Massive data traffic demand for satellite networks has been increased with the emergence of global broadband services. Due to limited onboard processing capacity and imbalanced distribution of global traffic, severe link congestion may occur in hot spots, deteriorating the performance of the whole network. A link cost modification applied in load balancing algorithm based on artificial bee colony is proposed for routing and wavelength assignment problem to distribute traffic in advance. Moreover, congestion avoidance based on wavelength utilization is designed for unexpected congestion to minimize the adverse impact of congestion on network performance. Experiment results show that the method we proposed realizes high performance in communication success rate and average transmission delay and also achieves the maximum utilization of wavelength utilization under the condition of low blocking rate and the equalization of traffic load.
On the basis of multi-layer satellite network, this paper presents a GEO/LEO double-layer satellite optical network structure that can meet the global all-weather coverage. Due to the limited number of antennas on the satellite, the LEO satellites are divided into two categories according to the function. One of the categories, as cluster-head satellites, should both establish link with LEO satellites and GEO satellites. The cluster head satellites will also be grouped with the link distance as the index. Each group has the same number of satellites which communicate with the same GEO. A reasonable grouping method is used to avoid the problem of too many links being set up simultaneously with the same GEO satellite, which will affect the transmission delay and communication efficiency. In terms of route selection, the hop cost factor is introduced to improve the traditional KSP algorithm. Compared to the KSP algorithm at the cost of link distance, the designed algorithm limits the number of jumps during service transmission, so as to balance the link length and the number of hops well. Through MATLAB simulation, the proposed algorithm improves the efficiency of the utilization of interorbit link, reduces blocking rate, and makes the resource allocation more reasonable.
In the satellite optical network based on wavelength routing, the uneven distribution of global traffic is easily lead to network congestion and unreasonable utilization of resources. Besides, security of communication has attracted tremendous attention due to the openness of satellite network. In this paper, mobile agents are used to implement routing and wavelength assignment (RWA) in satellite networks while considering global traffic distribution. The simulation results show that the proposed algorithm can effectively balance the traffic load, reduce blocking rate and improve the communication success rate of the network on the basis of security mechanism.
Space division multiplexed (SDM) elastic optical network (EON) is considered to be a promising scheme for large-capacity optical communication networks. The static routing, modulation, spectrum, and space allocation (RMSSA) in SDM-EONs with bundles of single-mode fiber is studied. Considering the computational complexity of resource allocation formulation, a path-based integer linear programming (ILP) formulation with fewer variables and constraints is modeled to solve the static RMSSA problem. Then a heuristic algorithm named local optimal RMSSA (LO-RMSSA) is proposed to be applicable in large-scale network scenarios. The calculated metrics are the maximum index of utilized frequency slots, the local spectrum resource utilization, and the runtime of algorithms. The results show that the proposed ILP model and LO-RMSSA algorithm get higher computational efficiency with other metrics no worse than the existing one.
The optical frequency comb(OFC) technology is suitable for precise dimensional metrology for its low fractional uncertainty, while coherent optical communication has the advantages of high receiving sensitivity and capacity. To combine the benefits of both technologies, a novel single-polarization 272 Gb/s coherent optical communication scheme employing four wavelengths is proposed and evaluated. By introducing a 100MHz-reption rate home-made mode-lock fiber laser and optical band-pass filters, the 150GHz-bandwidth OFC signal is generated and transmitted with the coherent optical signals. By the demodulation of the real-time coherent optical receiver, the bit-error-rate (BER) results of four wavelengths are obtained. The proposed scheme provides a simple way to achieve wideband communication and the OFC signal transmission, which can be attractive for the application of onboard integration of communication and ranging.
Aiming at the problem of lightweight and miniaturization of satellite optical communication terminals and intersatellite optical communication in multi-layer satellite networks, The beaconless light tracking and acquisition technology in satellite optical communication is researched and analyzed. The link margin of the satellite laser link under direct detection mode is analyzed , the track and the capture process is designed, the influence of satellite platform attitude error, inter-satellite link communication distance and other factors on capture time and capture probability are simulated and analyzed. The scheme designed uses the active side to emit signal light to scan the FOU, and the passive side uses the capture. The way the detector gaze is captured, ie the gaze-scan capture method. The research shows that in the designed multi-layer satellite network optical communication scenario, the acquisition time of GEO satellite to MEO satellite and GEO satellite to LEO satellite communication is 2034 seconds and 351 seconds respectively, and the capture probability is 95.28% and 99.99% respectively. The acquisition time of MEO satellite and LEO satellite communication is 216 seconds, and the probability of capture is 87.32%, which can meet the requirements of optical communication links of different orbit satellites in multi-layer satellite networks.
To solve the satellite repeater’s flexible and wide-band frequency conversion problem, two novel microwave photonic repeater schemes of generating four and eight different output RF frequencies from one input RF carrier are proposed by adjusting the dual-parallel Mach-Zehnder Modulator’s(DPMZM) electrical configurations. Both schemes can realize simultaneous inter- and intra-band frequency conversion in one single structure and need only one onboard frequency-fixed microwave source. In the first scheme, one C-band RF signal’s 6 GHz carrier can be successfully converted to 2GHz, 4GHz, 16GHz and 22GHz, while the other scheme demonstrates the frequency conversion from 16GHz to eight different frequencies(6GHz, 26GHz, 22GHz, 42GHz, 4GHz, 36GHz, 12GHz and 52GHz).
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