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Design and Fabrication of Optical and Fiber-Optic Humidity Sensors
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2018
The details of the laser packaging can be critically important for many applications as well (Allen 1998). Fiber-coupled systems are often preferred for their simplicity and the ease with which the laser light can be transported over distances of hundreds of meters. For stable transmission, single-mode fibers, where a single transverse mode structure is supported in the waveguide, are superior. Larger diameter, multimode fibers tend to exhibit uncontrolled bending losses and interference effects associated with multiple transverse modes. Depending on the guided wavelength, the core diameter for single-mode fibers ranges between 5 and 10 µm, introducing extreme alignment tolerances at the coupler. Careful attention by the manufacturer to alignment and thermal stabilization of this alignment is critical for a well-behaved device (Allen 1998).
Journey of Cables – From Coppers to Optical Fiber
Published in Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez, Network Evolution and Applications, 2023
Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez
A single-mode optical fiber is a type of optical fiber used in fiber-optic communication that is designed for transmission of only a single mode of light, i.e., the transverse mode, through it. It is a common type of the optical fiber which is used to transmit the optical signals over longer distances, composed of a single glass fiber strand to transmit a single mode or ray of light. The single-mode optical fiber cable has a fairly slim core diameter single glass fiber strand. It has very less internal reflection involved for the light rays to pass through it, which reduces attenuation and allows high-speed data transfer over a long distance. It is also sometimes known as a unimode optical fiber, monomode optical fiber, or single-mode optical waveguide. A single-mode fiber has a core diameter of nominally 9 µm, where its small core coupled with a single light wave helps in eradicating distortion caused by light pulses overlapping. It offers the highest transmission speed with a minimal signal attenuation, where the modes of the light waves are the possible solutions of the Helmholtz equation obtained by combining Maxwell’s equations and the boundary conditions, which further define the distribution of the wave in space or the way the wave travels through space. Same mode waves can be with different frequencies which can be used to propagate in the single-mode fibers. Waves having the same mode and different frequencies are similarly distributed in space, which means that the same mode light with all the different frequency waves will give a single ray of light. The single-mode fiber is also called as the transverse mode due to the reason that the electromagnetic oscillations of the waves occur perpendicular (transverse) to the length of the fiber. Charles K. Kao was awarded the Nobel Prize in Physics for his theoretical work on the single-mode optical fiber in 2009 [15].
P
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
protective relay scattering of the radio waves by dust and other particles in the troposphere. The ionized trails of meteors can also act as scatterers. (2) in waveguides, used at microwave frequencies, propagation mode refers to the arrangement of electrical and magnetic fields within the waveguide. Modes can be classified as being transverse electric (TE) or transverse magnetic (TM), depending on whether the electric field or magnetic field is transverse to the direction of wave propagation within the waveguide. The mode that exists for the lowest frequency that can be transmitted by the waveguide is known as the dominant mode of the waveguide. propagation path the route along which a radio wave propagates from the transmitting antenna to the receiving antenna. If this is a straight line, the path is a line of sight path. Otherwise, reflection, diffraction, and other phenomena may change the direction of propagation so that the path can be envisioned as made up of several straight-line segments. See also line of sight, multipath propagation. proper 2-D transfer matrix matrix T (z 1 , z 2 ) = the 2-D transfer proper mode a mode as obtained from a boundary value problem defined over a finite interval and relative to a second-order differential equation with real coefficients. See also improper mode. proper subgraph a subgraph that does not contain all of the edges of the given graph. proportional control control scheme whereby the actuator drive signal is proportional to the difference between the input/desired output and measured actual output. proportional-integral-derivative (PID) control a control scheme whereby the signal that drives the actuator equals the weighted sum of (1) the difference, (2) time integral of the difference, and (3) time derivative of the difference between the input and the measured actual output. It is a widely used control scheme in industry that can be tuned to give satisfactory performance based on knowledge of dominant system time constant. protection control access to information in a computer's memory, consistent with a particular policy or mechanism. Ring numbering was introduced in the Multics system as one basis for limiting access and protecting information. The term "security" is used when the constraints and policies are very restrictive. protection fault an error condition detected by the address mapper when the type of request is not permitted by the object's access code. protective relay a device that monitors the condition of the electric power system and determines the presence of faults or other system anomalies. The protective relay monitors current flow, voltage level, or other parameter. When it operates due to a fault or other event, it initiates a trip signal intended to open the appropriate circuit breaker(s) or other protective devices.
Tuneable ferroelectric liquid crystal microlaser
Published in Liquid Crystals, 2020
A. V. Ryzhkova, R. Pratibha, M. Nikkhou, I. Muševič
The theory of WGMs in optically isotropic micro-resonators is very well developed because of their importance in basic and applied science, see Ref. [24,25] and the references therein. In spherically symmetric and isotropic resonators, the WGMs are solutions of Maxwell’s equations that appear in a form of spherical harmonic functions and spherical Bessel functions [26]. These eigen-waves are characterised by three integer mode numbers, i.e. the polar mode number (), the azimuthal mode number () and the radial mode number (). Furthermore for each mode characterised by , there are two orthogonal polarisations: transverse electric (TE) and transverse magnetic (TM) polarisation. The radial mode number counts the number of maxima of the radial intensity distribution, whereas the polar mode number counts the number of wavelengths (oscillations in space) for one circulation.