Suppression of sideband frequency shifts in the modulational instability spectra of wave propagation in optical fiber systems

Abstract

In standard optical fibers with constant chromatic dispersion, modulational instability (MI) sidebands execute undesirable frequency shifts due to fiber losses. By means of a technique based on average-dispersion-decreasing dispersion-managed fibers, we achieve both complete suppression of the sideband frequency shifts and fine control of the MI frequencies, without any compromise in the MI power gain.

Loss effects in the spectra of polarization modulational instability in weakly birefringent optical fibers

“…The second major effect of the losses is the generation of a sideband frequency drift, as figure 3(b1) shows. These two undesirable effects, namely, the saturation of the MI gain and the sideband frequency drift, are similar to those occurring in the scalar MI in a non-birefringent fiber [13]. However, we will see in the next section that it is also possible to completely suppress the frequency drifts in the spectra of PMI, but by means of a technique that presents a major difference compared to the one used in previous work for the scalar MI [13].…”

“…As MI occurs only in the anomalous dispersion regime in a standard fiber, no sideband will appear on the pump axis in the normal dispersion regime. Throughout our study we will precisely operate in the normal dispersion regime in order to suppress the scalar MI considered in previous work [13]. Thus, the instability conditions will be entirely determined by equation (7b).…”

“…Thus, the loss effects have two major consequences on MI processes: they impose an upper limit for the accumulated gain (available) for amplification of sidebands, and they cause sideband frequency drifts. Previous work has demonstrated the suppression of the frequency drift of sidebands in a scalar MI process [13]. In this process, the phase matching results from a compensation between the self-phase modulation and second order-dispersion.…”

“…In this process, the phase matching results from a compensation between the self-phase modulation and second order-dispersion. The suppression technique reported in [13] consists in decreasing exponentially the magnitude of dispersion along the fiber, in a proportion equivalent to the power decrease induced by losses [13]. This method, called A3DMF (average dispersion-decreasing dispersion-managed fibers) avoids, during propagation, any modification of the respective weights of the dispersion and nonlinearity in the phase matching condition.…”

“…However, to the best of our knowledge, all previous works have focused on the case of scalar MI [13]. Therefore the question arises as to the applicability of the A3DMF method to non-scalar MI processes.…”