Temperature and Twist Sensor Based on the Sagnac Interferometer with Long-Period Grating in Polarization-Maintaining Fiber.

We utilized a CO2 laser to carve long-period fiber gratings (LPFGs) on polarization-maintaining fibers (PMFs) along the fast and slow axes. Based on the spectra of LPFGs written along two different directions, we found that when LPFG was written along the fast axis, the spectrum had lower insertion loss and fewer side lobes. We investigated the temperature and twist characteristics of the embedded structure of the LPFG and Sagnac loop and ultimately obtained a temperature sensitivity of -0.295 nm/°C and a twist sensitivity of 0.87 nm/(rad/m) for the LPFG. Compared to the single LPFG, the embedded structure of the LPFG and Sagnac loop demonstrates a significant improvement in temperature and twist sensitivities. Additionally, it also possesses the capability to discern the direction of the twist. The embedded structure displays numerous advantages, including easy fabrication, low cost, good robustness, a wide range, and high sensitivity. These features make it highly suitable for applications in structural health monitoring and other related fields.

100Gb/s coherent optical secure communication over 1000†km based on analog-digital hybrid chaos.

In recent years, the transmission capacity of chaotic secure communications has been greatly expanded by combining coherent detection and multi-dimensional multiplexing. However, demonstrations over 1000 km fiber are yet to be further explored. In this paper, we propose a coherent optical secure transmission system based on analog-digital hybrid chaos. By introducing an analog-digital converter (ADC) and a bit extraction into the feedback loop of entropy source, the broadband analog chaos is converted into a binary digital signal. This binary digital signal is then mapped to a 65536-level pulse amplitude modulation (PAM) signal and injected into the semiconductor laser (SL) to regenerate the analog chaos, forming a closed loop. The binary digital signal from the chaos source and the encrypted signal are transmitted via wavelength division multiplexing (WDM). By using conventional digital signal processing (DSP) algorithms and neural networks for post-compensation, long-haul high-quality chaotic synchronization and high-performance secure communication are achieved. In addition, the probability density distribution of the analog chaotic signal is effectively improved by adopting the additional higher-order mapping operation in the digital part of the chaos source. The proof-of-concept experimental results show that our proposed scheme can support the secure transmission of 100 Gb/s quadrature phase shift keying (QPSK) signals over 1000 km of standard single-mode fiber (SSMF). The decrypted bit error rate (BER) reaches 9.88 × 10-4, which is well below the 7% forward error correction (FEC) threshold (BER = 3.8 × 10-3). This research provides a potential solution for high-capacity long-haul chaotic optical communications and fills the gap in secure communications based on analog-digital hybrid chaos.

High-Sensitivity Temperature Sensor Based on Fiber Fabry-Pérot Interferometer with UV Glue-Filled Hollow Capillary Fiber.

Optical fiber Fabry-Pérot (FP) interferometer sensors have long been the focus of researchers in sensing applications because of their simple light path, low cost, compact size and convenient manufacturing methods. A miniature and highly sensitive optic fiber temperature sensor using an ultraviolet glue-filled FP cavity in a hollow capillary fiber is proposed. The sensor is fabricated by fusion splicing a single-mode fiber with a hollow capillary fiber, which is filled with ultraviolet glue to form a FP cavity. The sensor has a good linear response in the temperature testing and high-temperature sensitivity, which can be increased with the length of the FP cavity. The experimental results show that the temperature sensitivity reaches 1.174 nm/°C with a high linear response in the range of 30-60 °C. In addition, this sensor is insensitive to pressure and can be highly suitable for real-time water temperature monitoring for ocean research. The proposed ultraviolet glue-filled structure has the advantages of easy fabrication, high-temperature sensitivity, low cost and an arbitrary length of capillary, which has broad application prospects for marine survey technology, biological diagnostics and environmental monitoring.

Secure key distribution based on the polarization reciprocity of fiber and a coherent reception architecture.

Secure key distribution (SKD) schemes based on the interaction between a broadband chaotic source and the reciprocity of a fiber channel exhibit reliable security and a high key generation rate (KGR). However, under the intensity modulation and direct detection (IM/DD) architecture, these SKD schemes cannot achieve a long distribution distance due to the limitations on the signal-to-noise ratio (SNR) and the receiver's sensitivity. Here, based on the advantage of the high sensitivity of coherent reception, we design a coherent-SKD structure where orthogonal polarization states are locally modulated by a broadband chaotic signal and the single-frequency local oscillator (LO) light is transmitted bidirectionally in the optical fiber. The proposed structure not only utilizes the polarization reciprocity of optical fiber but also largely eliminates the non-reciprocity factor, which can effectively extend the distribution distance. The experiment realized an error-free SKD with a transmission distance of 50 km and a KGR of 1.85 Gbit/s.

Adgrg1 is a new transcriptional target of Hand1 during trophoblast giant cell differentiation.

The placenta, forming the maternal-fetal interface, is essential for the survival and development of the fetus. It has been shown that the basic helix-loop-helix (bHLH) transcription factor Hand1 plays an important role in trophoblast giant cells (TGCs) differentiation during placental development in mice. However, the underlying molecular mechanism remains elusive. We hereby report that Adgrg1 (GPR56), a G protein coupled receptor, was a new transcriptional target of Hand1. Hand1 activated the expression of Adgrg1 by binding to its promoter region during TGCs differentiation. Double in situ hybridization revealed co-expression of Hand1 and Adgrg1 in Prl2c2+ TGCs located in the junctional zone of the placenta. Knockdown of Adgrg1 not only led to increased Prl2c2 expression, but also the improvement of cell migration and invasion during TGC differentiation. Moreover, the ligand of Adgrg1, Tgm2, was expressed in Prl2c2+ TGCs located in the placental junctional zone and Tgm2 Knockdown increased cell migration and invasion, suggesting Tgm2 is a potential ligand involved in the functions of Adgrg1 during TGC differentiation in the manners of autocrine. Collectively, these results demonstrate that Adgrg1 is a new transcriptional target of Hand1, affecting Prl2c2 expression as well as cell migration and invasion during TGCs differentiation. As a transmembrane receptor, Adgrg1 perhaps could act as a potential therapeutic target for placental-associated diseases caused by abnormal trophoblast migration and invasion, providing new insights for the preventions and therapies of placenta-related diseases.

Optical Fiber Probe Microcantilever Sensor Based on Fabry-Perot Interferometer.

Optical fiber Fabry-Perot sensors have long been the focus of researchers in sensing applications because of their unique advantages, including highly effective, simple light path, low cost, compact size, and easy fabrication. Microcantilever-based devices have been extensively explored in chemical and biological fields while the interrogation methods are still a challenge. The optical fiber probe microcantilever sensor is constructed with a microcantilever beam on an optical fiber, which opens the door for highly sensitive, as well as convenient readout. In this review, we summarize a wide variety of optical fiber probe microcantilever sensors based on Fabry-Perot interferometer. The operation principle of the optical fiber probe microcantilever sensor is introduced. The fabrication methods, materials, and sensing applications of an optical fiber probe microcantilever sensor with different structures are discussed in detail. The performances of different kinds of fiber probe microcantilever sensors are compared. We also prospect the possible development direction of optical fiber microcantilever sensors.

High-Temperature Measurement of a Fiber Probe Sensor Based on the Michelson Interferometer.

In this paper, a fiber probe high-temperature sensor based on the Michelson Interferometer (MI) is proposed and experimentally verified. We used a fiber splicing machine to fabricate a taper of the single-mode fiber (SMF) end. The high order modes were excited at the taper, so that different modes were transmitted forward in the fiber and reflected by the end face of the fiber and then recoupled back to the fiber core to form MI. For comparison, we also coated a thin gold film on the fiber end to improve the reflectivity, and the reflection intensity was improved by 16 dB. The experimental results showed that the temperature sensitivity at 1506 nm was 80 pm/°C (100 °C~450 °C) and 109 pm/°C (450 °C~900 °C). The repeated heating and cooling processes showed that the MI structure had good stability at a temperature up to 900 °C. This fiber probe sensor has the advantages of a small size, simple structure, easy manufacturing, good stability, and broad application prospects in industrial and other environments.

LncRNA SOX2OT rs9839776 Polymorphism Reduces Sepsis Susceptibility in Southern Chinese Children.

BACKGROUND: Sepsis in children is one of the main causes of death in pediatric intensive care units (PICUs); however, the pathogenesis of sepsis is not fully clear. Previous studies revealed that many genetic variations were related to sepsis susceptibility. A long non-coding RNA SOX2 overlapping transcript (SOX2OT) may play a role in mitochondrial homeostasis and antioxidative activity, but the relationship between the lncRNA SOX2OT polymorphism and sepsis susceptibility has not been reported. METHODS: In this study, 474 pediatric sepsis patients and 678 healthy controls were recruited from southern China. After genotyping, the strength of the associations was evaluated through odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: The SOX2OT rs9839776 T allele was associated with decreased susceptibility to sepsis in southern Chinese children (TT/CT vs CC adjusted OR = 0.778, 95% CI = 0.610-0.992; P = 0.0431). Moreover, the difference in susceptibility was greater in children of age >60 months (adjusted OR = 0.458, 95% CI = 0.234-0.896; P = 0.0225), survivors (adjusted OR = 0.758, 95% CI = 0.585-0.972; P = 0.0358), males (adjusted OR = 0.655, 95% CI = 0.479-0.894; P = 0.0077) and the sepsis subgroup (adjusted OR = 0.548, 95% CI = 0.343-0.876; P = 0.0120). CONCLUSION: The rs9839776 T allele may contribute to decreased sepsis risk in Chinese children. Future studies with a larger sample size are needed to verify these results.

Hyperactivated Wnt-ß-catenin signaling in the absence of sFRP1 and sFRP5 disrupts trophoblast differentiation through repression of Ascl2.

BACKGROUND: Wnt signaling is a critical determinant for the maintenance and differentiation of stem/progenitor cells, including trophoblast stem cells during placental development. Hyperactivation of Wnt signaling has been shown to be associated with human trophoblast diseases. However, little is known about the impact and underlying mechanisms of excessive Wnt signaling during placental trophoblast development. RESULTS: In the present work, we observed that two inhibitors of Wnt signaling, secreted frizzled-related proteins 1 and 5 (Sfrp1 and Sfrp5), are highly expressed in the extraembryonic trophoblast suggesting possible roles in early placental development. Sfrp1 and Sfrp5 double knockout mice exhibited disturbed trophoblast differentiation in the placental ectoplacental cone (EPC), which contains the precursors of trophoblast giant cells (TGCs) and spongiotrophoblast cells. In addition, we employed mouse models expressing a truncated ß-catenin with exon 3 deletion globally and trophoblast-specifically, as well as trophoblast stem cell lines, and unraveled that hyperactivation of canonical Wnt pathway exhausted the trophoblast precursor cells in the EPC, resulting in the overabundance of giant cells at the expense of spongiotrophoblast cells. Further examination uncovered that hyperactivation of canonical Wnt pathway disturbed trophoblast differentiation in the EPC via repressing Ascl2 expression. CONCLUSIONS: Our investigations provide new insights that the homeostasis of canonical Wnt-ß-catenin signaling is essential for EPC trophoblast differentiation during placental development, which is of high clinical relevance, since aberrant Wnt signaling is often associated with trophoblast-related diseases.

Feasibility of ultrasound-assisted catheter-directed thrombolysis for submassive pulmonary embolism: A meta-analysis of case series.

BACKGROUND: During the past few years, there has been a surge in the use of ultrasound-assisted catheter-directed thrombolysis (UACDT) for submassive pulmonary embolism (SPE). However, few studies evaluated the feasibility of UACDT for SPE. PURPOSE: To evaluate the feasibility of UACDT in treating SPE. METHODS: A comprehensive search of online databases was performed. Search terms UACDT in SPE were entered into PubMed, Embase, Scopus and the Cochrane Library to identify related articles published until October 2018. A quality assessment and data extraction were performed by two researchers. Meta-analysis was performed using R statistical software. RESULTS: Twelve studies with 485 patients were included in this meta-analysis. The pooled right ventricular/left ventricular ratio decrease and pulmonary artery systolic pressure drop after treatment was -0.34 (95% CI: -0.43, -0.25) and -15.05 (95% CI: -18.10, -12.00) mm Hg, respectively. The pooled major bleeding rate was 1.0% (95% CI: 0.0%, 3.0%), and the in-hospital mortality was 0.0% (95% CI: 0.0%, 1.0%). CONCLUSION: This up to data meta-analysis confirms that UACDT is a feasible treatment for SPE.

Spatiotemporal coordination of trophoblast and allantoic Rbpj signaling directs normal placental morphogenesis.

The placenta, responsible for the nutrient and gas exchange between the mother and fetus, is pivotal for successful pregnancy. It has been shown that Rbpj, the core transcriptional mediator of Notch signaling pathway, is required for normal placentation in mice. However, it remains largely unclear how Rbpj signaling in different placental compartments coordinates with other important regulators to ensure normal placental morphogenesis. In this study, we found that systemic deletion of Rbpj led to abnormal chorioallantoic morphogenesis and defective trophoblast differentiation in the ectoplacental cone (EPC). Employing mouse models with selective deletion of Rbpj in the allantois versus trophoblast, combining tetraploid aggregation assay, we demonstrated that allantois-expressed Rbpj is essential for chorioallantoic attachment and subsequent invagination of allantoic blood vessels into the chorionic ectoderm. Further studies uncovered that allantoic Rbpj regulates chorioallantoic fusion and morphogenesis via targeting Vcam1 in a Notch-dependent manner. Meanwhile, we also revealed that trophoblast-expressed Rbpj in EPC facilitates Mash2's transcriptional activity, promoting the specification of Tpbpα-positive trophoblasts, which differentiate into trophoblast subtypes responsible for interstitial and endovascular invasion at the later stage of placental development. Collectively, our study further shed light on the molecular network governing placental development and functions, highlighting the necessity of a spatiotemporal coordination of Rbpj signaling for normal placental morphogenesis.

Anomalous thermally-activated NIR emission of ESIPT modulated Nd-complexes for optical fiber sensing devices.

Highly sensitized NIR emission was modulated using an ESIPT ligand in a Nd-complex, to achieve a substantially elongated NIR lifetime in cyclohexane suspension with a value of 16.89 µs at RT, and anomalous themally-activated NIR emission with the temperature increasing from 77 to 300 K for the first time, which was further designed into a remote and in situ optical fiber sensing device.

Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias.

A stable phase demodulation system for diaphragm-based acoustic sensors is reported. The system is based on a modified fiber-optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter-propagating waves, avoiding the use of complicated active servo-control. A 100 nm-thick graphite diaphragm-based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 µPa/Hz(1/2) and an output signal stability of less than 0.35 dB over an 8-hour period. The system may be useful as a universal phase demodulation unit for diaphragm-based acoustic sensors as well as other sensors operating in a reflection mode.

Micro-bending vector sensor based on six-air-hole grapefruit microstructure fiber using lateral offset splicing.

A one-dimensional micro-bending vector sensor based on two-mode interference has been introduced. This device was fabricated by lateral offset splicing a piece of six-air-hole grapefruit microstructure fiber (GMF) with single mode fiber (SMF). Variation of effective mode index occurred by micro-bending was investigated in simulation and experiment. This device exhibits micro-bending sensitivities of 0.441 nm/m(-1) and -0.754 nm/m(-1) at 0° and 180° bending orientations, respectively. Moreover, this sensor is immune to surrounding refractive index (SRI) and presents a low crosstalk of temperature.

Passively mode-locking erbium-doped fiber lasers with 0.3 nm single-walled carbon nanotubes.

We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3 nm as the saturable absorber. These ultrasmall SWNTs are fabricated in the elliptical nanochannels of a ZnAPO4-11 (AEL) single crystal. By placing an AEL crystal into an EDFL cavity pumped by a 980 nm laser diode, stable passive mode-locking is achieved for a threshold pump power of 280 mW, and 73 ps pulses at 1563.2 nm with a repetition rate of 26.79 MHz.

Ambient refractive index-independent bending vector sensor based on seven-core photonic crystal fiber using lateral offset splicing.

A novel, simple, and compact optical fiber directional bending vector sensor based on Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated. The device consists of a piece of seven-core photonic crystal fiber (PCF) sandwiched between two single mode fibers (SMFs) with a lateral offset splicing joint that covering two cores of PCF. Bending sensitivity of the seven-core PCF based MZI is changed by an axial rotation angle, which shows its capacity for recognizing positive and negative directions. Within a curvature range of -7.05 m-1 to 7.05 m-1, the calculated bending sensitivities of two resonant central wavelengths with opposite fiber orientations are 1.232 nm/m-1 and 1.174 nm/m-1, respectively. This novel MZI is formed by invoking interference between the LP01-like supermode and other higher order supermodes in the core, which leads to insensitive to ambient refractive index (ARI). We have also investigated the transmission characteristics of the sensor with the temperature change.

Diode-pumped simultaneously Q-switched and mode-locked YVO4/Nd:YVO4/YVO4 crystal self-Raman first-Stokes laser.

A diode-end-pumped simultaneously Q-switched and modelocked self-Raman YVO(4)/Nd:YVO(4)/YVO(4) laser at first-Stokes wavelength of 1175.9 nm was demonstrated. The shortest mode-locked pulse width of the laser was obtained to be ~23.57 ps, with the corresponding timebandwidth product of ~0.51. The maximum average output power, the highest pulse energy and the highest peak power were obtained to be 1.83 W, 6.1 µJ and 220 kW, respectively. The nonlinear Raman process improved the Q-switched mode-locking performance of the Stokes pulses.

In-line flat-top comb filter based on a cascaded all-solid photonic bandgap fiber intermodal interferometer.

In this paper, an in-line comb filter with flat-top spectral response is proposed and constructed based on a cascaded all-solid photonic bandgap fiber modal interferometer. It consists of two short pieces of all-solid photonic bandgap fiber and two standard single-mode fibers as lead fibers with core-offset splices between them. The theoretical and experimental results demonstrated that by employing a cut and resplice process on the central position of all-solid photonic bandgap fiber, the interference spectra are well tailored and flat-top spectral profiles could be realized by the controllable offset amount of the resplice. The channel position also could be tuned by applying longitudinal torsion with up to 4 nm tuning range. Such a flat-top fiber comb filter is easy-to-fabricate and with a designable passband width and flat-top profile.

Mode-beating-enabled stopband narrowing in all-solid photonic bandgap fiber and sensing applications.

In this paper, core-cladding modal beating in a short piece of all-solid photonic bandgap fiber (AS-PBF) is observed in longitudinal propagation direction. It is demonstrated that at the stopband range of AS-PBF, the power could transfer back and forth between the fiber core and the first layer of high-index rods. Both experimental results and the theoretical analysis from transverse coupled mode theory confirm that the 3-dB width of the sharp stopband could be significantly narrowed by multicycles of such core-cladding modal couplings, which is of great benefit to the high-resolution sensing applications. Based on such a guiding regime, a high-temperature sensor head is also made and its response to temperature is tested to be of 59.9 pm/°C.

Sensitivity-enhanced high-temperature sensing using all-solid photonic bandgap fiber modal interference.

A wavelength-encoded interferometric high-temperature sensor based on an all-solid photonic bandgap fiber (AS-PBF) is reported. It consists of a small piece of AS-PBF spliced core offset with standard single-mode fibers. Two core modes LP(01) and LP(11) are conveniently utilized as optical arms to form Mach-Zehnder-type interference at both the first and the second photonic bandgaps, and the maximum extinction ratio exceeds 25 dB. Experimental and theoretical investigation of its response to temperature confirms that high temperatures up to 700 °C can be effectively sensed using such an AS-PBF interferometer, and benefiting from a large effective thermo-optic coefficient of fiber structure, the sensitivity can be significantly enhanced (71.5 pm/°C at 600 °C).