A large-scale disaster will affect multiple data centers of an optical cloud network and the contents stored in these data centers should be evacuated for recovery as soon as possible. This paper addresses the problem of data evacuation in a Content-Fragmentation (CF) based optical cloud network before a large-scale disaster. We formulate this problem as a Mixed Integer Linear Programming (MILP) model and develop an efficient Least Delay (LD) based evacuation algorithm. Numerical results show that the performance of proposed LD algorithm is similar to that of the MILP model. In addition, compared to the content replication scheme, the CF based optical cloud network using LD algorithm always takes shorter times to evacuate data.

The Luby Transform (LT)codes is the first digital fountain codes that has practical values. LT codes can demonstrate excellent performance in noisy channels, and it has been widely applied in Free Space Optical Communications (FSO). In this article, the basic principle of LT codes is introduced, and the advantages and disadvantages of LT codes and other common encoding schemes for FSO are listed. Besides that, the progress of both domestic and foreign researches on the applications of LT codes in FSO systems is summarized. Then, the strategies for enhancing the performance of LT codes in FSO systems are elaborately described in two aspects, i.e., novel degree distributions and improved decoding schemes. Finally, the incompletions of the existing researches on LT codes are indicated, and some directions of further researches on LT codes in FSO are depicted.

For the two pairs of pulses separated by time delay, the transmission characteristics between the pulses will be affected according to the changes of phase and delay, and the interference phenomenon will occur in the pulse overlap area due to the influence of cross-phase modulation. The article proposes to observe the transmission characteristics of pulse pairs in a dispersion-decreasing fiber loop mirror. The research results show that according to the changes in phase and delay between the pulse pairs, the time domain characteristics and chirp characteristics of the pulse pairs can be observed, and the transmission characteristics of the pulse pairs under different conditions are analyzed.

To solve the problem of high Peak to Average Power Ratio (PAPR) in Direct Current biased Optical-Orthogonal Frequency Division Multiplexing (DCO-OFDM) system in visible light communication, the selective mapping method can be used to reduce the PAPR of the system. Because the selective mapping algorithm can only select the local optimum in a limited set of phase rotation sequences, the genetic algorithm is introduced to search for the global optimum solution. Meanwhile, the genetic algorithm has the problem of premature convergence. In order to solve this issue, we apply several methods including the adaptive adjustment mechanism, the adaptive multi-point crossover mechanism, the optimal solution protection mechanism and the immediate elimination mechanism to improve the genetic algorithm. Therefore, an Improved Genetic Algorithm- Selected Mapping (IGA-SLM) is proposed. The simulation results show that the proposed algorithm can significantly reduce the PAPR of DCO-OFDM system.

Signals transmitted in the optical fiber are affected by attenuation, dispersion and nonlinear effects, resulting in distortion of the signal contained in the waveform or spectrum. Eigenvalue communication is used to overcome dispersion and nonlinear effects. In this paper, Darboux Transformation(DT) is used to synthesize soliton signal bearing information. By comparing with the analytical method and numerical method in Nonlinear Fourier Transform (NFT), the appropriate method is used to demodulate the recovered information. The eigenvalue communication method is verified by simulation. The factors such as the amplitude, pulse duration and sampling points of the eigenvalues in the transmission process are studied. The simulation results show that the communication distance can reach more than 2 000 km. On this basis, the selection range of the eigenvalues is optimized, so that the information carried by the eigenvalue can be demodulated more accurately at the receiver side.

The modulation bandwidth of the white-light Light Emitting Diode (LED) indoor visible light communication system is limited. Under the condition that the modulation bandwidth is limited, how to further increase the communication speed becomes a hot research topic. A Multi-ary Variable Amplitude & Period Modulation(MVAPM) technique is designed. The modulation symbol structure and its symbol parameter configuration are given. The modulation methods based on On-Off Key (OOK), Pulse Position Modulation (PPM) and Digital Pulse Interval Modulation (DPIM) are analyzed and compared in terms of bandwidth requirements, transmission capacity, average transmit power, and packet error rate. The theoretical analysis and simulation results show that compared with the commonly used digital baseband modulation method, MVAPM has the characteristics of lower modulation bandwidth, higher symbol transmission capacity, symbol-free synchronization, higher modulation efficiency, which effectively improves the communication rate of the system.

In order to support the large-capacity communication transmission based on Orbital Angular Momentum (OAM), this paper discusses the design and fabrication of new OAM signal transmission fibers to meet the needs of special optical fibers which can greatly improve the spectral efficiency and capacity of communication systems. This paper simulates and evaluates the mode characteristics and propagation effects of OAM modes in optical fibers with different waveguide structures. The implementation includes a gradient-index single-ring core OAM fiber supporting 28 effective OAM channels for 50 km transmission, and a three-ring core-structure OAM transmission fiber supporting 96 active OAM channels. Moreover, the optical fiber fabrication technology that supports more stable OAM modes transmission, such as polarization-maintaining OAM transmission fiber, is explored through numerical simulation and experimental demonstration.

As the core module in optical communication system, the optical transceiver module achieves the core function of converting electrical signals into optical signals and optical signals into electrical signals. Its performance plays a decisive role in the overall communication quality. This paper proposes an improved high-speed, low power consumption, low-cost 4-channel 25 Gbit/s optoelectronic interconnect transceiver module package design. Based on the traditional driver chip and modulator as the transmitter and the detector and trans-impedance amplifier as the receiver, we add a clock data recovery circuit to the transceiver module and optimize the package structure, and improve link performance by suppressing link jitter and reducing reflection caused by impedance mismatch at the same time. The back-to-back eye diagram test results of the optimized transceiver module show that the error rate of the system is below 1E-13 at 25 Gbit/s, and the total power of the transceiver module is only 3.9 W.

Aiming at the problem that the optical fiber temperature sensing device generally has a complicated structure and low sensitivity, an elliptical stomata temperature sensing device with high sensitivity is proposed and investigated in this paper. Temperature sensing is achieved based on surface plasmon and optical fiber temperature sensing technologies. It is mainly coated with a metal film on the outside of the fiber. The substance under test uses a mixture of chloroform and alcohol as a temperature-sensitive substance, which is simulated through the finite element vector software COMSOL. Simulation results show that when the incident wavelength is increased from 0.5 μm to 1.0 μm, the temperature measurement range is -20 ~120 ℃, the maximum spectral sensitivity is 6 nm/℃, the resolution is 1 337.12 RIU-1, and the measurement accuracy is 2.85×10-5 RIU.

With the extensive deployment of optical communication equipment in different regions and environments, there are many failures of optical module due to sulfurization corrosion caused by the unqualified environment of the equipment room. Therefore, the demand for the work life prediction of optical module in sulfur-containing environment is rapidly increasing. In this paper, we propose a method to establish a life prediction model for the resistors and beads inside the optical module that are corroded in the accelerated corrosion condition. In this method, Weibull distribution is used as the reference failure function, and the same environmental stress or different environmental stress is used as the covariate. Then the parameters of prediction model are analyzed by using the failure rate data of resistors and beads in the accelerated test. It shows that the accelerated test results are consistent with the failure data in the field. Therefore, the model can meet the needs of life prediction of optical modules at the communication office.

To balance the trade-off between the measurement sensitivity and range of the Fiber Bragg Grating (FBG) ultrasonic detection sensor, a demodulation scheme based on Fabry Perot (FP) cavity and π-phase-shifted FBG (π-FBG) is proposed. The principle of demodulation based on FP cavity is analyzed and numerically simulated in detail. A group of demodulators consisting of two longitudinal modes of the FP cavity can double the system sensitivity, and has good linearity. A demodulator array can be constructed when expanding to multiple modes, which can greatly increase the system range, and effectively balance the trade-off between measurement sensitivity and range. Numerical simulation results show that this scheme is feasible under the practical parameters, and has the merits of high sensitivity and fast response speed.

In order to study the reliability of the flexible optoelectronic interconnect structure in practical engineering applications, a finite element model of the optoelectronic interconnect structure with optical fiber embedded in flexible substrate is established. According to the optical device standard Telcordia GR-468, thermal cycle is loaded. The solder joint stress, fiber stress and optocoupler efficiency is analyzed in the optoelectronic interconnect structure. The results show that the maximum equivalent stress of the solder joint and the optical fiber is in the safe range under the thermal-structure analysis. The maximum photoelectric coupling loss is 0.7 dB, which indicates that the effect of photoelectric transmission is not significant. It can be determined that the photoelectric interconnect structure in flexible printed circuit board can ensure the stability of photoelectric transmission under the load of thermal cycle.

In 5G mobile communication systems, millimeter Wave (mmWave) can provide greater bandwidth and higher transmission rates. The mmWave base station can transmit a high gain directional narrow beam through a large-scale antenna array to increase signal coverage. When mmWave base station are densely deployed, users have to search a large number of narrow beams which sent by multiple base stations to find the optimal beam. This process can take a lot of time and computational resources. Therefore, this paper designs a system-level simulation model in a multi-base station scenario, focusing on the layout of users and base stations, large-scale fading, beam-orientation gain, and characteristics of mmWave channels. Finally, a beam search algorithm based on machine learning is designed. Compared with the traditional exhaustive algorithm, this algorithm has lower latency and computational overhead.

The excessive signaling delay of the traditional handover process in Ultra-Dense Network (UDN) leads to the increase of the total delay of the handover, which results in the degradation of user experience quality. This paper proposes an ultra-dense network mobility management algorithm based on the combination of Software Defined Networking (SDN) and Network Function Virtualization (NFV). The algorithm presents a network architecture model that combines SDN and NFV, which adapts to ultra-dense networks. Based on this, an optimized handover signaling process is proposed and a mathematical model is built for performance analysis. The simulation results show that compared with the traditional algorithm, the algorithm can reduce the total delay of handover.

For the existing Unmanned Aerial Vehicle Ad-Hoc Network (UANET)media access control protocol Statistical Priority-based Multiple Access Protocol (SPMA), the full-load threshold calculation process has slow convergence, and the full-load threshold cannot be adaptively changed with the channel carrying capacity. This paper proposes a low-delay UANET threshold adaptive access protocol. The full-load threshold fast convergence mechanism shortens the threshold calculation time after the system is turned on, reduces the transmission delay of the accumulated data in the initial stage, and adopts the full-load threshold adaptive adjustment mechanism. Therefore, the system can be adapted when the external channel environment changes. The full-load threshold of the channel is adjusted, and the channel carrying capacity can match the actual transmission. When the external channel environment changes, the channel’s full load threshold is adaptively adjusted to match the channel load capacity with the actual channel load. When the channel load capacity is reduced, the data can be adjusted to increase the data transmission success rate while maintaining constant throughput with reduced data transmission delay. The simulation results show that the performance of the protocol in the UANET is better than that of the existing UANET SPMA protocol.