All-Fiber Electric Field Sensor Based on Organic Electro-Optic Polymer
Objective With the rapid advancement of science and technology,the demand for precise electric field measurements is increasing across fields such as electric power,communication,industrial automation,and biomedicine.In real-world applications,electric field sensors often face complex and variable environmental conditions,including temperature fluctuations and electromagnetic interference.Traditional electric field sensors frequently struggle to meet high-precision measurements,but sensors based on micro-nano tapered two-mode fibers(TTMFs)combined with a disperse red 1/polymethyl methacrylate polymer(DR1/PMMA)offer a promising solution for achieving high-precision measurements.In this paper,we aim to develop and validate a novel all-fiber electric field sensor,leveraging the combination of TTMF's sensitivity and the exceptional electro-optic properties of the DR1/PMMA.The primary objective of this research is to design an electric field sensor with high sensitivity,fast response,low temperature sensitivity,and excellent stability.The TTMF's dual-mode interference effect,paired with its unique geometry,provides high sensitivity.The all-fiber structure simplifies the sensor fabrication process and enables seamless integration with other fiber optic devices,significantly facilitating the construction of complex fiber-optic sensing networks while reducing system integration challenges and costs.When combined with DR1/PMMA,the sensor exhibits significant output signal changes even with minor variations in the electric field,making it highly suitable for high-precision measurement scenarios.In addition,DR1/PMMA's picosecond-level response speed allows the sensor to rapidly detect dynamic electric field changes,providing robust technical support for real-time monitoring and applications with high real-time demands.Unlike traditional liquid crystal(LC)-based electric field sensors,DR1/PMMA-based sensors are largely insensitive to temperature changes,which enhances their stability and reliability in diverse environmental conditions while minimizing measurement errors caused by ambient temperature fluctuations.Methods For the material selection,we choose DR1/PMMA film as the electro-optic material due to its excellent electro-optic effect,allowing its refractive index to vary with the applied voltage.Tapered optical fibers are chosen as the sensing elements due to their low loss,strong evanescent field,miniaturized size,and high sensitivity,making them ideal for constructing highly sensitive sensors.We apply electropolarization to the DR1/PMMA film to enhance its electro-optic coefficient,a critical factor for achieving high electric field sensitivity.The tapered waist region of the TTMF is then integrated onto the surface of the electropolarized DR1/PMMA film,ensuring close contact between the fiber and the film to maximize light-polymer interaction.In the tapered region of the TTMF,modal interference occurs between higher-order modes and the fundamental mode.Since the refractive index of the DR1/PMMA film changes with applied voltage,this causes a modulation of the transmitted light within the fiber,leading to a shift in the interference pattern or a change in light intensity at a specific wavelength.To evaluate the sensor's performance,we construct an experimental setup,integrating the TTMF with the electropolarized DR1/PMMA film,and apply different voltages to observe the optical field modulation effect.Simulation software is also used to model the sensor structure,verifying its working principles and performance characteristics.Results and Discussions In this paper,we propose several key innovations.Firstly,the all-fiber structure design significantly reduces the interference from external electromagnetic coupling,allowing the sensor to maintain high precision in complex electromagnetic environments and enhancing system stability and reliability.Secondly,the compact size of the device facilitates portability and deployment,enabling its use across a broader range of scenarios.The sensor's optical signal modulation capability ensures high-speed signal transmission,shortening response time and enhancing electromagnetic interference resistance.This makes it ideal for capturing electric field changes in environments with strong electromagnetic fields.The sensor's design exhibits excellent sensitivity and low signal distortion,crucial for high-precise applications such as monitoring electric fields in medical equipment or troubleshooting precision electronics.Structurally,the sensor is straightforward and easy to fabricate,reducing production costs and simplifying maintenance.Notably,the use of DR1/PMMA,an organic electro-optic polymer,provides both ease of processing and molding,along with a high electro-optic coefficient,forming a solid material foundation for high-sensitivity sensing.In addition,the innovative use of TTMF as the modal interferometer substrate fully exploits the characteristics of tapered fibers,such as low loss,strong evanescent fields,and compact size.The design also strengthens the fiber's mechanical resilience,reducing the risk of damage from external forces and further enhancing the durability and longevity of the sensor.Conclusions In this paper,we propose an innovative all-fiber electric field sensor architecture by integrating a highly sensitive TTMF with a DR1/PMMA electro-optic film.The core of the design is the DR1/PMMA film,which boasts a remarkable electro-optic coefficient of 3.68 pm/V,providing a strong foundation for the sensor's performance.By utilizing the high refractive index sensitivity(8154.76 nm/RIU)of the DR1/PMMA film,we have achieved a sensor design capable of rapid and highly sensitive electric field detection.Experimental validation demonstrates that the sensor's impressive electric field sensitivity of 0.86 dB/V,along with a 3 dB bandwidth of 1.4 kHz,enabling broad signal transmission coverage.In addition,the sensor effectively limits harmonic distortion to less than 2.5%in the AC electric field range of 1 to 5 kHz,ensuring high-fidelity signal transmission.Looking ahead,applying the proposed structure and fabrication methods to other polymers with high electro-optic coefficients opens up new possibilities for creating high-performance fiber-optic electric field sensors.
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