Research And Suppression Of Time-Domain ASE In Pulse Fiber Laser

In recent years,1.5-?m band lasers have attracted people's great attention with the “eye-safe” feature.Due to the low optical and atmospheric transmission,1.5-?m band lasers have been widely used in the fields of material,communication,laser ranging and so on.With the high peak power,1.5-?m band laser source can be used for mid-infrared supercontinuum generation.Around the erbium-ytterbium co-doped fiber amplifier(EYDFA),the output characteristics of amplifier spontaneous emission(ASE)have been studied in this paper at continuous wave and pulse pumping.The main contents are shown as follows:1.Programming to achieve the timing synchronization in EYDFA at pulse pumping.the design of module and configuration based on FPGA can be realized on standard TTL level signal output,which the repetition,duty cycle,and delay between multiple signals can be arbitrarily adjusted.And the biggest repetition is 150 MHz.As the external trigger signal in the each module of EYDFA system,Standard TTL signals have solved the problem of controlling the timing synchronization in the measurement of the output ASE.2.Designing a measurement scheme of ASE between the output pulses.The measurement scheme of ASE,measurement system has been set up by a acousto-optic modulator in the time domain for closing the signal and measuring the ASE;When calculating the proportions of ASE,respectively calculating the acousto-optic modulator insertion loss under different conditions of the spectral broadening caused by nonlinear effect.3.The research on the time domain characteristic of ASE and ratio analysis between the output pulses of EYDFA under continuous wave pumped have been carried out.Firstly.ASE proportion under the condition of no ASE in the seed source has been studied in the influence of repetition and pulse width(~nanosecond).Secondly,by viewing the ASE time-domain characteristics between the amplifier output pulses,observed ASE generation after the signal light by about 10?s,and the proportion of ASE is increased as seed source with lower repetition frequency and narrower pulse width.And then,the ratios of the ASE in EYDFA have been discussed in the influence of the proportions of ASE in the seed.4.The study on the time domain characteristic of ASE and ratio analysis between the output pulse of pulse-pumped EYDFA have been presented.Under the condition of seed source output without ASE,the factors of pump pulse widths and delay between pump pulse and the seed are studied in amplifier output power and the ASE time domain features,The experiment proved that the pulse pump can effectively inhibit ASE proportion in the output of EYDFA,and there is a optimum pump pulse width makes the amplifier efficiency highest when the rising edge of seed pulse at the falling edge of pump pulse.In contrast,the influence of different seed source ASE proprortion to the time domain ASE properties of EYDFA have been investigated.