The first demonstration of noise-like rectangular pulses (NLRPs) with a record pulse energy of 5.2 µJ and a peak power of 160 W at 1565 nm is presented. This is achieved through a linear-cavity fiber laser system with a power-symmetric nonlinear optical loop mirror as the mode locking element. Stable and highly energetic pulses are generated by extending the cavity length and carefully choosing the coupling ratio of the fiber loop mirror. The laser self-starts at a pump threshold of 1.12 W, and as the pump power increases to 10.5 W, the pulse duration extends from 2.2 to 32.2 ns, while the average output power increases from 0.14 to 2 W, yielding a high slope efficiency of 19.1%. Operating at a fundamental repetition rate of 392 kHz, this laser system delivers the highest reported pulse energy and peak power for NLRPs at a wavelength of 1565 nm in a linear cavity. Its cost-effectiveness, stability, and high performance make it a promising tool for applications such as LIDAR, supercontinuum generation, laser materials processing, and nonlinear spectroscopy.

In this work, we report the formation of multiple mode-locking states in an Erbium/Ytterbium co-doped fiber laser, such as domain-wall (DW) dark pulses, high-order dark harmonic pulses, dissipative soliton resonance (DSR) pulses, and dual-wavelength h-shaped pulses. By increasing the pump power and adjusting the quarter-wave retarder (QWR) plates, we experimentally achieve 310th-order harmonic dark pulses. DSR pulses emerge at a pump power of 1.01 W and remain stable up to 9.07 W, reaching a maximum pulse width of 676 ns and a pulse energy of 1.608 µJ, while Dual-wavelength h-shaped pulses have a threshold of 1.42 W and maintain stability up to 9.07 W. Using a monochromator, we confirm that these h-shaped pulses result from the superposition of a soliton-like pulse and a DSR-like pulse, emitting at different wavelengths but locked in time. The fundamental repetition rate for dark pulsing, DSR, and h-shaped pulses is 321.34 kHz. This study provides new insights into complex pulse dynamics in fiber lasers and demonstrates the versatile emission regimes achievable through precise pump and polarization control.