Full C- and L-band covered second-order OAM mode generator based on a thinned helical long-period fiber grating.

A full C- and L-band covered second-order orbital-angular-momentum (OAM) mode generator has been proposed and experimentally demonstrated, which is realized by using a helical long-period fiber grating (HLPG) but inscribed in a thinned four-mode fiber. By optimizing the design of grating period and fiber diameter of the proposed HLPG, an ultra-broadband rejection filter with a depth of ∼23 dB, a bandwidth of ∼156 nm @-10 dB (ranging from 1522 nm to 1678 nm) and a bandwidth of ∼58 nm @-20 dB (ranging from 1574 nm to 1632 nm), has been successfully obtained as a typical sample. To the best of our knowledge, this is the first demonstration of such ultra-broadband second-order OAM mode generator by using only one fiber component, i.e., the thinned HLPG. In addition, the proposed generator is less polarization-dependent and less temperature-sensitive than those of the conventional HLPGs, which is believed to be considerably helpful to find potential applications of the device itself in wavelength division multiplexing (WDM) and OAM mode division multiplexing (MDM) optical fiber communication systems.

Temperature-insensitive high-sensitivity refractive index sensor based on a thinned helical fiber grating with an intermediate period.

A temperature-insensitive high-sensitivity refractive index sensor is proposed and experimentally demonstrated, which is based on utilization of a thinned helical fiber grating but with an intermediate period (THFGIP). Attributed to the reduced diameter and an intermediate period of the grating, the proposed sensor has a high surrounding refractive-index (SRI) sensitivity and a low temperature sensitivity. The average SRI sensitivity of the proposed sensor is up to 829.9 nm/RIU in the range of 1.3410-1.4480 RIU. Moreover, unlike the traditional sensitivity-enhancement method by increasing the waveguide dispersion factor, here the waveguide dispersion factor at the resonant wavelength was decreased by reducing the diameter of the fiber grating and as a result, the crosstalk effect due to the temperature change can be further suppressed. The proposed temperature-insensitive SRI sensor has the superiorities of simple structure, ease fabrication, and low cost, which could be found more potential applications in the SRI sensing fields.

Periplaneta Americana (L.) extract activates the ERK/CREB/BDNF pathway to promote post-stroke neuroregeneration and recovery of neurological functions in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Periplaneta americana (L.) (PA) has been used in traditional Chinese medicine for thousands of years for the effect of invigorating blood circulation and removing blood stasis. Modern pharmacological research shown that PA extract exhibits promising effects in promoting wound healing and regeneration, as well as in brain diseases such as Parkinson's disease (PD). However, whether it is effective for neuroregeneration and neurological function recovery after stroke still unknown. AIM OF THE STUDY: This study aims to investigate the potential effect of PA extract to promote brain remodeling through the activation of endogenous neurogenesis and angiogenesis, in addition, preliminary exploration of its regulatory mechanism. METHODS: Firstly, BrdU proliferation assay and immunofluorescence (IF) staining were used to evaluate the effect of PA extract on the neurogenesis and angiogenesis in vitro and in vivo. Subsequently, the effects of PA extract on brain injury in stroke rats were assessed by TTC and HE. While mNSS score, adhesive removal test, rota-rod test, and morris water maze test were used to assess the impact of PA extract on neurological function in post-stroke rats. Finally, the molecular mechanisms of PA extract regulation were explored by RNA-Seq and western blotting. RESULTS: The number of BrdU+ cells in C17.2 cells, NSCs and BMECs dramatically increased, as well as the expression of astrocyte marker protein GFAP and neuronal marker protein Tuj-1 in C17.2 and NSCs. Moreover, PA extract also increased the number of BrdU+DCX+, BrdU+GFAP+, BrdU+CD31+ cells in the SGZ area of transient middle cerebral artery occlusion model (tMCAO) rats. TTC and HE staining revealed that PA extract significantly reduced the infarction volume and ameliorated the pathological damage. Behavioral tests demonstrated that treatment with PA extract reduced the mNSS score and the time required to remove adhesive tape, while increasing the time spent on the rotarod. Additionally, in the morris water maze test, the frequency of crossing platform and the time spent in the platform quadrant increased. Finally, RNA-Seq and Western blot revealed that PA extract increased the expression of p-ERK, p-CREB and BDNF. Importantly, PA extract mediated proliferation and differentiation of C17.2 and NSCs reversed by the ERK inhibitor SCH772984 and the BDNF inhibitor ANA-12, respectively. CONCLUSION: Our study demonstrated that PA extract promoted neurogenesis and angiogenesis by activating the CREB/ERK signaling pathway and upregulating BDNF expression, thereby recovering neurological dysfunction in post-stroke.

Probe-type all-fiber tiny-displacement sensor based on orbital-angular-momentum interferometry.

In this study, a probe-type all-fiber tiny-displacement sensor is proposed and experimentally demonstrated, which is realized by using an all-fiber orbital-angular-momentum (OAM) interferometer, where a probe is especially adopted and inserted into the testing arm of the OAM interferometer. The proposed device takes full advantages of the OAM interferometer and the probe-type fiber sensor, making it completely available to the tiny-displacement measurement. As a result, changes in displacement (ranging from 0 nm to 750 nm) with a real resolution of ∼8.81 nm have been successfully measured. To our knowledge, this is the first demonstration of an all-fiber probe-type OAM interferometer, which may find potential application to high-precision tiny displacement in a small confined space.

Recognition of the orbital-angular-momentum spectrum for hybrid modes existing in a few-mode fiber via a deep learning method.

In this study, we theoretically and experimentally demonstrate that the convolutional neural network (CNN) in combination with the residual blocks and the regression methods can be used to precisely and quickly reconstruct the OAM spectrum of a hybrid OAM mode no matter how the consistent OAM modes have the same or different order indices in both the azimuthal and the radial direction. For cases of the simulation testing, the mean errors of all recognized parameters for hybrid OAM modes in a four-mode fiber (4MF) and a six-mode fiber (6MF) are smaller than 0.003 and 0.008, respectively. To the best of our knowledge, this is the first time that all the OAM modes, probably existing in the core of 4MFs or 6MFs, can be precisely and quickly recognized from intensity distribution of the hybrid OAM mode itself via the deep learning method.

Full C-band covered and DWDM channelized high channel-count all-fiber orbital-angular-momentum mode generator based on the fiber gratings.

To generate the orbital-angular-momentum (OAM) modes at multiple wavelengths, which exactly fit with the dense-wavelength-division-multiplex (DWDM) channel grids, is important to the DWDM-based OAM mode-division-multiplex (MDM) fiber communication system. In this study, a full C-band covered and DWDM channelized OAM mode generator is firstly proposed and experimentally demonstrated, which is realized especially by using a broadband helical long-period fiber grating (HLPG) combined with a phase-only sampled multichannel fiber Bragg grating (MFBG). As a proof-of-concept example, the DWDM channelized two complementary 51-channel OAM mode generators have been successfully demonstrated, each of which has a channel spacing of 100 GHz (∼0.8 nm), an effective bandwidth of ∼40 nm, a high azimuthal-mode conversion efficiency of 90%, and high uniformities in both inter- and intra-channel spectra as well. To the best of our knowledge, this is the first time for proposal and experimental demonstration of such a high channel-count and DWDM channelized first-order OAM mode (l = 1) generator, which can also be used for multichannel higher-order OAM mode generation as long as the utilized HLPG is capable of generating a broadband higher-order OAM mode. The proposed device has potential applications to DWDM-based OAM fiber communications, OAM comb lasers, OAM holography, and OAM sensors as well.

Synthesizing the complex orbital-angular-momentum spectrum of hybrid modes existed in a few-mode fiber.

In this study, a simple and reliable method enabling to well synthesize the complex orbit-angular-momentum (OAM) spectrum of hybrid mode in a few-mode fiber is proposed and numerically demonstrated, which is realized by using the so-called inverse scattering method based on the genetic algorithm (GA), where the main Fourier components of a specially-selected ring in intensity distribution of the hybrid mode is used as the optimization objective. As a proof-of-concept example, power spectrum of a hybrid mode consisted of the first- and second-order OAM modes was successfully reconstructed with an accuracy higher than 0.99. This is the first time, to the best of our knowledge, that the complex OAM spectrum of a fiber hybrid mode consisted of more than two kinds of OAM modes is synthesized directly from the intensity distribution of the hybrid mode itself.

Ultra-broad edge filter based on a periodically twisted graded-index fiber and its application to a power-interrogated temperature sensor.

A novel and reliable method enabling to produce an ultra-broad edge-filter (UBEF) is firstly proposed and demonstrated both theoretically and experimentally, which is realized by using a periodically-twisted graded-index few-mode fiber (GI-FMF). By using the proposed method, an UBEF with a dynamic wavelength-range up to ∼380 nm is numerically obtained. Furthermore, an UBEF with a linear dynamic range larger than ∼300 nm in wavelength and ∼12.7 dB in power was successfully demonstrated in experiment, which represent the highest performances among all those achieved from the fiber-based optical edge-filters (OEFs) reported to date. The proposed UBEF can be used as an ultra-broadband power interrogation component to well demodulate the wavelength-dependent signal, meanwhile it can be used as a highly-sensitive power-interrogated sensor as well. As typical application example of the proposed UBEF, a power-interrogated temperature sensor has been successfully demonstrated. The temperature responsivities with respect to the power change and the spectral shift are 0.0179 dB/°C and ∼0.49 nm/°C, respectively. The UBEF-based power-interrogated sensing system has the advantages of fast response, low cost, small size and high reliability.

The efficacy of Da Chaihu decoction combined with metformin tablets for type 2 diabetes mellitus: A systematic review and meta-analysis.

OBJECTIVE: To assess the efficacy of Da Chaihu decoction combined with metformin tablets on patients with type 2 diabetes compared with metformin alone. METHODS: This systematic review and meta-analysis is written based on 2020 PRISMA Extension for Chinese Herbal Medicines 2020 (PRISMA-CHM 2020) reporting guidelines. We reviewed all the relevant studies from a search of the following databases from inception to February 2022 without any language restriction: Excerpta Medica Database (EMBASE), Google Scholar, PubMed, Cochrane Library, China National Knowledge Infrastructure (CNKI), VIP Information, Wanfang Data, and the Chinese Biomedical Literature Database(CBM). Data were extracted and the quality was independently evaluated by two reviewers, based on the inclusion and exclusion criteria. Data were analyzed using the Cochrane software RevMan 5.3. RESULTS: Six randomized controlled trials comprising 516 participants were included. The meta-analysis revealed the Da Chaihu decoction combined with metformin tablets group was significantly superior to the metformin tablets group in terms of fasting blood glucose(FPG) (-0.66 mmol/L; 95 % CI (confidence intervals) [- 1.28, - 0.04]), plasma glucose 2 h after meal (2-h PG) (-1.18 mmol/L; 95 % CI [-1.94, -0.42]) in six RCTs, body mass index (BMI) (-3.07 mmol/L; 95 % CI [-6.89, 0.75]) in three RCTs, glycosylated hemoglobin (HbAlc) (-0.36 mmol/L; 95 % CI [-1.04, 0.31]) in three RCTs, and triglycerides (TG) (-0.76 mmol/L; 95 % CI [-1.37, -0.15]) in two RCTs. In two RCTs, there were significant differences in terms of total cholesterol (TC) (-0.97 mmol/L; 95 % CI [-1.18, -0.76]). CONCLUSIONS: Very low-quality research shows that Da Chaihu decoction combined with metformin tablets exert a certain level of efficacy on patients with type 2 diabetes compared with metformin alone. However, random sequence generation methodology was reported in five studies leading to the low quality of the included studies. None of the six studies depicted the blinding method, allocation concealment, selective reporting, and assessed the purity and potency of the product. This observation requires verification through high-quality, multi-center, double-blinded randomized controlled trials, and assesses the purity and potency of the product.

Broadband flat-top second-order OAM mode converter based on a phase-modulated helical long-period fiber grating.

In this study, a broadband flat-top second-order orbital angular momentum mode (OAM) converter is proposed and demonstrated using a phase-modulated second-order helical long-period fiber grating (HLPG). The proposed HLPG is designed to be inscribed in a thinned four-mode fiber and operated at wavelengths near the dispersion turning point (DTP). In contrast to most of the HLPG-based OAM mode generators reported to date, where the high-order OAM mode and flat-top broadband have rarely been achieved simultaneously, a second-order OAM(OAM-2) mode converter with a flat-top bandwidth of 113 nm @ -20 dB (ranging from 1530-1643 nm) and a depth fluctuation of less than 3 dB @-26 dB has been successfully demonstrated in this study, such flat-top bandwidth covers the entire C + L bands and represents the best result of the HLPGs reported to date. Tolerance analyses for the fabrication of the designed HLPG were also performed. It is believed that the proposed HLPG may find applications in all-fiber vortex lasers as well as the OAM mode division multiplex (MDM) system.

Simultaneous generation of the second- and third-order OAM modes by using a high-order helical long-period fiber grating.

An all-fiber orbital angular momentum (OAM) mode generator enabling simultaneous generation of the second- and the third-order OAM modes with conversion efficiencies larger than 95% has been proposed and experimentally demonstrated, which is realized by using a high-order helical long-period fiber grating (HLPG) written in a thinned four-mode fiber. This is the first time, to the best of our knowledge, that two such OAM modes have been simultaneously obtained at wavelengths ranging from 1450 to 1620 nm by using only one fiber component, i.e., the HLPG. The proposed method provides a new way to simultaneously generate different orders of the OAM modes, which would further expand the OAM's applications to the fields of the optical tweezers, microscopy, and fiber communication, etc.

Demonstration of the mode-selection rules obeyed in a single-helix helical long-period fiber grating.

A simple method enabling the validation of the mode-selection rules obeyed in a single-helix helical long-period fiber grating (SHLPG) has been demonstrated both theoretically and experimentally, which is realized by investigating and analyzing the circular dichroism (CD) and the polarization dependence loss (PDL) spectra of the utilized SHLPG. It is confirmed for the first time, to the best of our knowledge, that in terms of the SHLPG's helicity, the core mode ${{\rm HE}_{\textbf{11}}}$HE11 with either the left circular polarization or the right circular polarization will be selectively coupled into the higher HE or the TE/TM mode, respectively. As a result, the SHLPG would exhibit an enhanced CD, as well as an enhanced PDL near the resonant wavelengths of the HE and TE/TM modes, respectively. The results presented in this Letter will be helpful for efficiently designing and producing SHLPG-based circular polarizers and orbital-angular-momentum generators.

All-fiber second-order orbital angular momentum generator based on a single-helix helical fiber grating.

An all-fiber orbital angular momentum (OAM) generator enabling direct turning of the fundamental mode (${{\rm HE}_{11}}$HE11) to the second OAM modes (${ l} = {\pm 2}$l=±2) with an efficiency of $\sim90\% $∼90% has been proposed and experimentally demonstrated, which is realized based on utilization of a second-order helical fiber grating written in a few-mode fiber. This is the first time, to the best of our knowledge, that an all-fiber second-order OAM has been achieved with using only one component, i.e., the helical long-period fiber grating. The proposed method opens a new way to efficiently generate an all-fiber higher-order OAM using a conventional multimode fiber.

Optimal design and fabrication of multichannel helical long-period fiber gratings based on phase-only sampling method.

In this study, a novel and efficient method enabling fabrication of a multichannel helical long-period fiber grating (HLPG) with almost the same channel spacing and the same rejection depth has been proposed and demonstrated for the first time both theoretically and experimentally, which is realized based on utilization of the so-called phase-only sampling technique. Unlike the previous amplitude-type sampling method where either a strong rectangular-type or a Sinc-like index-modulation distribution is generally demanded, the proposed method requires the minimum as well as a uniform index-modulation to the designed multichannel gratings, which considerably facilitates the fabrication process and makes the multichannel HLPGs to be fabricated in even a conventional single-mode fiber (SMF) by using the CO2 laser writing technique. As examples, a 3-channel and a 9-channel HLPGs have been successfully demonstrated numerically and experimentally. The experimental results agree with the designed ones, which represents the first realization of a multichannel HLPG, to the best of our knowledge. It is believed that the proposed multichannel HLPG could find potential applications to multi-wavelength orbit-angular-momentum (OAM) mode converter as well as the wavelength division multiplexing (WDM) sensors.

Analysis for the phase-diffusion effect in a phase-shifted helical long-period fiber grating and its pre-compensation.

Through analyzing the structure of the phase-shifted helical long-period fiber grating (HLPG), which is fabricated based on the thermally twisting method, we have shown that there exists a phase-diffusion effect when the thermal region is larger than the grating period itself, i.e., the inserted phase preset at particular period will be diffused to several neighboring periods, which causes a large distortion in the transmission spectrum. We have analytically proved that this kind of phase-diffusion effect can be quantified by doing the convolution between the preset phase function and the phase-diffusion function in spatial domain. According to the analytical results, we have proposed and successfully demonstrated a pre-compensation method to solve the phase diffusion effect. As an example, a phase-shifted HLPG with π phase-shift precisely inserted at middle position of the grating has been presented.

Phase-shifted helical long-period fiber grating and its characterization by using the microscopic imaging method.

We demonstrate a simple and robust method to write a phase-shifted helical long-period fiber grating (HLPG), where an equivalent phase-shift is formed by changing the local period of the grating during the fabrication process. Furthermore, we propose and demonstrate a simple method to characterize the phase-shift formed in a HLPG, which is realized by directly analyzing the imaging pattern of the fabricated HLPG using a stereo microscope under a white light illumination. Unlike the previous methods which are indirectly realized either by measuring the transmission spectrum of the fabricated HLPG or by analyzing the differential interference contrast (DIC) microscopic images of the fabricated HLPG, the proposed method can be used to well estimate the grating period as well as the phase-shift inserted in the HLPG in situ, which could considerably facilitate the fabrication technique of the HLPG by using CO2 laser.

Helical long-period grating formed in a thinned fiber and its application to a refractometric sensor.

A new kind of helical long-period grating (HLPG) written by using a CO2 laser is proposed and experimentally demonstrated, in which a sapphire tube (to be used as a miniature oven with a constant temperature inside) is specially utilized in place of the commonly used ZnSe focused-lens. The proposed method allows fabrication of a HLPG in a thinned fiber with a diameter smaller than several tens of micrometers. As an application of this kind of HLPG, a unique fiber sensor that allows for temperature-insensitive measurement of the refractive index is proposed and experimentally demonstrated, which is based on utilization of two cascaded HLPGs but with different transverse diameters.

Flat-top band-rejection filter based on two successively-cascaded helical fiber gratings.

We propose and demonstrate a novel method to produce a flat-top band-rejection filter, which is realized by successively cascading two helical long-period fiber gratings (HLPG) with opposite helicities. Unlike most of the other LPG-based flat-top filters obtained to date, the proposed HLPGs have no complex apodization in the grating's amplitude, and only a relatively shorter length (less than 4.6 cm) is needed, thus making this kind of HLPGs easily and particularly suitable to be fabricated by using the CO2 laser technique. As an example, a flat-top filter with a bandwidth of ~13 nm@0.5dB and ~15 nm@1dB has been successfully obtained.

Power-interrogated and simultaneous measurement of temperature and torsion using paired helical long-period fiber gratings with opposite helicities.

A power-interrogated sensor which allows for simultaneous measurement of temperature and torsion is proposed and experimentally demonstrated, which is based on utilization of paired helical long-period fiber gratings (HLPG) with opposite helicities. Unlike most of the previous fiber grating-based sensing system, here the paired HLPGs are simultaneously used as both the sensing and the interrogating elements and thus the bulk and high-cost wavelength-interrogating device can be eliminated. Moreover not only the torsion but also the torsion direction can be determined simultaneously. The temperature sensitivity obtained is estimated to be ~41 pm/°C within a range of 20-150 °C, and the torsion responsivities obtained are ~-1.414 nm/rad/m and ~1.276 nm/rad/m, respectively within a rotation angle of -360°~360°.

The effect of tamoxifen on expression of ER, PR, Cerb-B2, and ki-67 in C3H mice spontaneous breast cancer model and the relation with chemotherapeutic effect.

To explore the effect of tamoxifen on expression of ER, PR, Cerb-B2, and ki-67 in C3H mice spontaneous breast cancer model and further explore its relation with chemotherapeutic effect. Forty male C3H mice with spontaneous breast cancer aged 10 months were selected, and randomly divided into model group and tamoxifen group, with 20 mice in either group. Model group received intraperitoneal injection of normal saline, tamoxifen group received 5 mg/Kg tamoxifen injection. Tumor volume was measured every 3 days for 12 days in total. After that the mice were killed to weigh the tumor for tumor growth inhibition rate calculation; breast cancer specimen was collected, and immunohistochemistry was used to detect ER, PR, Cerb-B2, and ki-67 positive cells, western blot was used to detect expression of ER, PR, Cerb-B2, and ki-67 in breast cancer. The tumor growth inhibition rate of tamoxifen on mice was 61.56 %. Compared with model group, tumor weight in mice from tamoxifen group was significantly lower, tumor growth rate in tamoxifen group was significantly lower than model group; immunohistochemical staining results showed that compared with model group, ER, PR, Cerb-B2, and ki-67 positive cells in tumor of tamoxifen group were significantly lower (P < 0.05). Among them, ki-67 expression in tamoxifen group was negative; western blot semi-quantitative results were in accordance with immunohistochemistry results. Tamoxifen is effective on C3H mice spontaneous breast cancer. After being treated with tamoxifen, expression levels of ER, PR, Cerb-B2 and ki-67 are changed, and change of ER, PR, Cerb-B2, and ki-67 can predict the therapeutical effect of tamoxifen.