Yequn Zhang

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Leveraging the advanced coherent optical communication technologies, this paper explores the feasibility of using four-dimensional (4D) nonbinary LDPC-coded modulation (4D-NB-LDPC-CM) schemes for long-haul transmission in future optical transport networks. In contrast to our previous works on 4D-NB-LDPC-CM which considered amplified spontaneous emission(More)
Inspired by recent demonstrations of orbital angular momentum-(OAM)-based single-photon communications, we propose two quantum-channel models: (i) the multidimensional quantum-key distribution model and (ii) the quantum teleportation model. Both models employ operator-sum representation for Kraus operators derived from OAM eigenkets transition(More)
An optimal signal constellation design algorithm suitable for the coherent optical channels dominated by the nonlinear phase noise is proposed. In this method, the cumulative log-likelihood-function is used as the optimization criterion. We demonstrate by simulation that the signal constellations obtained by using this algorithm significantly outperform(More)
In this invited paper, we describe the photon angular momentum based entanglement assisted quantum key distribution (QKD) protocols, analyse their security, and determine the secure finite key fraction rates. Two types of entanglement-assisted protocols, namely two-basis and (D+1)-basis protocols (D is dimensionality of corresponding Hilbert space), have(More)
In this paper, we consider quantum key distribution (QKD) using pulse-position modulation (PPM) and propose the PPM-based BB84 QKD protocol. With the adoption of PPM, the efficiency of utilizing weak laser pulses can be improved and hence the key rate. We first analyse the potential of using PPM from the perspective of raw key rate. We then provide detailed(More)
We review adaptive modulation in optical communications and present a pragmatic implementation to simplify the transponder complexity. We reveal that when adaptive modulation is employed in the DWDM optical transmission system channel launch powers should be rearranged to optimize the whole system. In addition, we introduce adaptive trellis-coded modulation(More)
In this paper, we study the four-dimensional LDPC coded-modulation scheme for use in long-haul beyond 100 Gb/s serial optical transport. With this novel coded-modulation scheme, transmission distance can be extended to 6500 km at 160 Gb/s aggregate date rate per single wavelength. Compared to the traditional polarization-multiplexed two-dimensional(More)
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