5G Flexible Optical Transport Networks with Large-Capacity, Low-Latency and High-Efficiency

The fifth generation(5G) of mobile communications are facing big challenges, due to the proliferation of diversified terminals and unprecedented services such as internet of things(IoT), high-definition videos, virtual/augmented reality(VR/AR). To accommodate massive connections and astonish mobile traffic, an efficient 5G transport network is required. Optical transport network has been demonstrated to play an important role for carrying 5G radio signals. This paper focuses on the future challenges, recent studies and potential solutions for the 5G flexible optical transport networks with the performances on large-capacity, low-latency and high-efficiency. In addition, we discuss the technology development trends of the 5G transport networks in terms of the optical device, optical transport system, optical switching, and optical networking. Finally, we conclude the paper with the improvement of network intelligence enabled by these technologies to deterministic content delivery over 5G optical transport networks.

The Analysis of Multiuser Relaying Mixed RF/FSO Networks over Exponentiated Weibull Fading Channel

In this paper,the performance of multiuser relaying mixed radio frequency(RF)/free space optical(FSO)networks over exponentiated Weibull Fading Channel is studied.Based on the transmit opportunistic scheduling,a unified cumulative distribution function(CDF)of the end-to-end signal to noise ratio(SNR)for multiuser dual-hop relaying system is derived.Then the average symbol error rate(ASER),outage probability and ergodic channel capacity are analyzed in detail.Furthermore,in order to simplify the analysis of system performance,the asymptotic results for the outage probability and ASER are derived at high SNR regime.We also demonstrate Monte Carlo simulation to ensure the effectiveness of the results.The simulation results show that deploying the transmit opportunistic scheme can improve the proposed system performance.And aperture averaging and heterodyne detection technique can suppress the impact of turbulence on FSO networks.

Real-time monitoring of hydrogel phase transition in an ultrahigh Q microbubble resonator

The ability to sense dynamic biochemical reactions and material processes is particularly crucial for a wide range of applications,such as early-stage disease diagnosis and biomedicine development.Optical microcavities-based label-free biosensors are renowned for ultrahigh sensitivities,and the detection limit has reached a single nanoparticle/molecule level.In particular,a microbubble resonator combined with an ultrahigh quality factor(Q)and inherent microfluidic channel is an intriguing platform for optical biosensing in an aqueous environment.In this work,an ultrahigh Q microbubble resonator-based sensor is used to characterize dynamic phase transition of a thermosensitive hydrogel.Experimentally,by monitoring resonance wavelength shift and linewidth broadening,we(for the first time to our knowledge)reveal that the refractive index is increased and light scattering is enhanced simultaneously during the hydrogel hydrophobic transition process.The platform demonstrated here paves the way to microfluidical biochemical dynamic detection and can be further adapted to investigating single-molecule kinetics.

Multi-channel phase regeneration of QPSK signals based on phase sensitive amplification

In this paper,we propose and demonstrate simultaneous phase regeneration of four different channels of QPSK signal based on phase sensitive amplification.The configuration can be divided into two parts.The first one uses four wave mixing in high nonlinear fiber(HNLF)to generate the corresponding three harmonic conjugates precisely at the frequency of the original signals.The other one uses optical combiner to realize coherent addition which is aimed at completely removing the interaction in phase regeneration stage.The simulation results suggest that this scheme can optimize signal constellation to a large extend especially in high noise environment.Besides,optical signal to noise ratio(OSNR)can improve more than 3 dB while the bit-error-rate(BER)reaches 10 – 3 with a constant white noise and 15° phase noise.

Microwave photonics: radio-over-fiber links, systems, and applications [Invited]

Microwave photonics(MWPs)uses the strength of photonic techniques to generate,process,control,and distribute microwave signals,combining the advantages of microwaves and photonics.As one of the main topics of MWP,radio-over-fiber(RoF)links can provide features that are very difficult or even impossible to achieve with traditional technologies.Meanwhile,a considerable number of signal-processing subsystems have been carried out in the field of MWP as they are instrumental for the implementation of many functionalities.However,there are still several challenges in strengthening the performance of the technology to support systems and applications with more complex structures,multiple functionality,larger bandwidth,and larger processing capability.In this paper,we identify some of the notable challenges in MWP and review our recent work.Applications and future direction of research are also discussed.

Single nanoparticle trapping based on on-chip nanoslotted nanobeam cavities

Optical trapping techniques are of great interest since they have the advantage of enabling the direct handling of nanoparticles. Among various optical trapping systems, photonic crystal nanobeam cavities have attracted great attention for integrated on-chip trapping and manipulation. However, optical trapping with high efficiency and low input power is still a big challenge in nanobeam cavities because most of the light energy is confined within the solid dielectric region. To this end, by incorporating a nanoslotted structure into an ultracompact onedimensional photonic crystal nanobeam cavity structure, we design a promising on-chip device with ultralarge trapping potential depth to enhance the optical trapping characteristic of the cavity. In this work, we first provide a systematic analysis of the optical trapping force for an airborne polystyrene(PS) nanoparticle trapped in a cavity model. Then, to validate the theoretical analysis, the numerical simulation proof is demonstrated in detail by using the three-dimensional finite element method. For trapping a PS nanoparticle of 10 nm radius within the air-slot, a maximum trapping force as high as 8.28 nN/mW and a depth of trapping potential as large as 1.15 × 10~5 k_BT mW^(-1) are obtained, where k B is the Boltzmann constant and T is the system temperature.We estimate a lateral trapping stiffness of 167.17 pN · nm^(-1)· mW^(-1) for a 10 nm radius PS nanoparticle along the cavity x-axis, more than two orders of magnitude higher than previously demonstrated on-chip, near field traps. Moreover, the threshold power for stable trapping as low as 0.087 μW is achieved. In addition, trapping of a single 25 nm radius PS nanoparticle causes a 0.6 nm redshift in peak wavelength. Thus, the proposed cavity device can be used to detect single nanoparticle trapping by monitoring the resonant peak wavelength shift. We believe that the architecture with features of an ultracompact footprint, high integrability with optical waveguides/circuits, and efficient trapping demonstrated here will provide a promising candidate for developing a lab-on-a-chip device with versatile functionalities.

Wide-bandwidth, high-gain, low-temperature cofired ceramic magneto-electric dipole antenna and arrays for millimeter wave radio-over-fiber systems

The designs of magneto-electric(ME)dipole antennas and 4×4 planar arrays on low-temperature cofired ceramic(LTCC)substrates are presented for radio-over-fiber(ROF)systems.The ME dipole antenna covers the four 2.16 GHz channels defined in the 60 GHz band from 57 to 66 GHz.It can be used as a 4×4 planar antenna array element for high gain performance.The results show that the proposed antenna array achieves a variation of peak gain from 15.0 to 18.1 dBi and a peak gain up to 17.67 dBi at 60 GHz.It is revealed that our design satisfies the 60 GHz standards ruled by IEEE 802.15.3c.