Even harmonic pulse train generation by cross-polarization-modulation seeded instability in optical fibers

Abstract

We show that, by properly adjusting the relative state of polarization of the pump and of a weak modulation, with a frequency such that at least one of its even harmonics falls within the band of modulation instability, one obtains a fully modulated wave at the second or higher even harmonic of the initial modulation. An application of this principle to the generation of an 80 GHz optical pulse train with high extinction ratio from a 40 GHz weakly modulated pump is experimentally demonstrated using a nonzero dispersion-shifted fiber in the telecom C band.

Polarization modulation instability in a Manakov fiber system

“…The validity of Eq. (1) in representing the MI of polarized waves or PMI in a randomly birefringent, low-PMD fiber was recently qualitatively confirmed in the anomalous GVD regime [26].…”

“…Despite extensive mathematical studies [18][19][20][21], experiments have been limited to only a small number of systems such as optical waveguides and Bose-Einstein condensates [22][23][24]. There is a need for more studies to quantitatively characterize nonlinear wave propagation described by the Manakov model, besides the soliton evidence and its qualitative application to the design of optical networks [16,25], and a vector extension of the well-known modulation instability (MI) in the anomalous dispersion regime of telecom fibers, leading to high-repetition-rate pulse trains [26]. As a result, the peculiar nonlinear dynamics and the associated instabilities [27,28] that can be predicted by using the Manakov model have remained so far largely quantitatively untested.…”

Nonlinear polarization effects in optical fibers: polarization attraction and modulation instability [Invited]

“…In this context, the efficient conversion of a modulated wave into a nearly sinusoidally modulated wave at harmonic frequencies has been demonstrated by means of XPolM-MI induced by multiple FWM in the case of a normally dispersive, highly birefringent fiber at visible wavelengths [130]. Furthermore, a recent work [131] has focused on XPolM-MI in the anomalous dispersion regime of a randomly birefringent fiber, where the self-and cross-induced nonlinear terms have the same weight (Manakov system [35]). This configuration applies to the relevant practical case of telecommunication fiber-optic links with random birefringence [36].…”

40 GHz pulse source based on cross-phase modulation-induced focusing in normally dispersive optical fibers

“…Basically, the nonlinear temporal compression of the initial beating is induced through the focusing regime of the nonlinear Schrödinger equation (NLS), taking advantage of the interplay between the nonlinear Kerr effect and the anomalous dispersive regime [2]. This particular technique has been demonstrated in a wide range of fiber arrangements to produce pedestal-free pulse trains at various repetition rates, ranging from GHz to several THz [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Nonetheless, it is noteworthy that even though various techniques of nonlinear compression of a beat signal have been reported in anomalous dispersive optical fibers, only a few exist for normally dispersive fibers. For instance, in two-stage techniques, it is known that an incident optical pulse can be first chirped through self-phase modulation, cross-phase modulation or through an opto-electronic phase modulator and then subsequently compressed by means of a dispersive element inducing an opposite sign of chirp such as a grating or a suitably designed fiber segment [17][18][19].…”

“…This particular technique has been demonstrated in a wide range of fiber arrangements to produce pedestal-free pulse trains at various repetition rates, ranging from GHz to several THz [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. To this aim, various fiber concatenation systems have been implemented including, dispersion decreasing fibers [3], comblike or step like fiber profiles [4,17], modulation instability [6], cross-phase modulation (XPM) [7], multiple four-wave mixing [8][9][10][11][12][13], parametric amplification [15] as well as Raman amplification [16].…”