Polarization-maintaining Photonic Crystal Fiber Research Articles

Temperature insensitive distributed wide-dynamic-range strain sensing based on polarization-maintaining photonic crystal fiber

In this paper, a temperature insensitive wide-dynamic-range distributed strain sensor with centimeter-level spatial resolution based on optical frequency domain reflection technology is proposed. It adopts a polarization-maintaining photonic crystal fiber as the sensing fiber, and experimental results demonstrate that its temperature sensitivity is much smaller than that of the standard polarization-maintaining fiber. Benefited from the specially designed cross-correlation algorithm, the sensor achieves the maximum measurable strain reaches 7000 μϵ with spatial resolution of 1.66 cm. This provides a new approach to address current issues with special fiber sensors, such as single-point sensing and low spatial resolution, which shows great significance for structural health monitoring of buildings, bridges and tunnels with urgent requirement of large dynamic range.

High sensitivity I-beam shaped polarization related vector curvature sensor with optical intensity modulation

This paper presents an innovative I-beam optical sensor combining Panda-type polarization-maintaining fiber (PMF) and thin-width polarization-maintaining photonic crystal fiber (PM-PCF), crafted using precision machining techniques like tapering and axially offset splicing. The study explores the impact of structural parameters on the device's optical performance using polarization mode coupling theory and assesses its effectiveness in vector curvature sensing, focusing on intensity sensitivity. A novel dual-parameter differential demodulation technique is proposed, achieving accurate bending angle measurements (error < 2°) through wavelength and intensity-curvature sensitivities. The experimental results highlight the device's impressive maximum intensity-curvature response of 9.36 dB/m−1. With notable responsiveness, low cross-talk, and robust polarization stability, this device holds substantial promise in the realms of fiber lasers and optical communications, serving as an ideal polarization-based, mechanically tunable optical device. Furthermore, it introduces innovative concepts and offers technological support for precision instrument measurements and related fields.

High Extinction-Ratio and Near-Zero Dispersion Chalcogenide Polarization Maintaining Photonic Crystal Fibers in Mid-Infrared

High Extinction-Ratio and Near-Zero Dispersion Chalcogenide Polarization Maintaining Photonic Crystal Fibers in Mid-Infrared

Polarization-maintaining photonic crystal fiber with high Brillouin gain coefficient for Brillouin lasers.

Stimulated Brillouin scattering (SBS) is effective for realizing a laser with an ultra-narrow linewidth. Although photonic crystal fiber (PCF) is considered an excellent medium to achieve SBS, it does not meet the requirements of low loss, large birefringence, and ease of fabrication. We propose a polarization-maintaining PCF (PM-PCF) structure and theoretically analyze the effects of the geometric structural parameters of the PM-PCF on various optical properties. Our theoretical analysis and experimental results contribute to the advancement of the field of ultra-narrow linewidth fiber lasers, distributed fiber sensing, and fiber-optic gyroscopes related to SBS.

Ultra-high sensitivity methane gas sensor based on vernier effect in double D-shaped and cryptophane-A film-coated photonic crystal fiber: Design and FEM simulation

Utilization of the vernier effect in fiber optic interferometers represents the latest approach to enhance the sensitivity and resolution in fiber optic sensors. In this paper, the Vernier effect in Sagnac interference (SI) with a double D-shaped photonic crystal fiber (PCF) was proposed for the methane gas sensing. The sensing arm in the SI was composed of a double D-shaped PCF which was coated with cryptophane-A film, while the polarization maintaining photonic crystal fiber (PM-PCF) is used as the reference arm. The sensing arm and the reference arm were cascaded in parallel to generate the Vernier effect. The influence of the structural parameters in the PCF on the sensing performance was analyzed using the finite element method. The sensing fiber uses a double-D structure, so methane gas is more easily in contact with the sensitive film. According to the simulation results, the wavelength sensitivity of the parallel Sagnac loops within the methane gas concentration range of 0–3.5% is as high as 170.58 nm/%, which is 3.14 times that of a single Sagnac loop. The proposed sensor exhibits a significant enhancement in sensitivity compared to the other fiber optic-based methane gas sensors, thereby providing a reference sample for the development of high-sensitivity methane gas sensors.

Radiation-Induced Magneto-Optic Fluctuations in Spaceborne Fiber-Optic Gyroscope

Radiation-induced magneto-optic fluctuations (RI-MOF) is a kind of environmental compounding effect of fiber optic gyroscope (FOG) in space application. Here, we suggested a model of RI-MOF and experimentally tested it in irradiated polarization-maintaining fibers (PMFs) and polarization-maintaining photonic crystal fibers (PM-PCFs). The test results reveal that the main sources of RI-MOF are the radiation-induced change of the Verdet constant and the modal birefringence. In a spacecraft with good thermal control conditions, an evaluation method based on the RI-MOF model can be summarized and implemented to suppress the environmental disturbance on the performance of FOG.

Polarization-maintaining photonic crystal fiber with high Brillouin gain coefficient for Brillouin lasers

Polarization-maintaining photonic crystal fiber with high Brillouin gain coefficient for Brillouin lasers

A Method for Suppressing Error of Fiber Optic Current Transformer Caused by Temperature Based on λ/4 Wave Plate Fabricated With Polarization-Maintaining Photonic Crystal Fiber

The beat length of λ/4 wave plate of fiber optic current transformer (FOCT) will change with the temperature fluctuation of environment, which will result in additional phase error, reducing the accuracy of current measurement. In the paper, we presented a FOCT based on λ/4 wave plate fabricated with polarization maintaining photonic crystal fiber (PCF). Combined with error model caused by λ/4 wave plate in FOCT, we analyzed the specific mechanism of temperature influence on λ/4 wave plate. Aiming at the problem of fusing PCF to panda polarization maintaining fiber, we optimized the related parameters of fiber fusion splicer to reduce the fusion loss of the fiber. It was experimentally verified that the beat length of PCF is less sensitive to temperature than that to elliptical core polarization maintaining fiber. Finally, we measured current of FOCT utilizing two kinds of λ/4 wave plates in full temperature range from -40 °C to 70 °C. It was verified that it is insensitive to temperature for FOCT when utilizing PCF λ/4 wave plate, with the corresponding system current measurement accuracy 0.5S level.

An impact-insensitive fiber optic current transformer based on polarization maintaining photonic crystal fiber delay coil

When the polarization-maintaining fiber (PMF) delay coil of a fiber optic current transformer (FOCT) is impacted, external forces on the optical fibers and change of their birefringence may lead to extra phase errors during the propagation of optical signals in the fibers. These errors increase the error in current measurement. In the paper, the environmental impact mechanisms influencing the PMF delay coil of FOCT were investigated with a mathematical error model. The method of replacing PMF with a polarization-maintaining photonic crystal fiber (PCF) as the delay coil was proposed. Also, the relationship between structural parameters of air holes and linear birefringence of the polarization maintaining PCF subjected to stress was investigated. The structural parameters of optical fibers were also optimized subsequently. Simulated impact experiments of FOCT with polarization-maintaining PCF and PMF as the delay coil, respectively, demonstrated the effective impact resistance of FOCT with polarization-maintaining PCF delay coil after the optimization of its structural parameters. The current measurement errors of the FOCTs with polarization maintaining PCF delay coil reduced by approximately 35% with respect to the FOCT with PMF delay coil.

An ultra-high sensitivity methane gas sensor based on Vernier effect in two parallel optical fiber Sagnac loops

Methane gas sensing has attracted great interest for its applications in agriculture production, industrial manufacturing, medical diagnosis, and environmental monitoring. In this paper, we proposed an ultra-high sensitivity methane gas sensor based on Vernier effect in two parallel optical fiber Sagnac loops. The reference arm contained a polarization maintaining photonic crystal fiber (PM-PCF), while sensing arm consists of a methane gas sensitive film coated PM-PCF. Vernier effect (VE) was generated and as a result the sensitivity was improved by multiple times. The finite element method (FEM) was used to assess the methane gas sensor’s sensing capabilities. According to the numerical simulation, the average sensitivity based on two parallel Sagnac loops in the methane gas concentration of 0-3.5% was 197.775 nm/%, which was 5.5 times in contrast to a single Sagnac loop. To our best knowledge, we presented the methane gas sensor based on VE in two parallel optical fiber Sagnac loops for the first time. The designed optical fiber methane gas sensor possessed the merits of ultra-high sensitivity, providing helpful guidelines for the fabrication of high-performance methane gas sensors.

High Extinction Ratio and Low Temperature Cross-Sensitivity Strain Sensor Based on Vernier Effect Through Hybrid Cascaded Sagnac Loop

Low extinction ratio (ER) and high temperature cross-sensitivity are serious but common problems for most strain sensors based on Vernier effect. In our work, we propose a strain sensor based on Vernier effect. It consists of hybrid cascaded Sagnac loop, one part is a microfiber coupler Sagnac loop (MFC–SL), and the other is a Sagnac loop connected to a Section of polarization-maintaining photonic crystal fiber (PMPCF–SL). Different from the traditional Vernier effect, in the proposed sensor, the spectra of two interferometers shift to opposite directions when the strain changes, which belongs to the enhanced Vernier effect. When ambient temperature varies, the spectra of the two interferometers shift to the same direction, which belongs to the reduced Vernier effect. Thus, its strain sensitivity is improved and its temperature cross sensitivity is reduced. In addition, the MFC–SL and PMPCF–SL exhibit a high fringe ER due to their good transmission of two orthogonal modes. Experimental show that the sensitivity of strain is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 124.17\,\,\text {pm}/\mu \varepsilon $ </tex-math></inline-formula> , while the temperature sensitivity is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.13~\text {pm}/^{\circ }\text{C}$ </tex-math></inline-formula> , and the ER of envelope is about 9 dB. Its robustness can be enhanced by the method of packaging with silicone adhesive. It will have a potential application in the field of strain sensing.

Temperature and Strain Sensing Characteristics of Polarization-Maintaining Photonic Crystal Fiber Based on Sagnac Interference

Temperature and Strain Sensing Characteristics of Polarization-Maintaining Photonic Crystal Fiber Based on Sagnac Interference

Sagnac Interferometric Temperature Sensor Based on Boron-Doped Polarization-Maintaining Photonic Crystal Fibers

A sensitive temperature sensor was demonstrated using boron-doped polarization-maintaining photonic crystal fiber (PM-PCF) as a Sagnac interferometer (SI). This boron-doped PM-PCF combines both the geometric birefringence introduced by the PCF structure design and the stress birefringence introduced by the boron-doped stress-applying parts. However, we found that the stress birefringence dominates the total birefringence of the sensor by numerical analysis. In the experiments, the fabricated sensor exhibited the highest temperature sensitivity of −1.83 nm/°C within the wide temperature range of 28~76 °C. The temperature sensitivity was mainly derived from the stress birefringence of boron-doped PM-PCF SI. These findings provide some support for the designation of high-precision temperature sensors.

Wavelength-switchable dual-wavelength thulium-doped fiber laser utilizing photonic crystal fiber

A dual-wavelength thulium-doped fiber laser with a wide switchable single-wavelength range is demonstrated by employing a polarization-maintaining photonic crystal fiber. A new type of comb filter is designed and its spectrum is simulated. A nonlinear polarization rotation module is inserted into the laser cavity to suppress intense gain competition. An output power instability as low as 0.84 dB has been attained. The switchable range of single-wavelength operation is 43.64 nm, and the slope efficiency is 1.79%, attained by optimizing the splicer parameter between the polarization-maintaining photonic crystal fiber and the single-mode fiber. There are five regions of dual-wavelength output from 1978.04 to 1986.51 nm, and the maximum and minimum wavelength intervals are 6.11 nm and 1.9 nm.

Tunable and interval-adjustable multiwavelength Erbium-doped fiber laser based on a compound filter

We propose and experimentally demonstrate a multiwavelength erbium-doped fiber laser (EDFL) based on a compound filter. The compound filter is composed of polarization controllers (PCs), polarizers and a piece of home-made polarization-maintaining photonic crystal fiber (PM-PCF). Due to the high birefringence and few-mode properties of the PM-PCF, Lyot filter and multimode interference filter can be realized simultaneously in the compact structure. Hence, the EDFL can achieve flexible lasing output. By adjusting PCs, the lasing can obtain single-, dual-, triple- and quad-wavelength output, respectively. The tuning range of single-wavelength lasing output can exceed 20 nm with side-mode suppression ratio (SMSR) above 40 dB. For dual-wavelength lasing output, the tuning range with fixed interval can reach 16 nm. Besides, the wavelength interval can be adjusted from 2.5 nm to 17.4 nm. The great interval adjustability is also observed in triple-wavelength output. The wavelength interval can be adjusted from 8.2 nm to 14.7 nm. Compact structure, flexible lasing output, and good stability make our proposed EDFL more convenient and practical to the applications such as sensing and wavelength division multiplexing.

Noise in supercontinuum generated using PM and non-PM tellurite glass all-normal dispersion fibers.

Intensity fluctuations in supercontinuum generation are studied in polarization-maintaining (PM) and non-PM all-normal dispersion tellurite photonic crystal fibers. Dispersive Fourier transformation is used to resolve the shot-to-shot spectra generated using 225-fs pump pulses at 1.55 μm, with experimental results well reproduced by vector and scalar numerical simulations. By comparing the relative intensity noise for the PM and non-PM cases, supported by simulations, we demonstrate the advantage of the polarization-maintaining property of the PM fibers in preserving low-noise dynamics. We associate the low-noise in the PM case with the suppression of polarization modulation instability.

Non-centrosymmetric solid core photonic crystal fiber for suppressing parasitic twist in fiber sensing coil

During the fabrication of fiber sensing coils, the parasitic twist of fibers would lead to the undesired elliptical birefringence in the fiber, which is the main cause of magnetically induced bias error for fiber optic gyroscope(FOG). For the purpose of suppressing the parasitic twist in the fiber coil, a polarization-maintaining solid core photonic crystal fiber (PCF) with non-centrosymmetric distribution of bending stiffness is proposed and investigated. The proposed PCF would bend towards a particular direction under the external forces, resulting in the consistency of birefringent axes arrangement, thus suppressing the nonreciprocal errors induced by both radial and axial components of the magentic field simultaneously. Dependence study of the fiber bending stiffness distribution on several key parameters is provided. The optical properties are also explored and compared with the previously studied PCF. Fiber coils fabricated with the proposed PCF are promising in reducing the magnetical sensitivity of FOG, thus making it possible for FOG to get rid of the thick magnetic shield, which is significant for the miniaturization of FOG.

Advances in Silica-Based Large Mode Area and Polarization-Maintaining Photonic Crystal Fiber Research.

In recent years, photonic crystal fibers (PCFs) have attracted increasing attention. Compared with traditional optical fibers, PCFs exhibit many unique optical properties and superior performance due to their high degree of structural design freedom. Using large-mode area (LMA) fibers with single-mode operation is essential to overcoming emerging problems as the power of fiber lasers scales up, which can effectively reduce the power density and mitigate the influence of nonlinear effects. With a brief introduction of the concept, classification, light transmission mechanism, basic properties, and theoretical analysis methods of PCFs, this paper mainly compiles the worldwide development of large-mode area and polarization-maintaining (PM) PCFs, and finally proposes possible technical routes to realize the single-mode operation of LMA-PCFs and PM-LMA-PCFs. Finally, the future development prospects of the PCFs are discussed.

PM-PCF birefringence distribution measurement over a wide wavelength range based on SSFS and LSSI.

A linear self-reference spectral interferometry has been proposed to measure the distribution of polarization-maintaining photonic crystal fiber (PM-PCF) birefringence over a wide wavelength range combined with the soliton self-frequency shift and birefringence effect. The birefringence of PM-PCF is measured experimentally over the range of 800-970 nm, which is larger than 5×10-4 and shows a segmented change trend. The air micropore structure has a significant effect on the characteristics of PM-PCF, which makes it have a highly nonlinear coefficient, and at the same time, changes the dispersion and birefringence distributions of the PM-PCF. The distribution of PM-PCF birefringence, measured by experiment, provides a new dimension for the design of PM-PCF, which is helpful for a detailed fiber model and an iterative optimization of fiber structure.

Highly sensitive strain sensing using a polarization-maintaining photonic crystal fibre based Mach–Zehnder interferometer

A novel all-fibre highly sensitive strain sensor based on polarization-maintaining photonic crystal fibre (PMPCF) is proposed and demonstrated experimentally. The sensing structure is formed by splicing a segment of PMPCF between two segments of thin core fibres (TCFs). Since the responses of the resonance dips induced by different order cladding modes interference with core mode are different, the strain sensitivity can be obtained by monitoring the shifts of the resonance dips. The experimental results show that the sensitivity of strain of the MZI is 4.03 pm/µϵ within the strain range from 0 µϵ to 1600 µϵ, respectively. And the temperature characteristics are also researched. This type of sensor has outstanding advantages of convenient manufacture, high-cost efficiency and insensitivity to temperature, so it has potential application prospects in physical, biological and chemical sensing.