The continuously bandwidth-tunable pulse generation in the SWNT mode-locked fiber laser is achieved by only tuning the intracavity polarization state. By introducing the in-line polarizer with 2-meter-long polarization maintaining fiber pigtails in a typical ring fiber laser, a bandwidth-tunable SWNT mode-locked fiber laser is constructed. The mode locker is the single-wall carbon nanotube saturable absorber, which is fabricated by optical deposition in the ~0.27 w.t % ultrasonic carbon nanotube alcohol solution. By only tuning the intracavity polarization controllers, the spectral bandwidth is continuously tuned in the range of 0.94 to 3.04 nm. We attribute the upper limit of the spectral bandwidth to the limit of the free spectral range determined by Lyot filter, which consists of polarization controllers and in-linepolarizer in the cavity. These results provide a simple way to achieve bandwidth-tunable subpicosecond pulse, which should be attractive to the applications requiring ultrafast sources with tunable bandwidth or pulsewidth.
Recently, a series of researches have been emphasized on developing advanced satellite networks, mostly because of its advantage in providing spaced-based global communication service. But most of these work prefer to focus on the timevarying topologies, large delays and intermittent connections of satellite networks. However, there is another issue worthy of attentions, i.e., the scarcity and preciousness of satellite resources, owing to the shortage of orbit resources and the high cost of launching a satellite. Therefore, it is significantly important to consider the efficient utilization of resources during designing routing strategies for satellite networks. In this paper, we propose two routing algorithms to optimize the number of used inter-satellite links, which will directly improve the bandwidth utilization and save resources for LEO satellite networks. The basic idea is to reduce the number of links used by lower-priority traffic through scheduling them to links used by highest-priority services, and simultaneously introduce the load balancing strategies to control the aggregation of network flow. Simulation results show that with the price of little longer latency and load unbalancing, our algorithms can effectively decrease the total number of used links, and thus improve the resource utilization and save energy for satellite networks.