Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion

Abstract

A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

A Dual-Wavelength Fiber Laser Sensor with Temperature and Strain Discrimination

“…Among previous applications, the need for equalization in the emitted wavelengths of a fiber laser is especially important for telecommunications and sensing [5]. This equalization can be achieved by using complicated cavities and non-lineal effects [6], by using a wavelength-flat amplification media [7] or by using special gain flattening filters [8]. These methods complicate the laser structure, or increase the cost of the laser.…”

Observation of stable bound soliton with dual-wavelength in a passively mode-locked Er-doped fiber laser

“…[15] A tunable narrow-line-width multi-wavelength Erdoped fiber (EDF) laser based on a high birefringence fiber loop mirror and an auto-tracking filter was obtained, [16] in which a fiber loop mirror and a polarization controller acted as a filter for the dual-wavelength output. The dual-wavelength square pulse was generated in a figure-of-eight EDF laser with ultra-large net-anomalous dispersion, [17] in which a 2.7km single mode fiber (SMF) with small birefringence supported the Sagnac interference filter to manage the dualwavelength lasing. The tunable dual-wavelength passively mode-locked thulium-doped fiber laser using carbon nanotubes was reported.…”