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  • Optica Publishing Group  (13)
  • Tian, Qinghua  (13)
  • 2020-2024  (13)
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Publisher
  • Optica Publishing Group  (13)
Person/Organisation
Language
Years
  • 2020-2024  (13)
Year
  • 1
    Online Resource
    Online Resource
    Chaotic physical layer encryption scheme based on phase ambiguity for a DMT system
    Optica Publishing Group ; 2022
    In:  Optics Express Vol. 30, No. 9 ( 2022-04-25), p. 14782-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 9 ( 2022-04-25), p. 14782-
    Abstract: Chaotic encryption is a promising scheme for physical layer security. By solving the multi-dimensional chaotic equations and transforming the obtained results, both bit-level and symbol-level encryption can be realized. One of the mainstream symbol-level encryption solutions is the constellation shifting (CS) scheme, which treats the chaotic sequence as artificial noise and adds it to the QAM signal sequence to achieve encryption. However, this scheme has several technical flaws in practical application, in terms of computational complexity and coexistence with blind equalization algorithm and the probabilistic shaping (PS) technique. In this paper, we propose a novel symbol-level encryption scheme based on phase ambiguity (PA), which converts the two sequences originally used to generate artificial noise into a set of phase rotation keys and complex conjugate keys, so that the encrypted symbols are still on the ideal constellation point coordinates. Simulation verification is carried out in a discrete multi-tone (DMT) system with 64QAM modulation. Results show that the proposed scheme can fully retain the shaping gain brought by the PS technique and avoid the error convergence of the blind equalizer. Moreover, the time required to solve the chaotic equations is only 38% of the CS scheme. Experimental verification is carried out, and the obtained results once again prove the superiority of the proposed encryption algorithm, which is a practical alternative for future physical layer secure optical communications.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.454432
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
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  • 2
    Online Resource
    Online Resource
    Data rate measurement method with selectable range in linear optical sampling
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 6 ( 2023-03-13), p. 9362-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 6 ( 2023-03-13), p. 9362-
    Abstract: Linear optical sampling (LOS) is one of the most powerful techniques for high-speed signal monitoring. To measure the data-rate of signal under test (SUT) in optical sampling, multi-frequency sampling (MFS) was proposed. However, the measurable data-rate range of the existing method based on MFS is limited, which makes it very difficult to measure the data-rate of high-speed signals. To solve the above problem, a range selectable data-rate measurement method based on MFS in LOS is proposed in this paper. Through this method, the measurable data-rate range can be selected to match the data-rate range of SUT and the data-rate of SUT can be measured precisely, independently of the modulation format. What’s more, the sampling order can be judged using the discriminant in the proposed method, which is key for plotting eye diagrams with correct time information. We experimentally measure the baud-rates of PDM-QPSK signal from 800 MBaud to 40.8 GBaud in different ranges and judge the sampling orders. The relative error of measured baud-rate is less than 0.17% while the error vector magnitude (EVM) is less than 0.38. Compared with the existing method, under the same sampling cost, our proposed method realizes the selectivity of the measurable data-rate range and the judgment of sampling order, greatly extends the measurable data-rate range of SUT. Hence, the data-rate measurement method with selectable range has great potential for high-speed signal data-rate monitoring.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.484562
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 3
    Online Resource
    Online Resource
    Probabilistic shaping and forward error correction scheme employing uneven segmentation mapping for data center optical communication
    Optica Publishing Group ; 2021
    In:  Optics Express Vol. 29, No. 4 ( 2021-02-15), p. 6209-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 4 ( 2021-02-15), p. 6209-
    Abstract: The combination of probabilistic shaping (PS) technology and forward error correction (FEC) technology can significantly boost the performance of a transmission system. In this paper, we propose a probabilistic shaping distribution matching algorithm employing uneven segmentation for data center optical networks, while keeping extremely low computational complexity for both encoding and decoding. Based on the proposed probabilistic shaping distribution matching algorithm, we develop a novel integrated scheme of PS and FEC coding that lifts the restrictions on the use of FEC technology and increases the use of interleaver. An experiment used to evaluate the probabilistically shaped data transmission is successfully conducted over a 25 km standard single-mode fiber (SSMF) with 16 quadrature amplitude modulation (16-QAM). Simultaneously, we use a simulation software to analyze the bit error rate performance at higher resolution. The results show that the joint coding scheme can achieve a 0.4dB performance improvement compared with the single FEC system.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.416175
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
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  • 4
    Online Resource
    Online Resource
    Mitigating the ambiguity problem in the CNN-based wavefront correction
    Optica Publishing Group ; 2022
    In:  Optics Letters Vol. 47, No. 13 ( 2022-07-01), p. 3251-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 47, No. 13 ( 2022-07-01), p. 3251-
    Abstract: In this work, we propose an attention-based adaptive optics method that uses a non-local block to integrate phase diversity with a convolutional neural network (CNN). The simulation results showcase the effectiveness of the proposed method to mitigate the ambiguity problem of phase retrieval and better performance than traditional CNN-based wavefront correction.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.459799
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
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  • 5
    Online Resource
    Online Resource
    Static resource allocation of advanced reservation requests in elastic optical networks
    Optica Publishing Group ; 2020
    In:  Applied Optics Vol. 59, No. 5 ( 2020-02-10), p. 1420-
    Details
    In: Applied Optics, Optica Publishing Group, Vol. 59, No. 5 ( 2020-02-10), p. 1420-
    Abstract: Considering the flexibility characteristic of advanced reservation (AR) requests, the problem of static routing, modulation, spectrum, and time assignment (RMSTA) of AR requests in elastic optical networks is studied in this paper, in order to deploy the spectrum resource economically and enable more requests to be served. The multi-objective integer linear program (ILP) model, which can minimize the maximum utilized frequency and time slot indices as well as find a trade-off between them, is used to formulate the RMSTA problem. Then the proportion optimal RMSTA (PO-RMSTA) heuristic algorithm with three sorting strategies is proposed to get the sub-optimal solutions. The PO-RMSTA algorithm and sorting strategies, ascending order of elastic time (AET), descending order of data volume (DDV), and ascending order of alternative schemes (AAS) , are simulated in our work and proved to obtain the approximate optimal solutions. The sorting policy AET achieved the best performance when minimizing the maximum utilized frequency slot index, whereas the sorting policy DDV worked best when minimizing the maximum utilized time slot index. As for the compromise between two indices, both AET and AAS provided satisfying results.
    Type of Medium: Online Resource
    ISSN: 1559-128X , 2155-3165
    URL: Article
    DOI: 10.1364/AO.385140
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
    detail.hit.zdb_id: 207387-0
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  • 6
    Online Resource
    Online Resource
    Hidden conditional random field-based equalizer for the 3D-CAP-64 transmission of OAM mode-division multiplexed ring-core fiber communication
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 18 ( 2023-08-28), p. 28747-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 18 ( 2023-08-28), p. 28747-
    Abstract: As a key technique for achieving ultra-high capacity optical fiber communications, orbital angular momentum (OAM) mode-division multiplexing (MDM) is affected by severe nonlinear impairments, including modulation related nonlinearities, square-law nonlinearity and mode-coupling-induced nonlinearity. In this paper, an equalizer based on a hidden conditional random field (HCRF) is proposed for the nonlinear mitigation of OAM-MDM optical fiber communication systems with 20 GBaud three-dimensional carrierless amplitude and phase modulation-64 (3D-CAP-64) signals. The HCRF equalizer extracts the stochastic nonlinear feature of the OAM-MDM 3D-CAP-64 signals by estimating the conditional probabilities of the hidden variables, thereby enabling the signals to be classified into subclasses of constellation points. The nonlinear impairment can then be mitigated based on the statistical probability distribution of the hidden variables of the OAM-MDM transmission channel in the HCRF equalizer. Our experimental results show that compared with a convolutional neural network (CNN)-based equalizer, the proposed HCRF equalizer improves the receiver sensitivity by 2 dB and 1 dB for the two OAM modes used here, with l  =  + 2 and l  =  + 3, respectively, at the 7% forward error correction (FEC) threshold. When compared with a Volterra nonlinear equalizer (VNE) and CNN-based equalizer, the computational complexity of the proposed HCRF equalizer was found to be reduced by 30% and 41%, respectively. The bit error ratio (BER) performance and reduction in computational complexity indicate that the proposed HCRF equalizer has great potential to mitigate nonlinear distortions in high-speed OAM-MDM fiber communication systems.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.495146
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 7
    Online Resource
    Online Resource
    Temperature compensated three-dimension fiber optic vector magnetic field sensor based on an elliptical core micro fiber Bragg grating
    Optica Publishing Group ; 2020
    In:  Optics Express Vol. 28, No. 5 ( 2020-03-02), p. 7721-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 28, No. 5 ( 2020-03-02), p. 7721-
    Abstract: In this paper, a temperature-compensated three-dimension vector fiber optic magnetic field sensor based on an elliptical core micro fiber Bragg grating (FBG) has been proposed and experimentally demonstrated. The elliptical core fiber was tapered to form a microfiber, in which a FBG was inscribed. Due to the magnetism-manipulation of the anisotropic aggregation of ferromagnetism nanoparticles around the fiber surface, the effective refractive index of the evanescent field for two orthogonal polarization modes was modulated, and the magnetic field orientation can be detected by interrogating the wavelength interval between two reflection peaks. However, two reflection peaks show the identical response to ambient temperature. Hence the proposed sensor can achieve the measurements of the magnetic field intensity and the orientation simultaneously without the temperature cross-sensitivity. The experimental results show that the magnetic field orientation sensitivity of 15 pm/deg and intensity sensitivity of 81 pm/mT can be achieved, and the maximum standard variation of the temperature cross-sensitivity is only 0.02 nm. The proposed elliptical core micro FBG appears to have potential applications in navigation, vehicle detection, and current sensing.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.384926
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
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  • 8
    Online Resource
    Online Resource
    Carrier phase recovery friendly probabilistic shaping scheme based on a quasi-Maxwell–Boltzmann distribution model
    Optica Publishing Group ; 2020
    In:  Optics Letters Vol. 45, No. 17 ( 2020-09-01), p. 4883-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 45, No. 17 ( 2020-09-01), p. 4883-
    Abstract: A novel probabilistic shaping (PS) scheme based on the quasi-Maxwell–Boltzmann (quasi-MB) distribution model is proposed in order to solve the incompatibility between PS and carrier phase recovery (CPR) algorithms, such as blind phase search (BPS) and principal component-based phase estimation (PCPE). In the proposed quasi-MB model, the same occurrence probability is assigned to each constellation point on the same square-ring, rather than on the same circle. Signals obeying the quasi-MB model have superior CPR friendliness compared to traditional PS signals. For a PS 64 quadrature amplitude modulation system, the simulation results indicate up to 51% and 21% normalized generalized mutual information (NGMI) improvements for PCPE and BPS, respectively. Experimental verification of the proposed quasi-MB scheme was demonstrated in a 10 Gbaud coherent detection system. The results show that when the optical signal-to-noise ratio (OSNR) is low, the quasi-MB model can help the BPS algorithm to achieve better NGMI performance and, when the OSNR is high, the proposed model can also solve the incompatibility between the PCPE algorithm and PS.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.402198
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
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  • 9
    Online Resource
    Online Resource
    Jointly recognizing OAM mode and compensating wavefront distortion using one convolutional neural network
    Optica Publishing Group ; 2020
    In:  Optics Express Vol. 28, No. 25 ( 2020-12-07), p. 37936-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 28, No. 25 ( 2020-12-07), p. 37936-
    Abstract: In this work, a new recognition method of orbital angular momentum (OAM) is proposed. The method combines mode recognition and the wavefront sensor-less (WFS-less) adaptive optics (AO) by utilizing a jointly trained convolutional neural network (CNN) with the shared model backbone. The CNN-based AO method is implicitly applied in the system by providing additional mode information in the offline training process and accordingly the system structure is rather concise with no extra AO components needed. The numerical simulation result shows that the proposed method can improve the recognition accuracy significantly in different conditions of turbulence and can achieve similar performance compared with AO-combined methods.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.412455
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
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  • 10
    Online Resource
    Online Resource
    Probabilistic neural network equalizer for nonlinear mitigation in OAM mode division multiplexed optical fiber communication
    Optica Publishing Group ; 2022
    In:  Optics Express Vol. 30, No. 26 ( 2022-12-19), p. 47957-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 26 ( 2022-12-19), p. 47957-
    Abstract: Orbital angular momentum (OAM) mode-division multiplexing (MDM) is a key technique to achieve ultra-high-capacity optical fiber communications. However, the high nonlinear impairment from optoelectronic devices, such as spatial light modulators, modulators, and photodiodes, is a long-standing challenge for OAM-MDM. In this paper, an equalizer based on a probabilistic neural network (PNN) is presented to mitigate the nonlinear impairment for an OAM-MDM fiber communication system with 32 GBaud Nyquist pulse amplitude modulation-8 (PAM8) intensity-modulation direct-detection (IM-DD) signals. PNN equalizer can calculate the distribution of the nonlinearity using Bayesian decision theory and thus mitigate the stochastic nonlinear impairment of the received signal. Experimental results show that compared with the convolutional neural network (CNN) equalizer, the PNN equalizer improves the receiver sensitivity by 0.6dB and 2dB for two OAM modes with l  = + 3 and l  = + 4 at the 20% FEC limit, respectively. Moreover, compared with Volterra or CNN equalizers, the PNN equalizer can reduce the computation complexity significantly, which has great potential to mitigate the nonlinear signal distortions in high-speed IM-DD OAM-MDM fiber communication systems.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.456908
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
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