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By applying recirculating frequency shifter technology to generate optical comb as neighboring channels, we have experimentally investigated the interchannel nonlinear tolerance of 256-Gbit/s polarization-division multiplexing return-to-zero 16-ary quadrature amplitude modulation (PDM-RZ-16QAM) in a co-propagation with 32-Gbaud on-off keying, binary phase-shift keying, quadrature phase-shift keying (QPSK) signals in 792-km large-area fiber transmission system. The results show that the experimental back-to-back optical signal-to-noise ratio requirement of 256-Gbit/s (32-GBaud) PDM-RZ-16QAM signal is shifted by 4.8-dB penalty in comparison with the theoretical limits. The cross-phase modulation (XPM) tolerance for 256-Gbit/s PDM-RZ-16QAM in 32-Gbaud phase-modulated neighboring channels is better than in 32-Gbaud intensity-modulated neighbors. Moreover, the performance of XPM tolerance for 256-Gbit/s PDM-RZ-16QAM in 32-Gbaud QPSK neighboring channels is the best among other kinds of modulation neighboring formats. [ABSTRACT FROM AUTHOR]

Based on recirculating frequency shifter, we generate 20 high-quality multicarrier optical combs with a tone-to-noise ratio >25 dB. We also experimentally demonstrate 2.56-Tb/s, polarization division multiplexing return-to-zero 16-ary quadrature amplitude modulation, coherent optical wavelength division multiplexing transmission over 800 km standard single-mode fiber with 25-GHz channel spacing, and the spectrum efficiency is 5.1 b/s/Hz. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A hybrid shaping scheme, carrier-less amplitude and phase modulation geometric-probabilistic hybrid shaping 16QAM (CAP-GPS-16QAM), is proposed for data center networks. The probabilistic shaping is achieved by applying the proposed probabilistic subset shaping to the constellation after geometric shaping (GS). An intensity modulation/direct detection experimental system of 5 GBaud is built to verify the proposal. The results show that the gains of the proposed scheme are 2.4, 2.6, and 3 dB compared with CAP-GS-16QAM, CAP-PAS-16QAM, and CAP-square-16QAM, respectively, at BER = 10-3. Meanwhile, in terms of generalized mutual information, the proposal improves the performance by 0.078, 0.125, and 0.153 bits/symbol compared with CAP-GS-16QAM, CAP-PAS-16QAM, and CAP-square-16QAM. [ABSTRACT FROM AUTHOR]

A constellation-designed 32QAM method is proposed using geometric shaping (GS) and probabilistic shaping (PS). In addition, a 50-Gbaud polarization division multiplexed multispan optical fiber link for the proposed scheme is set up. The simulation results show that when the net data rate reaches 211 Gbit/s, the proposed 32QAM with GS and PS is capable of achieving about 0.1- and 0.3-dB OSNR gain over PS-32QAM and regular 32QAM (R-32QAM), respectively. When 213 Gbit/s net data rate transmission is achieved, the use of the proposed 32QAM can increase the transmission length by ~60 km over PS-32QAM and ~210 km over R-32QAM. Moreover, when OSNR is set to 19 dB and signal bandwidth is 40 Gbaud, the net data rate of the proposed 32QAM is 2 and 7.5 Gbit/s larger than PS-32QAM and R-32QAM, respectively. [ABSTRACT FROM AUTHOR]

A scheme to realize the flexible photonic frequency multiplication at millimeter-wave (mm-wave) and radio over fiber (RoF) transmission has been proposed and demonstrated. To enable the generated multiplefrequency signal to have a better performance of phase preserving, we theoretically investigated the phase change during the generation and transmission and proposed an adaptive coding algorithm to reduce the impact of phase fluctuation. The coding algorithm brings the frequency multiplication and fiber transmission distance together into consideration and adjusts the phase of the signal consequently. Due to the proposed coding algorithm, the system not only realizes the flexible frequency multiplication but also eliminates the phase deviation induced by the modulation and fiber dispersion, which effectively increases the transmission distance of fiber link. In addition, it also reduces the complexity of phase retrieval at receiver side. A 50-GHz to 100-GHz RoF system with 1 Gbit/s radio signal has been implemented by numerical simulation, and the result shows that the adaptive mm-wave RoF system could realize arbitrary multiple-frequency of quadrature phase shift-keying signal from double to decuple and reliable transmission of the tenfold signal at least 50 km. [ABSTRACT FROM AUTHOR]

A rate-adaptive multilevel coded modulation (RA-MLC) scheme based on fixed code length and a corresponding decoding scheme is proposed. RA-MLC scheme combines the multilevel coded and modulation technology with the binary linear block code at the transmitter. Bits division, coding, optional interleaving, and modulation are carried out by the preset rule, then transmitted through standard single mode fiber span equal to 100 km. The receiver improves the accuracy of decoding by means of soft information passing through different layers, which enhances the performance. Simulations are carried out in an intensity modulation-direct detection optical communication system using MATLAB®. Results show that the RA-MLC scheme can achieve bit error rate of 1E-5 when optical signal-to-noise ratio is 20.7 dB. It also reduced the number of decoders by 72% and realized 22 rate adaptation without significantly increasing the computing time. The coding gain is increased by 7.3 dB at BER = 1E-3. [ABSTRACT FROM AUTHOR]

Dense wavelength division multiplexed (DWDM) transmission equal to 1.2 Tbps over 25 to 50 km across standard single-mode fiber (SSMF) in the C band is performed based on an optical frequency comb generator. Sixty-one flattened optical frequency tones were realized with 30-GHz frequency spacing, high side-mode suppression ratio over 35 dB, and minimum amplitude difference was realized using amplitude modulator for first time in cascade mode with two Mach--Zehnder modulators (MZMs) where all the modulators were tailored by RF signals. 20 x 61 Gbps DWDM-based differential quadrature phase shift keying modulated signals were successfully transmitted over SSMF and analyze its transmission capability for range of 25 to 50 km with acceptable power penalties and bit error rates. [ABSTRACT FROM AUTHOR]

We experimentally investigate the polarization insensitivity and cascadability of an all-optical wavelength converter for differential phase-shift keyed (DPSK) signals for the first time. The proposed wavelength converter is composed of a one-bit delay interferometer demodulation stage followed by a single semiconductor optical amplifier. The impact of input DPSK signal polarization fluctuation on receiver sensitivity for the converted signal is carried out. It is found that this scheme is almost insensitive to the state of polarization of the input DPSK signal. Furthermore, the cascadability of the converter is demonstrated in a two-path recirculating loop. Error-free transmission is achieved with 20 stage cascaded wavelength conversions over 2800 km, where the power penalty is <3.4 dB at bit error rate of 10-9. [ABSTRACT FROM AUTHOR]

Elastic software-defined optical networks greatly improve the flexibility of the optical switching network while it has brought challenges to the routing and spectrum assignment (RSA). A multilayer virtual topology model is proposed to solve RSA problems. Two RSA algorithms based on the virtual topology are proposed, which are the ant colony optimization (ACO) algorithm of minimum consecutiveness loss and the ACO algorithm of maximum spectrum consecutiveness. Due to the computing power of the control layer in the software-defined network, the routing algorithm avoids the frequent link-state information between routers. Based on the effect of the spectrum consecutiveness loss on the pheromone in the ACO, the path and spectrum of the minimal impact on the network are selected for the service request. The proposed algorithms have been compared with other algorithms. The results show that the proposed algorithms can reduce the blocking rate by at least 5% and perform better in spectrum efficiency. Moreover, the proposed algorithms can effectively decrease spectrum fragmentation and enhance available spectrum consecutiveness. [ABSTRACT FROM AUTHOR]

The wavelength-division multiplexing passive optical network (WDM-PON) is a potential technology to carry multiple services in an optical access network. However, it has the disadvantages of high cost and an immature technique for users. A software-defined WDM/time-division multiplexing PON was proposed to meet the requirements of high bandwidth, high performance, and multiple services. A reasonable and effective uplink dynamic bandwidth allocation algorithm was proposed. A controller with dynamic wavelength and slot assignment was introduced, and a different optical dynamic bandwidth management strategy was formulated flexibly for services of different priorities according to the network loading. The simulation compares the proposed algorithm with the interleaved polling with adaptive cycle time algorithm. The algorithm shows better performance in average delay, throughput, and bandwidth utilization. The results show that the delay is reduced to 62% and the throughput is improved by 35%. [ABSTRACT FROM AUTHOR]

We propose a technique for the generation of optical frequency comb from a single source, which reduces the costs of optical access networks. Two Mach-Zehnder modulators are cascaded with one phase modulator driven by radiofrequency signals. With 10-GHz frequency spacing, the generated 40 optical multi-carriers have good tone-to-noise ratio with least excursions in their comb lines. The laser array at the optical line terminal of the conventional wavelength division multiplexed passive optical network (WDM-PON) system has been replaced with optical frequency comb generator (OFCG), which may result in cost-effective optical line terminal (OLT) supporting a large-capacity WDM-PON system. Of 40 carriers generated, each carrier carries 10 Gbps data based on differential phase-shift keying. Four hundred Gbps multiplexed data from all channels are successfully transmitted through a fiber span of 25 km with negligible power penalties. Part of the downlink signal is used in uplink transmission at optical network unit where intensity-modulated on-off keying is deployed for remodulation. Theoretical analysis of the proposed WDM-PON system based on OFCG are in good agreement with simulation results. The metrics considered for the analysis of the proposed OFCG in a WDM-PON system are power penalties of the full-duplex transmission, eye diagrams, and bit error rate. [ABSTRACT FROM AUTHOR]