Multimodal Components Research Articles

Fabrication of a planar grating spectrograph by deep-etch lithography with synchrotron radiation

Abstract A three-layer resist system has been developed which can be used for light guiding. By structuring these layers with deep-etch X-ray lithography, high-precision multimode lightguide components with a relatively low attenuation can be produced. As a first example, a planar grating spectrograph with a self-focusing reflection grating has been fabricated together with fibre-fixing grooves. The spectro-graph shows an excellent dispersion of the light as well as a low cross-talk between the channels.

Accurate modal characterization of passive components based on selective excitation of optical fibers

Abstract Modal performances of multimode optical passive components are measured by use of a selective excitation techique. Pure LPm1 modes up to LP15 1 mode are generated in a Ti: sapphire laser cavity and launched in the input fiber of the component under test. Azimuthal dependency of the LP11 mode excitation coefficient is used in an accurate centering technique of monomode and multimode splices or connectors.

Modeling and analysis of systems with multimode components and dependent failures: Khiem V. Le and Victor O. K. Li. IEEE Trans. Reliab.38(1), 68 (1989)

Summary & Conclurions - This paper presents a model for the reliability and performance analysis of systems where components can degrade in a statistically dependent manner. This cause-based multimode model is based on the idea that deviations of components from the up state have underlying physical causes which can be explicitly identified and are statistically independent. The effects of several causes can be combined in a flexible manner. System reliability & performance measures can be computed approximately by considering the most probable states. Such states can be efficiently generated by algorithms developed for the earlier multimode, statistically independent-failure model.

Efficient computation of most probably states for communication networks with multimode components

A general multimode model for jointly assessing the performance and reliability (performability) of a communication network is considered. The performability is computed by averaging the performance over the most probable network states. An efficient algorithm, superior to all previous algorithms in both speed and flexibility, is proposed to enumerate the most probable network states. The algorithm keeps generating the network states one by one, in order of decreasing probability, until some stopping rule (if specified) is met.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modeling and analysis of systems with multimode components and dependent failures

A model for the reliability and performance analysis of systems where components can degrade in a statistically dependent manner is presented. This cause-based multimode model is based on the idea that deviations of components from the up state have underlying physical causes which can be explicitly identified and are statistically independent. The effects of several causes can be combined in a flexible manner. System reliability and performance measures can be computed approximately by considering the most probable states. Such states can be efficiently generated by algorithms developed for the earlier multimode, statistically independent failure model. >

Reliability Analysis of a Communication Network with Multimode Components

This paper presents a model to calculate the reliability of communication networks with multimode components. Previous research on network reliability has focused on models in which each component may be in one of two modes, namely, operative or failed. In reality, a component may undergo degradations in performance before a complete outage, and will therefore operate in more than two modes. Traditional network reliability measures, such as the probability that a pair of nodes is connected, are not meaningful in a multimode model. Therefore, the mean message delay of the network is defined as the performance measure. An exact calculation of this reliability measure is not feasible due to the large number of network states, corresponding to network components being in different modes. We have developed an approximation method to calculate this reliability measure. This method requires us to work with the states of the network in order of decreasing probability. An algorithm ORDER- M is developed to generate these states in the proper order.

Mode transition matrices for fibre-optic connectors

Mode transition matrices described the transfer of modes through a multimode fibre-optic component. These matrices are used to calculate the differential mode attenuation and thus the total loss of concatenated components. Here, matrices of connectors and their implementation into a system of concatenated couplers are presented. The experimental results demonstrate that the matrix is a powerful means to characterise the loss behaviour of a multimode fibre-optic network.

Mode-Specific Reflectometry in a Multimode Waveguide

A technique for measuring the voltage-standing-wave ratio (VSWR) created by a mismatch for a specific mode in a multimode waveguide is described. A heavlly loaded resonant cavity is used to launch the mode of interest and the variation in the cavity loaded Q is noted as the phase separation of the cavity and the mismatch is varied. The bandwidth of this technique is generally about 0.03 percent and VSWR as low as 1.05:1 may be measured accurately. Mode-specific VSWR measurements are of particular interest in analyzing the performance of multimode waveguide components, and in opthnizing muitfmode networks. The measurement technique may be used, for example, in the design and optitnization of transmission lines for electron cyclotron resonance heating systems in magnetic fusion devices.

Mode Analysis in Multimode Waveguides Using Voltage Traveling Wave

The voltage traveling were ratio (VTWR) equations are disscussed in general and the specific case of guided traveling waves in multimode circular waveguides is addressed in detail. An experimental technique for measuring VTWR's is described and sample experimental results are analyzed. Measurements of the VTWR's can be easily related to the fractions of total power propagating in each waveguide mode. This information may be used, for example, to examine the mode conversion properties of multimode waveguide components.

Polarisation preservation in multimode fibres

Birefringent multimode fibres have been found to preserve polarisation except for one mode near cutoff. Experimental observations and theoretical considerations show that polarisation ratios better than 20 dB are possible, offering the potential for building polarisation-sensitive multimode fibre components.

Multimode Fiber Devices for Optical Fiber Links, Printing, and Display

It is generally agreed that multimode graded index fiber has become the main fiber technology for optical communication applications. Multimode graded index fibers provide sufficient bandwidth for most applications without the critical tolerances of single mode fibers. In this paper, multimode fiber devices and components based on packaging miniaturized optical components for a GaAs laser array source package, and multichannel waveguides will be discussed. Experimental results, fabrication process and technology limitation for some of the multimode devices will be included. One major drawback of using multimode fibers is the difficulty to obtain simple and efficient switches and taps which are essential for data bus or other optical links. Some possible solutions for multimode fiber switches with miniaturized bulk wave devices will be presented.

Analysis of nonhomogeneous sequences of evoked potentials

Changes in mode of response can occur within a sequence of evoked potentials. It is possible to separately average evoked potentials of different wave shapes corresponding to these different modes. A procedure is presented which identifies multimodal sequences and the latencies of the multimodal components of evoked potentials. Essentially this procedure indicates whether a sequence of evoked potentials can be divided into two or more subsequences whose averages will contain components which significantly differ from each other. When this procedure is used in conjunction with a previously published method, averages from unimodal subsequences can be computed.