Optical Fibres john v How Fibre Optic cables work Light travels down a fiber optic cable by bouncing off the walls of the cable repeatedly. Each light particle (photon) bounces down the pipe with continued internal mirrorlike reflection.The light beam travels down the core of the cable. - explain how total internal reflection (TIR) is made use of - In general, total internal reflection takes place at the boundary between two transparent media when a ray of light in a medium of higher index of refraction approaches the other medium at an angle of incidence greater than the critical angle. For a water-air surface the critical angle is 48.5°. https://www.britannica.com/science/total-internalreflection - explain TIR (include Snells’ law) Total internal reflection. When light propagates from air into glass or from glass in to air it may change its direction of travel. Snell's law reveals the relationship between the directions of travel in the two media. sinθ2 = (n1/n2)sinθ1 = 1.5 sinθ1. What is TIR? total internal reflection, in physics, complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle. Why refractive index matters The higher the refractive index the slower the light travels, which causes a correspondingly increased change in the direction of the light within the material. What this means for lenses is that a higher refractive index material can bend the light more and allow the profile of the lens to be lower. - conditions needed for TIR to occur? The light ray moves from a more dense medium to a less dense medium. The angle of incidence must be greater than the critical angle. Choices made in Design and Materials (for Fibre Optic) - impact of material choice on quality of signal? - multimode? How signal is transmitted Light travels down a fiber optic cable by bouncing off the walls of the cable repeatedly. Each light particle (photon) bounces down the pipe with continued internal mirror-like reflection. The light beam travels down the core of the cable. The core is the middle of the cable and the glass structure - why light? - We send digital information through these cables using a bunch of light pulses. A strong pulse of light indicates a one, and no pulse indicates a zero. Through rapid changes in the light, you can send highly complex signals down the cable. The nature of light is that it is unable to pass through opaque walls. This makes it easy to confine signals to within a single room, which increases the level of security of the network. "Light can carry more data than a wire, and it takes less energy to transmit photons than electrons," - How? - A fiber optic cable is a wire containing transparent materials that can carry light. The outside of the cable contains a material that will reflect the light, keeping it moving along the length of the cable. We send digital information through these cables using a bunch of light pulses. A strong pulse of light indicates a one, and no pulse indicates a zero. Through rapid changes in the light, you can send highly complex signals down the cable. These are most often used either for high speed internet connections, or for sending sound signals to home theater systems. Angle of Acceptance & Aperture - significance of angle of entry of light signal into end of cable - angle of acceptance? - The acceptance angle of an optic fiber is the maximum incident angle of light ray which can be used for injecting light into the fiber core or wave guide - numerical aperture? Attenuation -when light loses its strength time after time - causes of loss of signal strength? (2 main causes?) - as the distance increases, light intensity decreases. This is because as the distance away from a light source increases, photons of light become spread over a wider area. - As a beam of light, that holds signals, travels through the central region of the fiber optic, the light's power decreases. Therefore, the connection strength becomes more diminished. This decrease in light energy is commonly known as fiber optic loss or attenuation. - effect of too much cable bend? - the optical signal within the cable may refract and escape through the fiber cladding. Bending can also permanently damage the fiber by causing micro-cracks. Note that one fiber kinks and the other does not - check the manufacturer's spec for bend radius. https://news.stanford.edu/archivedcontent/#:~:text=%22Light%20can%20carry%20more%20data,Vuckovic%2C%2 0who%20led%20the%20research. https://cablesys.com/updates/fiber-loss-in-fiber-opticperformance/#:~:text=As%20a%20beam%20of%20light,fiber%20optic%20loss %20or%20attenuation. https://www.ppc-online.com/blog/do-you-know-how-far-you-can-bend-yourmicroduct-andfiber#:~:text=When%20a%20fiber%20cable%20is,manufacturer's%20spec%20f or%20bend%20radius. https://study.com/academy/lesson/transferring-information-withlight.html#:~:text=Fiber%20Optics%20and%20Infrared&text=A%20fiber%20optic%20cable%20is,a% 20bunch%20of%20light%20pulses. https://www.nai-group.com/optical-fiber-technology-how-itworks/#:~:text=Light%20travels%20down%20a%20fiber,cable%20and%20the%20glass%20structure. https://byjus.com/physics/total-internalreflection/#:~:text=Following%20are%20the%20two%20cond itions,greater%20than%20the%20critical%20angle. https://www.physicsclassroom.com/class/refrn/Less on-3/Total-InternalReflection#:~:text=TIR%20occurs%20because%20th e%20angle,bend%20away%20from%20the%20norma l. https://www.nai-group.com/optical-fiber-technology-howitworks/#:~:text=How%20Does%20a%20Fiber%20Optic,t he%20core%20of%20the%20cable. http://electron9.phys.utk.edu/optics421/modules/m1/to tal_internal_reflection.htm#:~:text=Total%20internal% 20reflection,travel%20in%20the%20two%20media.&t ext=sin%CE%B82%20%3D%20(n1%2F,sin%CE%B8 1%20%3D%201.5%20sin%CE%B81. https://www.physicsclassroom.com/class/refrn/Less on-3/Total-InternalReflection#:~:text=TIR%20occurs%20because%20th e%20angle,bend%20away%20from%20the%20norma l. https://www.britannica.com/science/total-internalreflection droberts@sbhs.school.nz
