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  • Optica Publishing Group  (9)
  • Liu, Jie  (9)
  • 2020-2024  (9)
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  • Optica Publishing Group  (9)
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Language
Years
  • 2020-2024  (9)
Year
  • 1
    Online Resource
    Online Resource
    Effects of wave-front tilt and air density fluctuations in a sensitive atom interferometry gyroscope
    Optica Publishing Group ; 2020
    In:  Optics Express Vol. 28, No. 8 ( 2020-04-13), p. 12189-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 28, No. 8 ( 2020-04-13), p. 12189-
    Abstract: We present a matter wave gyroscope with a Sagnac area of 5.92 cm 2 , achieving a short-term sensitivity of 167 nrad/s/Hz 1/2 . The atom interferometry gyroscope is driven by a π /2 −  π  −  π  −  π /2 Raman pulse sequence based on an atom fountain with a parabolic trajectory. The phase-locked laser beams for Raman transitions partly propagate outside of the vacuum chamber and expose to the air when passing through the two arms of the vacuum chamber. This configuration leads to the tilt of the laser’s wave-front and suffers the fluctuation of air density. The impacts on both the fringe contrast and long-term stability are experimentally investigated in detail, and effective schemes are developed to improve the performance of our atom gyroscope. The method presented here could be useful for developing large atom interferometry facilities with separated vacuum chambers.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.391780
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2020
    detail.hit.zdb_id: 1491859-6
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  • 2
    Online Resource
    Online Resource
    Depth-recognizable time-domain fluorescence molecular tomography in reflective geometry
    Optica Publishing Group ; 2021
    In:  Biomedical Optics Express Vol. 12, No. 7 ( 2021-07-01), p. 3806-
    Details
    In: Biomedical Optics Express, Optica Publishing Group, Vol. 12, No. 7 ( 2021-07-01), p. 3806-
    Abstract: Conventional fluorescence molecular tomography (FMT) reconstruction requires photons penetrating the whole object, which limits its applications to small animals. However, by utilizing reflective photons, fluorescence distribution near the surface could be reconstructed regardless of the object size, which may extend the applications of FMT to surgical navigation and so on. Therefore, time-domain reflective fluorescence molecular tomography (TD-rFMT) is proposed in this paper. The system excites and detects the emission light from the same angle within a field of view of 5 cm. Because the detected intensities of targets depend strongly on the depth, the reconstruction of targets in deep regions would be evidently affected. Therefore, a fluorescence yield reconstruction method with depth regularization and a weighted separation reconstruction strategy for lifetime are developed to enhance the performance for deep targets. Through simulations and phantom experiments, TD-rFMT is proved capable of reconstructing fluorescence distribution within a 2.5-cm depth with accurate reconstructed yield, lifetime, and target position(s).
    Type of Medium: Online Resource
    ISSN: 2156-7085 , 2156-7085
    URL: Article
    DOI: 10.1364/BOE.430235
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
    detail.hit.zdb_id: 2572216-5
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  • 3
    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
    detail.hit.zdb_id: 1491859-6
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  • 4
    Online Resource
    Online Resource
    Compact substrate-removed thin-film lithium niobate electro-optic modulator featuring polarization-insensitive operation
    Optica Publishing Group ; 2022
    In:  Optics Letters Vol. 47, No. 7 ( 2022-04-01), p. 1818-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 47, No. 7 ( 2022-04-01), p. 1818-
    Abstract: A compact polarization-insensitive electro-optic (EO) modulator, which allows the laser and modulator to be located at different locations while using a standard single-mode fiber to interconnect them, is highly desirable for 5G or future 6G wireless networks. Herein, we propose a modulator based on substrate-removed thin-film lithium niobate. The proposed device exhibits a polarization-dependent loss of 0.35 dB and on-chip loss of approximately 2 dB. The polarization insensitivity of the proposed device was experimentally demonstrated using a four-level pulse-amplitude modulation format at 50 Gbaud (100 Gb/ s).
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.454277
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2022
    detail.hit.zdb_id: 243290-0
    detail.hit.zdb_id: 1479014-2
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  • 5
    Online Resource
    Online Resource
    Data-defined naïve Bayes (DNB) based decision scheme for the nonlinear mitigation for OAM mode division multiplexed optical fiber communication
    Optica Publishing Group ; 2021
    In:  Optics Express Vol. 29, No. 4 ( 2021-02-15), p. 5901-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 29, No. 4 ( 2021-02-15), p. 5901-
    Abstract: In this manuscript, a data-defined naïve Bayes (DNB)-based decision scheme for nonlinear mitigation is presented for an orbital angular momentum (OAM) mode-division multiplexed optical fiber communication system. Due to the inherent nonlinearity characteristic of opto-electronic devices, the strong nonlinear impairments are deemed inevitable in OAM mode-division multiplexed transmission, leading to severely nonlinear effects. A DNB algorithm based on the prior probability distribution is adopted to mitigate the strong device nonlinearity of the OAM communication system, which is hard to solve using the conventional approaches due to the complex theoretical model of opto-electronic devices. An experiment using eight-mode OAM with a 32GBaud Nyquist QPSK signal optical fiber communication system is carried out with ring core fiber (RCF) transmission over 10 km to verify the effectiveness of the proposed scheme. The experimental results demonstrate that the nonlinear effects on OAM transmission can be effectively mitigated using a DNB-based decision with a bit error rate (BER) reduction of at most 66%. Moreover, compared with other nonlinear decision algorithms based on machine learning, such as support vector machine (SVM) or k-nearest neighbors (KNN), the digital signal processing complexity of the DNB algorithm is significantly reduced.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.415908
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2021
    detail.hit.zdb_id: 1491859-6
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  • 6
    Online Resource
    Online Resource
    400 Gbit/s 4 mode transmission for IM/DD OAM mode division multiplexing optical fiber communication with a few-shot learning-based AffinityNet nonlinear equalizer
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 14 ( 2023-07-03), p. 22622-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 14 ( 2023-07-03), p. 22622-
    Abstract: Nonlinear impairment in a high-speed orbital angular momentum (OAM) mode-division multiplexing (MDM) optical fiber communication system presents high complexity and strong stochasticity due to the massive optoelectronic devices. In this paper, we propose an Affinity Network (AffinityNet) nonlinear equalizer for an OAM-MDM intensity-modulation direct-detection (IM/DD) transmission with four OAM modes. The labeled training and testing signals from the OAM-MDM system can be regarded as “small sample” and “large target”, respectively. AffinityNet can be used to build an accurate nonlinear model using “small sample” based on few-shot learning and can predict the stochastic characteristic nonlinearity of OAM-MDM with a high level of generalization. As a result, the AffinityNet nonlinear equalizer can effectively compensate the stochastic nonlinearity in the OAM-MDM system, despite the large difference between the training and testing signals due to the stochastic nonlinear impairment. An experiment was conducted on a 400 Gbit/s transmission with four OAM modes using a pulse amplitude modulation-8 (PAM-8) signal over a 2 km ring-core fiber (RCF). Our experimental results show that the proposed nonlinear equalizer outperformed the conventional Volterra equalizer with improvements in receiver sensitivity of 1.7, 1.8, 3, and 3.3 dB for the four OAM modes at the 15% forward error correction (FEC) threshold, respectively. In addition, the proposed equalizer outperformed a convolutional neural network (CNN) equalizer with improvements in receiver sensitivity of 0.8, 0.5, 0.9, and 1.4 dB for the four OAM modes at the 15% FEC threshold. In the experiment, a complexity reduction of 37% and 83% of the AffinityNet equalizer is taken compared to the conventional Volterra equalizer and CNN equalizer, respectively. The proposed equalizer is a promising candidate for a high-speed OAM-MDM optical fiber communication system.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.492795
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 7
    Online Resource
    Online Resource
    Bayesian generative adversarial network emulator based end-to-end learning strategy of the probabilistic shaping for OAM mode division multiplexing IM/DD transmission
    Optica Publishing Group ; 2023
    In:  Optics Express Vol. 31, No. 24 ( 2023-11-20), p. 40508-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 31, No. 24 ( 2023-11-20), p. 40508-
    Abstract: Orbital angular momentum (OAM) mode division multiplexing (MDM) has emerged as a new multiplexing technology that can significantly increase transmission capacity. In addition, probabilistic shaping (PS) is a well-established technique that can increase the transmission capacity of an optical fiber to close to the Shannon limit. However, both the mode coupling and the nonlinear impairment lead to a considerable gap between the OAM-MDM channel and the conventional additive white Gaussian noise (AWGN) channel, meaning that existing PS technology is not suitable for an OAM-MDM intensity-modulation direct-detection (IM-DD) system. In this paper, we propose a Bayesian generative adversarial network (BGAN) emulator based on an end-to-end (E2E) learning strategy with probabilistic shaping (PS) for an OAM-MDM IM/DD transmission with two modes. The weights and biases of the BGAN emulator are treated as a probability distribution, which can be accurately matched to the stochastic nonlinear model of OAM-MDM. Furthermore, a BGAN emulator based on an E2E learning strategy is proposed to find the optimal probability distribution of PS for an OAM-MDM IM/DD system. An experiment was conducted on a 200 Gbit/s two OAM modes carrierless amplitude phase-32(CAP-32) signal over a 5 km ring-core fiber transmission, and the results showed that the proposed BGAN emulator outperformed a conventional CGAN emulator, with improvements in modelling accuracy of 29.3% and 26.3% for the two OAM modes, respectively. Moreover, the generalized mutual information (GMI) of the proposed E2E learning strategy outperformed the conventional MB distribution and the CGAN emulator by 0.31 and 0.33 bits/symbol and 0.16 and 0.2 bits/symbol for the two OAM modes, respectively. Our experimental results demonstrate that the proposed E2E learning strategy with the BGAN emulator is a promising candidate for OAM-MDM IM/DD optic fiber communication.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.502563
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2023
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  • 8
    Online Resource
    Online Resource
    OAM mode-division multiplexing IM/DD transmission at 4.32 Tbit/s with a low-complexity adaptive-network-based fuzzy inference system nonlinear equalizer
    Optica Publishing Group ; 2024
    In:  Optics Letters Vol. 49, No. 3 ( 2024-02-01), p. 430-
    Details
    In: Optics Letters, Optica Publishing Group, Vol. 49, No. 3 ( 2024-02-01), p. 430-
    Abstract: Stochastic nonlinear impairment is the primary factor that limits the transmission performance of high-speed orbital angular momentum (OAM) mode-division multiplexing (MDM) optical fiber communication systems. This Letter presents a low-complexity adaptive-network-based fuzzy inference system (LANFIS) nonlinear equalizer for OAM-MDM intensity-modulation direct-detection (IM/DD) transmission with three OAM modes and 15 wavelength division multiplex (WDM) channels. The LANFIS equalizer could adjust the probability distribution functions (PDFs) of the distorted pulse amplitude modulation (PAM) symbols to fit the statistical characteristics of the WDM–OAM-MDM transmission channel. Therefore, although the transmission symbols in the WDM–OAM-MDM system are subjected to a stochastic nonlinear impairment, the proposed LANFIS equalizer can effectively compensate the distorted signals. The proposed equalizer outperforms the Volterra equalizer with improvements in receiver sensitivity of 2, 1.5, and 1.3 dB for three OAM modes at a wavelength of 1550.12 nm, respectively. It also outperforms a CNN equalizer, with improvements in receiver sensitivity of 1, 0.5, and 0.3 dB, respectively. Moreover, complexity reductions of 67%, 74%, and 99.9% are achieved for the LANFIS equalizer compared with the Volterra, CNN, and ANFIS equalizers, respectively. The proposed equalizer has high performance and low complexity, making it a promising candidate for a high-speed WDM–OAM-MDM system.
    Type of Medium: Online Resource
    ISSN: 0146-9592 , 1539-4794
    URL: Article
    DOI: 10.1364/OL.506507
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2024
    detail.hit.zdb_id: 243290-0
    detail.hit.zdb_id: 1479014-2
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  • 9
    Online Resource
    Online Resource
    End-to-end learning strategy based on a frequency domain feature decoupling network emulator with joint probabilistic shaping and equalization for a 300-Gbit/s OAM mode division multiplexing transmission
    Optica Publishing Group ; 2024
    In:  Optics Express Vol. 32, No. 8 ( 2024-04-08), p. 13809-
    Details
    In: Optics Express, Optica Publishing Group, Vol. 32, No. 8 ( 2024-04-08), p. 13809-
    Abstract: Mode coupling and device nonlinear impairment appear to be a long-standing challenge in the orbital angular momentum (OAM) mode division multiplexing (MDM) of intensity modulation direct detection (IM/DD) transmission systems. In this paper, we propose an end-to-end (E2E) learning strategy based on a frequency domain feature decoupling network (FDFDnet) emulator with joint probabilistic shaping (PS) and equalization for an OAM-MDM IM/DD transmission with three modes. Our FDFDnet emulator can accurately build a complex nonlinear model of an OAM-MDM system by separating the signal into features from different frequency domains. Furthermore, a FDFDnet-based E2E strategy for joint PS and equalization is presented with the aim of compensating the signal impairment for the OAM-MDM IM/DD system. An experiment is carried out on a 300 Gbit/s carrierless amplitude phase-32 (CAP-32) signal with three OAM modes over a 10 km ring-core fiber transmission, and the results show that the proposed FDFDnet emulator outperforms the traditional CGAN emulator, with improvements in the modelling accuracy of 30.8%, 26.3% and 31% for the three OAM modes. Moreover, the receiver sensitivity of the proposed E2E learning strategy is higher than for the CGAN emulator by 3, 2.5, 2.2 dBm and the real channel by 5.5, 5.1, and 5.3 dBm for the three OAM modes, respectively. Our experimental results demonstrate that the proposed FDFDnet emulator-based E2E learning strategy is a promising contender for achieving ultra-high-capacity interconnectivity between data centers.
    Type of Medium: Online Resource
    ISSN: 1094-4087
    URL: Article
    DOI: 10.1364/OE.519842
    Language: English
    Publisher: Optica Publishing Group
    Publication Date: 2024
    detail.hit.zdb_id: 1491859-6
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