Numerical modelling of the pump-to-signal relative intensity noise transfer in two-pump fibre optical parametric amplifiers

Abstract

An accurate numerical model to investigate the pump-to-signal relative intensity noise (RIN) transfer in two-pump fibre optical parametric amplifiers (2-P FOPAs) for low modulation frequencies is presented. Compared to other models in the field, this model takes into account the fibre loss, pump depletion as well as the gain saturation. As a result, the model allows to include a wide range of practical circumstances, both in and beyond the undepleted pump regime, related to different applications of FOPAs. In the small-signal or undepleted pump regime, the model predicts the ripples of the RIN spectrum very well and yields better results than those of other models. It is shown that beyond the small-signal regime, pump power variations do not remain unchanged over the length of the amplifier and for high signal powers, when the FOPA saturates, minimum pump-to-signal RIN transfer occurs. The results of the model are also compared with the available experimental data in the field and a very good agreement can be seen.

Optimized design of six-wave fiber optical parametric amplifiers by using a genetic algorithm

“…Frequency assignments of the six-wave model are given in Refs. [6,17,21], which are shown in Fig. 1 .…”

“…Since the signal is close to the pump1, also in the condition when the signal power is relatively high, some new wavelength components would be generated due to cascaded FWM [20], thus the second idler, at frequency 5 ω , is generated on the left side of pump1 owing to the degenerate FWM of the pump1 and the signal waves at the same time. This idler is symmetric to the signal with respect to the pump1 so that getting 1 2ω ω ω = + [6,17,21]. We have limited ourselves to situation in which all the waves are launched into the fiber with the same linear state of polarization (SOP) and remain in that state along the entire fiber [17].…”

“…We have limited ourselves to situation in which all the waves are launched into the fiber with the same linear state of polarization (SOP) and remain in that state along the entire fiber [17]. When the fiber losses are neglected, and under the assumption that the six-waves are sufficiently separated in frequency, the 6-coupled equations governing the complex field amplitudes evolution of the two pumps (waves 1 and 2), one signal (wave 3), and three generated idlers (waves 4, 5 and 6) along the fiber can be written as [6,17,21].…”

“…Compared with the one-pump architecture, the two-pump FOPA can offer a flatter and broader gain spectrum, which makes the two-pump FOPA more attractive for optical communication applications. In practice, when the signal wavelength is not far away from the pump wavelength and the signal power is amplified to relatively high, some new wavelength components would be generated due to cascaded four wave mixing (FWM) [20], consequently leading to the occurrence of six-wave mixing (SWM) for two-pump FOPA [6,21], which consists of two pump waves, one signal wave and three idler waves.…”

“…For the high frequent appearance of the six-wave FOPA in practice, recently, some studies of the six-wave FOPA have been done [6,15,17,21], however, the gain property did not have good quality compared with the four-wave FOPA, because the more waves interaction could not lead to the better gain spectrum. In this paper, we focus on optimizing the gain characteristics of the six-wave FOPA by using the GA under the condition of the pump depletion, since in order to achieve the higher signal gain, the pump depletion should be considered [19].…”