hi students let us continue with the topic transmission media so the transmission media is of two types guided and unguided so in the guided we are discussed about the twisted pair cable and the coaxial cable and the third type of wired cable is the fiber optic cable now let us see what is this fiber optic cable so this is relatively new transmission means they are used by telephone companies it is a new transmission media when compared to the coaxial or the twisted pair so this fiber optic is a new transmission new transmission medium used by telephone companies in a place of long-distance trunk lines so used in place of long distance lines long distance lines and also used by private companies in implementing local data communication network so used by private companies private companies in implementing local data in implementing local data communication network communication network and it is also it requires the light sources with the injection laser diode or light emitting diodes so it requires this fiber optic cables requires a light source light sources with injection laser diode we call it as il D or light emitting diode LEDs okay so these are the features of these fiber-optic cables so this fiber optic cables consists of three centric sections let us see what is those three centric sections the three central sessions present in fiber optics is this is one session and next this is another session and next this is another session so this fiber optic cable consists of three centric sessions so this is the plastic jacket this is a plastic chat clip and here this is the glass or plastic this is glass for plastic cladding glass or plastic cladding and this one is the fiber core fiber sorry fiber coat so this fiber optic cables is consisted of three pumps in concentric sections that is a plastic jacket glass glass cladding and the fiber core okay so the fiber optic type there are three types of fiber optics so one is the multimode step-index fiber so the first type is the multimode step-index fiber so what does multimode step-index fiber is - the reflective also the reflective walls of the fiber more the light pulse movie light pulses to the receiver so this is operation this multimode step-index fiber will do the reflective walls of the fiber no the light pulses to the receiver and next coming in second one that is the multimode graded index fibers so this is a step index fiber and next is a graded index fiber so this multimode graded index fiber acts as acts to refract the acts to refract the light towards the center of the towards the center of the fiber towards the center of the fiber by variation density by variation in density so that is about the multimode graded index fiber and the next two fiber optic type is a single mode fiber now let us see what is this single mode fiber so the third one is the single mode fiber so the single mode fiber here the light is guided the light is guided down the center of an extremely narrow cold stream d narrow good so if your fiber optic is a single mode fiber here the light is guided down the center of an extremely narrow Co so this is about the fiber optic cable now let us see what are the advantages and disadvantages of fiber optics advantages so it is having the greater capacity when compared to twisted-pair or coaxial cable it is having the greater capacity so the decay a greater capacity is betray the bandwidth is up to two gigabits per second and this fiber optics is smaller size smaller size and lighter weight smaller size and the lighter weight and it is having the low lower attention problems when compared to the fiber so require actual or the twisted paid the fiber optics is having the lower attenuation and aminute immunity to environment interfaces also high immunity to environment and it is highly secured due to tap difficulty and lack of signal radiation this is highly secured so these are the advantages of the fiber optics now let us see the disadvantages what are the disadvantages if you use the fiber optics the first disadvantage and the main disadvantage is expensive over short distance if you go if you are using a short distance it is waste because it is more expensive expensive over short distance and it requires highly skilled installers twins to install the fiber optics and trained persons we need whereas the twisted pair or the coaxial cable anyone can understand so with a little knowledge they can install the people can install but if you are using the fiber optics requires highly skilled installers and adding additional nodes is difficulty in fiber optics so this is one more disadvantage adding additional nodes is difficult if you are using the fiber optic cable so these are the three different types of the fiber guided transmission media so twisted pair cables or actual cable and the fiber optics cable thank you