A learning-based dynamic routing and spectrum allocation algorithm (L-DRSA) is proposed for the satellite elastic optical network. In the routing selection stage, L-DRSA selects the routing path with the highest long term benefits based on the deep reinforcement learning algorithm. In the spectrum allocation stage, the spectrum is allocated greedily with the aim of minimizing the spectrum fragmentation of the network. Finally, several simulation experiments were conducted to evaluate the performance of the L-DRSA and the results demonstrate that our proposed algorithm outperforms than the baseline algorithms.
A functional flexible photonics-assisted frequency measurement (PFM) based on polarization multiplexing and coarse/accurate (C/A) compensation is proposed. Under the same system configuration, it can support fast frequency measuring with moderate accuracy (<0.2 GHz) and wideband range (1 GHz-31 GHz) for radar warning receiver (RWR) using a Mach-Zehnder interferometer (MZI). Moreover, based on the coarse measurement result, a more accurate frequency measurement can be given for electronic countermeasures receiver (ECMR). It is implemented by stimulated Brillouin scattering and improves the accuracy to 20 MHz. Especially, the electro-optic (E/O) modulation section is performed with the assistance of polarization multiplexing, which improves the stability and simplifies the system.
A dispersion-tolerant full-duplex radio-over-fiber (RoF) system based on modified quadrupling-frequency optical millimeter (mm)-wave generation using an integrated nested Mach–Zehnder modulator (MZM), an electrical phase modulator, and an electrical gain is proposed. Not only does the scheme reduce the cost and complexity of base station by reusing the downlink optical carrier, but also the generated optical mm-wave signal with base-band data carried only by 1-s order sideband can overcome both the fading effect and bit walk-off effect caused by the fiber dispersion. Simulation results show that the eye diagram keeps open and clear even when the quadrupling-frequency optical mm-wave is transmitted over 120-km single-mode fiber, and the bidirectional 2.5 Gbit/s data are successfully transmitted over 40 km for both upstream and downstream channels with <1-dB power penalty.
Based on non-regenerative relays, the bit error probability expressions of CSI-assisted relay and
fixed-gain relays for high altitude platform multi-hop optical communication is given. The effect of the factors, including
atmospheric turbulence pointing error and relay node position, on the performance of multi-hop optical links is analyzed.
The simulation results show that the influence of atmospheric turbulence on optical links is greater than that of pointing
error. The improvement of average SNR per hop and transmit power on multi-hop optical communications may be
restricted by pointing error. Compared to CSI-assisted relay, fixed-gain relay is suited to more hops links with the
condition of high average SNR per hop.
Optical satellite communication with the advantages of broadband, large capacity and low power consuming broke the
bottleneck of the traditional microwave satellite communication. The formation of the Space-based Information System
with the technology of high performance optical inter-satellite communication and the realization of global seamless
coverage and mobile terminal accessing are the necessary trend of the development of optical satellite communication.
Considering the resources, missions and restraints of Data Relay Satellite Optical Communication System, a model of
optical communication resources scheduling is established and a scheduling algorithm based on artificial intelligent
optimization is put forwarded. According to the multi-relay-satellite, multi-user-satellite, multi-optical-antenna and
multi-mission with several priority weights, the resources are scheduled reasonable by the operation: “Ascertain Current
Mission Scheduling Time” and “Refresh Latter Mission Time-Window”. The priority weight is considered as the
parameter of the fitness function and the scheduling project is optimized by the Genetic Algorithm. The simulation
scenarios including 3 relay satellites with 6 optical antennas, 12 user satellites and 30 missions, the simulation result
reveals that the algorithm obtain satisfactory results in both efficiency and performance and resources scheduling model
and the optimization algorithm are suitable in multi-relay-satellite, multi-user-satellite, and multi-optical-antenna
recourses scheduling problem.
With the continuous increase of output power of double cladding fiber lasers, the researches of the techniques of fiber
laser beam combination have become a new focus. With the inherent characters of small volume, light weight, good
beam quality and system stability. Once the high power output laser was achieved, there would be broad applications in
industry, scientific researches and military field. Incoherent beam combination is much easier to be realized compared
with coherent beam combination, and with better system stability, thus it became an promising technique to achieve
small volume and high power laser source.
In an incoherent fiber laser beam combination system, the transform lens and diffractive grating play an important role in
determining the coupling efficiency. Through theoretic analysis and numerical simulations, it has been proved that the
optimum focal length of transform lens should be around 20cm in order to ensure a high system coupling efficiency
under some selected simulation parameters. Also the lower frequency of diffractive grating is preferred, and a
contradiction is present that is the higher frequency of diffractive grating is favorable in the consideration of maximum
fiber array width, thus a moderate value was chosen as 200mm-1 with comprehensive consideration. The lower grating
thickness is helpful in improving the diffractive efficiency, while it faced the problem of heat resistance and
manufacturing difficulty, therefore the grating thickness between 2mm and 4mm is preferred. Under such optimized
parameters, the coupling efficiency would be 70% or even higher with small deviation angle and wavelength. An
example of effective jamming distance of combined fiber laser to visible light silicon CCD has been given, whose results
had proved the application foreground of combined fiber laser.
With the continuous increase of output power of double cladding fiber lasers, more effort is put into the researches of the technique of fiber laser beam combination, especially for incoherent laser beam combination because it is easier and with better system stability. Once high power output laser beam is achieved, there would be broad applications in industry, especially for manufacturing and material processing. The combination system's coupling efficiency plays an important role in determining the output power. Through theoretical analysis and numerical simulations, it has been proved that lower lateral off-set and higher grating period would be favorable, also an optimum spot radius exists which corresponds to a maximum value of coupling efficiency. Although lower focal length is helpful in improving the coupling efficiency, there is a contradiction that it makes a narrower fiber array width, which would limits the number of fiber lasers that could be utilized. Thus a moderate value of 20cm is chosen. Based on such optimized parameters, the beam quality M2 is around 2, also a method of two parallel gratings is introduced, which ensures the M2 factor to be around 1. Such combined fiber laser would be of great potential applications in manufacturing and material processing.
A novel multiple access model of satellite formation flying is brought forward, which has the advantages of shared signal
bandwidth, asynchronous access etc, at the same time it overcomes the problems of difficulty of constructing the
addressing codes in the optical code division multiple access and that of hardware implementing in wavelength division
multiple access. The model makes use of delay difference between two arms of Mach-Zender interferometer (MZI) to
encode and decode at the end of transmitter and receiver respectively, that's to say when the delay difference of
receiving end is close to that of transmitting end, the received optical power would be maximum. Frequency shift keying
modulation is adopted to achieve the coherent multiplexing multiple access. Then when the micro-satellite beam is
transmitted in atmosphere condition of weak turbulence, the receiving optical field is described by the Rytov model
based on the premise of independent optical field interference, the formula of SNR and BER is deduced. The simulation
results show that given the turbulence amplitude, 1/SNR ascends along with increasing of satellite number, furthermore
the larger turbulence amplitude, the more quickly 1/SNR rises, this proves number of satellites and turbulence amplitude
are the dominating parameters which affect the system performance.
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