Research On MOPA Transmit Technology Of Optical PPM System Based On Pump Power Limitation

In deep space optical communication,because the communication link is extremely remote,and is affected by channel characteristics such as background light noise and atmospheric turbulence,it will have a certain impact on the receiving end,so its requirements on the laser emitting end are relatively high.At this time,Pulse Position Modulation(PPM)and Master Oscillator Power-Amplifier(MOPA)technologies are two key technologies widely used at present.In the previous research on PPM modulation and MOPA amplification technology,it mainly focused on the improvement of laser emission power and the improvement of nonlinear effects in the optical amplification process,but did not analyze the effect of PPM modulation order on the output signals of different optical amplification systems and The influence of PPM modulation parameters on the output power characteristics of optical amplifiers.Aiming at these two aspects,this thesis simulates and optimizes the optical PPM communication system based on 1064 nm ytterbium-doped fiber and 1550 nm erbium-doped fiber amplification.Aiming at the problem of the average transmission power of the pulse signal at different PPM modulation orders at the transmitter end in optical communication,the effect of PPM modulation parameters on the output power of the optical amplifier is studied without changing the hardware.The scheme is mainly to build a laser emission method based on MOPA amplification,use a two-stage amplification system,and optimize the gain fiber length to simulate and analyze the output power characteristics of the optical emission system under different modulation orders.The comparison and analysis of the relative power values of the average power and the peak power of the pulse under different modulation orders in the traditional mode and the mode of this subject.The simulation results show that in 1064 nm ytterbium-doped fiber amplification,the optimal fiber length at different modulation orders has less effect on the output power.When the hardware of the optical transmission system is fixed,the PPM modulation order is changed.Restricted systems,not even peak power limited systems.In the 1550 nm erbium-doped fiber amplifier,when the hardware of the transmission system is fixed,the output power after the first-stage amplification and the second-stage amplification are approximately equal under different modulation orders,which meets the average power limited system.In the two kinds of doped fiber,other conditions are certain,and only the material of the doped fiber has an effect on it,so these characteristics need to be considered when designing the PPM modulation order.Finally,considering the influence of the PPM modulation parameters on the output signal characteristics of the optical amplifier,the optimal design scheme of the optical PPM communication system is studied.By establishing a transmission and reception system,comparing the waveforms of 4-PPM modulated signal optical pulses under different time slot widths,it is found that the waveform oscillation is larger when the time slot width is too narrow.In order to improve the quality of the optical pulse waveform at the transmitting end,first analyze the waveform of the optical amplification signal at different duty cycles.Due to jitter problems,the pulses have a greater impact at high duty cycles.Reducing the duty cycle can optimize the waveform,but the average power is also will be reduced accordingly,and then through the error analysis of the receiving end under different duty cycles.Finally,the effect of different protection time slots on the performance is studied.By increasing the protection time slots,the problem of waveform oscillation of adjacent time slots is improved.Simulation results show that the proposed duty cycle and protection time slot optimization scheme can improve the performance of the optical PPM communication system.