Pub Date : 2026-01-13DOI: 10.1016/j.optcom.2026.132914
Xiaowei Qin , Jianjun Li , Jun Deng, Hao Zhai, Yiyang Xie
Distributed Bragg Reflectors (DBRs), consisting of alternating material layers with quarter-wavelength optical thickness, are extensively utilized in optoelectronic devices. Deviations of DBRs layer thickness will result in degraded reflectivity, reduced reflection bandwidth, and shifted reflection phase. However, conventional thickness monitoring and measurement methods struggle to achieve efficient and accurate DBRs thickness calibration. In this paper, we propose an accurate calibration method for the quarter-wavelength optical thickness of DBRs layer by complementary resonant cavities. By comparing the cavity mode wavelengths of both cavities, this method can not only determine layer thickness deviations, but also precisely calibrate the layer thickness to quarter-wavelength. In experiments, the optical thickness of each layer in AlGaAs DBRs grown by Metal-Organic Chemical Vapor Deposition (MOCVD) was calibrated to the quarter-wavelength corresponding to 670 nm, verifying the proposed method.
{"title":"Accurate calibration for quarter-wavelength optical thickness of DBRs layer by complementary resonant cavity","authors":"Xiaowei Qin , Jianjun Li , Jun Deng, Hao Zhai, Yiyang Xie","doi":"10.1016/j.optcom.2026.132914","DOIUrl":"10.1016/j.optcom.2026.132914","url":null,"abstract":"<div><div>Distributed Bragg Reflectors (DBRs), consisting of alternating material layers with quarter-wavelength optical thickness, are extensively utilized in optoelectronic devices. Deviations of DBRs layer thickness will result in degraded reflectivity, reduced reflection bandwidth, and shifted reflection phase. However, conventional thickness monitoring and measurement methods struggle to achieve efficient and accurate DBRs thickness calibration. In this paper, we propose an accurate calibration method for the quarter-wavelength optical thickness of DBRs layer by complementary resonant cavities. By comparing the cavity mode wavelengths of both cavities, this method can not only determine layer thickness deviations, but also precisely calibrate the layer thickness to quarter-wavelength. In experiments, the optical thickness of each layer in AlGaAs DBRs grown by Metal-Organic Chemical Vapor Deposition (MOCVD) was calibrated to the quarter-wavelength corresponding to 670 nm, verifying the proposed method.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132914"},"PeriodicalIF":2.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039243","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}
Pub Date : 2026-01-13DOI: 10.1016/j.optcom.2026.132893
Andrew MacRae , Connor Kupchak
We study the limitations on observing transient amplification in atomic systems exhibiting electromagnetically induced transparency (EIT) and we evaluate the limits of optical Bloch equation (OBE) models. Using propagation-based Maxwell–Bloch simulations, we show that single-atom, spatially uniform OBE treatments overestimate gain by neglecting propagation dynamics. In two-level systems, this yields incorrect predictions of the transmission, while in three-level systems, it predicts unrealistically large amplification. Furthermore, we show that Doppler averaging in warm vapor suppresses oscillatory ringing and the maximum achievable gain. Our results explain discrepancies between OBE predictions and experimental observations, and establish practical limits on transient gain in cold and thermally broadened EIT media.
{"title":"Propagation dynamics and transient amplification in warm and cold atomic EIT systems","authors":"Andrew MacRae , Connor Kupchak","doi":"10.1016/j.optcom.2026.132893","DOIUrl":"10.1016/j.optcom.2026.132893","url":null,"abstract":"<div><div>We study the limitations on observing transient amplification in atomic systems exhibiting electromagnetically induced transparency (EIT) and we evaluate the limits of optical Bloch equation (OBE) models. Using propagation-based Maxwell–Bloch simulations, we show that single-atom, spatially uniform OBE treatments overestimate gain by neglecting propagation dynamics. In two-level systems, this yields incorrect predictions of the transmission, while in three-level systems, it predicts unrealistically large amplification. Furthermore, we show that Doppler averaging in warm vapor suppresses oscillatory ringing and the maximum achievable gain. Our results explain discrepancies between OBE predictions and experimental observations, and establish practical limits on transient gain in cold and thermally broadened EIT media.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132893"},"PeriodicalIF":2.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980884","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}
Pub Date : 2026-01-13DOI: 10.1016/j.optcom.2026.132883
Jabir Hakami , Abu Mohamed Alhasan , A.Y. Madkhli , Salah Abdulrhmann
In this article, we present findings on the impacts of external optical feedback (OFB), non-radiative recombination (NRR), and injection current on the lasing field fluctuations and the spectral characteristics of laser diodes (LDs). Utilizing an advanced simulation model, we explore OFB as a series of round trip time delays in the external-cavity. Our research categorizes laser dynamics through bifurcation diagrams of photon numbers and analyzes noise characteristics across three operational regions: continuous-wave (CW) operation under weak OFB, chaotic behavior under moderate OFB, and stable CW operation under strong OFB. Notably, lower NRR stabilize laser output, facilitating periodic oscillation (PO) or CW modes essential for high performance. Reducing the NRR in solitary lasers narrows the line shape, enhancing optical performance. In CW operation under strong OFB conditions, low-frequency components of relative intensity noise (RIN) and frequency noise (FN) are substantially suppressed. However, noise levels increase during coherence collapse and at higher NRR. Our findings indicate that while moderate OFB can induce coherence collapse leading to broadened spectral peaks, very strong OFB enhances coherence, yielding sharp central peaks and allowing for CW or PO. Overall, our research highlights the critical role of a low NRR in enhancing the stability of laser diodes while revealing that a higher NRR can improve coherence in specific contexts. These insights pave the way for future advancements in laser technology, particularly for applications requiring precision and reliability.
{"title":"Impact of non-radiative recombination and optical feedback strength on field fluctuations, noise, and spectral line shape in laser diodes","authors":"Jabir Hakami , Abu Mohamed Alhasan , A.Y. Madkhli , Salah Abdulrhmann","doi":"10.1016/j.optcom.2026.132883","DOIUrl":"10.1016/j.optcom.2026.132883","url":null,"abstract":"<div><div>In this article, we present findings on the impacts of external optical feedback (OFB), non-radiative recombination (NRR), and injection current on the lasing field fluctuations and the spectral characteristics of laser diodes (LDs). Utilizing an advanced simulation model, we explore OFB as a series of round trip time delays in the external-cavity. Our research categorizes laser dynamics through bifurcation diagrams of photon numbers and analyzes noise characteristics across three operational regions: continuous-wave (CW) operation under weak OFB, chaotic behavior under moderate OFB, and stable CW operation under strong OFB. Notably, lower NRR stabilize laser output, facilitating periodic oscillation (PO) or CW modes essential for high performance. Reducing the NRR in solitary lasers narrows the line shape, enhancing optical performance. In CW operation under strong OFB conditions, low-frequency components of relative intensity noise (RIN) and frequency noise (FN) are substantially suppressed. However, noise levels increase during coherence collapse and at higher NRR. Our findings indicate that while moderate OFB can induce coherence collapse leading to broadened spectral peaks, very strong OFB enhances coherence, yielding sharp central peaks and allowing for CW or PO. Overall, our research highlights the critical role of a low NRR in enhancing the stability of laser diodes while revealing that a higher NRR can improve coherence in specific contexts. These insights pave the way for future advancements in laser technology, particularly for applications requiring precision and reliability.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132883"},"PeriodicalIF":2.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980883","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}
Pub Date : 2026-01-13DOI: 10.1016/j.optcom.2026.132904
Michael G. Taylor
This paper describes the passage of light through a system of waveplates mathematically in terms of quaternions, an extension of the complex numbers, instead of the more usual Jones vectors and Jones matrices. Both the light beam and the waveplate are represented by a quaternion. It is possible to manipulate the quaternion expression more readily than the Jones matrix-vector expression; for example it can be inverted. The quaternion form of a waveplate is compactly related to its retardance and fast/slow axes, and the quaternion of a signal is closely related to its state of polarization (SOP), either expressed as a vector on the Poincaré sphere or as a polarization ellipse. The paper presents rules to decide if two optical signals are aligned or orthogonal in phase or in polarization from their quaternions, and presents the quaternion operations to change the phase or change the SOP. Several mathematical tools are identified, such as partial conjugation, to rearrange a quaternion expression, a tricky operation because multiplication does not commute. Put together, these advances let us understand how waveplates can act on a light beam to produce desired behavior. Finally, the quaternion math is put to work on two problems. A new endless optical phase shift system is designed out of waveplates. A prior solution to the problem used five waveplates, and in this paper the same task is done with only three waveplates. Also, failures of a polarization controller are studied, and found to be caused by singularities, which can occur frequently.
{"title":"Application of quaternions to obtain analytic solutions to systems of polarization components","authors":"Michael G. Taylor","doi":"10.1016/j.optcom.2026.132904","DOIUrl":"10.1016/j.optcom.2026.132904","url":null,"abstract":"<div><div>This paper describes the passage of light through a system of waveplates mathematically in terms of quaternions, an extension of the complex numbers, instead of the more usual Jones vectors and Jones matrices. Both the light beam and the waveplate are represented by a quaternion. It is possible to manipulate the quaternion expression more readily than the Jones matrix-vector expression; for example it can be inverted. The quaternion form of a waveplate is compactly related to its retardance and fast/slow axes, and the quaternion of a signal is closely related to its state of polarization (SOP), either expressed as a vector on the Poincaré sphere or as a polarization ellipse. The paper presents rules to decide if two optical signals are aligned or orthogonal in phase or in polarization from their quaternions, and presents the quaternion operations to change the phase or change the SOP. Several mathematical tools are identified, such as partial conjugation, to rearrange a quaternion expression, a tricky operation because multiplication does not commute. Put together, these advances let us understand how waveplates can act on a light beam to produce desired behavior. Finally, the quaternion math is put to work on two problems. A new endless optical phase shift system is designed out of waveplates. A prior solution to the problem used five waveplates, and in this paper the same task is done with only three waveplates. Also, failures of a polarization controller are studied, and found to be caused by singularities, which can occur frequently.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"607 ","pages":"Article 132904"},"PeriodicalIF":2.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080155","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132908
Jie Zhao , Zizhuo Li , Zhenxing Sun , Yanqiu Xu , Jin Zhang , Kaifei Tang , Jiaqiang Nie , Rulei Xiao , Xiangfei Chen
In this work, we present a high-order colliding pulse mode-locked lasers (CPML) based on a 500 μm cavity length Fabry-Perot saturable absorber (FP-SA) unit operating in the C-band. The laser employs a high-power epitaxial structure and asymmetric reflectance coatings, featuring a 95 % high-reflective (HR) coating on one facet and a naturally cleaved facet on the other. This design enhances intracavity energy density, optimizes pulse compression, and achieves cavity-length extension and performance refinement through modular multi-stage cascading. We systematically investigate the mode-locking dynamics of the SA-FP unit and cascaded systems (second to fourth order), demonstrating stable generation of optical pulses with 88.2 GHz longitudinal mode spacing and robust stability against current and temperature variations. Furthermore, to enable high-speed transmission on individual comb lines, a four-channel DWDM experiment is conducted at the 4th-order CPML’s central wavelength. Utilizing a thin-film LiNbO3 Mach-Zehnder interferometer (MZI) modulator, each channel achieve 25 Gb/s non-return-to-zero (NRZ) modulation capability. The proposed high-order CPML architecture serves as a superior comb source for energy-efficient optical interconnects and high-bandwidth data transmission, offering a scalable platform for next-generation photonic systems.
{"title":"High-order colliding-pulse mode-locked lase with high power and mode stability for optical I/O technology","authors":"Jie Zhao , Zizhuo Li , Zhenxing Sun , Yanqiu Xu , Jin Zhang , Kaifei Tang , Jiaqiang Nie , Rulei Xiao , Xiangfei Chen","doi":"10.1016/j.optcom.2026.132908","DOIUrl":"10.1016/j.optcom.2026.132908","url":null,"abstract":"<div><div>In this work, we present a high-order colliding pulse mode-locked lasers (CPML) based on a 500 μm cavity length Fabry-Perot saturable absorber (FP-SA) unit operating in the C-band. The laser employs a high-power epitaxial structure and asymmetric reflectance coatings, featuring a 95 % high-reflective (HR) coating on one facet and a naturally cleaved facet on the other. This design enhances intracavity energy density, optimizes pulse compression, and achieves cavity-length extension and performance refinement through modular multi-stage cascading. We systematically investigate the mode-locking dynamics of the SA-FP unit and cascaded systems (second to fourth order), demonstrating stable generation of optical pulses with 88.2 GHz longitudinal mode spacing and robust stability against current and temperature variations. Furthermore, to enable high-speed transmission on individual comb lines, a four-channel DWDM experiment is conducted at the 4th-order CPML’s central wavelength. Utilizing a thin-film LiNbO<sub>3</sub> Mach-Zehnder interferometer (MZI) modulator, each channel achieve 25 Gb/s non-return-to-zero (NRZ) modulation capability. The proposed high-order CPML architecture serves as a superior comb source for energy-efficient optical interconnects and high-bandwidth data transmission, offering a scalable platform for next-generation photonic systems.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132908"},"PeriodicalIF":2.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981668","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132901
Peng Song, Le Li, Chengtao Liu, Lijian Zhang, Hua Guo
To address the intrinsic limitations imposed by the low received signal strength and the consequent restrictions on coverage range, in ultraviolet non-line-of-sight (UV NLOS) communication, this study establishes a three-dimensional spatial light-field distribution model for ultraviolet reflective channels. By integrating bidirectional reflectance distribution function (BRDF) theory with light reflection theory for rough surfaces, we calculate the reflectivity of ultraviolet light reflected from such surfaces and develop a three-stage physical model that characterizes the energy transfer of ultraviolet photons via a reflective surface to a sampling point. A Monte Carlo method is proposed to compute the three-dimensional spatial distribution of the ultraviolet reflection channel. Experimental verification employs a combined micro- and macro-scale approach. At the microscopic level, experiments confirm the accuracy of the BRDF model for cement surfaces within the solar-blind band under varying incident and reflection azimuth angles. At the macroscopic level, field experiments, supplemented by light-field simulations, reveal the effects of LED divergence angle and transmitter elevation angle on the energy distribution of the reflected light-field. The strong correlation between experimental and simulation results verifies the effectiveness of the proposed reflected light-field calculation method. This study provides a new approach for overcoming the distance bottleneck in UV NLOS communication and offers valuable insights for the design of covert communication systems in complex environments.
{"title":"Light-field distribution analysis in reflective ultraviolet communication channels","authors":"Peng Song, Le Li, Chengtao Liu, Lijian Zhang, Hua Guo","doi":"10.1016/j.optcom.2026.132901","DOIUrl":"10.1016/j.optcom.2026.132901","url":null,"abstract":"<div><div>To address the intrinsic limitations imposed by the low received signal strength and the consequent restrictions on coverage range, in ultraviolet non-line-of-sight (UV NLOS) communication, this study establishes a three-dimensional spatial light-field distribution model for ultraviolet reflective channels. By integrating bidirectional reflectance distribution function (BRDF) theory with light reflection theory for rough surfaces, we calculate the reflectivity of ultraviolet light reflected from such surfaces and develop a three-stage physical model that characterizes the energy transfer of ultraviolet photons via a reflective surface to a sampling point. A Monte Carlo method is proposed to compute the three-dimensional spatial distribution of the ultraviolet reflection channel. Experimental verification employs a combined micro- and macro-scale approach. At the microscopic level, experiments confirm the accuracy of the BRDF model for cement surfaces within the solar-blind band under varying incident and reflection azimuth angles. At the macroscopic level, field experiments, supplemented by light-field simulations, reveal the effects of LED divergence angle and transmitter elevation angle on the energy distribution of the reflected light-field. The strong correlation between experimental and simulation results verifies the effectiveness of the proposed reflected light-field calculation method. This study provides a new approach for overcoming the distance bottleneck in UV NLOS communication and offers valuable insights for the design of covert communication systems in complex environments.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132901"},"PeriodicalIF":2.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981661","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132875
Heyam Hassan , Saud Althunibat , Scott Miller , Mazen Hasna , Khalid Qaraqe
Hybrid Free-Space Optical (FSO)/millimeter wave (mmWave) communication systems have garnered significant attention due to their ability to deliver high data rates while maintaining reliable connectivity across diverse atmospheric conditions. However, traditional switching mechanisms, such as signal-to-noise ratio (SNR) threshold-based, rely only on the link’s instantaneous SNR, ignoring the link’s bandwidth, which degrades the overall system’s reliability and efficiency. In order to mitigate this challenge, a channel capacity-based switching scheme for a hybrid FSO/mmWave system is proposed in this paper. Unlike existing schemes, the proposed mechanism dynamically switches between FSO and mmWave links based on the estimated channel capacity of the two links, rather than relying only on instantaneous channel conditions. This ensures that the system always selects the link with the highest achievable capacity, thereby improving the system’s throughput. The analysis incorporates both intensity modulation/direct detection (IM/DD) and heterodyne detection (HD) techniques under various weather conditions, including clear, hazy, and rainy scenarios. The FSO channel is modeled using the Gamma–Gamma (GG) distribution, while the mmWave link follows the Nakagami-m fading model. Closed-form expressions for key performance metrics, including link utilization and channel capacity for FSO, RF, and the proposed hybrid scheme, are derived and validated through simulation. Additionally, a comparative analysis conducted against existing switching mechanisms demonstrates that the proposed approach significantly enhances the performance of the hybrid FSO/mmWave system.
{"title":"A new selection mechanism for hybrid FSO/mmWave systems","authors":"Heyam Hassan , Saud Althunibat , Scott Miller , Mazen Hasna , Khalid Qaraqe","doi":"10.1016/j.optcom.2026.132875","DOIUrl":"10.1016/j.optcom.2026.132875","url":null,"abstract":"<div><div>Hybrid Free-Space Optical (FSO)/millimeter wave (mmWave) communication systems have garnered significant attention due to their ability to deliver high data rates while maintaining reliable connectivity across diverse atmospheric conditions. However, traditional switching mechanisms, such as signal-to-noise ratio (SNR) threshold-based, rely only on the link’s instantaneous SNR, ignoring the link’s bandwidth, which degrades the overall system’s reliability and efficiency. In order to mitigate this challenge, a channel capacity-based switching scheme for a hybrid FSO/mmWave system is proposed in this paper. Unlike existing schemes, the proposed mechanism dynamically switches between FSO and mmWave links based on the estimated channel capacity of the two links, rather than relying only on instantaneous channel conditions. This ensures that the system always selects the link with the highest achievable capacity, thereby improving the system’s throughput. The analysis incorporates both intensity modulation/direct detection (IM/DD) and heterodyne detection (HD) techniques under various weather conditions, including clear, hazy, and rainy scenarios. The FSO channel is modeled using the Gamma–Gamma (GG) distribution, while the mmWave link follows the Nakagami-m fading model. Closed-form expressions for key performance metrics, including link utilization and channel capacity for FSO, RF, and the proposed hybrid scheme, are derived and validated through simulation. Additionally, a comparative analysis conducted against existing switching mechanisms demonstrates that the proposed approach significantly enhances the performance of the hybrid FSO/mmWave system.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132875"},"PeriodicalIF":2.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981669","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132906
Xuan Chen, Minghua Cao, Yue Zhang, Huiqin Wang
Optical filter-bank multicarrier with index modulation (OFBMC-IM) suffers from reduced spectral efficiency due to inactive subcarriers. To address this issue, we propose a dual-mode scheme for OFBMC-IM system (DM-OFBMC-IM), which assigns distinct constellation modes to all subcarriers, thereby achieving full carrier utilization while preserving the diversity gain of index modulation. To further enhance bit error rate (BER) performance, phase rotation and amplitude scaling are introduced to adjust both the angular and radial positions of constellation points, generating IM-preferable constellations. Additionally, a deep learning-aided detector, named DMOFIMNet, is developed to recover index and symbol information under channel turbulence, and its hyperparameters are optimized using the Artificial Lemming Algorithm (ALA), thereby maximizing the achievable performance. Simulation and experimental results demonstrate that the proposed DM-OFBMC-IM system not only achieves higher spectral efficiency than benchmark systems but also improves BER performance. In addition, compared to the classical maximum-likelihood detector, the proposed detector reduces computational complexity by approximately 25% while achieving near-optimal BER performance.
{"title":"Deep learning-aided dual-mode index modulation FBMC for optical wireless communications","authors":"Xuan Chen, Minghua Cao, Yue Zhang, Huiqin Wang","doi":"10.1016/j.optcom.2026.132906","DOIUrl":"10.1016/j.optcom.2026.132906","url":null,"abstract":"<div><div>Optical filter-bank multicarrier with index modulation (OFBMC-IM) suffers from reduced spectral efficiency due to inactive subcarriers. To address this issue, we propose a dual-mode scheme for OFBMC-IM system (DM-OFBMC-IM), which assigns distinct constellation modes to all subcarriers, thereby achieving full carrier utilization while preserving the diversity gain of index modulation. To further enhance bit error rate (BER) performance, phase rotation and amplitude scaling are introduced to adjust both the angular and radial positions of constellation points, generating IM-preferable constellations. Additionally, a deep learning-aided detector, named DMOFIMNet, is developed to recover index and symbol information under channel turbulence, and its hyperparameters are optimized using the Artificial Lemming Algorithm (ALA), thereby maximizing the achievable performance. Simulation and experimental results demonstrate that the proposed DM-OFBMC-IM system not only achieves higher spectral efficiency than benchmark systems but also improves BER performance. In addition, compared to the classical maximum-likelihood detector, the proposed detector reduces computational complexity by approximately 25% while achieving near-optimal BER performance.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132906"},"PeriodicalIF":2.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981666","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132909
Pankaj Rakheja
The proposed quantum-based image encryption framework introduces an asymmetric mechanism for standard grayscale and iris biometric images by integrating quantum theory, unequal modulus decomposition, umbrella mapping, LU decomposition, fractional Fourier and Fresnel transforms. Biometric uniqueness is explicitly embedded within cryptographic operations; the scheme achieves high robustness and security while ensuring confidentiality and authentication. The numerical simulations demonstrate the superior performance of the proposed scheme, achieving average execution time of seconds, entropy of bits, and strong statistical metrics, including and confirming robust encryption and perfect image reconstruction fidelity. The system shows strong resistance to noise, brute force, special, differential, and traditional cryptographic attacks, supported by an extended key space. Despite generating a complex cipher and being vulnerable to occlusion attack, the designed scheme ensures reliability, scalability, and security. This makes the scheme suitable for real-life applications in multiple domains like healthcare, defense, and multimedia communication, with potential enhancements through hardware implementations.
{"title":"Robust quantum optical encryption framework using chaotic umbrella maps and fractional transforms with holographic techniques","authors":"Pankaj Rakheja","doi":"10.1016/j.optcom.2026.132909","DOIUrl":"10.1016/j.optcom.2026.132909","url":null,"abstract":"<div><div>The proposed quantum-based image encryption framework introduces an asymmetric mechanism for standard grayscale and iris biometric images by integrating quantum theory, unequal modulus decomposition, umbrella mapping, LU decomposition, fractional Fourier and Fresnel transforms. Biometric uniqueness is explicitly embedded within cryptographic operations; the scheme achieves high robustness and security while ensuring confidentiality and authentication. The numerical simulations demonstrate the superior performance of the proposed scheme, achieving average execution time of <span><math><mrow><mn>0.1132</mn></mrow></math></span> seconds, entropy of <span><math><mrow><mn>7.9955</mn></mrow></math></span> bits, and strong statistical metrics, including <span><math><mrow><mi>N</mi><mi>P</mi><mi>C</mi><mi>R</mi><mo>=</mo><mn>99.6063</mn><mo>,</mo><mi>U</mi><mi>A</mi><mi>C</mi><mi>I</mi><mo>=</mo><mn>33.3283</mn><mo>,</mo><mi>C</mi><mi>C</mi><mo>=</mo><mn>1</mn><mtext>,</mtext></mrow></math></span> and <span><math><mrow><mi>M</mi><mi>S</mi><mi>E</mi><mo>=</mo><mn>0</mn><mtext>,</mtext></mrow></math></span> confirming robust encryption and perfect image reconstruction fidelity. The system shows strong resistance to noise, brute force, special, differential, and traditional cryptographic attacks, supported by an extended key space. Despite generating a complex cipher and being vulnerable to occlusion attack, the designed scheme ensures reliability, scalability, and security. This makes the scheme suitable for real-life applications in multiple domains like healthcare, defense, and multimedia communication, with potential enhancements through hardware implementations.</div></div>","PeriodicalId":19586,"journal":{"name":"Optics Communications","volume":"606 ","pages":"Article 132909"},"PeriodicalIF":2.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146039186","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}
Pub Date : 2026-01-12DOI: 10.1016/j.optcom.2026.132911
Ankit Kumar , Abdul Khader Jilani Saudagar , Abhishek Kumar
Quantum Key Distribution (QKD) is emerging as a foundational technology for secure communications in the quantum era, offering information-theoretic security based on the principles of quantum mechanics. However, despite notable progress, the real-world adoption of QKD continues to encounter obstacles, such as limited scalability, high implementation costs, challenges in integration with classical and cloud-native infrastructures, and reduced performance over long distances. To address these issues, this study introduces the Scalable Modular QKD (SM-QKD) framework, an innovative architecture designed to support modularity, scalability, and hybrid quantum-classical orchestration. SM-QKD incorporates adaptive optimization and seamless cloud-native integration to overcome the limitations of traditional quantum key distribution (QKD) systems. Extensive benchmarking across urban, cloud-based, and cross-domain environments revealed significant performance gains: a 41 % increase in throughput, 47 % reduction in latency, 9 % improvement in error correction success, and 33 % greater interoperability with current digital infrastructures compared to existing commercial and research-based QKD solutions. These advancements establish SM-QKD as a robust, cost-efficient, and deployment-ready framework for achieving quantum-resilient secure communications across national, enterprise, and cross-border networks and will play vital role in future economics.
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