Recent progress in designing optimized microstructured optical fiber spreads an application scenario of optical fiber sensing. Here, we investigate the bending measurement based on a specially designed hollow core photonic crystal fiber (HC-PCF). Numerical simulation indicates that the bending sensitivity is mainly determined by the diameter of the hollow core and also depends on the coupled modes. Experimentally, a direction-independent bending sensor is fabricated by sandwiching a segment of specially designed HC-PCF into two segments of single mode fibers. The bending sensitivity of our device is improved 10 times by increasing the diameter of the hollow core. Bending measurement is validated at two orthogonal planes. The maximum sensitivity up to 2.8 nm/deg is obtained at 14° bending angle. Additionally, a low thermal sensitivity of 2.5 pm/°C is observed from 18°C to 1000°C. The sensor is robust, easy to fabricate and cost effective, which is promising in the field of small-angle bending measurement under a large temperature range.

A helical Yb³⁺-doped three-core microstructure fiber (YTMF) amplifier is proposed in this paper, so as to solve the problem of generation and transmission of the orbital angular momentum (OAM) beams. The fiber is composed of three Yb³⁺-doped cores with a regular triangle shape and a longitudinal helical structure. The experimental results show that the 1064nm laser can be amplified due to the fluorescence amplification characteristics of the doped material Yb³⁺. Furthermore, theoretical analysis indicates the modes in YTMF at 1064nm, which is located in the amplified wavelength, can support nine modes carrying OAM. Therefore, the related experiments were performed and verified that the transmission modes can respectively carry 1, 2, and 3-order OAM at 1064nm in different coupling cases. These excellent properties indicate that the combination of doped materials and helical fiber provide favorable conditions for the generation and amplification of OAM, which provides a basis for the further development of OAM beams in the field of quantum communication and dense space division multiplexing.

With the development of laser technology, microstructured optical fibers (MOFs) have become an important part of ultrafast optics, providing excellent platforms for ultrafast laser pulse generation, amplification, and compression, promoting the development of fiber laser systems to generate high power, high pulse energy, and few-cycle duration pulses. MOFs extend the ultrafast laser spectrum to the vacuum ultraviolet (VUV) and even extreme ultraviolet (EUV) regions based on dispersive wave emission and high harmonic generation, as well as to the mid-infrared region based on soliton self-frequency shift (SSFS), contributing compact and low-cost light sources for precision microscopy and spectroscopy. In this paper, first several common types of MOFs are introduced, then the various applications of MOFs in ultrafast optics are discussed, mainly focusing on the aspects of ultrafast laser pulse scaling in pulse energy and spectral bandwidth, and finally the possible prospects of MOFs are given.

Temperature monitoring plays a key role in the kinetics of chemical reaction. In this paper, a sensitive dynamic temperature monitoring sensor based on the rhodamine6G (R6g) film coated anti-resonance fiber (ARF) is proposed. Because of the high thermo-dependent fluorescence intensity of R6g, the ARF coated with R6g film is highly sensitive to the temperature variation, forming the basis of our proposed temperature sensor application. To enhance the temperature monitoring performance and strengthen the florescence intensity, one of the ARF ends spliced a silica ball for reflecting the input signal, and the other end is inserted with two tapered multimode fiber (MMF), acting as bridges for the input of pump light and the output of signal light, respectively. The dual-peak reached the temperature resolution of 3.946×10-2 °C and 3.991×10-3 °C with linearity of 0.99914 and 0.99953 respectively. The experiment results show that the output fluorescence and pump light intensity decrease with the increasing temperature. These excellent characteristics demonstrate a highly sensitive dual-peak sensor for temperature calibration with wide potential applications, such as environmental monitoring, mine monitoring and other fields of chemical kinetics.

With the development of the volume of information exchange and perception increases, the demands for intelligent, miniaturized and integrated optical devices for information acquisition are also increasing. In the meanwhile, different from the traditional optical fibers as optical nerves, microstructured optical fibers (MOFs) give new vitality to optical functional devices due to its flexible structure and controllable optical properties. Due to the diversified air-hole structure, various functional materials can be introduced into the cladding of MOF to realize optical signal shaping, external mechanical field or biochemical sensing in different environments. Besides, various modifiable structural properties of MOF are also important in functional applications. Recently, several notable breakthroughs and progresses on promoting the modification methods have been achieved, enabling MOFs with specific functionality and engaging significant applications. In this paper, we briefly summarize different kinds of MOFs, and review the optical characterization and implementation of MOFs based on optical functional devices, crossed by our developments of the metal and twist modification studies of MOF for sensing fields. Moreover, the challenges, prospects and promising opportunities of future functional MOF for sensing applications are also presented.