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1.
Curr Osteoporos Rep ; 2024 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-38652430

RESUMO

PURPOSE OF REVIEW: This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms. RECENT FINDINGS: OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

2.
Front Pharmacol ; 15: 1337876, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38628641

RESUMO

Background: Depression is a severe mental disorder that poses a significant threat to both the physical and mental wellbeing of individuals. Currently, there are various methods for treating depression, including traditional Chinese herbal formulations like Chaihu-Shugan-San (CSS), which have shown effective antidepressant effects in both clinical and animal research. Objective: This review aims to provide a comprehensive synthesis of evidence related to CSS, considering both preclinical and clinical studies, to uncover its potential multi-level, multi-pathway, and multi-target mechanisms for treating depression and identify its active ingredients. Methods: A thorough search was conducted in electronic databases, including PubMed, MEDLINE, Web of Science, Google Scholar, CNKI, and Wanfang, using keywords such as "Chaihu Shugan" and "depression" to retrieve relevant literature on CSS and its active ingredients. The review process adhered to the PRISMA guidelines. Results: This review consolidates the mechanisms underlying antidepressant effects of CSS and its active ingredients. It emphasizes its involvement in the regulation of monoaminergic neurotransmitter systems, synaptic plasticity, and the hypothalamic-pituitary-adrenal axis, among other aspects. Conclusion: CSS exerts a pivotal role in treating depression through various pathways, including the monoaminergic neurotransmitter system, the hypothalamic-pituitary-adrenal axis, synaptic plasticity, inflammation, brain-derived neurotrophic factor levels, and the brain-gut axis. This review facilitates a comprehensive understanding of the current state of CSS research, fostering an in-depth exploration of the etiological mechanisms of depression and the potential discovery of novel antidepressant drugs.

3.
4.
Front Behav Neurosci ; 18: 1329638, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38292326

RESUMO

Background: Despite the increasing global prevalence of depression, existing treatment methods have limitations. Acupuncture has been recognized for its potential to alleviate various diseases by regulating inflammatory cytokines. However, a comprehensive systematic analysis of the effects of acupuncture on depression through inflammatory cytokines is currently lacking. This review aims to evaluate the impact of acupuncture on inflammatory cytokines in animal models of depression. Methods: A comprehensive search was conducted in PubMed, EMBASE, MEDLINE, and the Research Information Service System to identify studies that met predefined inclusion and exclusion criteria. The quality of each included study was assessed using a 10-item checklist adapted from the Cochrane Collaboration methods and animal data review. Meta-analysis was performed using STATA 17.0 software for literature that met the inclusion criteria. Results: The meta-analysis included a total of 21 studies involving 376 rodents. The overall quality of the included reports was rated as moderate or higher. The results demonstrated that acupuncture had a significant effect on the reduction of pro-inflammatory cytokines, including: IL-1ß [SMD = 3.36, 95% CI (2.73, 4.00), I2 = 73.3%, p < 0.05], IL-6 [SMD = 3.05, 95% CI (2.45, 3.64), I2 = 68%, p < 0.05], and TNF-α [SMD = 3.30, 95% CI (2.53, 4.06), I2 = 74.5%, p < 0.05]. Conversely, acupuncture was associated with an increased expression of anti-inflammatory cytokines, notably: IL-4 [SMD = -1.64, 95% CI (-2.46, -0.82), I2 = 4.1%, p = 0.307] and IL-10 [SMD = -1.45, 95% CI (-2.24, -0.66), I2 = 0, p = 0.678]. These results suggest that acupuncture modulates cytokine levels in depressed rodents, including reducing the expression of pro-inflammatory cytokines and increasing the expression of anti-inflammatory cytokines, thereby regulating the immune-related antidepressant pathway. Conclusion: While this study is limited by the number of included studies, the results suggest that acupuncture may be a viable option for the treatment of depression, and this effect is achieved through the regulation of various inflammatory cytokines. Systematic review registration: This research endeavor was duly registered with PROSPERO (ID: CRD42023420919, https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=420919).

5.
Artigo em Inglês | MEDLINE | ID: mdl-38038878

RESUMO

BACKGROUND: Intro-aortic balloon pump (IABP) is widely used in cardiac surgery patients nowadays. This study aimed to analyze the predictor of short-term survival in cardiac valvular surgery patients with intra-aortic balloon pump implantation. METHODS: This was a retrospective study and a total of 102 cardiac valvular surgery patients who received intra-aortic balloon pump implantation were consecutively included. We retrospectively collected the baseline characteristics and short-term outcomes. Baseline characteristics were compared between survivors with non-survivors, and logistic regression was performed to identify predictors for short-term mortality. RESULTS: Among all the patients, there were 71 (69.6%) patients successfully weaned from IABP and survived to discharge, the other 31 (30.4%) patients failed to wean from IABP and died within the first 30 days after surgery. When compared with non-survivors, survivors had a higher proportion of males (62% vs 32.3%, p = 0.006), a lower rate of Atrial fibrillation (38% vs 62%, p < 0.03). After IABP implantation, vasoactive drug use was significantly lower in survivors compared with non-survivors, and survivors showed significant improvements in cardiac function and urine volume. Univariate and multivariate logistic regression analysis indicated that atrial fibrillation and combined use of continuous renal replacement therapy (CRRT) were significant independent predictors for short-term mortality. CONCLUSION: Timely implantation of IABP can improve patients' cardiac and renal function and reduce the dosage of vasoactive drugs. Atrial fibrillation and combined use of CRRT are independent predictors for short-term mortality in patients who underwent cardiac valvular surgery with IABP implantation.

6.
Opt Lett ; 48(23): 6204-6207, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-38039227

RESUMO

Non-orthogonal multiple access (NOMA) in a radio over fiber (RoF) link based on optical-domain power allocation is proposed and demonstrated. The NOMA is implemented at the RoF transmitter where two spectrum-overlapped microwave vector signals with an identical power level are modulated on an optical carrier to generate two orthogonally polarized optical signals. By passing the optical signals through a polarization controller (PC) and a polarizer, the power levels of the two optical signals are controlled to achieve optical power allocation (OPA). The optical signals are then transmitted over a fiber to the receiver. Since the power levels of the two microwave vector signals applied to the modulator are identical and the power allocation is implemented in the optical domain, the nonlinearity due to the higher-power input microwave vector signal is reduced, leading to an increase in the dynamic range. At the receiver, the two optical signals are detected at a photodetector (PD). To demultiplex the two microwave vector signals, a digital signal processing (DSP) algorithm is developed. The proposed approach is evaluated experimentally. The results show that the transmission performance in terms of error vector magnitude (EVM) is improved thanks to the increased dynamic range.

7.
Acta Biochim Biophys Sin (Shanghai) ; 55(11): 1806-1818, 2023 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-37654075

RESUMO

Effective and non-toxic therapeutic agents are lacking for the prevention and treatment of colitis. Previous studies found that methyl cinnamate (MC), extracted from galangal ( Alpinia officinarum Hance), has anti-inflammatory properties. However, whether MC is effective as anti-colitis therapy remains unknown. In this study, we investigate the therapeutic effects of MC on dextran sulfate sodium (DSS)-induced colitis in mice and further explore its potential mechanism of action. MC treatment relieves symptoms associated with DSS-induced colitis, including the recovery of DSS-induced weight loss, decreases the disease activity index score, and increases the colon length without toxic side effects. MC treatment protects the integrity of the intestinal barrier in mice with DSS-induced colitis and inhibits the overexpression of pro-inflammatory cytokines in vivo and in vitro. Moreover, the MAPK signaling pathway is found to be closely related to the treatment with MC of colitis. Western blot analysis show that phosphorylation of the p38 protein in colon tissues treated with MC is markedly reduced and phosphorylation levels of the p38, JNK and ERK proteins are significantly decreased in RAW 264.7 cells treated with MC, indicating that the mechanism of MC in treating DSS-induced colitis could be achieved by inhibiting the MAPK signaling pathway. Furthermore, 16S RNA sequencing analysis show that MC can improve intestinal microbial dysbiosis in mice with DSS-induced colitis. Altogether, these findings suggest that MC may be a novel therapeutic candidate with anti-colitis efficacy. Furthermore, MC treatment relieves the symptoms of colitis by inhibiting the MAPK signaling pathway and improving the intestinal microbiota.


Assuntos
Colite , Camundongos , Animais , Sulfato de Dextrana/toxicidade , Camundongos Endogâmicos C57BL , Colite/induzido quimicamente , Colite/tratamento farmacológico , Colite/prevenção & controle , Transdução de Sinais , Colo/metabolismo , Modelos Animais de Doenças
8.
CNS Neurosci Ther ; 29(11): 3612-3623, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37269080

RESUMO

AIM: Blood-brain barrier (BBB) dysfunction is one of the hallmarks of ischemic stroke. USP14 has been reported to play a detrimental role in ischemic brain injury. However, the role of USP14 in BBB dysfunction after ischemic stroke is unclear. METHODS: In this study, we tested the role of USP14 in disrupting BBB integrity after ischemic stroke. The USP14-specific inhibitor IU1 was injected into middle cerebral artery occlusion (MCAO) mice once a day. The Evans blue (EB) assay and IgG staining were used to assess BBB leakage 3 days after MCAO. FITC-detran test was slected to examine the BBB leakage in vitro. Behavior tests were conducted to evaluate recovery from ischemic stroke. RESULTS: Middle cerebral artery occlusion increased endothelial cell USP14 expression in the brain. Furthermore, the EB assay and IgG staining showed that USP14 inhibition through IU1 injection protected against BBB leakage after MCAO. Analysis of protein expression revealed a reduction in the inflammatory response and chemokine release after IU1 treatment. In addition, IU1 treatment was found to rescue neuronal loss resulting from ischemic stroke. Behavior tests showed a positive effect of IU1 in attenuating brain injury and improving motor function recovery. In vitro study showed that IU1 treatment could alleviate endothelial cell leakage induced by OGD in cultured bend.3 cells through modulating ZO-1 expression. CONCLUSIONS: Our results demonstrate a role for USP14 in disrupting the integrity of the BBB and promoting neuroinflammation after MCAO.


Assuntos
Barreira Hematoencefálica , Lesões Encefálicas , Isquemia Encefálica , AVC Isquêmico , Animais , Camundongos , Barreira Hematoencefálica/metabolismo , Lesões Encefálicas/metabolismo , Isquemia Encefálica/metabolismo , Células Endoteliais/metabolismo , Azul Evans/metabolismo , Azul Evans/farmacologia , Imunoglobulina G , Infarto da Artéria Cerebral Média/complicações , Infarto da Artéria Cerebral Média/tratamento farmacológico , Infarto da Artéria Cerebral Média/metabolismo , AVC Isquêmico/metabolismo , Doenças Neuroinflamatórias , Acidente Vascular Cerebral/metabolismo
9.
Opt Lett ; 48(12): 3179-3182, 2023 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-37319056

RESUMO

A simple polarization-insensitive coherent radio-over-fiber (RoF) link with increased spectrum efficiency and transmission capacity is proposed and demonstrated. Instead of using two polarization splitters (PBSs), two 90° hybrids, and four pairs of balanced photodetectors (PDs) in a conventional polarization-diversity coherent receiver (PDCR), a simplified PDCR with only one PBS, one optical coupler (OC), and two PDs is employed in the coherent RoF link. At the simplified receiver, a novel, to the best of our knowledge, digital signal processing (DSP) algorithm is proposed to achieve polarization-insensitive detection and demultiplexing of two spectrally overlapping microwave vector signals as well as the elimination of the joint phase noise originating from the transmitter and the local oscillator (LO) laser sources. An experiment is performed. The transmission and detection of two independent 16QAM microwave vector signals at identical microwave carrier frequencies of 3 GHz with a symbol rate of 0.5 GSym/s over a 25-km single-mode fiber (SMF) is demonstrated. Thanks to the spectrum superposition of the two microwave vector signals, the spectral efficiency as well as the data transmission capacity is increased.


Assuntos
Telecomunicações , Desenho de Equipamento , Análise de Falha de Equipamento , Processamento de Sinais Assistido por Computador
11.
Opt Express ; 31(8): 13140-13153, 2023 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-37157458

RESUMO

Self-interference (SI) due to signal leakage from a local transmitter is an issue in an in-band full-duplex (IBFD) transmission system, which would cause severe distortions to a receiving signal of interest (SOI). By superimposing a local reference signal with the same amplitude and opposite phase, the SI signal can be fully canceled. However, as the manipulation of the reference signal is usually operated manually, it is difficult to ensure a high speed and high accurate cancellation. To overcome this problem, a real-time adaptive optical SI cancellation (RTA-OSIC) scheme using a SARSA(λ) reinforcement learning (RL) algorithm is proposed and experimentally demonstrated. The proposed RTA-OSIC scheme can automatically adjust the amplitude and phase of a reference signal by adjusting a variable optical attenuator (VOA) and a variable optical delay line (VODL) achieved through an adaptive feedback signal, which is generated by evaluating the quality of the received SOI. To verify the feasibility of the proposed scheme, a 5 GHz 16QAM OFDM IBFD transmission experiment is demonstrated. By using the proposed RTA-OSIC scheme, for an SOI at three different bandwidths of 200, 400, and 800 MHz, the signal can be adaptively and correctly recovered within 8 time periods (TPs), which is the required time of a single adaptive control step. The cancellation depth for the SOI with a bandwidth of 800 MHz is 20.18 dB. The short- and long-term stability of the proposed RTA-OSIC scheme is also evaluated. The experimental results indicate that the proposed approach could be a promising solution for real-time adaptive SI cancellation in future IBFD transmission systems.

12.
Opt Express ; 31(10): 16833-16844, 2023 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-37157753

RESUMO

A broadband photonic-assisted microwave receiver with high cross-channel interference suppression and image rejection is proposed and experimentally demonstrated. At the input of the microwave receiver, a microwave signal is injected into an optoelectronic oscillator (OEO), which functions as a local oscillator (LO) to generate a low-phase noise LO signal as well as a photonic-assisted mixer to down-convert the input microwave signal to the intermediate frequency (IF). A microwave photonic filter (MPF), realized by the joint operation of a phase modulator (PM) in the OEO and a Fabry-Perot laser diode (FPLD), is used as a narrowband filter to select the IF signal. Thanks to the wide bandwidth of the photonic-assisted mixer and the wide frequency tunable range of the OEO, the microwave receiver can support broadband operation. The high cross-channel interference suppression and image rejection are enabled by the narrowband MPF. The system is evaluated experimentally. A broadband operation from 11.27 to 20.85 GHz is demonstrated. For a multi-channel microwave signal with a channel spacing of 2 GHz, a cross-channel interference suppression ratio of 21.95 dB and an image rejection ratio of 21.51 dB are realized. The spurious-free dynamic range (SFDR) of the receiver is also measured to be 98.25 dB·Hz2/3. The performance of the microwave receiver for multi-channel communications is also experimentally evaluated.

13.
Nat Commun ; 14(1): 3000, 2023 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-37225707

RESUMO

Convolutional neural networks are an important category of deep learning, currently facing the limitations of electrical frequency and memory access time in massive data processing. Optical computing has been demonstrated to enable significant improvements in terms of processing speeds and energy efficiency. However, most present optical computing schemes are hardly scalable since the number of optical elements typically increases quadratically with the computational matrix size. Here, a compact on-chip optical convolutional processing unit is fabricated on a low-loss silicon nitride platform to demonstrate its capability for large-scale integration. Three 2 × 2 correlated real-valued kernels are made of two multimode interference cells and four phase shifters to perform parallel convolution operations. Although the convolution kernels are interrelated, ten-class classification of handwritten digits from the MNIST database is experimentally demonstrated. The linear scalability of the proposed design with respect to computational size translates into a solid potential for large-scale integration.

14.
BMC Endocr Disord ; 23(1): 53, 2023 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-36879275

RESUMO

BACKGROUND: The relationship between headache and thyrotoxicosis has been occasionally mentioned in case reports, but there are few related reports. Thus, the relationship cannot be determined. Few cases of subacute thyroiditis (SAT) presenting as simple headache have been reported. CASE PRESENTATION: This case report describes a middle-aged male patient who came to our hospital with acute headache for 10 days. He was initially misdiagnosed as meningitis due to headache, fever, and increased C-reactive protein. Routine antibacterial and antiviral therapy did not improve his symptoms. Blood test suggested thyrotoxicosis, and color ultrasound suggested SAT sonography. He was diagnosed with SAT. With the treatment of SAT, the headache was relieved after the thyrotoxicosis improved. CONCLUSION: This patient is the first detailed report of SAT presenting with simple headache, which is helpful for clinicians to differentiate and diagnose atypical SAT.


Assuntos
Meningite , Tireoidite Subaguda , Tireotoxicose , Pessoa de Meia-Idade , Humanos , Masculino , Tireoidite Subaguda/complicações , Tireoidite Subaguda/diagnóstico , Cefaleia/diagnóstico , Cefaleia/etiologia , Erros de Diagnóstico
15.
Opt Lett ; 48(1): 143-146, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36563389

RESUMO

By exploring the relationship between the gain/loss and the coupling coefficient, parity-time (PT) symmetry has been well explored in the photonics and optoelectronics fields to achieve unique functions, such as sidemode suppression, non-reciprocal light propagation, and unidirectional invisibility. In general, a PT-symmetric system has an architecture with two identical coupled resonators or loops. In this Letter, we explore the possibility of implementing a PT-symmetric system having an architecture with one resonator having a loop length that is a rational number of times the length of the other resonator, to increase the sidemode suppression ratio. A theoretical analysis is performed, which is validated by a proof-of-concept experiment in which a fiber ring laser having two loops with a length ratio being a rational number of 200/3, supporting single-longitudinal-mode lasing at 1555.88 nm, is demonstrated. Thanks to the non-identical loop lengths, the sidemode suppression ratio is increased, which is 53.2 dB in the experiment.

16.
J Pediatr Endocrinol Metab ; 36(2): 212-215, 2023 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-36473093

RESUMO

OBJECTIVES: Liddle syndrome is an autosomal dominant hereditary disease caused by a single gene mutation. Typical clinical manifestations are early-onset hypertension and hypokalemia. CASE PRESENTATION: This report describes a 17-year-old male with hypertension and hypokalemia. We performed Captopril inhibition and postural stimulation test to diagnose and type primary aldosteronism. The plasma renin activity was consistently low, and aldosterone levels were high, hence the patient was initially diagnosed with primary aldosteronism. After genetic analysis, a diagnosis of Liddle syndrome was made due to the presence of a p. Pro617Ser mutation in the SCNN1B gene. After diagnosis, the patient was prescribed one tablet of amiloride twice a day. The patient's blood pressure (average in 120-135/70-80 mmHg) and serum potassium levels (3.6-4.0 mmol/L) returned to normal and was well-controlled after treatment. CONCLUSIONS: Adolescent hypertension may be secondary to underlying medical conditions affecting the heart, kidneys, or endocrine system or primary with no known underlying disease process. Although in an adolescent with hypertension, hyperaldosteronism, and low plasma renin activity, the initial diagnosis suggested primary hyperaldosteronism, the failure of aldosterone receptor antagonist's therapy led to the diagnosis of Liddle syndrome. Increased aldosterone levels should always be evaluated with caution before a definitive diagnosis to prevent misdiagnosis. Genetic testing is the gold standard for the diagnosis of Liddle syndrome. Early diagnosis and early precise treatment can restore normal blood pressure and prevent severe sequelae of chronic hypertension in patients.


Assuntos
Hiperaldosteronismo , Hipertensão , Hipopotassemia , Síndrome de Liddle , Masculino , Adolescente , Humanos , Síndrome de Liddle/complicações , Síndrome de Liddle/diagnóstico , Síndrome de Liddle/genética , Hipopotassemia/complicações , Hipopotassemia/genética , Aldosterona , Renina , Hipertensão/complicações , Hipertensão/diagnóstico , Hipertensão/tratamento farmacológico , Hiperaldosteronismo/complicações , Hiperaldosteronismo/diagnóstico , Erros de Diagnóstico
17.
Opt Lett ; 47(24): 6464-6467, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36538463

RESUMO

We propose and experimentally demonstrate a multi-task photonic time-delay reservoir computing (RC) system based on polarization modulation. The key component in the system is a polarization modulator (PolM) that functions, jointly with a polarization controller (PC) and a polarizer, as an equivalent Mach-Zehnder modulator (MZM) to perform electrical to optical conversion and to provide nonlinear operation. By adjusting the bias of the equivalent MZM, the nonlinear function can be optimized for different tasks to achieve the best multi-task performance. In this paper, the task-independent information processing capacity (IPC) of the time-delay RC system is evaluated. The results show that the readout bias of the equivalent MZM leads to a different IPC which can be optimized for different tasks. Two benchmark tasks (NARMA10 and IPIX radar signal prediction) are performed experimentally. The readout bias is adjusted independently for each of the two tasks to give a minimum normalized mean square error (NMSE), which are 0.2103 and 0.0031 for the NARMA10 and IPIX radar signal prediction tasks at a speed of 1.06 Mb/s, respectively.

18.
Opt Express ; 30(12): 20809-20819, 2022 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-36224817

RESUMO

A single-longitudinal-mode narrow-linewidth fiber ring laser with stimulated Brillouin scattering (SBS) assisted parity-time (PT) symmetry for mode selection in a single fiber loop is proposed and experimentally demonstrated. When an optical pump is launched into the fiber loop along one direction, an SBS gain for the Stokes light along the opposite direction is produced. For two light waves at the Stokes frequency propagating along the two opposite directions, one will have a net gain and the other will have a net loss. By incorporating a fiber Bragg grating (FBG) with partial reflection in the loop, mutual coupling between the two counterpropagating Stokes light waves is achieved. The SBS gain can be controlled by tuning the angle between the polarization directions of the pump and the Stokes light waves through a polarization controller (PC). Once the gain and loss coefficients between the two counterpropagating light waves are controlled to be identical in magnitude, and that the gain coefficient is greater than the coupling coefficient caused by the FBG, PT symmetry breaking is achieved, making the mainmode to sidemode ratio highly enhanced, single mode lasing is thus achieved. The approach is evaluated experimentally. For a fiber ring laser with a cavity length of 8.02 km, single-mode lasing with a narrow 3-dB linewidth of 368 Hz and a sidemode suppression ratio of around 33 dB is demonstrated. The wavelength tunable range from 1550.02 to 1550.18 nm is also demonstrated.

19.
Appl Opt ; 61(22): 6671-6676, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-36255894

RESUMO

Photonics-assisted instantaneous frequency measurement of a microwave signal using a silicon integrated microring resonator (MRR) is proposed and experimentally demonstrated. The frequency of a microwave signal has a unique relationship with the power ratio between the two microwave signals at the outputs of two microwave photonic filters (MPF) with complementary frequency responses. The key device to implement the MPFs is a silicon integrated MMR, which is employed to convert a phase-modulated optical signal to an intensity-modulated optical signal by placing two optical carriers at the complementary slopes of the MRR. For a given frequency measurement range and resolution, an MRR is designed and fabricated, and its use for instantaneous microwave frequency (IMF) measurement is implemented. For the fabricated MRR, an IMF measurement range of 14-25 GHz with a measurement accuracy of ±0.2GHz is achieved.

20.
Opt Express ; 30(16): 28774-28782, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-36299066

RESUMO

An optoelectronic oscillator (OEO) with improved sideband suppression by joint use of the spectral Vernier effect and parity-time (PT) symmetry is proposed and experimentally demonstrated. The spectral Vernier effect is implemented using two mutually coupled loops with different loop lengths, to increase the effective free spectral range (FSR). To further increase the mode selection capability to ensure stable single-frequency oscillation with an increased sidemode suppression ratio (SMSR), PT symmetry is implemented, in which the two mutually coupled loops are controlled with balanced gain and loss. Thanks to the combined effects, stable single-mode oscillation with a significantly increased SMSR is achieved. The proposed OEO is studied theoretically and evaluated experimentally. The results show that for a generated microwave signal at 10 GHz, the SMSR is 67.68 dB, which is increased by 11.20 dB or 26.05 dB, when using only the spectral Vernier effect or only the PT symmetry. Thanks to the long length of the longer loop, good phase noise performance is still maintained. The measurement shows that a phase noise as low as -124.5 dBc/Hz at an offset frequency of 10 kHz is achieved.

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