Transverse mode switchable mode-locked laser with narrow bandwidth.

Transverse mode switchable ultrashort optical pulses with narrow bandwidths can create potential for exploring what we believe are new physical effects. We demonstrate the generation of transverse mode switchable ultrashort pulses with narrow bandwidths in an all-fiber mode-locked laser by exploring a mode-selective photonic lantern (MSPL). The laser cavity serves not only as a ring resonator but also as an intrinsic spectral filter. For mode-locking with the LP01, LP11a, and LP11b modes, the bandwidths are 3.0 nm, 86.7 pm and 101.7 pm, respectively. The narrowband pulses with higher-order modes are generated by an intrinsic spectral filter due to the spectral-domain intermodal interference. Mode-locked pulses with a signal-to-noise ratio better than 60 dB for LP01, LP11a, and LP11b modes are independently generated, i.e., transverse mode switchable by changing the input port of the MSPL. The mode-locked wavelength can be tuned for the LP11a mode and LP11b mode by adjusting the state of polarization. Furthermore, our experimental results also show that, the slope efficiency of LP11a and LP11b modes can be improved, by the use of LP11 mode pump scheme. We anticipate that, narrowband pulses with complex mode profiles can be generated by simultaneously phase-locked transverse and longitudinal modes.

Simultaneous realization of high gain and low DMG of four-mode EDFA under bidirectional hybrid-mode pump.

We theoretically and experimentally verify that, the bidirectional hybrid-mode pumping scheme can address the optimization problem of trade-off between high gain and low differential modal gain (DMG) of four-mode erbium-doped fiber amplifier (4M-EDFA), in comparison with traditional both forward and backward hybrid-mode pumping scheme. It is noticed that, when the total pump power is fixed, the bidirectional hybrid-mode pumping scheme can not only achieve higher gain, but also suppress DMG due to different overlap integrals for the forward and backward pumping schemes. The bidirectional hybrid-mode pumped 4M-EDFA is developed with the forward pumping at LP02 mode and the backward pumping at LP21 mode, under a pump power ratio of 30%:70%. Thus, we can achieve an average gain of up to 21.16 dB and a low DMG of 0.43 dB at 1550 nm, and an average gain of up to 20.64 dB with a DMG of less than 1.6 dB over the C-band. In particular, the bidirectional hybrid-mode pumping scheme allows us to tailor the gain characteristics of the few-mode erbium-doped fiber amplifiers (FM-EDFAs), by adjusting the power ratio between forward and backward pumps.

Alleviatory Role of Panax Notoginseng Saponins in Modulating Inflammation and Pulmonary Vascular Remodeling in Chronic Obstructive Pulmonary Disease: mechanisms and Implications.

COPD is an inflammatory lung disease that limits airflow and remodels the pulmonary vascular system. This study delves into the therapeutic potential and mechanistic underpinnings of Panax notoginseng Saponins (PNS) in alleviating inflammation and pulmonary vascular remodeling in a COPD rat model. Symmap and ETCM databases provided Panax notoginseng-related target genes, and the CTD and DisGeNET databases provided COPD-related genes. Intersection genes were subjected to protein-protein interaction analysis and pathway enrichment to identify downstream pathways. A COPD rat model was established, with groups receiving varying doses of PNS and a Roxithromycin control. The pathological changes in lung tissue and vasculature were examined using histological staining, while molecular alterations were explored through ELISA, RT-PCR, and Western blot. Network pharmacology research suggested PNS may affect the TLR4/NF-κB pathway linked to COPD development. The study revealed that, in contrast to the control group, the COPD model exhibited a significant increase in inflammatory markers and pathway components such as TLR4, NF-κB, HIF-1α, VEGF, ICAM-1, SELE mRNA, and serum TNF-α, IL-8, and IL-1ß. Treatment with PNS notably decreased these markers and mitigated inflammation around the bronchi and vessels. Taken together, the study underscores the potential of PNS in reducing lung inflammation and vascular remodeling in COPD rats, primarily via modulation of the TLR4/NF-κB/HIF-1α/VEGF pathway. This research offers valuable insights for developing new therapeutic strategies for managing and preventing COPD.

Reconfigurable ultra-broadband mode converter based on a two-mode fiber with pressure-loaded phase-shifted long-period alloyed waveguide grating.

We present a reconfigurable ultra-broadband mode converter, which consists of a two-mode fiber (TMF) and pressure-loaded phase-shifted long-period alloyed waveguide grating. We design and fabricate the long-period alloyed waveguide gratings (LPAWG) with SU-8, chromium, and titanium via the photo-lithography and electric beam evaporation technique. With the help of the pressure loaded or released from the LPAWG onto the TMF, the device can realize reconfigurable mode conversion between the LP01 mode and the LP11 mode in the TMF, which is weak sensitive to the state of polarization. The mode conversion efficiency larger than 10 dB can be achieved with operation wavelength range of about 105 nm, which ranges from 1501.9 nm to 1606.7 nm. The proposed device can be further used in the large bandwidth mode division multiplexing (MDM) transmission and optical fiber sensing system based on few-mode fibers.

Three-dimensional mode multiplexer based on adiabatic-tapered waveguides forming vertical directional couplers over C + L band and beyond.

We present a mode multiplexer based on vertical directional couplers that are formed by adiabatic-tapered waveguides. We design and fabricate the device via the micro-fabrication processing to (de)multiplex the E11, E21, and E12 modes from the few-mode bus waveguide. Our experimental device shows a coupling ratio higher than 98.6% and 97.0% for the E21 and E12 modes, respectively, over the C + L band and beyond. The modal cross talk of this device can be lower than -17.1 dB, -18.4 dB, and -15.1 dB caused by the unintended E11, E21, and E12 modes, respectively. This mode multiplexer can work over a broader wavelength range with weak polarization sensitivity, which could be used in the mode-division-multiplexing systems where mode (de)multiplexing is required in the expanded communication wavelength window other than the C-band.

Intensity-interrogated hot-wire anemometer based on chirp effect of a fiber Bragg grating.

An intensity-interrogated optical fiber hot-wire anemometer based on the chirp effect of fiber Bragg grating (FBG) is presented. The FBG is coated with a silver film and heated optically by a 1480 nm laser beam, which is coupled into the fiber cladding by a long-period grating (LPG) and absorbed by the silver film to convert to thermal heat. Due to the gradual decrease of laser power along the length of the FBG, a temperature gradient is formed that induces a chirp effect to the FBG. Bandwidth of the FBG's reflection spectrum is therefore broadened that increases its reflected light power. The chirp rate of the FBG reduces with airflow velocity since the temperature gradient is weakened under the cooling effect of the airflow, resulting in a certain relationship between the reflected power of the FBG and airflow velocity. In the experiment, by detecting the reflected power of the FBG, airflow velocity measurement is achieved successfully with a high sensitivity up to -28.60 µW/(m·s-1) at airflow velocity of 0.1 m/s and a dynamic response time of under one second. The measurement range is up to 0 to 11 m/s. The intensity interrogation scheme of the FBG hot-wire anemometer reduces its cost greatly and makes it a promising solution for airflow velocity measurement in practical applications.

Ultra-broadband LP11 mode converter with high purity based on long-period fiber grating and an integrated Y-junction.

We report an ultra-broadband LP11 mode converter with high purity based on integrated two shunt-wound long-period fiber gratings (LPFGs) and an adiabatic Y-junction, together with a high-order-mode bandpass filter. Two shunt-wound LPFGs are inscribed by CO2 laser in a two-mode fiber to achieve a 10 dB bandwidth of 50 nm and 51 nm at resonance wavelengths of 1530 nm and 1570 nm, respectively. Meanwhile, the Y-junction fabricated by lithography can be operated over S + C+L band to combine the converted LP11 mode. The presented ultra-broadband mode converter is able to achieve a mode conversion efficiency of 95%, together with a wavelength-dependent loss of less than 3 dB over the S + C+L band. This device has low modal crosstalk of 17 dB between the LP01 and LP11 modes, because most of the residual LP01 mode is further filtered by a high-order-mode bandpass filter at the output port of the Y-junction. The insertion loss of mode converter is estimated to be lower than 2.7 dB, due to the use of low loss polymer material during the fabrication. The proposed ultra-broadband LP11 mode converter with high purity is promising for the application of ultra-broadband mode-division-multiplexing transmission systems.

All-optical light manipulation based on graphene-embedded side-polished fiber.

We present a study of all-optical light manipulation arising in a graphene-embedded side-polished fiber (SPF) with a Norland Optical Adhesives (NOA)-coated structure. With the help of the Pauli blocking effect, such an all-fiber device serves to manage the loss of transverse-electric-polarized light when the control light and the signal light are polarized along the direction parallel to the graphene surface. The insertion loss of this device can be effectively reduced with the NOA coating. An enhanced interaction between the graphene and the propagated light can be achieved via the strong evanescent field of the SPF and longer interaction length. This results in effective all-optical manipulation of light with a modulation depth of 10.4 dB (or modulation efficiency of ∼91%) and a modulation slope of ∼1.3, where the required control power is only about 14 dBm. The device has broadband operation wavelength. The insertion loss for both the signal light and the control light are only about 0.6 dB. The experimental results are well-fitting with the simulation study. Such an all-fiber device has the potential for all-optical signal processing.

Ring core few-mode fiber sensor for curvature measurement.

An all-fiber Mach-Zehnder interferometer (MZI) using ring core few-mode fiber (RC-FMF) for curvature sensing is proposed and experimentally demonstrated. The MZI was fabricated by splicing a segment of RC-FMF between two pieces of single-mode fiber (SMF). With the benefit of a RC of the central axis of the RC-FMF, the sensor is more sensitive to curvature compared to other fiber sensors based on ordinary SMF or FMF. Curvature measurement can be achieved by monitoring the wavelength shift of interference dips. Experimental results have shown that the sensitivity of curvature sensing can reach up to -4.370nm/m-1, within the range of 1.199-1.549m-1. Also, the temperature sensing characteristics of the sensor are measured, and the maximum temperature sensitivity is 57.6 pm/°C, ranging from 25°C to 45°C. The proposed MZI sensor has excellent potential for curvature measurement of building structural health monitoring, bridge engineering, and more.

Wideband low confinement loss anti-resonant hollow core fiber with nested U-shape tube.

We propose a nested U-shape tube anti-resonant hollow core fiber (UARF) that can effectively reduce the confinement loss (CL) as well as the loss oscillations. The key parameters of UARF have been optimized via numerical analysis. Simulation results show that the CL of proposed UARF is lower than 0.01dB/km over a 550 nm operational bandwidth range from 1.3 µm to 1.85 µm. This CL is nearly one order of magnitude lower than the nested anti-resonant nodeless fiber (NANF). Moreover, the loss ratio between higher-order modes to the fundamental mode is verified to be more than 100,000 over a ultrawide bandwidth of 1000 nm, which indicates its excellent single mode performance. The tolerance towards the structure deformation of UARF has been evaluated for the purpose of practical fiber fabrication. Thus, the proposed UARF has potential application in large capacity data transmission, nonlinear optics, gas sensing and so on.

Distributed refractive index sensing based on bending-induced multimodal interference and Rayleigh backscattering spectrum.

A distributed refractive index (RI) sensor based on high-performance optical frequency domain reflectometry was developed by bending a piece of standard single-mode fiber to excite sets of higher-order modes that penetrate the surrounding medium. External variations in RI modifies the profiles of the sets of excited higher-order modes, which are then partially coupled back into the fiber core and interfere with the fundamental mode. Accordingly, the fundamental mode carries the outer varied RI information, and RI sensing can be achieved by monitoring the wavelength shift of the local Rayleigh backscattered spectra. In the experiment, an RI sensitivity of 39.08 nm/RIU was achieved by bending a single-mode fiber to a radius of 4 mm. Additionally, the proposed sensor maintains its buffer coating intact, which boosts its practicability and application adaptability.

Hardware-efficient blind frequency offset estimation for digital subcarrier multiplexing signals.

Since the frequency offset estimation (FOE) must be implemented before the subcarrier de-multiplexing and chromatic dispersion compensation (CDC) for digital subcarrier multiplexing (DSM) signals, traditional FOE algorithms for single carrier transmission is no longer suitable. Here, we propose a hardware-efficient blind FOE solution for the DSM signals by monitoring spectral dips in the frequency domain. With the use of a smoothing filter, the estimation accuracy of FOE can be significantly increased. Moreover, we identify that the proposed FOE method is robust to various transmission impairments, including amplified spontaneous emission (ASE) noise, optical filtering, and fiber nonlinearity. The effective function of the proposed FOE method is numerically and experimentally verified under scenarios of both back-to-back (B2B) and the 2560 km standard single-mode fiber (SSMF) transmission, leading to a FOE error less than 100 MHz with a FFT size of 1024.

10-W power light co-transmission with optically carried 5G NR signal over standard single-mode fiber.

Efficient co-transmission of 10-W power light and optically carried 5G new radio (NR) signal over standard single-mode fiber (SSMF) is experimentally demonstrated, with an optical power transmission efficiency (OPTE) of power light up to 71.8%. This efficiency record is enabled by carefully manipulating the linewidth of the power light and appropriately adjusting the wavelength spacing between the power light and 5G NR optical signal to effectively mitigate the nonlinear effect arising in the SSMF. In the experiment, the optically carried 5G NR 64-level quadrature amplitude modulation orthogonal frequency division multiplexing signal at 1550 nm, with a data rate of 1.5 Gbit/s, is successfully co-propagated with 10-W power light at 1064 nm over 1-km SSMF. The error-vector magnitude (EVM) is 0.48% under a received electrical power of -25dBm. In comparison with back-to-back transmission, only slight EVM degradation of 0.02% is observed, showing that the 5G NR optical signal is almost unaffected by the existence of power light. Moreover, the power fluctuation of the collected power light is less than 0.2% over 6 h, while the EVM fluctuation is smaller than 0.01% within 30 min. Our scheme is promising to realize an optically powered remote antenna unit through the existing 5G fronthaul SSMF link.

Adaptive intensity transformation-based phase retrieval with high accuracy and fast convergence.

Phase-retrieval (PR) receivers can reconstruct complex-valued signals from two de-correlated intensity measurements, without the assistance of any optical carriers. However, both the calculation complexity with hundreds of iterations and the limited PR accuracy prevent it from being applied to high-speed photonic interconnections. Here we propose and demonstrate a PR receiver based on adaptive intensity transformation, with the capability of both fast convergence and high accuracy. Then we numerically reconstruct 56 GBaud QPSK signals after the 80 km standard single-mode fiber transmission by using our proposed PR receiver with only 50 iterations. In comparison with the recently reported PR receiver with the phase reset, our proposed PR receiver can reduce the required optical signal-to-noise ratio by 1.95 and 1.89 dB, in terms of 20% soft-decision and 7% hard-decision forward-error correction, respectively.

Bending-loss-resistant distributed Brillouin curvature sensor based on an erbium-doped few-mode fiber.

We developed a bending-loss-resistant distributed Brillouin curvature sensor based on an erbium-doped few-mode fiber (Er-FMF) and differential pulse-width pair Brillouin optical time-domain analysis. With Er ion amplification compensating for bending-induced optical loss, radii in the ∼0.3 to 2.02 cm range could be monitored correctly. The corresponding Brillouin frequency shift variations were in the range of 91.7 to 9 MHz, which agrees well with theoretical calculations. The sensitivity of the Er-FMF device increased inversely with the bending radius, with the optimal sensitivity of 292.7 MHz/cm obtained at a radius of 0.3 cm. To the best of our knowledge, this is the smallest radius of curvature detected and highest sensitivity reported to date, indicating potential applications in distributed sharp-bend sensing, such as intelligent robotics and structural health monitoring.

Luteolin ameliorates inflammation and Th1/Th2 imbalance via regulating the TLR4/NF-κB pathway in allergic rhinitis rats.

OBJECTIVE: Luteolin has an anti-allergic effect but its mechanism is not clear. This study attempted to determine the mechanisms of luteolin in rhinitis. METHODS: Allergic rhinitis rat model was established by ovalbumin (OVA) stimulation. Then, the rats were treated with normal saline, luteolin, or lipopolysaccharide (LPS) for 14 days. Nasal symptoms were scored; the histopathological changes of nasal mucosa were detected by hematoxylin-eosin staining. Serum levels of Th1 type cytokines (IFN-γ, IL-2), Th2 type cytokines (IL-4, IL-5, IL-13), and OVA-specific IgE (sIgE) were determined by ELISA. The expressions of Toll-like receptor 4 (TLR4) and p65 in nasal mucosa were detected by Western blot or immunohistochemistry. RESULTS: Luteolin decreased symptom scores, specifically, the scores in control group, model group, model + 0.1 mg/kg luteolin, model + 1 mg/kg luteolin, and model + 10 mg/kg luteolin groups were 0.63 ± 0.52, 7.88 ± 0.83, 1.38 ± 0.52, 2.75 ± 0.46, and 5.00 ± 0.53, respectively. Luteolin ameliorated nasal mucosa inflammation by promoting the down-regulated levels of Th1 type cytokines, and suppressing the up-regulated levels of Th2 type cytokines, OVE-sIgE, TLR4, and p65. LPS further increased symptom scores, aggravated nasal mucosa inflammation, improved the unbalance of Th1/Th2 type cytokines, and lowered the expressions of OVE-sIgE, TLR4, and p65. Moreover, LPS reversed the effect of luteolin on allergic rhinitis rats. CONCLUSION: Luteolin ameliorated inflammation and Th1/Th2 imbalance via regulating the TLR4/NF-κB pathway in allergic rhinitis rats. This study provided novel evidence that luteolin could be used as a candidate drug in allergic rhinitis treatment.

Silencing of miR-17-5p suppresses cell proliferation and promotes cell apoptosis by directly targeting PIK3R1 in laryngeal squamous cell carcinoma.

BACKGROUND: Increasing evidence has suggested that microRNAs (miRNAs) act as key post-transcriptional regulators in tumor progression. Previous studies have confirmed that miR-17-5p functions as an oncogene in multiple cancers and contributes to tumor progression. However, the role and biological functions of miR-17-5p in the development of laryngeal squamous cell carcinoma (LSCC) still remain unknown. METHODS: qRT-PCR was used to detect miRNA and mRNA expression levels in LSCC tissues and cell lines. CCK-8 assay was used to measure cell viability and flow cytometry was performed to evaluate cell apoptosis. Western blot analysis was used to detect the protein levels of BAX, BCL-2, cleaved Caspase-3, PIK3R1 and AKT. Luciferase reporter assay was used to detect the effect of miR-17-5p on PIK3R1 expression. Xenograft animal model was used to test the effect of miR-17-5p on LSCC cell in vivo. RESULTS: In the present study, we found that miR-17-5p expression level was upregulated in LSCC tissues and cell lines. Depletion of miR-17-5p in LSCC cells significantly reduced cell proliferation and promoted cell apoptosis in vitro and in vivo. Mechanically, knockdown of miR-17-5p in LSCC cells inhibited BCL-2 expression while enhanced BAX and cleaved Caspase-3 protein expression. Moreover, depletion of miR-17-5p in LSCC cells suppressed AKT phosphorylation but did not influence PTEN expression. Importantly, miR-17-5p positively regulated PIK3R1 expression by directly binding to its 3'-untranslated region (UTR). Additionally, PIK3R1, which expression was downregulated in LSCC tissues and cell lines, was involved in LSCC cell survival by modulating the activation of AKT signal pathway. Dysregulation of miR-17-5p/PIK3R1 axis was participated in LSCC cell proliferation and apoptosis by inhibiting the activation of the PI3K/AKT signaling pathway. CONCLUSIONS: In conclusion, our study indicates that the miR-17-5p/PIK3R1 axis plays an essential role in the development of LSCC and provides a potential therapeutic target for LSCC treatment.

Upregulation of circFLNA contributes to laryngeal squamous cell carcinoma migration by circFLNA-miR-486-3p-FLNA axis.

BACKGROUND: Accumulating evidence shows that circular RNAs (circRNAs) plays vital roles in tumor progression. However, the biological functions of circRNAs in laryngeal squamous cell carcinoma (LSCC) metastasis is still unclear. METHODS: qRT-PCR was used to detect circFLNA, miRNAs and FLNA mRNA expression. Transwell assay and western blot were performed to evaluate cell migration ability and to detect FLNA, MMP2 and MLK1 protein expression, respectively. RNA pull-down analysis was used to find the binding-miRNAs of circFLNA. Luciferase reporter assay was used to examine the effect of circFLNA on miRNAs and miR-486-3p on FLNA expression. RESULTS: In this study, we confirmed that a Filamin A (FLNA)-derived hsa_circ_0092012 known as circFLNA, was upregulated in LSCC, and the higher expression of circFLNA was correlated with LSCC lymph node metastasis. Increased circFLNA facilitates LSCC cell migration ability through upregulating FLNA and MMP2 protein expression. Mechanistically, we find that circFLNA sponges miR-486-3p in LSCC cells, relieving miR-486-3p-induced repression of FLNA which promotes LSCC cell migration. Accordingly, FLNA mRNA is overexpressed in LSCC tissues and a higher FLNA level is correlated with poor survival. Dysregulation of the circFLNA/miR-486-3p/FLNA regulatory pathway contributes to LSCC migration. CONCLUSIONS: In summary, our study sheds light on the regulatory mechanism of circFLNA in LSCC migration via sponging miR-486-3p, which downregulates the FLNA protein expression. Targeting circFLNA/miR-486-3p/FLAN axis provides a potential therapeutic target for aggressive LSCC.

Investigation of the effect of gold coating of gold-coated fiber on distributed strain measurement by differential pulse pair Brillouin optical-time analysis.

Gold-coated fiber (GCF) shows the potential to sense strain at high temperature owing to the hermeticity of gold coating that prevents hydrogen penetration. Nevertheless, there are trivial details of the gold coating of GCF that need to be addressed before using GCF to measure strain at high temperature. In this study, we thoroughly investigate the effect of the gold coating of GCF on strain measurement both at room temperature and high temperature up to 700°C with differential pulse pair Brillouin optical-time analysis (DPP-BOTDA). Owing to the inhomogeneity of gold coating induced by the manufacturing process, it is necessary to select the GCF with the gold coating of better homogeneity via DPP-BOTDA. Due to the residual stress that solidified in the GCF during the cooling process of coating, the GCF would first undergo plastic deformation and then elastic deformation in the strain measurement. After one-time strain measurement to remove the residual stress of GCF, the standard deviation of the strain coefficients at room temperature and high temperature are $ \pm {0.5}\% $±0.5% and $ \pm {1.3}\% $±1.3%, respectively, which is mainly due to the nonuniform thickness of the gold coating and the nonuniformity of silica fiber at high temperature.

High speed and high resolution interrogation of a fiber Bragg grating sensor based on microwave photonic filtering and chirped microwave pulse compression.

High speed and high resolution interrogation of a fiber Bragg grating (FBG) sensor based on microwave photonic filtering and chirped microwave pulse compression is proposed and experimentally demonstrated. In the proposed sensor, a broadband linearly chirped microwave waveform (LCMW) is applied to a single-passband microwave photonic filter (MPF) which is implemented based on phase modulation and phase modulation to intensity modulation conversion using a phase modulator (PM) and a phase-shifted FBG (PS-FBG). Since the center frequency of the MPF is a function of the central wavelength of the PS-FBG, when the PS-FBG experiences a strain or temperature change, the wavelength is shifted, which leads to the change in the center frequency of the MPF. At the output of the MPF, a filtered chirped waveform with the center frequency corresponding to the applied strain or temperature is obtained. By compressing the filtered LCMW in a digital signal processor, the resolution is improved. The proposed interrogation technique is experimentally demonstrated. The experimental results show that interrogation sensitivity and resolution as high as 1.25 ns/µÎµ and 0.8 µÎµ are achieved.