{"title":"ROF-based antenna-PDM system employing DSM and DD-weight-pruning Volterra nonlinear equalization","authors":"","doi":"10.1016/j.optcom.2024.131235","DOIUrl":"10.1016/j.optcom.2024.131235","url":null,"abstract":"<div><div>The radio over fiber (ROF) system based on Delta-sigma modulation (DSM) can meet the requirements of the fronthaul system with its high signal fidelity and mature digital fronthaul interface specification. However, nonlinear impairments in ROF systems can seriously affect the performance of DSM signals. To reduce the impact of nonlinear effects on DSM signals with low complexity, we have designed a nonlinear equalizer based on the Volterra series. The complexity of the Volterra nonlinear equalizer (VNLE) is reduced through a weight pruning strategy. And by using directed decision instead of training sequences, we eliminate the redundancy introduced by VNLE while simultaneously ensuring its stability within the DSM system. Ultimately, we transmit one-bit single-carrier loaded DSM signals over 20 km of SMF-28 fiber and 3 m of wireless distance in an antenna polarization division multiplexing (APDM) intensity modulation and direct detection (IM/DD) system. For the first time, we add decision-directed weight-pruning Volterra nonlinear equalization (DD-PVNLE) algorithm in the APDM-IM/DD system to overcome the signal damage by the nonlinearity of the system. The BER of the Delta-sigma modulated on-off keying (DSM-OOK) signal reduces from 1 × 10<sup>−3</sup> to 1.1 × 10<sup>−4</sup>. The high-fidelity 1024QAM, 2048QAM, and 4096QAM are recovered successfully whose BERs below the soft decision threshold 2.4 × 10<sup>−2</sup> and hard decision threshold 3.8 × 10<sup>−3</sup> respectively.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A novel signal detection method for photon-counting communications with nonlinear distortion effects","authors":"","doi":"10.1016/j.optcom.2024.131237","DOIUrl":"10.1016/j.optcom.2024.131237","url":null,"abstract":"<div><div>This paper proposes a method for estimating and detecting optical signals in practical photon-counting receivers. There are two important aspects of non-perfect photon-counting receivers, namely, (i) dead time which results in blocking loss, and (ii) non-photon-number-resolving, which leads to counting loss during the gate-ON interval. These factors introduce nonlinear distortion to the detected photon counts. The detected photon counts depend not only on the optical intensity but also on the signal waveform, and obey a Poisson binomial process. Using the discrete Fourier transform characteristic function (DFT-CF) method, we derive the probability mass function (PMF) of the detected photon counts. Furthermore, unlike conventional methods that assume an ideal rectangle wave, we propose a novel signal estimation and decision method applicable to arbitrary waveform. We demonstrate that the proposed method achieves superior error performance compared to conventional methods. The proposed algorithm has the potential to become an essential signal processing tool for photon-counting receivers.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Double-slot micro-ring resonators with trapezoidal subwavelength grating as ultra-sensitive biochemical sensors","authors":"","doi":"10.1016/j.optcom.2024.131256","DOIUrl":"10.1016/j.optcom.2024.131256","url":null,"abstract":"<div><div>Silicon-based refractive index sensors are of significance in the detection of gases, biological substances and chemical compounds. Among these, optical microcavities can confine the optical field to the micrometre-scale region, and possess the advantages of high <em>Q</em> factor, small size and easy integration. In this paper, a trapezoidal subwavelength grating (SWG) is introduced into a slot micro-ring resonator, and the mode splitting is employed to enrich the supported standing wave modes and optimize the spatial profiles of the resonant modes. The modes’ <em>Q</em> factor is improved and the high sensitivity and low detection limit is achieved. The optimal trapezoidal subwavelength grating double slot micro-ring resonator (T-SWGDSMRR) structure is obtained by designing the structural parameters and analyzing their effects on the sensing performance parameters and spectral characteristics. The T-SWGDSMRR, designed for detecting the glucose solution, demonstrated a low detection limit of <span><math><mrow><mn>3.3</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math></span> RIU and an ultra-high <em>Q</em> factor of up to 100825, accompanied by a refractive index sensitivity of 424 nm/RIU. Finally, a cascaded double micro-ring sensor is proposed using the vernier effect, through cascading the T-SWGDSMRR with a referential ring, the sensitivity is enhanced to 12828 nm/RIU, and the limit of detection is <span><math><mrow><mn>3.12</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math></span> RIU.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Er3+ -doped oxyfluoroborosilicate glass ceramics with embedded CaF2 nanoparticles for 1.53 μm broad band applications","authors":"","doi":"10.1016/j.optcom.2024.131243","DOIUrl":"10.1016/j.optcom.2024.131243","url":null,"abstract":"<div><div>The CaF<sub>2</sub> based oxyfluoroborosilicate glasses and glass ceramics doped with Er<sup>3+</sup> ions were prepared via melt quench process followed by heat treatment and characterized for 1.53 μm broadband applications. The optimized glass ceramic sample was obtained at 450<sup>o</sup>C/1h heat treatment. The Er<sup>3+</sup> concentration was optimized as 1.0 mol% for efficient emission at 460 nm excitation through concentration dependent luminescence analysis. The spectroscopic parameters such as Ω<sub>λ = 2,4,6</sub> parameters and the radiative parameters such as spontaneous transition probability rates (A<sub>R</sub>), branching ratios (β<sub>R</sub>) and decay times (τ<sub>R</sub>) were calculated applying the standard Judd-Ofelt theory. The effective bandwidth (Δλ<sub>eff</sub>), stimulated emission cross-section (σ<sub>e</sub>), gain bandwidth (σ<sub>e</sub> × Δλ<sub>eff</sub>), quantum efficiency (η) and figure of merit (σ<sub>e</sub> × τ<sub>R</sub>) were calculated as 25.78 nm, 13.42 × 10<sup>−21</sup> cm<sup>2</sup>, 3.46 × 10<sup>−26</sup> cm<sup>3</sup>, 82.83% and 5.32 × 10<sup>−23</sup> cm<sup>2</sup>s, respectively for the optimized glass ceramic sample. The exchange type of energy transfer among the excited Er<sup>3+</sup> ions results the quenching in luminescence and the non-exponentiality in decay curves. The systematic investigations carried out indicate that the glass ceramic obtained at 450<sup>o</sup>C/1h heat treatment was proficient for 1.53 μm broadband fiber lasers and optical amplifiers in S and C band communication window.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Photonic crystal fibers based on Dirac point-guiding","authors":"","doi":"10.1016/j.optcom.2024.131242","DOIUrl":"10.1016/j.optcom.2024.131242","url":null,"abstract":"<div><div>—In this work photonic crystal fibers of different cross-sectional patterns are studied. Dirac points of these various lattices are explored, propagation diagrams showing positions of the Dirac spectrums are obtained, and their application in fiber guiding is discussed. A quasi-3D FDTD simulation method, which is simpler and more efficient than a commercial 3D FDTD simulation software, is developed for photonic crystal fiber. This method is then applied to the new photonic crystal fiber proposed in [Fiber guiding at the Dirac frequency beyond photonic bandgaps, Light Sci. & App. 4 (2015) e304.]. Dirac-point guidance, which is based on Dirac localization of photons, is verified for these fibers.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A low heat release cladding pump coupler","authors":"","doi":"10.1016/j.optcom.2024.131248","DOIUrl":"10.1016/j.optcom.2024.131248","url":null,"abstract":"<div><div>Few-mode erbium-doped fiber amplifiers (FM-EDFAs) have opened up the possibility of realizing the next generation of high-capacity, high-rate communication systems. However, the leakage of pump light during continuous operation of the FM-EDFA is likely to cause the temperature of the cladding pump coupler to be too high and thus destabilize the amplifier. In this work, a low heat release cladding pump coupler was designed and the corresponding FM-EDFA was constructed. The cladding pump coupler in the 8 h of continuous operation of the FM-EDFA is at 27.8 °C for maximum, 23.7 °C for minimum, and 26 °C for average temperatures, respectively, which are in a low-temperature safe transmission state. The FM-EDFA performance test was performed on this basis, and the results show that when the input pump power is 7 W, the maximum gain fluctuation of each mode of FM-EDFA at 1550 nm in 0∼8 h is only 1.5 dB, the gain of all modes is greater than 23 dB and the differential mode gain (DMG) is less than 2 dB. In addition, the FM-EDFA still has good performance in the C-band after 8 h of continuous operation. The gain for all modes is greater than 21 dB, DMG is less than 2 dB, and wavelength flatness is 3.6 dB. The low heat release cladding pump coupler is conducive to the stable amplification transmission of FM-EDFA, which is of great significance to achieving the upgrading and expansion of the communication system.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Desensitization design method of an off-axis three-mirror anastigmatic optical system based on the nodal aberration theory","authors":"","doi":"10.1016/j.optcom.2024.131228","DOIUrl":"10.1016/j.optcom.2024.131228","url":null,"abstract":"<div><div>A design method for an off-axis three-mirror anastigmatic optical system with low misalignment sensitivity is proposed. Based on the transformed pupil coordinate and nodal aberration theory, the analytical expressions between the optical parameters and misalignments are derived and an as-built performance evaluation model is established. The effects of mirror spacings and the off-axis magnitude value on the misalignment sensitivity are analyzed. With the desensitization design method proposed in this paper, a low-sensitivity off-axis TMA optical system can be designed. The simulation experiments show that, the misalignment sensitivity of the off-axis TMA optical system obtained by our method is approximately 60% that of the system obtained by nominal performance optimization method, and the as-built performance is about 1.49<span><math><mo>∼</mo></math></span>1.54 times that of the nominal performance optimization method.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Mixed precision quantization of silicon optical neural network chip","authors":"","doi":"10.1016/j.optcom.2024.131231","DOIUrl":"10.1016/j.optcom.2024.131231","url":null,"abstract":"<div><div>In recent years, the field of neural network research has witnessed remarkable advancements in various domains. One of the emerging approaches is the integration of photonic computing, which leverages the unique properties of light for ultra-fast information processing. In this article, we establish a mixed precision quantization model to silicon-based optical neural networks and evaluates their performance on the MNIST and Fashion-MNIST datasets. Through a genetic algorithm-based optimization process, we achieve significant parameter compression while maintaining competitive accuracy. Our findings demonstrate that with an average quantization bitwidth of 4.5 bits on the MNIST dataset, we achieve an impressive 85.94% reduction in parameter size compared to traditional 32-bit networks, with only a marginal accuracy drop of 0.65%. Similarly, on the Fashion-MNIST dataset, we achieve an average quantization bitwidth of 5.67 bits, resulting in an 82.28% reduction in parameter size with a slight accuracy drop of 0.8%.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142525961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Deep learning techniques for quality of transmission estimation in optical networks","authors":"","doi":"10.1016/j.optcom.2024.131223","DOIUrl":"10.1016/j.optcom.2024.131223","url":null,"abstract":"<div><div>A large body of research has recently examined the estimation of the quality of transmission (QoT) in optical networks with deep learning. This paper discusses a lightpath’s quality of transmission to design fiber-optic communication and networks using deep learning algorithms. We need different major estimation parameters for advanced optical fiber communication and networks, i.e., modulation formats, baud rate, and code rate. Currently, the quality of transmission for unspecified optical paths depends on different estimation techniques i.e., (1) analytical models estimating physical layer impairments (PLIs) and (2) margined formulas. This paper focuses on deep-learning techniques that can be applied to optimization and complex systems. The deep learning algorithms contain different classifiers that can simulate results and estimate the bit-error rate, and signal-to-noise ratio of unspecified optical paths with threshold values, traffic volume, and modulation format. We must train and test the datasets for various classifiers, and classification features using Korean network topology. The classifier accuracy and Area Under the ROC Curve (AUC) simulation results are carried out using MATLAB.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enhancing dynamic target reconstruction and tracking based on ghost imaging and deep convolutional neural networks","authors":"","doi":"10.1016/j.optcom.2024.131224","DOIUrl":"10.1016/j.optcom.2024.131224","url":null,"abstract":"<div><div>Ghost imaging requires a large amount of sampling data, which limits its applications in the study of dynamic objects. Here, we propose an imaging technique based on deep convolutional neural networks (SaDunet) that can be used to examine the dynamics of target objects. By replacing the traditional correlation imaging reconstruction approach with SaDunet, the ability to recover high-quality images at low sampling rates is enhanced. The motion process of the target object is decomposed into multiple motion frames, and then each frame is imaged separately. Experiments show that the reconstructed image of the target object obtained by this scheme is of high quality, contains almost no noise, and accurately reflects the motion behavior of the target object.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142554509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}