Engineering Multi-wavelength Emission in All-Fiber Laser Mode-Locked Through Nonlinear Polarization Rotation

Abstract

The increasing demand for multi-wavelength optical sources to support dense wavelength-division multiplexing (DWDM) channels has driven the development of compact and reconfigurable multi-wavelength fiber lasers. Here, we demonstrate a continuously tunable and deterministically switchable multi-wavelength erbium-doped fiber laser based on nonlinear polarization rotation (NPR) in a compact all-fiber ring cavity. By controlling the intracavity birefringence, NPR acts as a reconfigurable comb filter that enables flexible wavelength selection without modifying the cavity architecture. The laser supports stable spectral states ranging from single- to seven-wavelength mode-locking, enabling reversible wavelength switching and activation/suppression of individual channels. The selectable spectral states can be mapped to binary bit operations, where each wavelength channel represents a controllable logical state. The behavior arises from the interplay between NPR-induced birefringent comb filtering and nonlinear phase modulation, providing a simple and compact platform for reconfigurable multi-channel ultrafast sources for DWDM and photonic signal processing.