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121.
122.
Junji Yamauchi Takashi Ando Yasuhiro Akimoto Hisamatsu Nakano 《Fiber and Integrated Optics》1996,15(4):353-363
A wavelength filter consisting of single-mode and few-mode fibers is investigated numerically. A simple finite-difference beam-propagation method, in which a transparent boundary condition can be imposed, is developed for circularly symmetric waveguides. After confirming the validity of the numerical method by the mode-mismatch loss, we calculate the propagating field in the fiber wavelength filter, in which interference between LP01, and LP02 modes occurs. To improve the filtering operation, a depressed-index fiber is employed for the few-mode fiber. The effects of the radius and refractive index of the depressed section on the transmission power are revealed and discussed. Power is suppressed to less than 0.1% at 1.3 μm, while maintaining power transmission of more than 85% at 1.55 μm. It is also found that the filtering operation shifts to higher wavelengths as the input power is increased when we choose a self-focusing nonlinear material in the depressed section. 相似文献
123.
124.
A VPN is an optical virtual private network (oVPN) built of wavelength paths within a multihop wavelength routing (WR) dense wavelength division multiplexing (DWDM) network. An efficient and general graph-theoretic model (the wavelength-graph (WG)) has been proposed along with an integer linear programming (ILP) formulation of setting up VPNs with given traffic requirements over a given WR-DWDM network with two protection scenarios. Here, we have exploited the advantages of traffic grooming, i.e., numerous traffic streams of a VPN can share a wavelength path. We have also generalized the model for setting up VPNs over a WR-DWDM system where multiple VPNs can share a single wavelength path. The objective of the optimization is in all cases to reduce resource usage at upper (electrical) layers (i.e., to reduce the load of the virtual routers), subject to constrained amount of capacity of each wavelength channel and limited number of wavelengths. Here, we propose and compare three basic methods for configuring oVPNs and investigate various parameter settings. 相似文献
125.
In this article, an unreserved restoration solution for fast failure restoration in intelligent photonic networks is proposed. The unreserved restoration scheme is a real-time restoration technique that allows for utilizing network capacity dynamically and with full flexibility. However, it has the disadvantage of having a long restoration time as real-time redials are required after a failure is detected. The restoration time is crucial because long restoration times can result in data loss that is not expected, especially in high-speed networks. The proposed method targets reducing the aggregated optical cross-connect switching time to minimize real-time failure restoration time. With the proposed solution, in an event of failure, the restoration time can be reduced to times that are similar to those achieved in the reserved schemes. Common unreserved schemes have an inherent need for retries because the first try after failure detection and notification cannot always be guaranteed due to lack of network resource. In this paper, an enhanced implementation for the proposed solution is designed and described, which allows the features of the proposed solution to be fully realized and overcomes the inherent drawback of redundant OXC switching events for retries in common unreserved schemes. Through simulation experiments, it is shown that under a given network condition, the real-time path setup time for failure restoration required in the proposed solution can be improved by 68% compared with the common unreserved schemes. 相似文献
126.
High-performance InGaAs/InGaAlAs multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) with InGaAlAs/InP distributed Bragg reflectors are proposed for operation at the wavelength of . The lasers have good heat diffusion characteristic, large index contrast in DBRs, and weak temperature sensitivity. They could be fabricated either by metal-organic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE) growth. The laser light-current characteristics indicate that a suitable reflectivity of the DBR on the light output side in a laser makes its output power increase greatly and its lasing threshold current reduce significantly, and that a small VCSEL could output the power around its maximum for the output mirror at the reflectivity varying in a broader range than a large VCSEL does. 相似文献
127.
Kameron Rausch N. Yurt D. F. Geraghty N. Eradat N. Peyghambarian Alan R. Kost 《Optical and Quantum Electronics》2007,39(7):611-622
Broadband arrayed waveguide gratings on InP are presented using a novel S-shape design. This design was utilized to accommodate
the large free spectral range required for broadband operation. Four and eight channel AWGs with a wavelength channel spacing
of 18 nm are discussed. The output peaks of the AWGs have a wide FWHM of 11 nm which provides insensitive operation to polarization,
temperature fluctuations, and chromatic dispersion. 相似文献
128.
采用有限差分法利用Matlab求解了方同轴波导的特性阻抗和高次模的截止波长,并将数据与国外文献数据进行了对比,证明了有限差分法结合Matlab在分析简.单截面的同轴波导时是简单可行的,而且计算精度较高,通用性强,可以用于传输线工程问题的设计和计算。最后计算了矩形同轴线的相关数据用于与方形同轴线作对比。 相似文献
129.
通过对光波长测量原理及企业实际需求进行分析,建立光波长标准,确定测试项目及方法,并对光波长标准的不确定度进行评定和验证。 相似文献
130.
Yoko Hirohara Yoshitaka OKawa Toshifumi Mihashi Tatsuo Yamaguchi Naoki Nakazawa Yasuko Tsuruga Hiroyuki Aoki Naoyuki Maeda Ichiro Uchida Takashi Fujikado 《Optical Review》2007,14(3):151-158
The purpose of this paper was to investigate the feasibility of a newly developed hyperspectral fundus imaging camera with
a liquid crystal tunable filter. The intensities of different wavelengths of light transmitted through an artery, vein, and
the area surrounding these vessels and reflected out were measured, and the differential spectral absorptions were analyzed.
Measurements were made from 16 normal eyes and from two artificial capillaries. The ratios of absorption (ROA) of arteries
to veins from 500 to 580 nm (range 1) and from 600 to 720 nm (range 2) were calculated. For all eyes, the ROArange1 was larger than ROArange2. The ROA obtained from the artificial capillary filled with blood saturated with oxygen or nitrogen was similar to that of
simulated data of oxy- and deoxyhemoglobin extinction rate. Most ROAs of human eyes were lower than those of the simulated
data and the artificial capillaries. Oxygen saturation analysis by hyperspectral fundus imaging of retinal vessels were qualitatively
in agreement with thein vitro analysis or simulated values. However, further improvements are necessary to evaluate the oxygen saturation quantitatively
in the retinal blood vessels. 相似文献