Virtual Fiber Research Articles

Virtual Fiber Configuration for Dynamic Lightpath Establishment in Large-scaled Optical Networks

Recently, progress has been made in the Generalized Multi-Protocol Label Switching (GMPLS) and Automatic Switched Optical Networks (ASON) standardizations. These technologies realize construction of large-scaled optical networks, interconnections among single-domain Wavelength Division Multiplexing (WDM) networks, and direct communication over multi-domain WDM networks. Meanwhile, it is known that the topology of the Internet exhibits the power-law attribute. Since the topology of the Internet, which is constructed by interconnecting ASs, exhibits the power-law, there is a possibility that large-scale WDM networks, which are constructed by interconnecting WDM networks, will also exhibit the power-law attribute. One of the structural properties of a topology that adheres to the power-law is that most nodes have just a few links, although some have a tremendous number of them. Another property is that the average distance between nodes is smaller than in a mesh-like network. A natural question is how such a structural property performs in WDM networks. In this paper, we first investigate the property of the power-law attribute of physical topologies for WDM networks. We compare the performance of WDM networks with mesh-like and power-law topologies, and show that links connected to high-degree nodes are bottlenecks in power-law topologies. To relax this, we introduce a concept of virtual fiber, which consists of two or more fibers, and propose its configuration method to utilize wavelength resources more effectively. We compare performances of power-law networks with and without our method by computer simulations. The results show that our method reduces the blocking probabilities by more than one order of magnitude.

Optical fiber interconnection for the scalable parallel computing system

In this paper, we discuss the optical fiber interconnection technologies applied in the two types of parallel processing systems: 1) a backplane interconnection in a parallel processor array system and 2) a computing cluster network. We have set up a parallel processor array system using optical fiber to make point-to-point interconnection between processor elements and are developing a low-cost virtual parallel optical fiber interconnection link (VPOFLink) complying with peripheral component interconnect (PCI) local bus specifications for the computing cluster. VPOFLink is integrated with the popular PCI bus interface in order to make the link hold the same bandwidth as that of the PCI bus. It was fabricated as an available peripheral device that can been inserted into the bus slots of commercial computers directly and can operate under the control of PCI bus. Also in this paper, we demonstrate the optical fiber link for a ring network and the architecture of the ring network.

Micromachining technology and biomedical engineering

Medical science and clinical medicine include many microscopic environments. Recent micromachining techniques fit the microscopic environments and are applied to microsurgery, fiberscopic operation, micromanipulation, artificial organs, and drug delivery systems. Microactuators, microsensors, and micro mechanical parts will be prepared for such medical devices and techniques. Virtual reality, stereovision, and fiber imaging support handling of cells and small targets of living body. The paper reports some perspectives of microtechnologies in biomedical engineering.

Efficient highly stable laser diode module for single-mode fiber employing a combination of hemispherical ended GRIN rod lens and virtual fiber

An efficient and practical laser diode module is demonstrated for single-mode fiber applications. The module is developed through use of an earlier proposed combination lens method, where a hemispherical ended graded index rod lens and virtual fiber are employed. Since lens and virtual fiber misalignment tolerances are large in this coupling method, the YAG laser welding technique is easily applicable. This laser diode module has not only a simple structure but also high coupling efficiency, excellent reproducibility, and extremely high reliability.

Coupling characteristics of lens systems for laser diode modules using single-mode fiber

The characteristics of lens systems for coupling InGaAsP laser diodes to single-mode (SM) fibers are studied. Two groups of lens systems are investigated. One group employs a combination of lenses and a SM fiber in a conventional configuration. The other group utilizes a combination of lenses and a virtual fiber, where the virtual fiber is formed by attaching a GRIN rod lens to the input endface of the SM fiber. The maximum coupling efficiency and misalignment tolerances for the optical circuit components in these lens systems are compared from the viewpoint of fabricating laser diode modules. It is confirmed that lens systems using virtual fibers offer better coupling characteristics than does the conventional coupling method.

Laser diode module for single-mode fiber based on new confocal combination lens method

A practical laser diode module is demonstrated for single-mode fiber applications. The module was developed through the use of a new combination lens method. The second lens in the confocal two-lens method is divided into two lenses. One is attached to the single-mode fiber front endface, thus forming a virtual fiber. Since both virtual fiber and lens misalignment tolerances are large in this coupling method, soldering is easily applicable. The laser diode module could be fabricated as easily as that for a multimode fiber. High coupling efficiency, excellent reproducibility, and high reliability were confirmed in trial-fabricated modules. Moreover, output power fluctuation due to reflected lightwaves was found to be very small.

A new confocal combination lens method for a laser-diode module using a single-mode fiber

A new confocal combination lens method is proposed, which can overcome severe misalignment tolerances for an InGaAsP laser diode to single-mode fiber coupling. Lens 2 in the confocal two-lens method is divided into two lenses, that is, lenses 21 and 22. The optimal distance between lenses 1 and 21 is found to be shorter than that for a confocal condition. Lens 22 is attached to the input endface of the single-mode fiber, thus forming a virtual fiber. Using 0.06- and 0.18-pitch GRIN rod lenses as lenses 21 and 22, the lateral and axial misalignment tolerances for the virtual fiber are improved by three and nine times, respectively, in comparison with those for the single-mode fiber. High-coupling efficiency of -3.0 dB of the laser diode to the single-mode fiber can be easily obtained including Fresnel reflections.

Combination lens method for coupling a laser diode to a single-mode fiber

A new combination lens method using a relatively large spherical lens and a virtual fiber is proposed for coupling an InGaAsP laser diode to a single-mode fiber. The virtual fiber is formed by attaching a GRIN rod lens to the input endface of the single-mode fiber. Coupling efficiency of from −3 to −4 dB is easily obtained. Alignment sensitivities of the proposed optical coupling circuit are investigated both theoretically and experimentally. The lateral and axial misalignment tolerances for the virtual fiber are improved three and nine times, respectively, in comparison with those for the single-mode fiber. The measured dependence of the coupling efficiency on the misalignments for the optical components agrees relatively well with the theoretical results through the ray matrix approach.