A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction, which can be seen as a kind of quasi-nondiffracting beam (Q-NDB). Due to its wide applications, recently, numerous researchers have used optical lenses or on-chip integrated optical diffractive elements to generate this kind of beam. We theoretically verify and experimentally demonstrate an all-fiber solution to generate a subwavelength inverted pin beam by integrating a simple plasma structure on the fiber end surface. The output beams generated by two kinds of plasma structures, i.e., nanoring slot and nanopetal structure, are investigated and measured experimentally. The results show that both the structures are capable of generating subwavelength beams, and the beam generated using the nanopetal structure has the sidelobe suppression ability along the x-axis direction. Our all-fiber device can be flexibly inserted into liquid environments such as cell cultures, blood, and biological tissue fluids to illuminate or stimulate biological cells and molecules in them. It provides a promising fiber-integrated solution for exploring light–matter interaction with subwavelength resolution in the field of biological research.

为了制备高质量螺旋光纤器件，提出一种四电极电弧光纤加热的方法。基于磁流体动力学模型建立四电极电弧等离子放电的有限元仿真模型，研究了电极夹角、电极距离与施加电压对电弧放电温度场的影响。根据实际情况，进行了相应的温度场仿真计算，结果表明四电极电弧放电形成了较宽的恒温区，宽恒温区不仅有利于光纤应力的释放，同时减少了光纤偏移带来的影响。基于仿真结果，研制了四电极电弧放电的宽恒温区等离子热熔扭转加工系统，当系统中被加热光纤最高温度约为1 050 ℃时，被加热光纤轴向上的恒温区长度约为2.12 mm。用研制的系统制备了不同光纤与不同周期下的螺旋长周期光纤光栅，在波长1.21~1.3 µm，透射光谱的光强波动小于1 dB，光强平均值大于-1 dB；在波长1.3~1.35 µm，光强平均值大于-1 dB；最深的透射光谱波谷大于22 dB。为更进一步验证所研系统的性能，用单模光纤、偏芯光纤、偏双芯光纤制备了不同周期的螺旋光纤结构，结果显示加工得到的螺旋光纤结构的包层边界清晰且平直，无显著的螺纹结构；光纤中央芯无显著的螺旋加工痕迹；光纤偏芯光滑且连续。

为了实现对多芯光纤在光网络系统中的接续并评价连接效果，给出了一种多芯光纤活动连接器的制备方法，用光学连续波反射计和光学低相干反射计分别构建了多芯光纤活动连接器插入损耗和回波损耗测量系统。详细地分析了外在因素和端面质量对多芯光纤活动连接器插入损耗和回波损耗的影响，提出了多芯光纤活动连接器制备和对接时需要满足的三项质量控制条件：精准对芯、物理接触和不相对转动。所制备的多芯光纤活动连接器具有标准的LC型接口，采用三维轮廓仪对多芯光纤活动连接器端面的三维参数（顶点偏移、曲率半径和光纤凹凸度）以及粗糙度进行了表征。用构建的测量系统测得制备的四芯光纤活动连接器中所有纤芯通道实现了平均0.089 dB的低插入损耗和52.31 dB的高回波损耗。为多芯光纤活动连接器走向实际应用提供了制备方法和性能评价方案。

Vector bending sensing has been consistently growing in many fields. A low-cost and high sensitivity vector bending sensor based on a chirped long-period fiber grating (LPFG) with an off-axis micro helix taper is proposed and experimentally demonstrated. The grating is composed of several sections of single-mode fiber with gradually larger lengths, and the off-axis micro helix tapers with fixed lengths when they are fabricated by using the arc discharge technology. The large refractive index modulation in the micro-helix taper greatly reduces the sensor size. The total length of the sensor is only 4.67 mm. The micro-helix taper-based LPFG can identify the bending direction due to the asymmetric structure introduced by the micro helix. The experimental results show that the transmission spectra of the sensor have distinct responses for different bending directions, and the maximum bending sensitivity is 14.08 nm/m^-1 in the range from 0.128 m^-1 to 1.28 m^-1. The proposed bending sensor possesses pronounced advantages, such as high sensitivity, small size, low cost, and orientation identification, and offers a very promising method for bend measurement.

We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber (MHSTM). Sensors with different taper waists and helical pitches are fabricated, and their transmission spectra are obtained and analyzed. The waist and length of the sandwiched seven-core fiber are finally determined to be 68 µm and 3 mm, respectively. The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and -1.123 nm/(rad/m), respectively. When tapered waist diameter reduces to 48 µm, a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0–4.24 nm/(rad/m) is obtained, which is 46 times as large as the traditional helical seven-core fiber structure. In addition, the MHSTM structure is also relatively stable to temperature variations.

The typical functions of the optical fiber are communication and sensing. However, the fiber functions need to extend to meet the requirements of the development of artificial intelligence. This paper achieves an all-fiber device with storage and logic computing functions using a single-mode fiber and Ge2Sb2Te5 (GST) material. We use the pulse amplitude modulation (the switching energy is about 50 nJ) to switch the GST state for performing the eight-level data storage (3-bit). The all-fiber memory device has the advantages of high optical contrast (about 38%), good reversibility, and high repeatability. We implement the all-optical logic operations (“AND” and “OR”) by using two memory cells in series and parallel. For the first time, we use the single-mode optical fiber to realize storage and computing functions, and this intelligent fiber has tremendous application potential in intelligent optical fiber communication and portends a new paradigm for brain-like computing.