Study And Design Of Fiber Raman Amplifier With DGSA And AGC Function

Because of their abilities to amplify broadband signal channels and the benefits of their smaller nonlinear impairments, lower noise figure, higher saturation output power compared to conventional EDFAs, fiber Raman amplifiers have become one of the key devices in ultra-long haul and high capacity DWDM system. The related technology of Raman amplification is one of the potential technologies in the development of the future intelligent optical networking in China with independent intellectual property rights.For a practical Raman amplifier, it will be encountered some unexpected external factors, such as increased channel loss, channel reconfiguration, sudden channel add/drop and system failure. These factors may lead to the tilt and volatility of the gain spectrum. To meet the improvement in overall network performance, not only dynamic gain spectrum adjustment(DGSA) function but also automatic gain clamp (AGC) function is needed. In this dissertation, we are aiming at designing a distributed broadband fiber Raman amplifier with the two functions mentioned above. We focused on choosing and verifying of control algorithm as well as the design of the control circuit. The primary achievements are as follows:1) The principles, characteristics and pumping forms of fiber Raman amplifier were studied. The advantages and disadvantages of various forms of pumping were discussed. Average power analysis algorithm was used to solve the Raman power coupling equations.2) The various Raman gain control algorithms with DGSA and AGC function were compared. A reasonable control algorithm was selected. The effectiveness of the proposed control algorithm was verified by programming based on MATLAB language and average power analysis algorithm. Various adjustment conditions were carried out including different types of fiber, different gain tilt as well as gain level. It was found that the adjustment process could be finished within 5 iterative under most conditions and the adjustment time was less than 1ms in case the high-speed DSP processors were used.3) The drawbacks of the formerly-made drive circuit were discussed and improved methods were proposed. On the basis of functional analysis of the Raman amplifier, the control circuit was determined to be realized by means of core-board combined with sub-board. The specific A/D and D/A circuit as well as a variety of interface circuits were demonstrated...