Design And Experiment On The Circuit Of Fiber Raman Amplifier By TDM Pumping

With the continuous development of modern communication technologies,the requirements for channel capacity of optical fiber communication systems are also improving.As an important component of optical fiber communication,optical amplifier is always the focus of research.Fiber Raman Amplifier(FRA)has become a key technology in modern optical fiber communication because of its wide bandwidth,low noise,and distributed amplification.It is widely used in dense wavelength division multiplexing systems.But,fiber Raman amplifiers also have their own disadvantages,for example,the gain spectrum is not flat due to different optical gains of different wavelengths,which leads to an increase in bit error rate.At present,people use multi-wavelength pumping sources pumping(WDM pumping).But this method will cause nonlinearity due to interference of waves of different wavelengths in the fiber.In order to solve the problem.This thesis applies TDM to FRA,so that there is only one wavelength of light wave at one time point,which avoiding the interaction between multiple pumping lights to produce nonlinearity such as four-wave mixing.We design the TDM-pumped FRA and design the structure diagram to introduce the functions of every part.Then,we the design the semiconductor laser driving which is the part of the TDM-pumped FRA,and we carried out the experiment.Firstly,we design the semiconductor laser driver circuit and simulate by Multisim,including the delay buffer circuit,which realizes a delay of 500 ms.It effectively prevents the current surge generated when the switch is closed.The protection circuit uses the relay to realize the overcurrent protection.And we innovate the existing design,add a voltage followed make the protection circuit more stable.As for the power of the laser,we design a constant current source to stably supply the laser.We use a reference voltage chip REF02 to design the reference voltage source to realize 5V output.Based on the temperature control chip MAX1978,we design the LD temperature control circuit.Based on the simulation results,we build the circuit for testing.The constant current source achieved a high stability output of 0.24%;the reference voltage source stability also reached 0.2%;the protection circuit was tested several times,and the overcurrent protection of the laser was successfully realized.The temperature control system is tested at different initial temperatures and we set different target,and we realize the temperature control successfully.The system is ready for the next step of TDM pumped FRA.