Optical modulation a tutorial introduction to optical modulation techniques by gary breed editorial director t his article introduces the subject of optical modulation, the process of applying information to a light wave. Satellite communications by timothy pratt, charles bostian and jeremy allnutt, 2. Sm fiber offers high bandwidth and low modal dispersion. This lowloss wavelength region ranges from 1260 nm to 1625 nm, and is divided into five wavelength bands referred to as the o, e, s, c and lbands, as shown in figure 1 and 2. Fibre is an integral part of modern day communication infrastucture and can be found along roads, in buildings, hospitals and machinary. The fractional bandwidth of this transmission can be calculated as.
The basic components are light signal transmitter, the optical fiber, and the photo detecting receiver. Advanced optical communication nptel online videos. Principles of optical fiber communications tutorialspoint. Our complete selection of sm fiber can be viewed here. Bandwidth limitations bandwidth of an optical fiber determines the data rate. The next piece of the jigsaw fell into place when the first optical fibers with a sufficiently low loss for communications purposes were developed in the 1970s. The light forms an electromagnetic carrier wave that is modulated to carry information. An overview of macrobending and microbending of optical fibers. The technical notes appeared in the late 1970s and early 1980s, which was the period of commercial.
In an optical fiber we find two types of dispersions 1 intramodal or chromatic dispersion present in single mode an multimode optical fiber. Optical communication pdf notes oc pdf notes smartzworld. Based on rayleigh backscattered light in an optical fiber single mode or multi mode it senses all points along the fiber and monitors acoustic perturbations to the fiber specifications frequency range 1mhz to 100khz spatial resolution 1 m length 50 km strong applications oil. Signal distortion on optical fibers attenuation nptel. A tutorial introduction to optical modulation techniques. The loss profile of an optical fiber with respect to frequency or wavelength is a very smooth. The fiber manufacture technology now helps us in precise desing of optical fibers as per requirements and using such sophisticated technology. Feb 15, 2012 the bottom picture shows the size comparison between a copper cable and an optical fiber, both carries the same bandwidth. This dispersion is due to finite bandwidth of the signal. A variety of semiconductor photodetectors may be used as fibre optic receivers. The bottom picture shows the size comparison between a copper cable and an optical fiber, both carries the same bandwidth. The first step in the design of an optical communication systems is to decide how the electrical signal should be converted into an bit stream. Revised march 19, 2020 page 2 of 4 aerial fiber optic cables fttx drop cables typical optical cable specifications. Fiberoptic communication systems and techniques provides solid background in wide ranging topics of fiberoptics.
Aug 11, 2017 the noise figure of soa optical amplifier is typically higher, the gain bandwidth can be similar, soas exhibit much stronger nonlinear distortions in the form of selfphase modulation and fourwave mixing. Optical fiber, its working principle, design, types, properties an. This is because the bandwidth of optical fibre is almost times. Fiberoptic communication systems and techniques course. Yet, the semiconductor optical amplifier is of small size and electrical pumped, which is often less expensive than edfa. Measuring bandwidth of 10g laseroptimized multimode fiber. Higher numerical aperature na mean higher coupling from source to fiber, and less losses across joints. Now, there is optical communication theory and optical communication engineering design. Optical communication is basically guided transmission of em waves based on the snells law. Recent years have seen an exponential increase in demand for large bandwidth and high data rate applications.
The communication system of fiber optics is well understood by studying the parts and sections of it. All the networks using optical fiber as transmission medium optical networks when transmitted signal remains in optical form till its arrival at destination all optical network. The raman optical amplifiers have a wide gain bandwidth up to 10 nm. An overview of macrobending and microbending of optical. Rp photonics encyclopedia bandwidth, optical spectrum. Fiber optic cables are lightweight, take up less space, and are also flexible. It is true that single mode fiber has unlimited bandwidth. What are the good sources to learn the basics of optical. Fiberoptic communication is mainly conducted in the wavelength region where optical fibers have small transmission loss. Optical communications became a possibility after the first lasers were developed in the 1960s. Power received can be related with the transmitted as. Photosensitive sm fiber photosensitive single mode fiber is designed to provide high photosensitivity for uv radiation. Electronics advanced optical communication youtube.
Fiber optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The topics covered include modes of optical fibers, impairments in optical fiber channel, lasers and photodiodes, optical amplifiers, wdm components, and digital fiber optic communications. Satellite communications by timothy pratt, charles bostian and jeremy allnutt, 2 edition, wiley student edition. Introduction to fiber optic sensors 5 temperature, high pressure, corrosive and toxic environments, high radiation, large electromagnetic fields and other harsh environments. There is truly no match for fibers bandwidth capabilities. The result is that pulses then begin to spread into one another and the symbols become indistinguishable. So a single mode fibre fibre with one bound eigenfield actually has in theory two such channels, one for each polarisation state of the bound eigenfield. For fiber optic cable, theoretically speaking, its bandwidth is infinitely high, transmission capacity is infinitely large and the transmission distance is infinitely far. A good order of magnitude rule of thumb for the maximum possible bandwidth of an optical fibre channel is about 1 petabit per second per optical mode. The core medium refractive is always greater than the cladding refractive index. The advantages of fiberoptic sensing are well known and have been widely presented 3, 4, 2123. Fiber optics go back as far as roman times, but the first was an optical telegraph, which allowed operators to relay a message from one tower to the next by a series of lights mounted on the towers. The design criteria for a fiber optic link design procedure is mainly divided into. A basic fiber optic sensor system consists of an optical fiber and a light modulating arrangement.
Typical block diagram of a digital communications system. Dispersion is the spreading of the optical pulses as they travel down the fiber. The major elements of an optical fiber communication system are shown in the following figure. The optical fiber mainly consists the following six parts as shown in figure core. Optical fibers are recognized as the superior medium for delivering high bandwidth communications signals over long distances. The bandwidth of single mode fibers is much higher than in mu lo. The advent of 850 nm vcsel light sources and 10g laseroptimized 50 m multimode om3 fiber has enabled costeffective 10g transmission for short reach enterprise applications. Optical fibre communication fiber telecommunications.
Mod1 lec11 practical issues in implementation of fiber link. These fibers offer lower splice loss than standard sm fibers and are suitable for a range of applications. Attenuation limit the optical power reaching the receiver. The mechanism that limits a fibers bandwidth is known as dispersion. Wdm optical network divide the vast transmission bandwidth available on a fiber into several different smaller capacity channels nonoverlapping bandwidths, each of these channels can be operated at a moderate bit rate 2. An antitank missile uses fiber optic cable for flight control. Fiber optic communication systems and techniques provides solid background in wide ranging topics of fiber optics.
Jun 30, 2015 optical communication is basically guided transmission of em waves based on the snells law. This is due to intrinsic properties of the material, glass. Lecture notes on veer surendra sai university of technology. In may 2002, the itut organization divided the fiber optical communication system into six bands as o, e, s, c, l and u6. What is the bandwidth and window of fiber optic cable. This lecture explains about one of the application of optical properties of material, i. Optical fiber optical fiber is made from thin strands of either glass or plastic it has little mechanical strength, so it must be enclosed in a protective jacket often, two or more fibers are enclosed in the same cable for increased bandwidth and redundancy in case one of the fibers breaks it is also easier to build a fullduplex system. Medical equipment uses fiber optics to illuminate and observe inside the body and in some cases to send highenergy laser pulses through the fiber to perform internal surgery. Fiber optical signal in fiber optical signal out pump power optical amp medium weak signal amplified signal some types of oas that have been demonstrated include. However these systems were limited in bandwidth and optical systems were investigated.
Bandwidth is a measure of the datacarrying capacity of an optical fiber. Introduction to fibre optics jodrell bank observatory. Besides, optical fiber cable is also light in weight, and all of these features make it an ideal medium for data transmission, which is capable of transmitting unlimited telephone and tv signal. Therefore, we note that uniform amplitude response condition is well satisfied for the optical. Fiberoptic communication is the most modern and advanced mode of data. To reduce fiber dispersion, new types of fiber were invented, including dispersionshifted fibers itu g.
It may be required to fix broken fiber connection or to tap the fiber for additionalconnections ee4367 telecom. Fibre optic receiver fiber receivers electronics notes. The traditional overfilled launch ofl method of measuring bandwidth in multimode fiber has been replaced by new, more advanced techniques. All the networks using optical fiber as transmission medium optical networks when transmitted signal remains in optical form till its arrival at destination alloptical network. For example, a fiber with a bandwidth of 500mhzkm megahertz kilometer can transmit data at a rate of 500mhz along one kilometer of fiber. Laser is understood to be the most efficient of em radiation and. Fiber connectors a fiber optic splice establishes an optical connection between two individual optical fibers. Depending on the type of application and the reach to be achieved, various types of.
The key attribute that enables this performance is very low attenuation, i. Fiber types in gigabit optical communications abstract fiber optic cables are the medium of choice in telecommunications infrastructure, enabling the transmission of highspeed voice, video, and data traffic in enterprise and service provider networks. Optical fiber communications by gerd keiser, 4th edition, mc grawhill international editions. The reason its called single mode is that only one mode of light can pass through at a time.
A raman optical amplifier is little more that a highpower pump laser, and a wdm or directional coupler. Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference are required. A bandwidth can also indicate the maximum frequency with which a light source can be modulated, or at which modulated light can be detected with a photodetector in the area of optical fiber communications, the term bandwidth is also often inaccurately used for the data rate e. Latency in optical transmission media is a consequence of limited velocity in the optical media. There are two typical choices for the modulation format of the signal. The bandwidth and window of fiber optic cable fs community.
Optical fiber characterization nbs special publication 637, optical fiber characterization 1, is a twovolume compilation of previously published nbs technical notes concerning the characterization of optical fibers used for telecommunications. The field of fibre optics communications has exploded over the past two decades. Those light waves may be sent through a transparent medium as a laser beam, or contained within a fiber optic cable. The topics covered include modes of optical fibers, impairments in optical fiber channel, lasers and photodiodes, optical amplifiers, wdm components, and digital fiberoptic communications. It is expressed as the product of frequency and distance. Multimode optical fiber at 850nm is known as the first window, singlemode optical fiber at o band is referred to as the second band. Fiberoptic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The fibre optic receiver is the essential component in this process as it performs the actual reception of the optical signal and converts it into electrical pulses. Semiconductor optical amplifiers soas fiber raman and brillouin amplifiers rare earth doped fiber amplifiers erbium edfa 1500 nm. The optical amplification occurs in the transmission fiber itself, distributed along the transmission path. The optical carrier frequency in the range 10 to 1016 hz generally in the near infrared around 1014 hz or 105 ghz yields a far greater potential transmission bandwidth than metallic cable systems i. Optical fiber networks have high capacity can be used for providing the high bandwidth services even in wireless, infrared means high bandwidth connectivity. A typical glass fiber consists of a central core material. Apr 16, 2018 62 videos play all fiber optic communication systems and techniques prof pradeep kumar k iit kanpur july 2018 acacia talks coherent understanding the cfp2 digitial coherent optics module.
Within the fibre optic receiver, the photodetector is the key element. There is truly no match for fiber s bandwidth capabilities. As a consequence of its optical characteristics, the chromatic dispersion of a fiber can be changed by acting on the physical properties of the material. Optical signals are amplified up to 10 db in the network optical fiber.
The first transatlantic telephone cable with optical fibre in 1988. Nptel video lectures, iit video lectures online, nptel youtube lectures. The diameter of the core is 50 m for a multimode optical fiber and nine m for a singlemode optical fiber. The diameter of the cladding is 125 m for both fiber types. Advanced optical communication advanced optical communication. Multiple choice questions and answers on optical fiber. Signal processing in optical fibers 303 source transmitter channel receiver user voice data encoding modulation optical fiber wireless demodulation decoding voice data figure 2. The technology ofusing multiple optical signals ont he same fiber iscalled wavee gth divisi utipexi g wdm. Advanced optical communication nptel online videos, courses.
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