 a optical communication lecture. I am Rahul Konapure from WIT, Sholapur. So, these are the learning outcomes. At end of this session, students will be able to explain optical communication system and its optical fiber. So, before starting to the optical communication, what is an optical communication? So, just recall. So, basic block diagram of an communication system. So now, as shown in this figure A and B, so this is the basic block diagram of an communication system and this is an optical fiber communication system. There is a slightly a modification done in the normal communication system here. So, what are those? So, we will understand by looking at this diagram. So, in basic communication system, there will be an information source, which can be a text file or video file or the whatever the data you want to send here. Then this information source is given to the transmitter section that is an modulator. So, that is known as an modulation. So, here all the things of an modulation can be done at the transmitter side here. Then whatever the signals are going to be there, first information signal is being converted into an electrical signal which is transmitted through a transmission medium. So, the transmission mediums are of two types that are nothing but the radio communication that is a wireless communication and wired communication. So, by depending on the applications, you want to send the signal, it has been chosen and it is given to the receiver side here. So, here whatever the modulation you have done, so we have to get back the original signal which is there at the transmitter side. So, the reverse process of an modulation is done here that is known as an demodulator and whatever the signals has been received, it is given to the destination. So, this one is known as the basic communication system, where there is three main blocks are there transmitter, a transmitter medium and receiver here. So, now let us understand what is the optical fiber communication system here. As we know that the information source will be the common for the communication system here. So, whatever the data you want to send, so that is been applied at the information source here. So, where you are going to convert that signal into the electrical transmit, here the main block which is added to the communication system of an optical fiber is this block that is the optical source. So, optical source are nothing but because in optical communication, so the data is being sent in the form of light here. So, in the form of light, so that is why there are only two sources available right now here that is an LED that is light dependent resistance like this and one more is the laser here. So, these are the two optical sources are used to transmit the data in the form of light here. Like what we have seen in this communication system, the transmission medium is used like an wireless and wired connection. So, basically after the optical source which has been used like a laser or LED depending on the application. If you want to transmit the data on the longer kilometers or the larger area, so then you have to make use of the lasers here. If you want to transmit the data at the shorter area then you have to make use of an LED here. So, which is given to the optical fiber cable here. So, it will be an wired communication here. So, the optical fiber is between the transmitter and the receiver here. So, optical fiber cables are given to the optical detector here because whatever the source is used like laser and LED where the modulation is done. So, that the reverse process often the optical source has to be done that is an optical detector here. So, the optical detectors should have the very fast response as because the transmission of the data in the optical fiber is very large or very fast as compared to the normal transmission medium here. So, the optical detectors used like an pin diode, APD that is avalanche photo diodes or photo transistors or photo detectors here. So, these are the optical detectors used to detect the light whatever the data you want to there and then again it will be an electrical receive here. So, that electrical signal is being converted into an original signal and that has been given to the destination here. So, slight modification in the optical fiber communication is that that is the optical source as and as well as the optical detector because the transmitting medium and the detecting mediums are different as compared to the normal communication system here. So, this is the block diagram of an optical communication system. Now, we will see what are the advantages of an optical fiber communication. So, as we have seen this the list of the advantages there is more advantages as we compared to the optical fiber communication here. So, the first and the most important thing about the advantage of using the fiber optical communication is the enormous potential bandwidth. So, as we know that if you transmit the data in the microwave region it is up to 10 raise to 9 gigahertz here, but in optical fiber communication it can be used up to 10 raise to 12 to 10 raise to 15 gigahertz, ok, terahertz of data here. So, that is the potential bandwidth, ok. So, when we see the optical fiber communication its size is very small and light in weight here. So, whenever you have seen the optical fiber communication, so its size is very small and its weight is very less here, ok. And next important thing is about the electrical isolation as we are not going to transmit the data in the copper or the wired material or wireless. So, there is no any interference of EMF generation here. So, that is why it is known as an electrical isolation. So, there will be a no EMF inducing between the two signals here that is why it is known as an electrical isolation here and immunity to interference and the crosstalk here. As we have seen in the basic block diagram of an communication system you make use of and the transmission medium like wired or the wireless. So, there is a crosstalk in between the two signals here like FDM and TDM. So, that is why we insert the guard beads into that because of this the transmission of data in the form of light. So, that is avoided in this year because there is an electrical isolation between the two signals here, ok. Next most important thing about the signal security is what you are transmitting the data in the form of light. So, that is why what happened if you try to tap that signal. So, the light will disperse in the environment here. So, it is very difficult to trap or to hack that signal here. So, that is why the most advantages of using the fiber optical communication is the signal as security here. And most important thing is that low transmission loss as the optical fiber is made up of silica and glass. So, there is a loss transmission is up to only 0.02 dB per kilometer which is very less as compared to the other transmission which is done in wired and wireless communication. So, it is very less as compared to other here, ok. And most important thing that is the system reliability and ease of maintenance here because the optical fiber is laid down into the earth. So, there is no any damages will takes place like an wired communication here. So, and it is easy to maintenance. Only the disadvantage of using the optical fiber communication is that while installation of a fiber optical it requires very high cost because of laid down of the optical fiber here and which is connected to widely for each and every city or the main main places all over the world here. So, now we will see the basic structure of an optical fiber here, ok. So, up till now what we have seen? We have seen the basic block diagram of an optical fiber communication system and after that we have seen the what are the advantages why we opt for an the optical fiber here, So, basically as shown in this figure here. So, it consists of a core and cladding here and above this there will be a one buffer coating and a mechanical coating of a black color here to avoid any damages here, ok. So, these are the now we will see the basic structure what is there core inside which the light is going to transmit the data here, ok. So, this is the thin glass at which the fiber core through which the light travel, ok. So, it should follow the total internal reflection. So, we will see all this in the coming lectures here what is total internal reflection, how light should be traveled inside the core only, ok. So, the next part is the cladding here. So, this is the outer material that protects the inner glass core from the elements and the light is reflected back into the core here, ok. Because the light should transmit only in this core section here. So, there has to be a some medium one more that is the N1 and N2 here. So, N1 will be the air suppose and N2 will be the glass here that is the denser medium and the lesser denser medium. So, that it should follows the law of reflection and law of refraction here because that light should stay inside the core only here, ok. And one more thing is that that is a buffer coating which is often the black color, ok. So, this is the plastic coating that protects the fiber from the damage and moisture from the outside world here. So, it is the black color coating which prevents or the protects the fiber from damage any damages here and the moisture from the outside world here, ok. So, this is the basic structure of an optical fiber here, ok. So, these are my references, ok. Thank you.