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Fiber Optics and Optical Communications|82 Article(s)
170 Gbps PDM underwater visible light communication utilizing a compact 5-
Zhilan Lu, Zhenhao Li, Xianhao Lin, Jifan Cai, Fujie Li, Zengyi Xu, Lai Wang, Yingjun Zhou, Chao Shen, Junwen Zhang, and Nan Chi
The next generation of mobile communication is committed to establishing an integrated three-dimensional network that encompasses air, land, and sea. The visible light spectrum is situated within the transmission window for underwater communication, making visible light laser communication a focus of intense research. In this paper, we design and integrate a compact 5-λ transmission module based on five laser diodes with different wavelengths, utilizing a self-developed narrow-ridge GaN blue laser. With this transmitter, we have developed a polarization division multiplexing (PDM) 5-λ underwater visible light laser communication (UVLLC) system based on this transmission module. To enhance the transmission quality of the system, we designed a dual-branch ResDualNet network as a reciprocal differential receiver that incorporates common-mode noise cancellation and equalization functions for post-processing the received signals. With the combined contribution of the devices and algorithms, we achieved a total transmission rate of 170.1 Gbps, which represents a 16.1 Gbps increase compared to systems that do not utilize ResDualNet. To the best of our knowledge, this is the highest communication rate currently achievable in a UVLLC system using a single laser transmission module. The next generation of mobile communication is committed to establishing an integrated three-dimensional network that encompasses air, land, and sea. The visible light spectrum is situated within the transmission window for underwater communication, making visible light laser communication a focus of intense research. In this paper, we design and integrate a compact 5-λ transmission module based on five laser diodes with different wavelengths, utilizing a self-developed narrow-ridge GaN blue laser. With this transmitter, we have developed a polarization division multiplexing (PDM) 5-λ underwater visible light laser communication (UVLLC) system based on this transmission module. To enhance the transmission quality of the system, we designed a dual-branch ResDualNet network as a reciprocal differential receiver that incorporates common-mode noise cancellation and equalization functions for post-processing the received signals. With the combined contribution of the devices and algorithms, we achieved a total transmission rate of 170.1 Gbps, which represents a 16.1 Gbps increase compared to systems that do not utilize ResDualNet. To the best of our knowledge, this is the highest communication rate currently achievable in a UVLLC system using a single laser transmission module.
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1654 (2025)
High-speed and versatile ONN through parametric-based nonlinear computation
Xin Dong, Yuanjia Wang, Xiaoxiao Wen, Yi Zhou, and Kenneth K. Y. Wong
Neural networks (NNs), especially electronic-based NNs, have been rapidly developed in the past few decades. However, the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware, facing its bottleneck due to the slowdown of Moore’s law. Optical neural networks (ONNs), in which NNs are realized via optical components with information carried by photons at the speed of light, are drawing more attention nowadays. Despite the advantages of higher processing speed and lower system power consumption, one major challenge is to realize reliable and reusable algorithms in physical approaches, particularly nonlinear functions, for higher accuracy. In this paper, a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber (HNLF). With the specially designed mode-locked laser (MLL) and dispersive Fourier transform (DFT) algorithm, the overall computation frame rate can reach up to 40 MHz. Compared to ONNs using only linear computations, this system is able to improve the classification accuracies from 81.8% to 88.8% for the MNIST-digit dataset, and from 80.3% to 97.6% for the Vowel spoken audio dataset, without any hardware modifications. Neural networks (NNs), especially electronic-based NNs, have been rapidly developed in the past few decades. However, the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware, facing its bottleneck due to the slowdown of Moore’s law. Optical neural networks (ONNs), in which NNs are realized via optical components with information carried by photons at the speed of light, are drawing more attention nowadays. Despite the advantages of higher processing speed and lower system power consumption, one major challenge is to realize reliable and reusable algorithms in physical approaches, particularly nonlinear functions, for higher accuracy. In this paper, a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber (HNLF). With the specially designed mode-locked laser (MLL) and dispersive Fourier transform (DFT) algorithm, the overall computation frame rate can reach up to 40 MHz. Compared to ONNs using only linear computations, this system is able to improve the classification accuracies from 81.8% to 88.8% for the MNIST-digit dataset, and from 80.3% to 97.6% for the Vowel spoken audio dataset, without any hardware modifications.
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1647 (2025)
Co-wavelength-channel integration of ultra-low-frequency distributed acoustic sensing and high-capacity communication
Long Gu, Chaocheng Liu, Meng Xiang, Pengbai Xu, Hailin Yang, Wei Sun, Jun Yang, Songnian Fu, Yuncai Wang, and Yuwen Qin
Integrating distributed ultra-low-frequency vibration sensing and high-speed fiber optical communication can provide additional functionality under the current submarine telecommunication network, such as ocean seismic monitoring and geological exploration. This work demonstrates an integrated sensing and communication (ISAC) system utilizing the same wavelength channel over a 38 km seven-core fiber for concurrent large-capacity transmission and ultra-low-frequency distributed acoustic sensing. Specifically, the digital subcarrier multiplexing (DSM) signal and the chirped-pulse sensing signal are frequency division multiplexed at the same wavelength channel, under the condition of the optimal protection interval bandwidth, relying on the DSM flexibility in spectral allocation. As a result, we successfully achieve a sensitivity of both 3.89 nε/Hz@0.1 Hz and 0.18 nε/Hz@10 Hz under a spatial resolution of 20 m, under the framework of direct detection and cross-correlation demodulation. Meanwhile, a transmission capacity record of 241.85 Tb/s is secured for the ISAC when wavelength and space division multiplexed DP-16QAM DSM signals are successfully transmitted to reach the 20% soft-decision feedforward correction coding threshold of 2×10-2. Integrating distributed ultra-low-frequency vibration sensing and high-speed fiber optical communication can provide additional functionality under the current submarine telecommunication network, such as ocean seismic monitoring and geological exploration. This work demonstrates an integrated sensing and communication (ISAC) system utilizing the same wavelength channel over a 38 km seven-core fiber for concurrent large-capacity transmission and ultra-low-frequency distributed acoustic sensing. Specifically, the digital subcarrier multiplexing (DSM) signal and the chirped-pulse sensing signal are frequency division multiplexed at the same wavelength channel, under the condition of the optimal protection interval bandwidth, relying on the DSM flexibility in spectral allocation. As a result, we successfully achieve a sensitivity of both 3.89 nε/Hz@0.1 Hz and 0.18 nε/Hz@10 Hz under a spatial resolution of 20 m, under the framework of direct detection and cross-correlation demodulation. Meanwhile, a transmission capacity record of 241.85 Tb/s is secured for the ISAC when wavelength and space division multiplexed DP-16QAM DSM signals are successfully transmitted to reach the 20% soft-decision feedforward correction coding threshold of 2×10-2.
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1611 (2025)
Multifunctional fronthaul architecture enabled by electro-optic comb cloning|Editors' Pick
Jingjing Lin, Chenbo Zhang, Weihan Liang, Yi Zou, Yixiao Zhu, Weisheng Hu, Zhangyuan Chen, Weiwei Hu, and Xiaopeng Xie
Beyond providing user access to the core network, the radio access network (RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality (VR) and drone fleets. To achieve this, fronthaul—the link connecting the central units/distributed units (CUs/DUs) to wireless remote units (RUs) in centralized RAN—must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs. However, existing solutions fall short of supporting these functions within one simple, cost-effective network. In this work, we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simplified DSP, using an electro-optic (EO) comb cloning technique to enable multifunctionality in fronthaul systems. Through the delivery of pilot comb lines, a 1 ps (integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing, realizing frequency synchronization between the CUs/DUs and RUs. Moreover, the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning, and supports wavelength division multiplexing (WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s. Thanks to the clock-synchronized and self-homodyne structure, DSP is streamlined, with digital timing recovery, carrier phase estimation, and frequency offset estimation all omitted. This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing. Beyond providing user access to the core network, the radio access network (RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality (VR) and drone fleets. To achieve this, fronthaul—the link connecting the central units/distributed units (CUs/DUs) to wireless remote units (RUs) in centralized RAN—must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs. However, existing solutions fall short of supporting these functions within one simple, cost-effective network. In this work, we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simplified DSP, using an electro-optic (EO) comb cloning technique to enable multifunctionality in fronthaul systems. Through the delivery of pilot comb lines, a 1 ps (integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing, realizing frequency synchronization between the CUs/DUs and RUs. Moreover, the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning, and supports wavelength division multiplexing (WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s. Thanks to the clock-synchronized and self-homodyne structure, DSP is streamlined, with digital timing recovery, carrier phase estimation, and frequency offset estimation all omitted. This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing.
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1591 (2025)
Concept and experimental demonstration of physics-guided end-to-end learning for optical communication systems
Qiarong Xiao, Chen Ding, Tengji Xu, Chester Shu, and Chaoran Huang
Driven by advancements in artificial intelligence, end-to-end learning has become a key method for system optimization in various fields, including communications. However, applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature. Existing methods typically require developing a precise differentiable digital model of the physical system, which is computationally complex and can cause significant performance loss after deployment. In response, we propose a novel end-to-end learning framework called physics-guided learning. This approach performs the forward pass through the actual transmission channel while simplifying the channel model for the backward pass to a simple white-box model. Despite the simplicity, both experimental and simulation results show that our method significantly outperforms other learning approaches for digital pre-distortion applications in coherent optical fiber systems. It enhances training speed and accuracy, reducing the number of training iterations by more than 80%. It improves transmission quality and noise resilience and offers superior generalization to varying transmission link conditions such as link losses, modulation formats, and scenarios with different transmission distances and optical amplification. Furthermore, our new end-to-end learning framework shows promise for broader applications in optimizing future communication systems, paving the way for more flexible and intelligent network designs. Driven by advancements in artificial intelligence, end-to-end learning has become a key method for system optimization in various fields, including communications. However, applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature. Existing methods typically require developing a precise differentiable digital model of the physical system, which is computationally complex and can cause significant performance loss after deployment. In response, we propose a novel end-to-end learning framework called physics-guided learning. This approach performs the forward pass through the actual transmission channel while simplifying the channel model for the backward pass to a simple white-box model. Despite the simplicity, both experimental and simulation results show that our method significantly outperforms other learning approaches for digital pre-distortion applications in coherent optical fiber systems. It enhances training speed and accuracy, reducing the number of training iterations by more than 80%. It improves transmission quality and noise resilience and offers superior generalization to varying transmission link conditions such as link losses, modulation formats, and scenarios with different transmission distances and optical amplification. Furthermore, our new end-to-end learning framework shows promise for broader applications in optimizing future communication systems, paving the way for more flexible and intelligent network designs.
Photonics Research
- Publication Date: May. 16, 2025
- Vol. 13, Issue 6, 1469 (2025)
High-performance all-fiber-integrated perovskite photodetector based on FA0.4MA0.6PbI3
Yuchen Zhang, Yinping Miao, Jie Liu, Chenghong Ma, Yanqi Fan, Chaoyuan Zhao, and Xiaolan Li
The performance of an all-fiber-integrated photodetector (AFPD) depends on the integration of the active layer, where FA0.4MA0.6PbI3 emerges as a promising candidate due to its high absorbance, long carrier diffusion distance, and self-assembly. In this study, we report an AFPD based on FA0.4MA0.6PbI3 perovskite, along with thickness design for enhancement. The active layer of the AFPD is regarded as a thin-film waveguide for thickness design. Theoretical analysis and simulation results indicate the presence of resonance mode, enhancing and confining the light field even in a thinned active layer. An FA0.4MA0.6PbI3 based metal-semiconductor-metal (MSM) photodetector is directly deposited onto a side-polished multimode fiber (SP-MMF). The transmitted light in fiber leaks from the core to the MSM photodetector through the polished surface of SP-MMF, inducing a detection response. Experimental results demonstrate that the device achieves a responsivity of 3.2 A/W to 650 nm light, with both rising and falling edges of the response time reaching 8 ms. The proposed AFPD and method exhibit potential to simultaneously achieve high responsivity, fast response, and low insertion loss, providing a reliable solution for high-performance photodetection. The performance of an all-fiber-integrated photodetector (AFPD) depends on the integration of the active layer, where FA0.4MA0.6PbI3 emerges as a promising candidate due to its high absorbance, long carrier diffusion distance, and self-assembly. In this study, we report an AFPD based on FA0.4MA0.6PbI3 perovskite, along with thickness design for enhancement. The active layer of the AFPD is regarded as a thin-film waveguide for thickness design. Theoretical analysis and simulation results indicate the presence of resonance mode, enhancing and confining the light field even in a thinned active layer. An FA0.4MA0.6PbI3 based metal-semiconductor-metal (MSM) photodetector is directly deposited onto a side-polished multimode fiber (SP-MMF). The transmitted light in fiber leaks from the core to the MSM photodetector through the polished surface of SP-MMF, inducing a detection response. Experimental results demonstrate that the device achieves a responsivity of 3.2 A/W to 650 nm light, with both rising and falling edges of the response time reaching 8 ms. The proposed AFPD and method exhibit potential to simultaneously achieve high responsivity, fast response, and low insertion loss, providing a reliable solution for high-performance photodetection.
Photonics Research
- Publication Date: Feb. 24, 2025
- Vol. 13, Issue 3, 618 (2025)
Tiansheng Huang, Tongyu Wu, Qi Fang, Guangzheng Luo, Li-Peng Sun, and Bai-Ou Guan
Semiconductor metal oxides with narrow bandgap have emerged as a promising platform for photoelectrochemical reactions, yet their photoelectron-induced photocorrosion effect has been a limitation for their wider applications. Understanding the conversion processes concomitant with photoelectrochemical reaction at the electrode–electrolyte interface plays a crucial role in revealing the corrosion mechanisms and advancing the development of efficient photocathodes. However, accurately and in situ tracking these dynamic chemical events remains a great challenge due to the fact that reaction processes occur at nanoscale interfaces. Here, we track the electrochemical growth and conversion of copper nanostructures at interface by the evanescent field of the surface plasmon wave by using a gold-coated optical fiber as an electrochemical electrode and light sensing probe. The results exhibit correlation between redox processes of copper species and plasmonic resonances. Furthermore, in situ fiber-optic detection reveals the photocorrosion dynamics under photoelectrochemical reaction, including photoelectron-induced self-reduction of copper oxide and self-oxidation of cuprous oxide. These demonstrations facilitate not only the diagnosis for the health condition of photocathode nanomaterial, but also the understanding of the underlying reaction mechanism, and thus are potentially crucial for advancing the development of highly efficient photocathodes in future energy applications. Semiconductor metal oxides with narrow bandgap have emerged as a promising platform for photoelectrochemical reactions, yet their photoelectron-induced photocorrosion effect has been a limitation for their wider applications. Understanding the conversion processes concomitant with photoelectrochemical reaction at the electrode–electrolyte interface plays a crucial role in revealing the corrosion mechanisms and advancing the development of efficient photocathodes. However, accurately and in situ tracking these dynamic chemical events remains a great challenge due to the fact that reaction processes occur at nanoscale interfaces. Here, we track the electrochemical growth and conversion of copper nanostructures at interface by the evanescent field of the surface plasmon wave by using a gold-coated optical fiber as an electrochemical electrode and light sensing probe. The results exhibit correlation between redox processes of copper species and plasmonic resonances. Furthermore, in situ fiber-optic detection reveals the photocorrosion dynamics under photoelectrochemical reaction, including photoelectron-induced self-reduction of copper oxide and self-oxidation of cuprous oxide. These demonstrations facilitate not only the diagnosis for the health condition of photocathode nanomaterial, but also the understanding of the underlying reaction mechanism, and thus are potentially crucial for advancing the development of highly efficient photocathodes in future energy applications.
Photonics Research
- Publication Date: Feb. 11, 2025
- Vol. 13, Issue 3, 561 (2025)
Photonic-frequency-interleaving-enabled broadband receiver with high reconfigurability and scalability
Jianwei Liu, Ruixuan Wang, Jiyao Yang, Weichao Ma, Henan Zeng, Chenyu Liu, Wen Jiang, Xiangpeng Zhang, Qinyu Xie, and Wangzhe Li
The photonic frequency-interleaving (PFI) technique has shown great potential for broadband signal acquisition, effectively overcoming the challenges of clock jitter and channel mismatch in the conventional time-interleaving paradigm. However, current comb-based PFI schemes have complex system architectures and face challenges in achieving large bandwidth, dense channelization, and flexible reconfigurability simultaneously, which impedes practical applications. In this work, we propose and demonstrate a broadband PFI scheme with high reconfigurability and scalability by exploiting multiple free-running lasers for dense spectral slicing with high crosstalk suppression. A dedicated system model is developed through a comprehensive analysis of the system non-idealities, and a cross-channel signal reconstruction algorithm is developed for distortion-free signal reconstruction, based on precise calibrations of intra- and inter-channel impairments. The system performance is validated through the reception of multi-format broadband signals, both digital and analog, with a detailed evaluation of signal reconstruction quality, achieving inter-channel phase differences of less than 2°. The reconfigurability and scalability of the scheme are demonstrated through a dual-band radar imaging experiment and a three-channel interleaving implementation with a maximum acquisition bandwidth of 4 GHz. To the best of our knowledge, this is the first demonstration of a practical radio-frequency (RF) application enabled by PFI. Our work provides an innovative solution for next-generation software-defined broadband RF receivers. The photonic frequency-interleaving (PFI) technique has shown great potential for broadband signal acquisition, effectively overcoming the challenges of clock jitter and channel mismatch in the conventional time-interleaving paradigm. However, current comb-based PFI schemes have complex system architectures and face challenges in achieving large bandwidth, dense channelization, and flexible reconfigurability simultaneously, which impedes practical applications. In this work, we propose and demonstrate a broadband PFI scheme with high reconfigurability and scalability by exploiting multiple free-running lasers for dense spectral slicing with high crosstalk suppression. A dedicated system model is developed through a comprehensive analysis of the system non-idealities, and a cross-channel signal reconstruction algorithm is developed for distortion-free signal reconstruction, based on precise calibrations of intra- and inter-channel impairments. The system performance is validated through the reception of multi-format broadband signals, both digital and analog, with a detailed evaluation of signal reconstruction quality, achieving inter-channel phase differences of less than 2°. The reconfigurability and scalability of the scheme are demonstrated through a dual-band radar imaging experiment and a three-channel interleaving implementation with a maximum acquisition bandwidth of 4 GHz. To the best of our knowledge, this is the first demonstration of a practical radio-frequency (RF) application enabled by PFI. Our work provides an innovative solution for next-generation software-defined broadband RF receivers.
Photonics Research
- Publication Date: Jan. 28, 2025
- Vol. 13, Issue 2, 395 (2025)
High spectral-efficiency, ultra-low MIMO SDM transmission over a field-deployed multi-core OAM fiber
Junyi Liu, Shuqi Mo, Zengquan Xu, Yuming Huang, Yining Huang, Zhenhua Li, Yuying Guo, Lei Shen, Shuo Xu, Ran Gao, Cheng Du, Qian Feng, Jie Luo, Jie Liu, and Siyuan Yu
Space-division multiplexing (SDM) systems based on few-mode multi-core fibers (FM-MCFs) utilize both spatial channels (fiber cores) and modes (optical modes per core) to maximize transmission capacity. Unlike laboratory FM-MCFs or field-deployed single-mode multi-core fibers (SM-MCFs), SDM transmissions over field-deployed FM-MCFs in outdoor settings have not been reported. Therefore, concerns remain that environmental interference and cabling stress could worsen inter-core and intra-core modal crosstalk and impact the performance of SDM systems over FM-MCFs. In this paper, we demonstrate successful bidirectional SDM transmission over a 5-km, field-deployed seven ring-core fiber (7-RCF) with a cladding diameter of 178 μm. Our measurements show no significant differences in attenuation and mode coupling compared to pre-cabling conditions, confirming the fiber’s resilience to environmental disturbances and adaptability to cable deployment. Using the field-deployed 7-RCF, bi-directional SDM transmission is implemented, achieving spectral efficiency (SE) of 2×201.6 bit/(s Hz) which sets a new record in field-deployed fiber cables that is a tenfold increase over previous systems. Furthermore, these results were achieved using a small-scale 4×4 multiple-input multiple-output (MIMO) scheme with a time-domain equalization (TDE) tap number not exceeding 15. These results demonstrate the substantial potential of using SDM techniques to significantly enhance SE and expand capacity in practical fiber-optic transmission applications. Space-division multiplexing (SDM) systems based on few-mode multi-core fibers (FM-MCFs) utilize both spatial channels (fiber cores) and modes (optical modes per core) to maximize transmission capacity. Unlike laboratory FM-MCFs or field-deployed single-mode multi-core fibers (SM-MCFs), SDM transmissions over field-deployed FM-MCFs in outdoor settings have not been reported. Therefore, concerns remain that environmental interference and cabling stress could worsen inter-core and intra-core modal crosstalk and impact the performance of SDM systems over FM-MCFs. In this paper, we demonstrate successful bidirectional SDM transmission over a 5-km, field-deployed seven ring-core fiber (7-RCF) with a cladding diameter of 178 μm. Our measurements show no significant differences in attenuation and mode coupling compared to pre-cabling conditions, confirming the fiber’s resilience to environmental disturbances and adaptability to cable deployment. Using the field-deployed 7-RCF, bi-directional SDM transmission is implemented, achieving spectral efficiency (SE) of 2×201.6 bit/(s Hz) which sets a new record in field-deployed fiber cables that is a tenfold increase over previous systems. Furthermore, these results were achieved using a small-scale 4×4 multiple-input multiple-output (MIMO) scheme with a time-domain equalization (TDE) tap number not exceeding 15. These results demonstrate the substantial potential of using SDM techniques to significantly enhance SE and expand capacity in practical fiber-optic transmission applications.
Photonics Research
- Publication Date: Dec. 16, 2024
- Vol. 13, Issue 1, 18 (2025)
Ultra-low loss Rayleigh scattering enhancement via light recycling in fiber cladding
Pengtao Luo, Fengyi Chen, Ruohui Wang, and Xueguang Qiao
Rayleigh backscattering enhancement (RSE) of optical fibers is an effective means to improve the performance of distributed optical fiber sensing. Femtosecond laser direct-writing techniques have been used to modulate the fiber core for RSE. However, in-core modulation loses more transmission light, thus limiting the sensing distance. In this work, a cladding-type RSE (cl-RSE) structure is proposed, where the femtosecond laser is focused in the fiber cladding and an array of scatterers is written parallel to the core. The refractive-index modulation structure redistributes the light in the cladding, and the backward scattered light is recovered, which enhances the Rayleigh backscattered signal with almost no effect on the core light. Experimentally, it was demonstrated that in an effectual cl-RSE structure, the insertion loss was reduced to 0.00001 dB per scatterer, corresponding to the lowest value for a point scatterer to date. The cl-RSE structure accomplished measurements up to 800°C. In particular, the temperature measurement fluctuation of the cl-RSE fiber portion is only 0.00273°C after annealing. These results show that the cl-RSE structure has effective scattering enhancement, ultra-low loss, and excellent high-temperature characteristics, and has great potential for application in Rayleigh scattering-enhanced distributed fiber sensing. Rayleigh backscattering enhancement (RSE) of optical fibers is an effective means to improve the performance of distributed optical fiber sensing. Femtosecond laser direct-writing techniques have been used to modulate the fiber core for RSE. However, in-core modulation loses more transmission light, thus limiting the sensing distance. In this work, a cladding-type RSE (cl-RSE) structure is proposed, where the femtosecond laser is focused in the fiber cladding and an array of scatterers is written parallel to the core. The refractive-index modulation structure redistributes the light in the cladding, and the backward scattered light is recovered, which enhances the Rayleigh backscattered signal with almost no effect on the core light. Experimentally, it was demonstrated that in an effectual cl-RSE structure, the insertion loss was reduced to 0.00001 dB per scatterer, corresponding to the lowest value for a point scatterer to date. The cl-RSE structure accomplished measurements up to 800°C. In particular, the temperature measurement fluctuation of the cl-RSE fiber portion is only 0.00273°C after annealing. These results show that the cl-RSE structure has effective scattering enhancement, ultra-low loss, and excellent high-temperature characteristics, and has great potential for application in Rayleigh scattering-enhanced distributed fiber sensing.
Photonics Research
- Publication Date: Aug. 01, 2024
- Vol. 12, Issue 8, 1813 (2024)
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