FM transmitters can use Class ____________________ amplifiers since amplitude linearity is not important.

FIBER OPTICSOptical fibers work on the principle ofTIRThe value of the angle of incidence for which the angle of reflection is 90o.Critical angleThe person who coined the word fiber opticsN.S. KappanyA device made by Alexander Graham Bell made of mirrors and selenium detectors that transmitted sound waves over a beam of light.photophoneThe two persons who first scanned and transmitted television images through uncoated fiber cables.John L. Baird and C.W. Hansel Fiber optics used in medical field developed by A.C.S. van Heel, H.H. Hopkins, and N.S. KappanyFlexible Fiberscope The two persons who proposed the use of cladded fiber cablesK.C. Kao and G.A. BockhamPersons who developed an optical fiber with losses less than 2 dB/km.Kapron, Keck, and MaurerCaused by high humidity which makes silicon dioxide crystals to interact, causing bonds to break down and results in fracture.Stress corrosion (sometimes called static fatigue) A coating which is applied to the outside of the cladding to avoid static fatigue.special lacquer, silicone, or acrylateMaterials commonly used for buffer jacket in fiber optics.Steel, fiberglass, plastic, flame-retardant PVC, Kevlar yarn, and paperThe outermost covering in a fiber optic cable.Polyurethane jacket Plastic fibers have higher attenuation characteristics and do not propagate light as effectively as glass. Therefore, plastic fibers are limited to relatively short cable runs, such as within a single building. But they are easier to install, can better withstand stress, are less expensive, and weigh approximately 60% less than glass.What does PCS mean?Plastic clad silicaPlastic clad silica (PCS) - slightly better than silica clad silica (SCS). PCS are less affected by radiation and is more rugged.What does SCS mean?Silica clad silicaSilica clad silica (SCS) have the best propagation characteristics and is easier to terminate than PCS fibers.A compound which prevents the intrusion of water in the fiber and thus prevents stress corrosion or static fatigue.Polyurethane compound The process of moving an electron from one energy level to another.AdsorptionThe process of decaying from one energy level to another energy level.Spontaneous decay or spontaneous emissionThe science of measuring only light waves that are visible to the human eye.PhotometryMeasures light throughout the entire electromagnetic spectrumRadiometryThe power which is sometimes called radiant fluxOptical power Violet wavelengths are refracted the most , whereas red wavelengths are refracted the least.Step index fibers uses reflection while graded index fibers uses refractionAdvantage of single-mode step index:Minimum dispersionWider bandwidth and higher transmission ratesDisadvantage of single-mode step index:Difficulty in coupling light into or outExpensive and difficult to manufactureThe advantage and disadvantage of multimode step index is the opposite of that of single-mode.A graphical representation of the magnitude of refractive index across the fiber.Index profile Used to describe the light-gathering or light-collecting ability of an optical ability of the fiber.Numerical Aperture (NA)

A type of absorption which is caused by valence electrons in the silica material from which fibers are manufactured.

Ultraviolet absorption A type of absorption which is a result of photons of light that are absorbed by atoms of the glass core molecules.Infrared absorption A type of absorption caused caused by OH- ions in the materialIon resonance absorption Chromium, Iron and copper molecules also cause ion absorptionLoss in light power due to light rays that escape the fiberRayleigh scattering lossThe other term for wavelength dispersionchromatic distortionChromatic distortion occurs only in fibers with single mode of transmission.Bending which occurs as a result of differences in the thermal contraction rates between the core and the cladding material.MicrobendingBends caused by excessive pressure and tension and generally occur when fibers are bent during handling or installation.Constant-radius bends Is sometimes called pulse spreading - caused by the difference in the propagation times of light rays that take different Modal dispersion Modal dispersion can occur only in multimode fibers. It can be reduced by using graded-index fibers and can be entirely eliminated by using single-mode step-index fibers.For multimode propagation, dispersion is often expressed asbandwidth length product (BLP) or bandwidth distance product (BDP)The wavelength equivalent of bandwidth.LinewidthLEDs emit light by spontaneous emission Spontaneous emission - light is emitted as a result of the recombination of electrons and holes.Devices which are often called surface emitters. Their primary disadvantage is the nondirectionality of their light emissions.Homojunction devices Devices are often called edge emitters. Advantages are: increase in current density generates a more brilliant spot, easy to couple light into a fiber, smaller capacitance which allows its use at higher speed.HeterojunctionA depletion-layer photodiode and is probably the most common device used as a light detector in fiber optic communication systems.PIN diodeA pipn structure. The process results in avalanche and thus, are more sensitive than PIN diodes and require less additional amplification. Disadvantage is lower transit time and more noise. APDResponsivity is expressed inamperes per wattDetermines the maximum bit rate possibleTransit time The wavelength values that a given photodiode will respond.Spectral response Developed the first laser using ruby crystals with a xenon flash lampTheodore Maiman Developed the helium laserA. Javin Lasers which use a mixture of helium and neonGas lasersLasers which use organic dyesLiquid lasersLasers which use a solid, cylindrical crystal, such as ruby, for an active medium. The ruby is excited by a tungsten lamp.Solid lasersCommonly called ILD. The output light from an ILD is easily modulated.Semiconductor lasers Causes laser action (lasing) to occur.Population inversion PROBLEMA fiber has an index of refraction of 1.6 for the core and 1.4 for the cladding. Calculate:a) the critical angleb) 2 for 1 = 30o b) 2 for 1 = 70oANSWERSa) 61ob) 34.8oc) 70oPROBLEMCalculate the numerical aperture and the maximum angle of acceptance for the fiber with index of refraction of 1.6 for the core and 1.4 for the cladding

ANSWER0.775 and 50.8oPROBLEMA single-mode fiber has a numerical aperture of 0.15. What is the maximum core diameter it could have for use with IR with a wavelength of 820 nm?

rmax = 0.383 / N.A.ANSWER4.2 mPROBLEMFind the energy, in electron-volts, in one photon at a wavelength of 1 mh = 6.67 x 10-34 J-s 1 eV = 1.6 x 10-19 JANSWER1.24 eV