We propose and demonstrate a novel optical orthogonal frequency-division multiple access (OFDMA)-based metro-access integrated network with dynamic resource allocation. It consists of a single fiber OFDMA ring and many single fiber OFDMA trees, which transparently integrates metropolitan area networks with optical access networks. The single fiber OFDMA ring connects the core network and the central nodes (CNs), the CNs are on demand reconfigurable and use multiple orthogonal sub-carriers to realize parallel data transmission and dynamic resource allocation, meanwhile, they can also implement flexible power distribution. The remote nodes (RNs) distributed in the user side are connected by the single fiber OFDMA trees with the corresponding CN. The obtained results indicate that our proposed metro-access integrated network is feasible and the power distribution is agile.

We thoughtfully investigate the feasibility of reducing the mode-coupling caused crosstalk by optimizing the practical parameters of the few-mode fiber (FMF), based on the linear coupling theory. According to our simulation results, the low crosstalk FMF could be achieved with the small fiber core, the low refractive-index (RI) related parameters, the long operating-wavelength and the low core-eccentricity (CE). Moreover, the transmission behaviors over the fixed coupling and the random coupling scenarios are also discussed. The power distribution and the signal to interference plus noise ratio (SINR) evolutions along FMF reveal the impacts from the mode-coupling induced crosstalk in the spatial division multiplexing (SDM) transmission system. The random nature of the mode coupling suggesting the turbulent results are obtained in our simulation, confirmed the observation in the SDM test. And only a 1.23 dB SINR degradation of 16-QAM signals can be realized after 100 km transmission with the optimized CE of lower than 4 × 10 ⁻³ .

A novel structure photonic crystal fibre (PCF) supporting orbital angular momentum (OAM) modes is proposed. The transmission layer is a ring core with high refractive index, sandwiched between the inner air-hole cladding and the outer cladding composed of nonuniform air-holes periodically arranged in silica. The diameters of the air-holes in the outer cladding gradually increase in the radial direction. The simulation results show that the designed PCF is capable of supporting 54 OAM modes over the 650 nm bandwidth ranging from 1200 nm to 1850 nm, and possesses some advantages in low confinement loss and flat dispersion, that is, the confinement loss is low to the order of magnitude of ${10}^{-11}\text{dB/m}$ and the dispersion slope is less than 0.2 $\text{ps/(n}{\text{m}}^2\cdot \text{km)}$.

Optical signal processing (OSP) technology is a crucial part of the optical switching node in the modern optical-fiber communication system, especially when advanced modulation formats, e.g., quadrature amplitude modulation (QAM), are applied. However, the conventional on–off keying (OOK) signal is still widely used in access or metro transmission systems, which leads to the compatibility requirement of OSP for incoherent and coherent signals. In this paper, we propose a reservoir computing (RC)-OSP scheme based on nonlinear mapping behavior through a semiconductor optical amplifier (SOA) to deal with the non-return-to-zero (NRZ) signals and the differential quadrature phase-shift keying (DQPSK) signals in the nonlinear dense wavelength-division multiplexing (DWDM) channel. We optimized the key parameters of SOA-based RC to improve compensation performance. Based on the simulation investigation, we observed a significant improvement in signal quality over 10 dB compared to the distorted signals on each DWDM channel for both the NRZ and DQPSK transmission cases. The compatible OSP achieved by the proposed SOA-based RC could be a potential application of the optical switching node in the complex optical fiber communication system, where incoherent and coherent signals meet.

Multi-wavelength regeneration free of inter-channel crosstalk is desirable for wavelength division multiplexing (WDM) systems, especially from the cost-effectiveness point of view. This paper presents the design rules of time-interleaved multi-wavelength 2R regeneration systems based on data-pump four wave mixing (FWM) effect, and several key factors, such as FWM bandwidth, wavelength assignment, and duty cycle, are comprehensively taken into account. The total data rate of time-interleaved WDM regeneration systems along with polarization multiplexing or bidirectional transmission are discussed, which are mainly determined by temporal overlap, spectral broadening and FWM bandwidth. As two examples, an eight-wavelength unidirectional regenerator using polarization multiplexing is designed by optimizing the fiber birefringence, and a six-wavelength bidirectional regenerator is demonstrated by experiment. Each is expected to have a total data rate of about 200Gb/s for the optical RZ-OOK signals, and the wavelength number is increased at the expense of spectral efficiency.