Manipulation of Strongly Interacting Solitons in Optical Fiber Experiments

The model underlying physics of guiding light in single-mode fibers-the one-dimensional nonlinear Schrödinger equation (NLSE)-reveals a remarkable balance of the fiber dispersion and nonlinearity, leading to the existence of optical solitons. With the inverse scattering transform (IST) method and its perturbation theory extension, one can go beyond single-soliton physics and investigate nonlinear dynamics of complex optical pulses driven by soliton interactions. Here, advancing the IST perturbation theory approach, we introduce the eigenvalue response functions, which provide an intuitively clear way to manipulate individual characteristics of solitons even in the case of their entire overlapping, i.e., very strong interactions. The response functions reveal the spatial sensitivity of the multisoliton pulse concerning its instantaneous perturbations, allowing one to manipulate the velocities and amplitudes of each soliton. Based on a recirculating optical fiber loop system and homodyne measurement, our experimental setup enables observation of long-distance spatiotemporal NLSE dynamics and complete phase-amplitude characterization of optical pulses containing several solitons, which provides accurate experimental IST spectra. Adding a localized phase perturbation on a box-shaped wave field, we change individual soliton characteristics and can detach solitons selectively from the whole pulse. The detached solitons exhibit velocities very close to the theoretical predictions, thereby demonstrating the efficiency and robustness of the response functions approach.