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Passively harmonic mode-locking has been experimentally demonstrated in an erbium-doped fiber laser with large normal dispersion using single-multi-single mode structure as artificial saturable absorber. By increasing the pump power under the same polarization setting, the mode-locking operation can switch from fundamental mode-locked to 5th order harmonic mode-locked. Highest repetition rate of 4.26 MHz (5th order harmonic) is observed, with pulse width and pulse energy ascertained at 290 fs and 3.0 nJ, respectively. Excellent signal-to-noise ratio (SNR) of above 50 dB is observed for all harmonic orders. The findings validated that SMS structure can be used to generate stable and switchable high order of harmonic mode-locked. The low-cost SMS fiber for harmonic mode-locked generation technique could lay the groundwork for future sustainable industrial growth. [ABSTRACT FROM AUTHOR]

Ensuring communication infrastructures always alive during disaster mitigation and recovery is of paramount importance. In this case, Unmanned Aerial vehicle (UAV) will be the ideal substitute for the malfunctioning ground base station due to disaster. Henceforth, we suggest a multi‐UAV and Search and Rescue (SAR) collaboration model in this letter. To improve its connectivity, we propose an optimal SAR elevation angle for the multi‐UAV and SARs to administer larger disaster areas effectively and efficiently. We evaluate the performance of the proposed model in terms of path loss, throughput, and coverage probability. The results demonstrate that the proposed model achieves a significant enhancement in serving the SARs. [ABSTRACT FROM AUTHOR]

The tremendous advancement in distributed computing and Internet of Things (IoT) applications has resulted in the adoption of fog computing as today’s widely used framework complementing cloud computing. Thus, suitable and effective applications could be performed to satisfy the applications’ latency requirement. Resource allocation techniques are essential aspects of fog networks which prevent unbalanced load distribution. Effective resource management techniques can improve the quality of service metrics. Due to the limited and heterogeneous resources available within the fog infrastructure, the fog layer’s resources need to be optimised to efficiently manage and distribute them to different applications within the IoT network. There has been limited research on resource management strategies in fog networks in recent years, and a limited systematic review has been done to compile these studies. This article focuses on current developments in resource allocation strategies for fog-IoT networks. A systematic review of resource allocation techniques with the key objective of enhancing QoS is provided. Steps involved in conducting this systematic literature review include developing research goals, accessing studies, categorizing and critically analysing the studies. The resource management approaches engaged in this article are load balancing and task offloading techniques. For the load balancing approach, a brief survey of recent work done according to their sub-categories, including stochastic, probabilistic/statistic, graph theory and hybrid techniques is provided whereas for task offloading, the survey is performed according to the destination of task offloading. Efficient load balancing and task-offloading approaches contribute significantly to resource management, and tremendous effort has been put into this critical topic. Thus, this survey presents an overview of these extents and a comparative analysis. Finally, the study discusses ongoing research issues and potential future directions for developing effective management resource allocation techniques. [ABSTRACT FROM AUTHOR]

A silver sulfide saturable absorber (SA) was successfully employed in an Erbium‐doped fiber laser (EDFL) cavity for short and ultrashort pulse generations. The Q‐switched laser was obtained with an operation wavelength of 1566 nm, pulse rate of 93.81 kHz, and pulse duration of 1.68 μs at a 187.04 mW pump. As the EDFL cavity was optimized for mode‐locking operation by adding 100 m long single mode fiber, a stable soliton pulse train operating at 1564 nm was realized with a constant repetition rate of 1.88 MHz and pulse duration of 3.01 ps. The good nonlinear characteristics of the SA make synergetic contributions to the generation of high‐performance Q‐switched and mode‐locked lasers. [ABSTRACT FROM AUTHOR]

Self-starting Q -switching, Q -switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time. The central wavelengths of Q -switching, Q -switched mode-locking and mode-locking operation modes are 1569.7 nm, 1570.9 nm, and 1572 nm, respectively. The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB. The results validate the capability of generating soliton pulse by doped fiber saturable absorber. Furthermore, the proposed fiber laser is beneficial to the applications of optical communication and signal processing system. [ABSTRACT FROM AUTHOR]