A Simple All-Fiber Solc Filter Based on 45-Tilted Fiber Gratings

A simple all-fiber Solc filter (AFSF), which consists of two 45°-tilted fiber gratings (45°-TFGs) UV-inscribed in the polarization-maintaining fiber (PMF) and a series of PMF cavities, is proposed and demonstrated. The performance of the proposed filter has been theoretically simulated and experimentally verified. Both the simulated and experimental results show that the bandwidth of the filter could be tuned by the PMF sub-cavity length and the number of PMF cavities. And the free spectral range (FSR) only depends on the sub-cavity length. As a proof of that, the bandwidths of AFSF with different number of PMF sub-cavity (N=2, N=3, N=4) and the same PMF sub-cavity length of 30cm are 4 nm, 2.6nm, and 2nm, respectively. The FSRs of 3-stage AFSF with different PMF sub-cavity length (L=20 cm and L=40 cm) are 15.3 nm and 7.97 nm, respectively. Furthermore, we have also investigated the tunability of the AFSF by controlling the temperature of PMF cavity with a tuning sensitivity around 1.205 nm°/c. Compared with existing fiber-optic Solc filters, the AFSF with prominent advantages such as extremely simple and robust structure, thermal tunability in wavelength, and low cost will bring a bright future for applications in optical communication and sensing systems

Theoretical analysis and experimental demonstration of the radiation mode distribution of 45° TFG

In this paper, we have theoretically analyzed and experimentally demonstrated the spatial distribution of the radiation mode of 45° tilted fiber grating (TFG). The simulation results have shown the intensity distribution of the radiation mode along the fiber axis exhibited an exponential reduction. In experiment, we have observed the radiation mode pattern of a 5-mm long 45°TFG. The captured profiles along the radial direction and axial direction were in good agreement with the simulated results of the model

Numerical and Experimental Characterization of Radiation Mode of 45° Tilted Fiber Grating

In this paper, we have numerically and experimentally investigated the radiation mode of 45° tilted fiber grating (45° TFG). By introducing the axial distributions into the volume current method, we have established a three-dimensional theoretical model to analyze spatial distributions of the radiation mode of 45° TFG, and measured the radiation mode spatial distributions in experiment. Both numerical and experimental results show that the radiation mode of 45° TFG exhibits an exponential reduction along the fiber axial direction, and a quasi-Gaussian profile along the radial direction of fiber. Additionally, we have also measured the detailed polarization-dependent azimuthal intensity distributions of radiation modes of both s-and p-polarized core modes. The degree of polarization of radiation mode is around 99.886%, which is independent of the length and the polarization extinction ratio of the grating. Moreover, for the first time, we have experimentally observed a very weak p-polarized component existing in the radiation mode, which has matched well with the simulation results

Multiwavelength Er-doped fiber laser using an all-fiber Lyot filter

We experimentally demonstrated a multiwavelength Er-doped fiber ring laser system by employing an all-fiber Lyot filter (AFLF) and a highly nonlinear fiber (HNLF). The AFLF was employed as a polarizing filter to generate a nonlinear polarization rotation effect and the highly dense and narrow bandwidth comb-like channels. A 1-km-long HNLF was used to enhance the nonlinearity of the laser cavity and suppress the mode competition for multiwavelength operation. In the experiment, 97 laser output channels within a 3 dB bandwidth simultaneously were excited under 224 mW pump power. The power fluctuation of lasing channels was less than 0.182 dB, and the wavelength shift was less than 0.04 nm in 100 min, after treating the AFLF in a thermostatic ice bath. Meanwhile, the output laser was highly polarized with a degree of polarization up to 99.9%

Theoretical analysis of diffraction grating based on 45°-tilted fiber gratings

We have theoretically analyzed the diffractive characteristics of radiation mode of 45° tilted fiber gratings. The simulated angular dispersion for the 45 ° TFG with 748nm period at 1550nm is around 0.053°/nm, which is quite close to the experimental result

Compact linear polarization spectrometer based on radiation mode shaped in-fiber diffraction grating

We propose a compact linear polarization spectrometer based on the in-fiber polarization-dependent diffraction grating. The beam profile of radiated light of the grating is shaped to be a Gaussian profile to improve the performance of the spectrometer, where the size of the focused light spot is reduced from 44 um to 33 um with the shaped radiation mode of the grating. Based on the experimental results, the proposed spectrometer can achieve 0.05 nm resolution and 115 nm wavelength responding range from 1495 nm to 1610 nm. To verify the performance of the proposed fiber spectrometer, we measure the transmission spectra of an excessively tilted fiber grating, which has a pair of orthogonal polarization transmission spectra. Compared with the traditional measuring method, the proposed fiber spectrometer integrates the polarizing and spectral analyzing functions in the measuring system and achieves the polarization-sensitive spectral analysis, which shows good wavelength consistency and perfect polarization characteristics

Transcription factor IRF8 directs a silencing programme for TH17 cell differentiation

TH17 cells are recognized as a unique subset of T helper cells that have critical roles in the pathogenesis of autoimmunity and tissue inflammation. Although RORγt is necessary for the generation of TH17 cells, the molecular mechanisms underlying the functional diversity of TH17 cells are not fully understood. Here we show that a member of interferon regulatory factor (IRF) family of transcription factors, IRF8, has a critical role in silencing TH17-cell differentiation. Mice with a conventional knockout, as well as a T cell-specific deletion, of the Irf8 gene exhibited more efficient TH17 cells. Indeed, studies of an experimental model of colitis showed that IRF8 deficiency resulted in more severe inflammation with an enhanced TH17 phenotype. IRF8 was induced steadily and inhibited TH17-cell differentiation during TH17 lineage commitment at least in part through its physical interaction with RORγt. These findings define IRF8 as a novel intrinsic transcriptional inhibitor of TH17-cell differentiation

Low-cost temperature- And strain-insensitive twist sensor based on a hybrid fiber grating structure

We proposed and experimentally demonstrated a temperature- and strain-insensitive twist sensor based on a hybrid fiber grating structure, in which the hybrid grating structure is constructed with a 45°-tilted fiber grating and a chirped fiber Bragg grating UV-inscribed in a single-mode fiber in series. The sensing performance has been evaluated by experimental and numerical analyses, which are in good consistency. The experimental results show that the hybrid-grating-structure-based twist sensor has a maximum twist sensitivity up to 15.037 dB/rad. Moreover, due to the invariability of the fiber birefringence and the state of polarization of the input light, such sensor has intrinsically low temperature and strain sensitivities of 7.86 × 10−3 dB∕°C and 6.7 × 10−5 dB∕με, corresponding to the maximum twist measurement error resulting from temperature and strain of 5.2 × 10−4 rad∕°C and 4.5 × 10−6 rad∕με, respectively

Low-cost temperature- And strain-insensitive twist sensor based on a hybrid fiber grating structure

We proposed and experimentally demonstrated a temperature- and strain-insensitive twist sensor based on a hybrid fiber grating structure, in which the hybrid grating structure is constructed with a 45°-tilted fiber grating and a chirped fiber Bragg grating UV-inscribed in a single-mode fiber in series. The sensing performance has been evaluated by experimental and numerical analyses, which are in good consistency. The experimental results show that the hybrid-grating-structure-based twist sensor has a maximum twist sensitivity up to 15.037 dB/rad. Moreover, due to the invariability of the fiber birefringence and the state of polarization of the input light, such sensor has intrinsically low temperature and strain sensitivities of 7.86 × 10−3 dB∕°C and 6.7 × 10−5 dB∕με, corresponding to the maximum twist measurement error resulting from temperature and strain of 5.2 × 10−4 rad∕°C and 4.5 × 10−6 rad∕με, respectively