High-frequency RIN transfer in fibre optic parametric amplifiers

Fibre optic parametric amplifiers (FOPAs) are versatile devices for amplification at arbitrary wavelengths, as well as a wide range of optical signal processing applications, including switching, wavelength conversion, regeneration, pulse generation etc. Transfer of intensity fluctuations from the pump to the signal (hereafter referred to as relative intensity noise transfer, RINT) affects the quality of the amplified signal due to the pump power dependence of the gain and the ultrafast nature of the Kerr nonlinearity. For high-speed signal processing applications, the pump may be modulated at several hundreds of GHz or Gbit/s and it is therefore important to quantify the RINT at such high frequencies. To the best of our knowledge, the frequency dependence of pump-to-signal RINT has only been investigated theoretically and experimentally in single-pump FOPAs for low intensity modulation frequencies (IMFs) (<;10 GHz), where the RINT is frequency independent. However, when the IMF of the pump is of the order of the reciprocal walk-off delay induced by group velocity mismatch between the pump and signal, the effect of walk-off can no longer be neglected. In this work, the high-frequency RINT behaviour is investigated numerically in single pump FOPAs.