FWM Implementation and Analysis Using MATLAB - Optical Signal Processing by Silicon Photonics - page 116

when the pump power is high. So increasing the pump power does not always
result in the increase of the CE, which is not only dependent on the range of the
pump power but also on the lifetime of the carriers. As it is well identified that
with increasing pump power the NF starts increasing but this increase is differ-
ent for different wavelengths, e.g., the NF degrades rapidly for wavelengths near
1,550 nm and slowly for wavelengths near 1,510 nm. This ultimately shows the
dependency of CE on wavelength at higher pump powers. Hence the optimum val-
ues of pump power, pump/signal wavelength, and the waveguide length are essen-
tial to achieve improved NF and maximum CE.
In this context, the pump power plays a significant role in wavelength con-
version efficiency in silicon waveguides, also TPA and FCA are both intensity-
dependent phenomenon.

9.3 Impact of Wavelength

As in the previous work, due to nonlinear losses and phase mismatching, the
wavelengths near 1,500 nm achieve higher gain and hence efficiency as compared
to those near 1,550 nm at peak powers. The wavelength detuning is defined in this
work as the wavelength difference of the signal wavelength to the pump wave-
length ∆λ = λ P − λ S . The effect of wavelength detuning on CE is simulated and
found that the results for positive and negative |∆λ| are almost the same. As shown
in Fig. ( 9.3 ) the CE is optimum at ∆λ ≈ 20 NM and it lowers for both the higher
and lower values of detuning. The drop of CE at lower detuning values is due to
the phase mismatch and nonlinear losses while at higher detuning values the drop
in CE is caused by the double peaks observed in Fig. 9.3 . Figure 9.4 concludes the

Fig. 9.3 Effect of effective area