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At theoretical model of three levels describing Holmium-doped fiber lasers (HDFL) pumped by Laser-diodes 1.15 µm is presented. Based on the model, each of the efficiency, output power depending on fiber core radius, fiber length, and ion concentration of active media were investigated, using the MATLAB program (R 2019 a). The results show that at a doped fiber core radius, 2, 5 & 10 µm pumped with a power range of 10 - 100 W got an output power ranging from 5 to 55 W, respectively, while slope efficiency (η) was 31.3%. Output power was 2.7 - 4 W, η = 50% at a fiber length of 0.01 m, and 81.7 - 83 W, η = 19.6% at a fiber length of 0.5 m. The output power ranged from 107.8 to 109 W & η = 4.7% for 3 m fiber length. The threshold power value of Pth = 0.05 W at fiber core radius 2 µm and Pth = 0.006 W at 3 µm was then gradually slightly increased from 4 to 10 µm. As a result, the output power and efficiency are no longer reliant on the diameter of the fiber core. [ABSTRACT FROM AUTHOR]

In this paper, we propose a Hartley-domain direct-detection faster-than-Nyquist (HD-DD-FTN) algorithm for asymmetrically clipped optical single-carrier frequency-division multiplexing (ACO-SCFDM) in optical-wireless communications (OWC). The HD-DD-FTN algorithm includes modified Hartley-domain equalization (HDE) and maximum likelihood sequence detection, which can simultaneously compensate serious high-frequency distortion and eliminate enhanced in-band noise for the bandwidth-limited OWC. Modified HDE can be implemented by real-valued operations, which is appropriate for dealing with real-valued signals. The simulation results show that ACO-SCFDM system using the HD-DD-FTN algorithm is more robust to inter-symbol interference than that using conventional HDE algorithm. Therefore, the bit error rate performance of the ACO-SCFDM system using HD-DD-FTN algorithm is better than that using the conventional HDE algorithm. In conclusion, the ACO-SCFDM system using the HD-DD-FTN algorithm shows great potential for bandwidth-limited OWC.

In this paper, we propose a Hartley-domain direct-detection faster-than-Nyquist (HD-DD-FTN) algorithm for asymmetrically clipped optical single-carrier frequency-division multiplexing (ACO-SCFDM) in optical-wireless communications (OWC). The HD-DD-FTN algorithm includes modified Hartley-domain equalization (HDE) and maximum likelihood sequence detection, which can simultaneously compensate serious high-frequency distortion and eliminate enhanced in-band noise for the bandwidth-limited OWC. Modified HDE can be implemented by real-valued operations, which is appropriate for dealing with real-valued signals. The simulation results show that ACO-SCFDM system using the HD-DD-FTN algorithm is more robust to inter-symbol interference than that using conventional HDE algorithm. Therefore, the bit error rate performance of the ACO-SCFDM system using HD-DD-FTN algorithm is better than that using the conventional HDE algorithm. In conclusion, the ACO-SCFDM system using the HD-DD-FTN algorithm shows great potential for bandwidth-limited OWC. [ABSTRACT FROM AUTHOR]