image: Figure. 1 An all-fiber EP-enhanced bending sensor.
Credit: OEA
A new publication from Opto-Electronic Advances, 10.29026/oea.2023.230019 discusses exceptional-point-enhanced sensitivity – a new paradigm for high-sensitivity fiber sensors.
The sensitivity of a fiber sensor can be enhanced severalfold using an exceptional point (EP), according to a recent paper published in OEA. The technique has the potential to transform fiber sensing technology toward a new era of precision and accuracy. While the researchers demonstrated this remarkable capability using a bending sensor, the true power of EP-enhanced sensitivity extends far beyond, with potential applications across various existing fiber sensors.
The foundation of this innovation is a carefully designed fiber-optic bending sensor, leveraging the EP concept to achieve extraordinary sensitivity. The sensor consists of two specialized Fabry-Perot (FP) resonators, each embedded with two fiber Bragg gratings (FBGs) inscribed in an erbium-ytterbium co-doped fiber (EYDF). By controlling the pumping power, the gain and loss of these resonators are precisely tuned to activate the sensitivity enhancement by operating the sensor near its exceptional point.
Once a bending force is applied to the sensor, its operation moves away from the exceptional point, leading to a distinctive frequency-splitting phenomenon. This unique frequency response enables the sensor to detect the slightest bend or curve with high sensitivity and precision.
To realize the full potential of this EP-enhanced sensitivity, the researchers devised a dual-passband microwave-photonic filter, converting the optical spectral response of sensor to the microwave domain. This clever integration allows for high-speed and high-resolution measurements, unleashing the full power of EP-enhanced sensing.
Through rigorous experimental evaluations, the EP-enhanced sensor showcased remarkable results. With a curvature sensing range from 0.28 to 2.74 m-1, it achieved an accuracy of 7.56 × 10-4 m-1 and an exceptionally high sensitivity of 1.32 GHz/m-1. These extraordinary outcomes surpassed previous fiber sensor capabilities, demonstrating the notable potential of EP-enhanced sensitivity.
The discovery of EP-enhanced sensitivity represents a paradigm shift in fiber sensing. Beyond the bending sensor application, this powerful technique can be easily deployed in many existing fiber sensors for elevated precision.
The authors of this article introduce an exceptional-point-enhanced bending sensor within an all-fiber optic structure. The study has achieved noteworthy results through careful design and experimental validation of the sensor.
The key innovation lies in utilizing the unique properties of EPs in optical fibers to achieve highly sensitive detection of bending forces near a specific point. When an external bending force is applied, the optical modes at the EP undergo splitting, resulting in a frequency splitting phenomenon. This phenomenon provides valuable information about the external bending force, enabling precise measurements.
In contrast to conventional linear sensors, the EP-enhanced sensor exhibits a nonlinear response near the EP, leading to significantly increased sensitivity. Additionally, to achieve high-speed and high-resolution sensor measurements, microwave photonics technique is employed, to translate the optical spectral response of the sensor to the microwave domain, enabling high-resolution measurements with enhanced overall performance.
This fiber optic sensing technology offers a cost-effective solution to improve the sensitivity of traditional Hermitian fiber optic sensors. The versatility of the technique allows for its application to various existing FBG sensors, making it easier to implement in scenarios where high sensitivity is required.
The ability of the EP-point-enhanced bending sensor to detect weak signals makes it extremely useful for safeguarding critical infrastructures, especially at the initial stages of safety accidents, such as tunnels, bridges, and nuclear power plants. Early warnings enabled by this sensor can mitigate economic and human losses, providing significant societal benefits.
In conclusion, this research represents a notable contribution to fiber optic sensing. The unique capabilities of the EP-enhanced bending sensor enhance precision and sensitivity in a cost-effective manner, making it a promising advancement in the field. The potential to apply this technology to existing fiber optic sensors and its application in safeguarding critical infrastructures signify the far-reaching impact it can have on safety and innovation in various industries. This work sets the stage for further advancements in fiber optic sensing, opening new possibilities for high-sensitivity measurements with implications for broader practical applications.
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The Microwave Photonics Group at Jinan University is at the forefront of an interdisciplinary field that explores the fascinating interaction between microwave and optical signals, focusing on applications such as telecommunications, radar, sensing, and instrumentation. As these applications demand ever-increasing speed, bandwidth, and dynamic range, there is a growing need for innovative solutions. Modern photonics, with its unique capabilities for processing ultra-wideband, high-frequency signals, emerges as a promising alternative to traditional digital electronics, which faces limitations in speed due to electronic sampling rates.
The MWP group themes encompass a wide array of cutting-edge topics, including optical signal processing, integrated photonics, fiber Bragg gratings, and microwave photonics sensors. The group has done several pioneer works in microwave signal generation, non-Hermitian photonics and sensing technologies, such as the first implementation of non-Hermitian photonic phenomena in an FBG platform, the induction of the photonic synthetic dimension in a microwave photonic system, and the realization of a truly programmable arbitrary waveform generator beyond the TSa/s. These diverse areas of exploration highlight the laboratory's commitment to pushing the boundaries of knowledge and technological capabilities.
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Opto-Electronic Advances (OEA) is a high-impact, open access, peer reviewed monthly SCI journal with an impact factor of 14.1 (Journal Citation Reports for IF2022). OEA is indexed in SCI, EI, DOAJ, Scopus, CA and ICI databases.
The journal is published by The Institute of Optics and Electronics, Chinese Academy of Sciences, aiming at providing a platform for researchers, academicians, professionals, practitioners, and students to impart and share knowledge in the form of high quality empirical and theoretical research papers covering the topics of optics, photonics and optoelectronics.
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Li Z, Chen JX, Li LZ, Zhang JJ, Yao JP. Exceptional-point-enhanced sensing in an all-fiber bending sensor. Opto-Electron Adv 6, 230019 (2023). doi: 10.29026/oea.2023.230019
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