Fine⁃Diameter Polarization⁃Maintaining Photonic Crystal Fiber for High Precision Miniaturized Fiber⁃Optic Gyro

Objective The fiber optic gyroscope (FOG) is a high-precision angular velocity sensor that serves as a key sensing component in modern high-accuracy inertial measurement technology. Currently, achieving high precision, miniaturization, and high environmental stability are the major challenges that hinder the development of FOGs for application in aerospace, satellite, strategic missile, and other inertial navigation systems. Fine-diameter polarization-maintaining photonic crystal fibers offer an opportunity for FOGs to break through the bottleneck of achieving high precision, miniaturization, and high environmental stability. Oriented to the urgent demand of high-precision miniaturized FOG, a fine-diameter polarization-maintaining photonic crystal fiber, with an 80 mu m cladding diameter, is designed and successfully manufactured. Methods The performance of dual-large-hole polarization-maintaining photonic crystal fibers (PM PCFs), with a cladding outer diameter of 80 mu m, was optimized using the finite-element method combined with a perfectly matched layer. Based on the optimal result, an optimal fine-diameter dual-large-hole PM PCF was designed. Then, a stack-and-draw method was employed to manufacture two types of working samples of dual-large-hole PM PCFs with imported and domestic pure silica tubes. The cut-back method and Sagnac interferometry were employed to test the loss and birefringence characteristics of the fiber sample. To validate its application in miniaturized FOG, the sample ' s bending characteristic was measured by bending it around cylinders with diameters of 5 mm and 16 mm. The temperature stability of birefringence, shown by the fiber sample, was evaluated within the temperature range from-40 degrees C to 60 degrees C by placing the test fiber in a temperature chamber. Finally, the performances of the two types of dual-large-hole PM PCFs, fabricated with imported and domestic pure silica tubes, were compared. Results and Discussions Experimental results demonstrate that the fiber exhibits a low loss of 1.13 dB/km and high birefringence of 5.5x10(-4) at 1550 nm (Fig. 4 and 5). Its birefringence temperature coefficient reaches 5x10(-8) degrees C-1 from -40 degrees C to 60 degrees C, and the low loss of 1.2 dB/km can be maintained at a bending radius of 16 mm (Fig. 6 and 8). This result demonstrates that the fabricated fiber can be utilized to develop high-precision miniaturized FOG owing to its small diameter, high birefringence, excellent temperature stability, and high bending performance. To promote the domestic development of high-precision FOG, a comparative study of optical fibers manufactured using imported and domestic pure silica tubes is performed. Fig. 9 demonstrates significant performance difference between the fibers fabricated with imported and domestic pure silica tubes. At a wavelength of 1550 nm, the fiber fabricated using imported tubes exhibits a transmission loss of 1.13 dB/km, whereas the domestic fiber shows a markedly high transmission loss of 7.36 dB/km. In addition, while both fibers display pronounced hydroxyl (OH?) absorption peaks at 1390 nm, the domestical fiber undergoes extreme degradation with a loss of 206.06 dB/km, which is 6.3 times higher than that of the imported fiber. Furthermore, in the wavelength range of 1400?1700 nm, the birefringence shown by the domestic fiber is relatively lower than that exhibited by the imported fiber. However, both fibers maintain birefringence magnitudes of the order of 10(-4), thus showing a good polarization-maintaining performance. Conclusions In this study, fine-diameter PM PCFs, exhibiting low losses, high birefringence, excellent temperature stability, and high bending performances, have been designed and successfully fabricated. These good optical performances confirm the feasibility of applying the fabricated fibers in high-precision miniaturized FOG. Simultaneously, the loss of the fiber prepared using the domestic pure silica tube at a wavelength of 1550 nm is higher than that of the fiber manufactured using the imported pure silica tube. This result is mainly attributed to the influence of the purity and geometrical accuracy of the domestic pure silica tubes, highlighting the manufacturing process of domestic pure silica tubes as a possible direction for improvement.