目的:利用光相干断层扫描(OCT)研究不同区域视网膜神经纤维层(RNFL)厚度与光反射信号值在青光眼中的变化情况。方法:病例对照研究。纳入49名健康受试者的49只眼及47名青光眼患者的47只眼进行以视盘为中心的三维OCT扫描。在半径为1.7 mm...目的:利用光相干断层扫描(OCT)研究不同区域视网膜神经纤维层(RNFL)厚度与光反射信号值在青光眼中的变化情况。方法:病例对照研究。纳入49名健康受试者的49只眼及47名青光眼患者的47只眼进行以视盘为中心的三维OCT扫描。在半径为1.7 mm、1.95 mm和2.2 mm的3个分析环下,导出视盘周围环形截面图像,然后通过Image J软件进行分析。对比两组间不同半径,分析环下不同象限RNFL厚度及光反射信号的改变。结果:青光眼组RNFL在不同分析半径不同象限下的厚度值及光反射信号值基本较对照组低(p t检验),其中在下方象限中两组厚度差别最大;在颞侧象限中光反射信号值差别最大。大部分区域RNFL厚度与视野MD呈中至高度正相关(p p p均 p均 Objective: To investigate the changes in the thickness of the retinal nerve fiber layer (RNFL) and light reflectivity in different regions in eyes with glaucoma using optical coherence tomography (OCT). Methods: A case-control study was conducted, including 49 eyes from 49 healthy subjects and 47 eyes from 47 glaucoma patients for three-dimensional OCT scans centered on the optic disc. Circular peripapillary sections were extracted at radii of 1.7 mm, 1.95 mm, and 2.2 mm and then analyzed using Image J software. The changes in RNFL thickness and light reflectivity in different quadrants under different radii of analysis rings were compared between the two groups. Results: The thickness and light reflectivity of the RNFL in the glaucoma group were generally lower than those in the control group at different analysis radii and in different quadrants (p t-test), with the greatest difference in thickness in the inferior quadrant and the greatest difference in light reflectivity in the temporal quadrant. The RNFL thickness in most areas showed a moderate to high positive correlation with visual field mean deviation (MD) (p p p p < 0.05). Conclusion: The light reflectivity of the RNFL in different regions reflects the degree and regional changes of RNFL damage in glaucoma to some extent and can be used as one of the auxiliary diagnostic indicators for glaucoma diagnosis.展开更多
The statistical properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto- and cross-correlation functions are calculated by a full saturati...The statistical properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto- and cross-correlation functions are calculated by a full saturation laser theory with backscattering. The theoretical predictions are in good agreement with the experimental measurements.Further investigation reveals that the backscattering can reduce the fluctuations in the system while the full saturation effect plays a major role when the laser is operated above threshold. It is also quite important to notice that the injected signal can drive the weak mode from incoherent light to coherent light.展开更多
We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting ...We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting （FBG） optical equaliser. Transmissions of 10-Gb/s non return-to-zero signals using a 1.2- GHz RSOA and FBG optical equaliser with different setups are demonstrated. Significant performance improvement and 40-kin standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pum- ped Erbium-Doped Fibre Amplifier （RP-EDFA）, where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal, respectively.展开更多
An interrogation system based on two semiconductor optical amplifiers for weak fiber Bragg gratings （FBGs） was proposed. The first semiconductor optical amplifier （SOA） was used to modulate the light, and the seco...An interrogation system based on two semiconductor optical amplifiers for weak fiber Bragg gratings （FBGs） was proposed. The first semiconductor optical amplifier （SOA） was used to modulate the light, and the second SOA separated the reflected signal from the different FBGs through delayed switching. The proposed system has lower insertion loss and higher spatial resolution, and can interrogate the time- and wavelength-division multiplexed FBG array. Up to 50 FBGs, with a reflectivity of 0.2% and a spatial resolution of 5 m along the optical fiber, were distinguished to demonstrate the interrogation system.展开更多
The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. ...The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG; and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.展开更多
文摘目的:利用光相干断层扫描(OCT)研究不同区域视网膜神经纤维层(RNFL)厚度与光反射信号值在青光眼中的变化情况。方法:病例对照研究。纳入49名健康受试者的49只眼及47名青光眼患者的47只眼进行以视盘为中心的三维OCT扫描。在半径为1.7 mm、1.95 mm和2.2 mm的3个分析环下,导出视盘周围环形截面图像,然后通过Image J软件进行分析。对比两组间不同半径,分析环下不同象限RNFL厚度及光反射信号的改变。结果:青光眼组RNFL在不同分析半径不同象限下的厚度值及光反射信号值基本较对照组低(p t检验),其中在下方象限中两组厚度差别最大;在颞侧象限中光反射信号值差别最大。大部分区域RNFL厚度与视野MD呈中至高度正相关(p p p均 p均 Objective: To investigate the changes in the thickness of the retinal nerve fiber layer (RNFL) and light reflectivity in different regions in eyes with glaucoma using optical coherence tomography (OCT). Methods: A case-control study was conducted, including 49 eyes from 49 healthy subjects and 47 eyes from 47 glaucoma patients for three-dimensional OCT scans centered on the optic disc. Circular peripapillary sections were extracted at radii of 1.7 mm, 1.95 mm, and 2.2 mm and then analyzed using Image J software. The changes in RNFL thickness and light reflectivity in different quadrants under different radii of analysis rings were compared between the two groups. Results: The thickness and light reflectivity of the RNFL in the glaucoma group were generally lower than those in the control group at different analysis radii and in different quadrants (p t-test), with the greatest difference in thickness in the inferior quadrant and the greatest difference in light reflectivity in the temporal quadrant. The RNFL thickness in most areas showed a moderate to high positive correlation with visual field mean deviation (MD) (p p p p < 0.05). Conclusion: The light reflectivity of the RNFL in different regions reflects the degree and regional changes of RNFL damage in glaucoma to some extent and can be used as one of the auxiliary diagnostic indicators for glaucoma diagnosis.
文摘The statistical properties of a homogeneously broadened ring laser with an injected signal are investigated and the normalized two-mode intensity auto- and cross-correlation functions are calculated by a full saturation laser theory with backscattering. The theoretical predictions are in good agreement with the experimental measurements.Further investigation reveals that the backscattering can reduce the fluctuations in the system while the full saturation effect plays a major role when the laser is operated above threshold. It is also quite important to notice that the injected signal can drive the weak mode from incoherent light to coherent light.
基金ACKNOWLEDGEMENT This work was supported by the National High Technology Research and Development Pro- gram of China under Grant No. 2011AA01A- 104 the National Natural Science Foundation of China under Grant No. 61302079 and the Fund of State Key Laboratory of Information Photonics and Optical Communications, Bei- jing University of Posts and Telecommunica- tions, China.
文摘We propose a 10-Gb/s Wavelength- Division-Multiplexed Passive Optical Network （WDM-PON） scheme with upstream transmi- ssion employing Reflective Semiconductor Op- tical Amplifier （RSOA） and Fibre Bragg Gra- ting （FBG） optical equaliser. Transmissions of 10-Gb/s non return-to-zero signals using a 1.2- GHz RSOA and FBG optical equaliser with different setups are demonstrated. Significant performance improvement and 40-kin standard single mode fibre transmission are achieved using FBG optical equaliser and Remotely Pum- ped Erbium-Doped Fibre Amplifier （RP-EDFA）, where they are used to equalise the output of the band-limited RSOA and amplify the seed light and upstream signal, respectively.
基金This work was supported in part by the National Science Foundation of China, NSFC （Gram No. 61205070）, and the Major Program of the National Natural Science Foundation of China, NSFC （Grant No. 61290311）.
文摘An interrogation system based on two semiconductor optical amplifiers for weak fiber Bragg gratings （FBGs） was proposed. The first semiconductor optical amplifier （SOA） was used to modulate the light, and the second SOA separated the reflected signal from the different FBGs through delayed switching. The proposed system has lower insertion loss and higher spatial resolution, and can interrogate the time- and wavelength-division multiplexed FBG array. Up to 50 FBGs, with a reflectivity of 0.2% and a spatial resolution of 5 m along the optical fiber, were distinguished to demonstrate the interrogation system.
文摘The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG; and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.
