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.
In this paper, a dispersion-assisted multi-functional scheme with compact structure and high cost-effectiveness based on microwave photonics is proposed. By virtue of the amplitude regulation mechanism of intermediate frequency signal induced by fiber dispersion, combined with the optical high-precision time delay matching, the image interference and the self-interference can be eliminated simultaneously. It avoids applying electrical tuning devices with lower precision and electrical couplers with limited bandwidth or extra optical filters which is beneficial to improve the system performance and compactness. It is also compatible with optical fiber transmission, which can be combined with radio over fiber technology to bring out the advantages of high spectrum utilization, distributed configuration and low loss transmission of in-band full-duplex radio over fiber systems.
A novel scheme with simultaneous measurement of Angle-of Arrival (AOA) and Doppler-frequency-shift (DFS) of microwave signal without direction ambiguity is proposed and demonstrated. At remote antenna unit (RAU), two received high-frequency microwave signals and a reference signal are modulated by a dual-polarization dual-drive Mach-Zehnder modulator (DPol-DDMZM). After transmission over a segment of fiber link, two signals in low-frequency bands are generated at central station (CS) through a frequency down-conversion. The DFS (including values and direction) and the non-ambiguous AOA in the range of 180° can be simultaneously calculated by monitoring the power and frequency of the two low-frequency electrical signals. The proposed structure not only improves the concealment and security of the CS but also can be extended to have multiple antenna elements in remote locations to realize multi-target detection.
In view of the problem faced in Aviation Information Network (AIN) that the unbalanced load of platforms caused by the dynamically arrived service function chains (SFCs), we formulate the SFC migration problem into a multi-objective optimization model and propose a coalitional game based migration algorithm (CGM). In this paper, we take the aviation platform as the game player, the virtual network function (VNF) as the game commodity, and perform the migration of VNFs through the comparation and swap between different platforms to realize the efficient management of network resources. Experimental results show that the proposed algorithm has the advantages of low computational complexity and fast convergence rate, which can effectively reduce the network energy consumption and migration overhead.
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 photonic microwave hybrid frequency and phase shift keying (FPSK) signal generator is proposed and demonstrated. In the scheme, a parallel structure is constructed to functions as an optical sidebands selector, in which a single-drive Mach-Zehnder modulator (MZM) is placed in parallel with another MZM and a phase modulator (PM). After the parallel structure, a following PM is employed to realize phase modulation. The output signal of the PM is combined with a local oscillator at the receiver after 6-km fiber transmission, and then a hybrid FPSK signal can be obtained after photodetection. The feasibility of the proposed scheme is verified by simulation through a transmission test in a radio over fiber (ROF) system, and a hybrid FPSK signal with frequencies of 5/15 GHz and phase shift of 𝜋 is successfully generated. The scheme features the advantages of polarization independence and good frequency tunability since no polarization multiplexing devices or frequency-dependent devices are applied.
In recent years, more attention has been paid to FSO(free space optical) communication system for the advantages of high security, easy installation and deployment and high transmission data compare to conventional frequency wireless communication. FSO communication has a wider prospect in application of civilian and military. However, the FSO link is easily affected by the atmospheric effects such as cloud, rain, fog and so on, which leads to the decline of the performance of the communication system. Orthogonal frequency division multiplexing (OFDM) is a kind of multicarrier transmission in which high data rate streams are split into lower rate streams and then transmitted simultaneously over several narrow-band subcarriers. OFDM subcarrier can use many different modulation modes. One of the main modulation modes is multilevel quadrature amplitude modulation (MQAM). OFDM is known for its increased robustness against frequency selective fading, narrow-band interference, and high channel efficiency and it is widely used in broadband wireless communication systems. Meanwhile, most of the current studies about free space optical communication are based on atmospheric turbulence models with lognormal, Gamma-Gamma and M distribution. There are not appropriate for aperture averaging reception condition. In 2012, Barrios R and Dios F proposed a new Exponentiated Weibull atmospheric turbulence model for the first time. Exponentiated Weibull atmospheric turbulence model is suitable for the weak to strong turbulence and the average diameter of the aperture. Therefore, this paper aimed at the combined effects of the Exponentiated Weibull atmosphere turbulence, geometric spread and pointing errors on airborne FSO communication system, the bit error rate (BER) performance of the OFDM airborne FSO communication link is investigated. The OFDM optical communication link model based on M-QAM is built, and the electrical carrier to noise ratio for OFDM optical communication link is obtained. The closed form mathematical expression for the total average BER performance is theoretically derived. The relationship between the BER performance and the transmitted optical power under different parameters such as the atmosphere turbulence, the normalized jitter standard deviation and the normalized beam-width is analyzed by simulation. The simulation results show that with transmission optical power increased, the performance of optical link which only under the influence of atmospheric turbulence is better improved than which combined effect of atmospheric turbulence and pointing error. The pointing error has a obvious deterioration in the performance of the system. The performance of the bit error rate improved by increasing the transmission optical power when not considered pointing error is 3 orders of magnitude higher than when considered pointing error. The bit error rate increases with the increase of turbulence intensity, the normalized jitter standard deviation and the normalized beam-width. The airborne system performance is similarly improved in different modulation orders by increasing the transmitted optical power. The BER performance is obviously improved by increasing the transmitted optical power when the normalized jitter standard deviation is less than 0.7. In practical application, the derived average error rate closed expression can be used to estimate the performance of the system and provide reference for the design of the airborne FSO communication system.
KEYWORDS: Signal generators, Modulators, Phase shifts, Modulation, Radio optics, Signal attenuation, Interferometers, Optical engineering, Single sideband modulation, Polarization
A tunable high-order single-sideband signal generator with optical carrier suppression (SSB-OCS generator) is proposed, which is based on frequency multiplication operation using dual-parallel Mach–Zehnder modulator (DPMZM) and Mach–Zehnder interferometer (MZI). By changing all the modulators at maximum or minimum transmission point simultaneously, the amplitude of input radio frequency (RF) signals and the phase difference between input RF signals, two high-order even or odd signals with opposite amplitude of one sideband, are generated by upper DPMZM and lower DPMZM, respectively. Then, two optical signals are coupled to reserve one sideband, and the coupled SSB-OCS signal is injected into an MZI to suppress high-order intermodulation components. The simulated results show that the first-, second-, and third-order SSB-OCS signals can be achieved, and the suppression ratio is over 30 dB, which agrees well with the theoretical prediction. This scheme is featured by the capability to generate tunable high-order SSB-OCS signal with high suppression ratio, and the operation is simple and flexible. Finally, an experiment was carried out to demonstrate the feasibility of the proposed scheme, and a first- and second-order SSB-OCS signal were obtained, respectively, and the suppression ratio is over 24 dB.
In this paper, by combining measurement-device-independent quantum key distribution (MDI-QKD) scheme with entangled photon sources, we present a modified MDI-QKD scheme with pairs of vector vortex(VV) beams, which shows a structure of hybrid entangled entanglement corresponding to intrasystem entanglement and intersystem entanglement. The former entanglement, which is entangled between polarization and orbit angular momentum within each VV beam, is adopted to overcome the polarization misalignment associated with random rotations in quantum key distribution. The latter entanglement, which is entangled between the two VV beams, is used to perform entangled-based MDI-QKD protocol with pair of VV beams to inherit the merit of long distance. The numerical simulations show that our modified scheme can tolerate 97dB with practical detectors. Furthermore, our modified protocol only needs to insert q-plates in practical experiment.
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.
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.
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.
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.
Based on the rate equations and light propagation equations, a novel theoretical model of double-cladding erbium-ytterbium co-doped superfluorescent fiber source (SFS) in double-pass forward (DPF) configuration has been presented. By optimum choosing the fiber length and pump power, the characteristics including mean wavelength stability, threshold, output power, and bandwidth of the SFS are theoretically analyzed in details. The effects of the variation in pump wavelength on the system performance are also been investigated. The analysis results show that a double-cladding erbium-ytterbium co-doped SFS in DPF configuration may serve as light source for the navigation-grade fiber-optic gyroscope applications.
In this paper, the operation principle of the broadband Er-Tm co-doped silica fiber amplifier when pumped at 980nm is presented. Numerical analysis of this broadband Er-Tm co-doped silica fiber amplifier has been performed based on the rate and propagation equations. The signal amplification gain as functions of the fiber length, the input pump power, the erbium-thulium concentration, as well as the pumping ways is described. The results show that the erbium- thulium co-doped silica fiber amplifier could provide more than 80 nm effective gain bandwidth, which is twice larger than the conventional singly erbium-doped fiber amplifier. The minimum gain value exceeds 9 dB when the launched pump power is higher than 400 mW. These results could be useful for the optimized design of DWDM amplifier in the near future.
The experimental results of erbium-ytterbium co-doped double-cladding fiber lasers (EYDCFLs) are reported. The output powers as functions of the input pump power, and the reflectivity of the cavity mirror are described. The maximum output power is about 733 mW, with a slope efficiency of about 30% and optical to optical conversion efficiency of 25.3 %. Numerical analysis of this EYDCFL was also performed based on the rate and propagation equations. The calculated output powers of 1.492 W and conversion efficiency of 51.4 % are doubled than the experimental results. That means further improvements could be made by optimum design of the laser, such as well cutting the fiber-end, adding dichroic mirror at the output end, or making fiber Bragg gratings directly in the fiber core.
The increasing capacity of wavelength-division multiplexing (WDM) transmission systems requires higher output power of erbium doped fiber amplifiers (EDFAs). The two improvements are the use of double cladding fibers (DCF) and the addition of ytterbium oxide as co-dopant in the glass base. In this paper, the operation principles of double-cladding erbium-ytterbium co-doped fiber amplifiers were analyzed. Numerical analysis of erbium-ytterbium co-doped DCF amplifiers using EY801 fiber manufactured by INO, Canada has been performed based on the rate and propagation equations. The maximum output power as functions of the fiber length, the input pump power, the erbium-ytterbium concentration and pumping ways were described. The results show that the ideal erbium-ytterbium co-doped DCF amplifier with EY801 fiber is that with the fiber length of about 62 meters, with as higher as possible pumping powers, and with doubled-ended pumping configuration.
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