore, control of EDFA gain tilt to compensate forlost due to fiber loss and stimulated Raman scattering, which can make the output opticalpower of the L-band optical fiber transmission system more flat.In this thesis, the main factors affecting the gain tilt of the EDFA was discussed and analyzed. In the course of this study, we find the most of the current literature focused only on theEDFA gain spectrum with gain flatness technology, while there is little study on gain tilt andthen explored in this thesis with the importance to study for the gain tilt. The main traditionalmethod of control the gain tilt of EDFA was discussed.Current traditional method of control gain tilt is changing the attenuate range of VOA insideof EDFA, but EDFA's dynamic gain range is not big enough by this method because thehigher attenuate range of VOA will bring much more noise and higher costs; In addition, theRED-C corporate clarified a new innovative type of gain switched variable gain EDFA basedon a variety of length of optical fiber and optical switch array to change control the gain tiltof EDFA, but it will cause to complexity structure and also higher cost. To considering botheffected factors for gain tilt and the traditional gain tilt control methods, we bring forward anew scenario to get gain flattened signal output by adjust the gain tilt using the method ofcontrolling the temperature of the erbium-doped fiber in a normal variable gain EDFA, thenthe variable gain EDFA can have a wide variable gain range, and also can avoid signaldistortion and noise issue. Also, an experiment was set to verify the scenario. To controlfibers temperature, it only need to add temperature control unit inside of the variable gainEDFA module, the temperature control unit in the EDFA can be smaller size, lower cost.Based on the experiment results, we can try to use a simply temperature control unit toachieve a wide range of variable gain EDFA by improving the gain tilt, it can be easily turn tomass production for industrial production factory.