Theoretical study on the signal pulse splitting phenomenon in continuous wave pumped fiber optical parametric amplifier

Taking into account pump depletion, numerical simulations have been undertaken to investigate the amplification of strong optical signal pulses in fiber optical parametric amplifiers (FOPAs). It is shown that a strong signal pulse experiences not only amplitude amplifying and temporal width broadening but also pulse splitting processes, which never be addressed in the FOPA studies. The pulse splitting phenomenon that the underlying mechanism is attributed to four-wave mixing, is explained intuitively by employing concept of signal gain saturation and optimum fiber length. Further calculations indicate that this phenomenon appears repeatedly as fiber length increased. Another interesting result is that a sub-pulse formed in the pulse splitting process is compressed by a factor of 9 and amplified by 19 times after evolution in FOPA for 2000m, compared with the incident Gaussian pulse. It indicates that there are potential applications of pulse splitting phenomenon in pulse compression, signal sampling and time-division multiplex system.