To meet the differentiated requirements of computing offloading traffic and traditional broadband traffic in multi-access edge computing(MEC) empowered fiber-wireless access networks, this paper proposes a cooperative offloading-aware(COA) dynamic wavelength and bandwidth allocation (DWBA) algorithm based on hybrid scheduling and cooperative offloading mechanism. The algorithm returns computing results by online scheduling, and divides the offline sub-cycle into the computing offloading sub-cycle and broadband traffic sub-cycle. The optical line terminal collaboratively schedules wavelength and bandwidth allocations and offloading decisions, and selects the offloading target for the overloaded MEC server by horizontal computing cooperative offloaing scheme preferentially, and then it offloads the remaining computing requirements to the remote centralized cloud. The simulation results show that the algorithm can improve the completion rate and reduce the completion time of computing tasks, and reduce the adverse impact on traditional broadband traffic and core network load.

The bandwidth allocation problem in the next generation passive optical network(NG-PON2) is one of the research hotspots. Aiming at the problem of how to reasonably allocate bandwidth resources according to the changing state of the network in the dynamic network environment, a dynamic bandwidth allocation algorithm based on statistical periodic quality of service(SPSQ) with adaptive ability is proposed. Combined with the characteristics of the periodic demand of network resources, the dynamic bandwidth allocation problem in passive optical networks is analyzed by statistical method. The simulation results show that the algorithm can adapt to the data transmission of the network and improve the quality of service of the network when the traffic changes.

Carrying 5G enhanced mobile broadband(eMBB) services and ultra-reliable low-latency communication (uRLLC) services based on passive optical network(PON) systems is the current research focus of optical and wireless access networks. How to meet the low-latency requirements of different services has become an urgent problem to be solved in the PON system. In this paper, a low-latency bandwidth allocation algorithm for Xhaul network which supports multi-service coexistence is proposed. By allocating guaranteed bandwidth for uRLLC traffic and prioritizing bandwidth allocation for fronthaul eMBB traffic, at the same time sacrificing the priority of midhaul eMBB traffic and reducing system bandwidth efficiency, to reduce the delay of uRLLC traffic and fronthaul eMBB traffic in this system. When option 2 is selected at the high level and option 6, option 7-3 and option 7-2 are respectively selected at the low level, Matlab software is used to simulate the delay under low load. The simulation results show that the three low-level function partitioning methods can meet the delay requirement of 0.25 ms, and the average delay and maximum delay of the algorithm under high load are lower than those of the algorithm in reference .

In space-division multiplexing elastic optical networks(SDM-EON) based on multicore fiber(MCF), one of the problems is the physical impairment of transmission signals due to inter-core crosstalk. From the perspective of spectrum allocation and core selection, this paper proposes a crosstalk-aware spectrum allocation algorithm for SDM-EON. In this algorithm, when allocating spectrum resources for service requests, crosstalk within a single request and between requests can be minimized by avoiding filling adjacent cores. The numerical simulation results show that the algorithm can effectively improve the crosstalk problem while maintaining a low bandwidth blocking probability in NSFNet and USNet network topologies.

In order to reduce spectrum and time fragmentation in elastic optical networks (EON), a fragmentation-aware routing and spectrum allocation (RSA) algorithm is proposed for advance reservation (AR) services. In the stage of route selection, the algorithm uses K-shortest path algorithm to select alternative path set by comprehensively considering the influence factors of path distance, hop count, spectrum resource consumption and adjacency link number. In the stage of resource allocation, local influence factors are used to count the possible spectrum and time fragmentation, so as to reduce the fragmentation of spectrum and time resources around the candidate resource blocks. The overall influence factors are used to concentrate the occupied resources at the boundary of the frequency axis as much as possible, so as to increase the continuity of intermediate idle resources. At the same time, time-domain resource utilization factors are introduced to avoid excessive resource occupation. The simulation results show that the algorithm improves bandwidth blocking probability performance and resource utilization.

In the virtual network functions service chain(VNF-SC), When a user applies for a service request and the network operator allocates spectrum and Internet technology(IT) resources for the request, due to the different service requests and resource release times, the spectrum resource utilization is often low, spectrum fragments are generated, and subsequent VNF-SC requests are blocked. A joint multi segment path algorithm for optimizing VNF-SC deployment in elastic optical network (IDC EON) between data centers is proposed. The algorithm divides each end-to-end path into multiple path segments with the data center as the boundary, and considers the impact of spectrum resource overhead and utilization on each path segment, selects the end-to-end path with the smallest objective function value to deploy the VNF-SC. The simulation results show that the proposed algorithm has a lower blocking probability than existing algorithms.

Traditional space division multiplexing flexible optical network (SDM-EON) only considers the unprotected allocation of fiber core spectrum resources, which lacks of survivability guarantee. This paper proposes an survivable routing core spectrum allocation(RCSA) improved algorithm based on shared risk group. The algorithm allocates the working frequency slots and the protection frequency slots in single multi-core fiber based on the idea of shared risk core group at the same time, and puts forward the priority parameter of service allocation based on the crosstalk mechanism, and the frequency slots allocation scheme which causes the least crosstalk is selected according to the priority. Simulation results show that the proposed algorithm can effectively reduce the bandwidth blocking probability and inter-core crosstalk while ensuring service survivability.

In order to improve the positioning accuracy in the indoor environment of visible light communication (VLC), an improved location fingerprint position algorithm based on the combination of bilinear interpolation and K-means clustering algorithm is proposed. The algorithm first establishes the initial fingerprint, then interpolates the fingerprint in the cluster domain where the location point is located, and finally selects a matching algorithm to achieve the final location by taking the partial regional fingerprint after interpolation as the reference fingerprint inventory. The VLC system model is established in the indoor room of 5 m×5 m×3 m, and the influence of fingerprint density on positioning accuracy and the comparison of positioning accuracy of the improved algorithm are simulated and analyzed. The simulation results show that the positioning accuracy increases with the decrease of the intensity. The positioning accuracy of the improved algorithm using the interpolated fingerprint database is improved by 21.5% compared with that using the initial fingerprint database, and the computational complexity is greatly reduced.

In order to save as much as possible of deep space optical network node energy, directional flood routing algorithm (DFRA), the algorithm is based on deep space optical communication is sensitive to angle and azimuth of features, based on the deep space node model of the interface, will air separation combination of reuse and frequency division multiplexing, supports the transfer of multiple hops routing orientation, in the process of the routing path finding only part of the nodes involved. The simulation results show that, compared with the traditional flood routing algorithm(TFRA), DFRA can avoid the non-directionality and blindness problems existing in TFRA, and is more energy efficient, and the performance of network transmission delay and delay jitter is better than TFRA.

In coherent optical fiber communication system, constant modulus algorithm(CMA) is one of the most common algorithm to suppress polarization mode dispersion(PMD). In order to further reduce the bit error rate(BER) after digital signal processing(DSP) of the receiver, a CMA improvement measure based on improving the transmission rate of optical fiber communication system is proposed. The BER of the traditional CMA and the improved CMA are calculated and compared, and the relevant simulation experiments are designed. The simulation results show that the improved CMA improve the compensated transmission rateby 3.46%(BER=0). If the BER requirement is 2×10-4, the transmission ratecan be further improve by 1.33%.

In view of the problem that commercial spectrometers can not realize spectral detection in the extremely weak light measurement environment, this paper puts forward a kind of spectral measurement system based on single photon detector array, using the single photon detector in a very weak light environment detection ability, the virtual image phase array(VIPA) and reflective diffraction grating of two dimensional dispersion structure are combined with single photon detector array. The two dimensional effect, relative spectral transmittance curve and single photon detection performance of the system are obtained by experimental test. The experimental results show that the system not only has high sensitivity, but also achieves wavelength resolution of 0.006 nm. Compared with the widely used spectral measurement system based on time-dependent single photon counting, the proposed system has better wavelength resolution and larger measurement bandwidth.

The choice of linear polarization mode in optical fiber is a key factor affecting transmission quality of mode division multiplexing system. Firstly, a direct detection optical fiber transmission system based on hybrid multiplexing of mode division and wavelength division is designed. Secondly, based on the theory of linear polarization mode in fiber, the transmission characteristics of LP01, LP11, LP02, LP12 and LP21 five modes in the optical fiber transmission system are simulated by Optisystem15.0 software. Then, four modes of LP01, LP11, LP02 and LP12 are multiplexed, and the simulation results show that when the core radius of graded-index multimode fiber changes in the range of 19~25 μm, the optimal core radius for each channel with Q factor above seven is 21~22 μm, and the optimal value does not change with the transmission distance. Finally, in the eight-channel hybrid multiplexing system, the direct detection method is used to realize the short distance transmission with bit error rate below 10-9 at 2.0 km.

This paper proposes an channel equalization method based on artificial neural network(CD-net), which for deals with the channel equalization problem of coherent optical filter bank multicarrier with offset quadrature amplitude modulation (CO-FBMC-OQAM)communication system. CD-net combines the advantages of convolutional neural network and deep neural network to perform the channel equalization task for the CO-FBMC-OQAM communication system. In CD-net, the convolutional neural network modular first performs feature extraction of the distorted signal at the receiving end. Then the deep neural network modular performs signal demodulation and channel equalization, and recovers the original information. The numerical simulation results show that compared with the traditional channel equalization method, the CD-net method has a greater advantage in bit error rate performance, which can better solve the channel distortion problem of the CO-FBMC-OQAM communication system.

Submarine communication optical cable is the main carrier of international communication, and the accelerated growth of international internet bandwidth has promoted the accelerated construction of submarine communication optical cable. This paper introduces the basic structure of the power supply system for submarine communication optical cable underwater equipment, analyzes the working principles and internal circuit design of submarine repeaters, submarine branch unit, and power supply equipment. This paper proposes the design method of power supply system design for submarine communication optical cable underwater equipment, and analysis the switching protection mechanism of the power supply system combined with a case.

In order to realize multi-channel microwave photonic down-conversion and improve the performance of frequency conversion link. In this paper, a single integrated modulator is used to realize the microwave photonic down-conversion scheme, the scheme uses the polarization multiplexing feature to realize the dual-channel down-conversion function. The simulation and experiment results show that when the sub-modulator is set to work at the minimum transmission point, the carrier-suppressed double-sideband modulation is realized, and the optical carrier-suppression ratio reaches 29 dB. Two channels independently down convert the radio frequency signal to intermediate frequency signals respectively, the spurious rejection ratio reaches about 30 dB, and the spurious free dynamic range(SFDR) of two channels reaches 110.4 dB·Hz2/3 and 113.4 dB·Hz2/3 respectively.

Multi-core fiber has the advantages of high integration and large transmission capacity. In order to realize its connection with single-core fiber array, a self-assembled ultra-low loss multi-core fiber fan-in and fan-out(FIFO) device design and preparation method based on high-precision ceramic ferrule is proposed. Through simulation and experiments, the optimal parameters of the taper fiber, such as taper power and taper speed were determined, and a high-performance seven-core fiber FIFO device is successfully fabricated. The transmission link used in the experiment includes a pair of FIFO devices and a 5 m long seven-core fiber. The average loss of the seven channels is 0.9 dB and the average crosstalk is -52 dB. In addition, the FIFO device achieves 7×10 Gb/s error-free transmission in a seven-core fiber with a wavelength of 1550 nm and a length of 1 km, and the consistency of each channel is good.

The current visible light and radio frequency(RF) hybrid links are still obviously limited to the Lambertian beam configuration with simple spatial radiation characteristics. For addressing this issue, based on the non-Lambertian space radiation characteristics of commercial LED, a soft switching scheme of hybrid link between visible light and RF based on typical LUXEON Rebel non-Lambertian beam is proposed, and simulation analysis is carried out. The simulation results show that when the RF access point is set at the proximal end(dr=10 m) and the distal end(dr=60 m), the maximum throughput of the hybrid link of the proposed heterogeneous non-Lambertian beam configuration is 370.72 Mb/s and 275.68 Mb/s, respectively. When the transmission power is from 2~15 W, the hybrid link can introduce a throughput gain of up to about 14 Mb/s compared with the traditional Lambertian beam configuration.

G.654.E fiber is used in the transmission system, because of the large cut-off wavelength and the coupling method with the transceiver end equipment, multi-path interference(MPI) may occur, which will affect the transmission performance. In order to explore the influencing factors of MPI, this paper analyzes the effects of fiber type, fiber length, looped condition, connection mode and the tail fiber type on the MPI through the narrow-band external cavity laser/optical power meter method in 1310 nm light source wavelength. The experiment results show that, for short-distance links, it is possible to reduce MPI by means of circular filtering and hot-splicing instead of active connectors, for long-distance links, try to avoid mixed connections of different types of optical fibers.

The investment in laying submarine cables is huge, and man-made failures in offshore areas are frequent. The current technology can only locate the breakpoint after the submarine cable is damaged, but cannot carry out real-time monitoring, early warning and event location for the potential hazard events of the submarine cable. In this paper, a bidirectional interference multi-domain correlation recognition technology is proposed, and the sensor system sensitive to external security violation events is constructed through the existing optical fiber in the submarine cable. Three kinds of events, namely non-event occurrence, knocking optical fiber and pulling optical fiber, are tested and analyzed. The experimental results show that the technique can effectively prevent submarine cable disasters and improve the safety and survivability of important submarine cables.