In this paper we report on the performance of a modular single mode pulsed fiber laser system operating in the C-band. With off-the-shelf telecom components and specialty-designed electronics, 3 kW peak power can be generated in a short (1 ns) pulse at 10 kHz at 1545 mn; however, the onset of nonlinear optical effects (SRS, FWM, and SPM) is observed at a 1kW peak power level. Using highly doped erbium fibers, peak powers up to 13kW and pulse energies of up to 20muJ have been generated with a pulse duration range of 0.6-5 nsec, repetition rates between 3kHz to 1 MHz, and at a wavelength of 15453nm and 1567.5 mn before the onset of nonlinear effects became noticeable. Therefore, with the use of highly doped erbium fiber, the onset of nonlinear effects can be increased by an order of magnitude. For narrowband amplification, stimulated Brillouin scattering (SBS) is the limiting nonlinear process. In this regime we recorded the onset of SBS at 8muJ/pulse with a duration of 2.5 nsec. Depending on the pulse shape and pulse duration, self phase modulation (SPM) was also observed, which spectrally broadens the output centered at the signal wavelength; however, the spectral broadening due to SPM is only minor compared to SRS and FWM. It was also demonstrated that pulse steepening is minimized with an appropriate seed waveform. A 3 ns, shaped, input pulse nearly maintained its pulse duration after amplification. Without pulse shaping, the pulse shortened to 1.1 ns.
