Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings.

Vortex beams have attracted much attention in recent years due to unique features of the phase or polarization singularity in the center part of beams. Various applications have been explored by the vortex beams including optical communication, optical tweezer, etc. Especially, the vortex beams for optical sensing applications have emerged. Compared with the traditional Gaussian beams, the vortex beams enable the optical sensing with the degree of freedom by controlling the spin and orbital phase and polarization. In this review article, we have discussed the theory of polarization and phase vortices, and then summarized the vortex beam generation in optical fiber and their sensing applications. It is hoped that the article can intrigue further research interest and development in fiber vortices for sensing applications.

The radiation-induced photoluminescence (PL) properties of Bi/Al-codoped silica optical fibers were investigated. The Bi/Al-related materials were doped into fiber core via atomic layer deposition. The pristine fiber samples were irradiated with different doses, and its absorption and PL properties were studied. A new absorption peak appeared at approximately 580 nm, and the intensity of absorption peaks is increased with the increasing of radiation doses. When the fiber samples were excited with a 532 nm pump, the intensity of the near infrared fluorescence decreased lightly. However, when the fiber samples were excited with a 980 nm pump the intensity of the fluorescence increased significantly with the increase of radiation doses (0-2.0 kGy). The intensity of fluorescence decreased when the radiation doses were increased up to 3.0 kGy. furthermore, the fluorescence intensity of the 1410 nm band increased much more than that the 1150 nm band. In addition, the microstructural characteristics of the Bi/Al-codoped silica optical fibers were analyzed using electron spin resonance (ESR). Many radiation-induced defect centers were present, and the intensity of the ESR signals also increased with the increase of radiation doses. The photoluminescence properties and microstructural characteristics were related in the radiated Bi-related silica optical fibers. A possible underlying mechanism for the radiation-induced photoluminescence enhancement process in the Bi/Al-doped silica fiber is discussed.

Targeting the huge unused bandwidth (BW) of modern telecommunication networks, Bi/Er co-doped silica optical fibers (BEDFs) have been proposed and developed for ultra-broadband, high-gain optical amplifiers covering the 1150–1700 nm wavelength range. Ultrabroadband luminescence has been demonstrated in both BEDFs and bismuth/erbium/ytterbium co-doped optical fibers (BEYDFs) fabricated with the modified chemical vapor deposition (MCVD) and in situ doping techniques. Several novel and sophisticated techniques have been developed for the fabrication and characterization of the new active fibers. For controlling the performance of the active fibers, post-treatment processes using high temperature, γ-radiation, and laser light have been introduced. Although many fundamental scientific and technological issues and challenges still remain, several photonic applications, such as fiber sensing, fiber gratings, fiber amplification, fiber lasers, etc., have already been demonstrated.

Perfect vortex beam has the characteristics of optical orbital angular momentum and is widely studied because of its advantages of a uniform ring profile and fixed radius. However, the current method of generating perfect vortex beam is mainly based on the phase modulation of spatial light modulator. We have proposed and demonstrated the fabrication of polymer-based phase plate to generate the first and higher-order perfect vortex beams by using maskless lithography exposure technique. According to the relationship of the lithographic depth of polymer and grayscale exposure, the phase plates with different topological charges and axicon parameters are fabricated. By using such polymer-based phase plate, the radius and ring width of perfect vortex beams are analyzed theoretically and experimentally. The fabricated phase plate shows high transmittance as well as perfect vortex beam generation with high quality in the bandwidth range from 1460 nm to 1640 nm. The obtained results prove the feasibility of the attempt of polymer to generate perfect vortex beams, showing great potential in the application of highly miniaturized and integrated optical vortex applications.

An opticalfiber vector magnetometer based on a thin-cladding polarization-maintaining fiber (TPMF) long-period fiber grating (LPFG) and magnetic fluid (MF) is proposed and experimentally demonstrated. The non-circular symmetric fiber structure and asymmetric evanescence field distribution of the LPFG induce a vector surrounding refractive index (SRI) response. Based on the magneto-optical properties of the MF nanoparticles and the directional SRI characteristics of the TPMF-LPFG, the resonance dip wavelength shift of the grating is dependent on the angle between the principal axis of TPMF and the external magnetic field direction when being applied to an external magnetic field. The achieved maximum sensitivity of the wavelength shift was −618 pm/mT when the magnetic intensity changes in the range of 0–10.5 mT. The achieved maximum orientation sensitivity of the sensor was 72 pm/degree, but the magnetic orientation can be detected only within the range of 0–90 degree. The minimum magnetic field intensity that can be detected is about 32.3 μT due to the 0.02 nm wavelength resolution of the optical spectrum analyzer. Our study proves that the high birefringence fiber based LPFG combined with MF can be developed as a high-performance vector magnetometer and such type of sensor is anticipated to find potential applications in magnetic or electric field systems.