Xianqing Jin

Gain equalization of a six-mode-group ring core multimode EDFA

We propose a 6-mode-group ring core multimode erbium doped fiber amplifier (RC-MM-EDFA) capable of providing almost identical gain among the six mode groups within the C band using either core- or cladding-pumped implementations.

Linearly polarized mode division multiplexed transmission over ring-index multimode fibres

LP modes in ring-index multimode fibres (RI-MMFs) are proposed to carry parallel-data for spatial multiplexing systems with low-complexity MIMO processing. Simulation shows that, with 3×3MIMO, 6×20Gb/s NRZ error-free transmission is achieved over 1km-RI-MMFs using IMDD.

Simplified impulse response characterization for mode division multiplexed systems

We present a single transceiver based modal characterization method for estimating the channel impulse response of MDM systems. Good agreements are found between the measured and simulated DGDs of a RCF supporting 5 mode groups.

All-optical mode-group division multiplexing over a graded-index ring-core fiber with single radial mode

We demonstrate mode-group division multiplexing over 100m graded-index ring-core fiber supporting 4 LP mode-groups with a single radial index using SLM-based mode (de)multiplexers to transmit 2×10Gbps NRZ signals without MIMO equalization.

Influence of refractive index profile of ring-core fibres for space division multiplexing systems

Modal properties of step/graded-index ring-core fibres (SI/GI-RCFs) are investigated and compared for application in space-division multiplexing systems.

Mode Coupling Effects in Ring-Core Fibers for Space-Division Multiplexing Systems

An optical fiber with weak mode coupling is desirable for future ultrahigh capacity space-division multiplexing (SDM) systems because mode coupling in an optical fiber results in extrinsic loss of the fiber and crosstalk between guided optical modes. To study the feasibility of a ring-core fiber (RCF) for SDM systems, in this paper, we investigate the mode coupling in the RCF supporting five or seven guided mode groups (MGs) at a wavelength of 1550 nm. For this purpose, the coupled mode/power theory with identified spatial power spectrum of random perturbations of fiber axis is used to estimate the bend loss/crosstalk of the RCF due to microbending. It is shown that based on the identified parameters for the spatial power spectrum in the 5/7-MG RCF, the estimated bend loss/crosstalk of the RCF agrees well with experimental results. In addition, the impact of the gradient parameter α and refractive index contrast Δ of the fiber refractive index profile on bend loss and crosstalk of the RCF is explored. Simulation results indicate that the Δ instead of the α significantly affects bend loss and crosstalk of the RCF. The magnitude improvement in bend loss by increasing the Δ is dependent on the spatial power spectrum.

Numerical investigation of microbending loss in optical fibres

Microbending plays a key role in the bend loss of optical fibres. To numerically investigate a microbending induced loss, an analytical model for microbending in optical fibres with arbitrary refractive index profiles is presented. In this model, random perturbations of the fibre core along the fibre axis are described by an analytical function whose power spectral density is derived from an exponential autocorrelation function. Using the model together with the beam propagation method, microbending loss is investigated for several different types of optical fibre, which include the traditional single-mode/multimode fibres (SMF/MMF) as used in existing optical networks, and typical few-mode/ring-core fibres (FMF/RCF) with the potential for future ultra high-speed optical networks. The validity of the proposed model is demonstrated by comparing the microbending loss of a SMF computed using coupled mode theory and the results. Simulation results show that, under the condition of launching only the fundamental mode into the optical fibres, the SMF and RCF supporting only one radial mode have nearly equal microbending loss, whilst the FMF and MMF have relatively low microbending loss. In addition, the microbending loss of the RCF is shown to be dependent on the ring core thickness.

All-optical mode-group multiplexed transmission over a graded-index ring-core fiber with single radial mode

We present a design of graded-index ring-core fiber (GI-RCF) supporting 3 linearly polarized (LP) mode-groups (i.e. LP01, LP11 and LP21) with a single radial index of one for mode-division multiplexed (MDM) transmission. Reconfigurable spatial light modulator (SLM) based spatial (mode) (de)multiplexers are used to systematically characterize spatial/temporal modal properties of the GI-RCF. We also demonstrate all-optical mode-group multiplexed transmissions over a 360m fabricated GI-RCF without using multiple-input multiple-output digital signal processing (MIMO DSP).