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  • Optica Publishing Group  (25)
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  • Optica Publishing Group  (25)
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  • 1
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 12 ( 2022-06-06), p. 21990-
    Abstract: A modulation format recognition (MFR) scheme based on multi-core fiber (MCF) is proposed for the next generation of elastic optical networks (EONs). In this scheme, multiple Stokes sectional planes images are used as signal features which are typed into a transfer learning (TL) assisted convolutional neural network (CNN) to realize MFR. Compared with the traditional Jones matrix, the Stokes space mapping method is insensitive to polarization mixing, carrier frequency skew and phase offset, therefore, it has better feature representation ability. TL is introduced to transfer the model used in standard single-mode fiber (SSMF) to MCF transmission, reducing the required training data and complexity. In addition, multiple Stokes sectional planes images are input simultaneously, which improves the accuracy of the neural network. Experimental verifications were performed for a polarization division multiplexing (PDM)-EONs system at a symbol rate of 12.5GBaud by 5 km MCF. Nine modulation formats, including three standard modulation formats (BPSK, QPSK, 8PSK), three uniformly shaped (US) modulation formats (US-8QAM, US-16QAM, US-32QAM) and three probabilistically shaped (PS) modulation formats (PS-8QAM, PS-16QAM, PS-32QAM), were recognized by our scheme. The experimental results show that the scheme achieves high recognition accuracy even at low optical signal-to-noise ratio (OSNR). Moreover, the required number of training samples is less 40% compared to the traditional CNN. The proposed scheme has a high tolerance to the crosstalk damage of MCF itself and can realize the short training time of large-capacity space division multiplexing (SDM)-EONs. Our findings have the potential to be used in the next generation of a SDM fiber transmission system.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 1491859-6
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  • 2
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 11 ( 2022-05-23), p. 20014-
    Abstract: Polarization, as an important property of light, has been widely discussed in modern detecting and radar systems. A polarization converter that can be used to achieve dynamic control is regarded as an excellent alternative for implementing the integrated functionalities of communication and stealth. In this work, we propose a paradigm of meta-converter for dynamic polarization states shifting from linear-to-linear (LTL) to linear-to-circular (LTC) polarization. The strategy is achieved by loading voltage-controlled PIN diodes on the double-arrows metallic meta-resonators. The operation modes can be switched by changing the bias voltage. When the PIN diodes are turned on, the polarization meta-converter (PMC) will reflect and convert a linearly polarized electromagnetic (EM) wave into a circularly polarized one in 5.6–15.5 GHz with an axial ratio (AR) below 3dB. When the PIN diodes are turned off, the PMC will reflect and convert a linearly polarized EM wave into the orthogonal counterpart in 7.6–15.5 GHz with a polarization conversion ratio (PCR) over 88%. Simulations and experimental results show a good agreement, which manifests the feasibility of our proposed meta-converter. Moreover, the proposed PMC has great potential for polarization-dependent communication and stealth systems.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
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  • 3
    In: Optics Express, Optica Publishing Group, Vol. 30, No. 13 ( 2022-06-20), p. 22931-
    Abstract: In this paper, an intelligent dynamic perturbation orthogonal chirp division multiplexing (OCDM) encryption scheme based on cellular neural network and biological genetic encoding for seven-core optical fiber is proposed for the first time to our knowledge. In this scheme, chaotic sequences generated by cellular neural network are employed to construct six masking vectors to achieve six dimensions of ultra-high security encryption. The transmitted bit data is interleaved according to the DNA operation rules. The subcarrier frequency, symbol matrix, and time are scrambled. Because the selected encoding rule, decoding rule, key base sequence, subcarrier frequency, symbol matrix, and scrambling position of time all change dynamically, the robustness against malicious attack is enhanced. Simultaneously, OCDM technology is employed to optimize the system, which effectively improves the anti-interference ability and bit error performance of the system. A 70 Gb /s (7×10 Gb /s) encrypted OCDM signal transmission experiment is carried out on a 2 km 7-core fiber, and an orthogonal frequency division multiplexing (OFDM) signal is transmitted under the same conditions for comparison and verification. The results show that the key space of the newly proposed encryption scheme can reach 10 1170 , and the receiver sensitivity of OCDM is 1.2 dB greater than that of OFDM when the bit error rate is 10 −3 . The scheme can improve the security of encrypted information and the performance of the system, which is very promising in the optical access network of the future.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
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  • 4
    In: Optics Letters, Optica Publishing Group, Vol. 47, No. 11 ( 2022-06-01), p. 2903-
    Abstract: In this Letter, we propose a secure orthogonal frequency division multiplexing (OFDM) transmission scheme based on chaotic encryption and noise-masking key distribution. With the implementation of a three-dimensional digital chaotic system, the security performance is effectively enhanced by scrambling the phase, symbol, and subcarrier frequency of the OFDM signal. The proposed noise-masking key distribution can mask the key information of the chaotic system into noise and transmit it with the chaotic encrypted signal simultaneously. By this mechanism, the legal receiver can realize uninterrupted authentication and decryption even if the key is constantly updated. Transmission of a 62.2-Gb/s quadrature phase shift keying (QPSK) and 124.4-Gb/s 16 quadrature amplitude modulation (16QAM) OFDM signal over a 2-km 7-core fiber using the proposed scheme is experimentally demonstrated. The results show that the proposed scheme can realize security enhancement and cost-effective key distribution without significant bit error ratio (BER) performance degradation.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 243290-0
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  • 5
    In: Optics Letters, Optica Publishing Group, Vol. 35, No. 19 ( 2010-10-01), p. 3225-
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2010
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  • 6
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 26 ( 2021-12-20), p. 43745-
    Abstract: Although the emerging isotropic and uniaxially anisotropic metasurfaces have been demonstrated to provide diverse ways for achieving the manipulation of electromagnetic waves, the simultaneous control of both amplitude and phase with designated spin states is still an academic challenge, especially in microwave domain. Here, a paradigm of shifting meta-atom symmetry is proposed to push the development of this difficult issue. A split-ring structure with four identical gaps is applied as a proof-of-principle. By properly arranging the relative positions of four gaps, the electromagnetic characteristics of the meta-atom can be shifted from isotropy to anisotropy. The amplitude of the cross-polarized component of reflective electromagnetic wave is smoothly changed from 0 to 1. Assisted by the Pancharatnam-Berry phase principle, the phase manipulation of anisotropic meta-atom is governed by the control of pivoting. The phase gradient metasurface with uniform amplitude modulation is used as preliminary verification. Subsequently, the complex-amplitude holographic meta-mirrors are designed to promote the proposed paradigm to the application level. Numerical simulations and experimental demonstrations are carried out to reconstruct the holographic images of “B”, “I”, and “T”. Encouragingly, the proposed paradigm may be extended in the applications of circular polarized meta-devices and on-chip systems.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
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  • 7
    In: Optics Letters, Optica Publishing Group, Vol. 47, No. 20 ( 2022-10-15), p. 5293-
    Abstract: In this Letter, we propose a novel, to the best of our knowledge, way to reduce the peak to average power ratio (PAPR) based on the selective mapping–partial transmit sequence (SLM-PTS) method, which uses chaotic sequences to give rise to random phases and random split positions. For the first time, the public and private keys are both used for encryption in the sparse code multiple access–orthogonal frequency division multiplexing (SCMA-OFDM) system. The public keys are used for improvement of the PAPR while the private keys show great promises in the protection of the privacy for different users. Meanwhile, the accurate phases and split positions at the receiver can be easily obtained by transmitting the initial values and parameters of the 3D Lorenz chaotic system simplifying the transmission of the sideband information significantly with the key space of nearly 10 1337 . In addition, the transmission of 42-Gb/s encrypted SCMA-OFDM signals have been experimentally demonstrated over a 2-km seven-core fiber, showing that the proposed scheme could improve the receiver sensitivity by 1.0 dB compared with the traditional SCMA-OFDM signals due to the great reduction in the PAPR. The bit error rate of the illegal optical network unit remains near 0.5, verifying the high security of the transmitted message.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 243290-0
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  • 8
    Online Resource
    Online Resource
    Optica Publishing Group ; 2023
    In:  Photonics Research Vol. 11, No. 7 ( 2023-07-01), p. 1154-
    In: Photonics Research, Optica Publishing Group, Vol. 11, No. 7 ( 2023-07-01), p. 1154-
    Abstract: Chiral mirrors can produce spin selective absorption for left-handed circularly polarized (LCP) or right-handed circularly polarized (RCP) waves. However, the previously proposed chiral mirror only absorbs the designated circularly polarized (CP) wave in the microwave frequency band, lacking versatility in practical applications. Here, we propose a switchable chiral mirror based on a pair of PIN diodes. The switchable chiral mirror has four working states, switching from the handedness-preserving mirror to the LCP mirror, RCP mirror, and perfect absorber. The basis of these advances is to change the chirality of two-dimensional (2D) chiral metamaterials and the circular conversion dichroism related to it, which is the first report in the microwave frequency band. Surface current distributions shed light on how switchable chiral mirrors work by handedness-selective excitation of reflective and absorbing electric dipole modes. Energy loss distributions verify the working mechanism. The thickness of the switchable chiral mirror is one-tenth of the working wavelength, which is suitable for integrated manufacturing. The measurement results are in good agreement with the simulation results.
    Type of Medium: Online Resource
    ISSN: 2327-9125
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 2724783-1
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  • 9
    In: Optics Express, Optica Publishing Group, Vol. 25, No. 12 ( 2017-06-12), p. 13567-
    Type of Medium: Online Resource
    ISSN: 1094-4087
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2017
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  • 10
    In: Optics Letters, Optica Publishing Group, Vol. 48, No. 20 ( 2023-10-15), p. 5253-
    Abstract: In this Letter, a new, to the best of our knowledge, geometric shaping method for an ultrahigh-order 16384-ary quadrature amplitude modulation (16384QAM) constellation based on the delta-sigma modulation technique is proposed. Based on the characteristics of delta-sigma modulation, the constellation was optimized to obtain greater constellation gain and improve the maximum performance of the system. Finally, the proposed scheme was demonstrated on an intensity-modulated direct detection (IMDD) system through a 25 km single-mode fiber transmission. On performing experiments, it was found that the suggested approach increases the receiver sensitivity of ultrahigh-order QAM communication systems based on delta-sigma modulation by around 0.5 dB and further enhances the error performance limit.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
    detail.hit.zdb_id: 243290-0
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