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We present an efficient 976 nm fiber laser achieved in a step index large-mode-area (LMA) fiber by 915 nm diode pumping. The 976 nm lasing was enabled using spectroscopic engineering in a fiber design that helps suppress the competing 1030 nm gain. Our study shows, alumino-phospho-silicate (Al:P) is advantageous for shaping a gain spectrum in favor of 976 nm compared to other widely used compositions, hence facilitating otherwise the challenging 976 nm lasing. In addition, a germanium (Ge)-cladding was introduced to achieve LMA and low numerical aperture step-index fiber, permitting a wavelength selective bending technique. By applying the bending technique, an efficient 976 nm lasing was achieved with up to 15 W output power (pump power limited) with 28% slope efficiency in the step-index LMA fiber. [ABSTRACT FROM AUTHOR]

Workflow-based Service-oriented WSNs have recently received a lot of attention from both academia and industry. With well-defined service components, various flexible WSN applications can be developed. However, the key characteristic of WSNs is resource constraints. Sensor nodes in WSNs have limited storage, computation and especially limited energy. As service components in WSNs rely on the data gathered by sensor nodes, they are also resource-constrained. Unfortunately, traditional workflow technologies (i.e., service selection, composition and adaptation) ignore the residual energy of services. This will bring unbalanced energy consumption and furthermore shorten the network lifetime. In order to resolve this issue, we proposed an energy-aware QoS-guaranteed workflow management mechanism. In this mechanism, a new QoS model is first presented to improve the QoS evaluation. Then, based on this QoS model, an efficient service selection schema, which considers both the energy and the QoS of services, is proposed. Furthermore, an adaptation mechanism for balanced energy consumption is also proposed. Experimental evaluations demonstrate the capability of our proposed approach. [ABSTRACT FROM AUTHOR]

Photodarkening in Yb-doped fibers is known to be dependent of Yb population inversion. In addition to this dependence, we report that pump wavelength selection plays a significant role in photodarkening dynamics. It is found that 976 nm pump source can lead to more severe photodarkening effects than 916 nm pumping at the same inversion levels. This observation is consistent in Yb-doped fibers with various compositions. Our work reveals pump wavelength is another determinant factor of photodarkening besides the inversion level and emphasizes the importance of pump wavelength selection in high power Yb-doped fiber lasers and amplifiers. [ABSTRACT FROM PUBLISHER]

We experimentally demonstrate switchable dual-wavelength mode-locking of thulium-doped fiber laser (TDFL), using single-wall carbon nanotubes as saturable absorber. Due to the cavity birefringence-induced comb filter, switchable mode-locking can be individually realized for the proposed TDFL among three wavelengths of 1947, 1945, and 1943 nm, with almost the same 3-dB spectral bandwidth of 2.2 nm, repetition rate of 13.6 MHz, and pulsewidth of 1.8 ps. Furthermore, after finely adjusting the intra-cavity birefringence, we are able to demonstrate switchable dual-wavelength mode-locking at either 1947/1945 or 1945/1943 nm. The optical spectra of dual-wavelength mode-locking have almost the same characteristics and can maintain stable operation for a long period. [ABSTRACT FROM PUBLISHER]