FWM Implementation and Analysis Using MATLAB - Optical Signal Processing by Silicon Photonics - page 119

than optical fibers, for a typical peak power. The short nonlinear length is due to
very high nonlinear parameter, also dispersion and nonlinear lengths are pulse-
width dependent. Thus, the dispersion length for a usual ps pulse is several orders
of magnitude longer than that for an fs pulse, but the nonlinear length is the same
for both short and long pulses as long as the pulse power is the same (Fig. 9.8 ).
The impact of waveguide length is shown in Fig. 9.9 , while the combined
resulted curves for CE and NF are depicted in Fig. 9.9 . The free carrier time used
in simulation is 1,000 ps for same waveguide length of 1 cm.
The curves clearly show that the increase in NF decreases the CE. The conver-
sion efficiency for longer waveguide lengths is lower at the same pump powers
while for short waveguides, it is higher. As in above figure the CE for 1, 1.5, and
3 cm is − 2, − 4, and − 8 dB, respectively.
Fig. 9.8 Conversion efficiency at different waveguide lengths
Fig. 9.9 Noise figure increases with the increase in power and waveguide length, which strongly
degrades the conversion efficiency