FIBER OPTICS COMMUNICATION AND APPLICATIONS Ritesh A. Jadhav 1, Dattatraya S. Shitole 2 1 Assistant Professor, 2 Research Scholar Electronics & Telecommunication Annasaheb Dange College of Engineering & Technology, Ashta. ABSTRACT Communication is an important part of our daily life. The communication process involves information generation, transmission, reception and interpretation. A technical overview of the emerging technologies of fiber optical communication and optical networking. It is now possible to perform all the major functions of optical communication in fiber based devices. This paper explains the implementation of fiber optics in electronic communication network with development in optical fiber communication. Its high bandwidth capabilities and low attenuation characteristics make it ideal for gigabit transmission. Fiber optic communication has revolutionized the telecommunications industry. It has also made its presence widely felt within the data networking community as well. Using fiber optic cable, optical communication shave enabled telecommunications links to be made over much greater distances and with much lower levels of losing the transmission medium and possibly most important to fall, fiber optical communications has enabled much higher data rates to be accommodated. Keywords: EMI, FDDI, FBG. INTRODUCTION Fiber optics is major building blocks in the telecommunication infrastructure. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter made a first step towards optical fiber communication, the Photophone, at Bell s newly established Volta Laboratory in Washington D.C. First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunications industry and have played a major role in the advent of the Information Age. The fiber optics revolution at America began in the early 1980s.At that time systems operated at 90Mb/s. At this data rate, a single optical fiber could handle approximately 1300 simultaneous voice channels. Today, systems commonly operate at 10 Gb/s and beyond. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world. As an innovation that transformed the landscape of global communications, optical fiber has a future as bright as the waves of light it beams throughout the world. Due to its compatibility with other technologies, growing cost-effectiveness, and nearly unlimited bandwidth, optical fiber has the capacity to grow and adapt to future consumer demands for voice, data, and video capability. The growth of the fiber optics industry over the past five years has been explosive. Analysts expect that this industry will continue to grow at a tremendous rate well into the next decade and beyond. 1
Figure 1: Virtual optical fiber communication network around the globe FIBER OPTICS- The principles and mechanism of optical fiber in telecommunications could be very complicated if there no basic understanding of optical fiber. Optical fiber cable use smooth hair-thin strands of glass or plastic to transmit data as a pulse of light and the cable is about the diameter of a human hair. A fiber optic cable is made up of three main sections. They are the core, cladding, and buffer coating. This is show in Figure 3. The core is at the middle of the cable and it is made up of silica. It functions as the light transmitting section of the fiber and act as a boundary layer for the cable. Next is the cladding. The cladding is made up of pure silica and it act like a guide for the light waves to travel down the cable. This component is very important because light moves in waves and will shoot out of the core if this component is not present. This cladding will eventually reflect back into the core. As for buffer, it is at the middle of these three layers. It is made up of acrylic polymer. This buffer layer protects cladding and core against ultraviolet light and gives the cable rigidity. This buffer coating is also useful to secure a data from electromagnetic interference. Figure 2: Three main sections of fiber optic cable. 2
The main two types of optical fibers cable in telecommunications network based on their modal properties. They are single-mode fiber and multimode fiber. Single mode fiber optic cable has a small diametral core that allows only one mode of light to propagate. Because of this, the number of light reflections created as the light passes through the core decreases, lowering attenuation and creating the ability for the signal to travel faster, further. This application is typically used in long distance; higher bandwidth runs by Telco s, CATV companies, and Colleges and Universities. As for multimode fiber, it has a much larger core than single-mode fiber, allowing hundred of signals to pass through the fiber simultaneously. From what we have just discussed, it may seem that multimode fibers carry more information than single-mode fibers, but in reality, single-mode can keep every light pulse over a longer distance because its transmission of dispersion or degradation is very small, allowing it to have a higher bandwidth. With the high bandwidth, the single-mode fiber is an ideal source of transmission medium for any applications and multimode only applies in the transmission distances within two miles. The two classes can be further divided into multimode index, multimode graded index, and single-mode step index. Step and graded index refers to the variation of the index of refraction with radial distance from the fiber axis. Ultimately, these fibers consist of air core surrounded by a cladding. Step index fiber is an optical fiber with a uniform refractive index core, where else in the graded-index fibers, the gradual decrease in the index of refraction with the distance will cause the light rays to bend back toward the axis as they propagate. These different types of fiber are displayed in Figure 3 Figure 3:Types of fiber optics cable. OPTICAL FIBER TECHNOLOGY Fiber optics is a medium for carrying information from one point to another in the form of light. Unlike the copper form of transmission, fiber optics is not electrical in nature. A basic fiber optic system consists of a transmitting device that accepts coded electronic pulses that are generated by the light-emitting diode (LED) or an injection-laser diode (ILD) after that transmitter converts an electrical signal into a light signal, an optical fiber cable that carries the light, and a receiver that accepts the light signal and then detector from receiver circuitry demodulate the signal and converts it back into an electrical signal. The complexity of a fiber optic system can range from very simple (i.e., local area network) to extremely sophisticated and expensive (i.e., long distance telephone). 3
Figure 4: Basic fiber optic communication system For example, the system shown in Figure 4 could be built very inexpensively using a visible LED, plastic fiber, a silicon photodetector, and some simple electronic circuitry. The overall cost could be less than $20. On the other hand, a typical system used for long-distance, highbandwidth telecommunication that employs wavelength-division multiplexing, erbium-doped fiber amplifiers, external modulation using DFB lasers with temperature compensation, fiber Bragg gratings, and high-speed infrared photodetectors could cost tens or even hundreds of thousands of dollars. The basic question is how much information is to be sent and how far does it have to go? With this in mind we will examine the various components that make up a fiber optic communication system and the considerations that must be taken into account in the design of such systems. ADVANTAGES Immunity to Electromagnetic Interference- Although fiber optics can solve data communications problems, they are not needed everywhere. Most computer data goes over ordinary wires. Most data is sent over short distances at low speed. In ordinary environments, it is not practical to use fiber optics to transmit data between personal computers and printers as it's too costly. Electromagnetic Interference is a common type of noise that originates with one of the basic properties of electromagnetism. Magnetic field lines generate an electrical current as they cut across conductors. The flow of electrons in a conductor generates a magnetic field that changes with the current flow. Electromagnetic Interference does occur in coaxial cables, since current does cut across the conductor. Fiber optics are immune to this EMI since signals are transmitted as light instead of current. Thus, they can carry signals through places where EMI would block transmission. Data Security- Magnetic fields and current induction work in two ways. They don't just generate noise in signal carrying conductors; they also let the information on the conductor to be leaked out. Fluctuations in the induced magnetic field outside a conductor carry the same information as the current passing through the conductor. Shielding the wire, as in coaxial cables can reduce the problem, but sometimes shielding can allow enough signal leak to allow tapping, which is exactly what we wouldn't want. 4
There are no radiated magnetic fields around optical fibers; the electromagnetic fields are confined within the fiber. That makes it impossible to tap the signal being transmitted through a fiber without cutting into the fiber. Since fiber optics do not radiate electromagnetic energy, emissions cannot be intercepted and physically tapping the fiber takes great skill to do undetected. Thus, the fiber is the most secure medium available for carrying sensitive data. Safety- Fiber optics cable doesn t transfers electrical signals,the data is transmitted in the form of light signals so making it safe in environment like gas pipe line. Use less energy- Because there is less signal loss,lower power transmitters can be used to send information through fiber cables than for copper cables where high-voltage electrical transmitter are needed.this reduces cost and maintenance,saving money for customers. APPLICATIONS Fiber optic sensors Fibers have many uses in remote sensing. In some applications, the sensor is itself an optical fiber. In other cases, fiber is used to connect a non-fiber optic sensor to a measurement system. Depending on the application, fiber may be used because of its small size, or the fact that no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using different wavelengths of light for each sensor, or by sensing the time delay as light passes along the fiber through each sensor. Time delay can be determined using a device such as an optical time-domain reflectometer.fiber optic sensors are small and light. Aircraft engineers often need hundreds or thousands of sensors for each application. Today, most fiber optic sensors for aerospace applications are used in ground tests and design. However, some aircraft are already flying with networks of fiber optic sensors on board. Sensor interrogation equipment is now smaller and more rugged, and can be made to perform to harsh MIL specs. The long term vision is that all new aircraft will fly with Fiber Bragg Grating (FBG) optical sensors. The knowledge FBG sensors provide will improve safety, prolong the life of airframes, reduce maintenance and improve the in-flight efficiency of engines. 5
Figure 5: Sensitive but strong: The value of fiber-optic sensor systems will grow at an average annual rate of 20.5% - from $1.34 billion to $3.39 billion per year - between 2011 and 2016 (all figures USD billion). Source: Electronicast Consultants. Networking- FDDI usually finds placement as a high-speed backbone for mission-critical or high traffic LANs, MANs or WANs. Operating at a data rate of 100 Mb/s, FDDI was originally designed for optical fiber transmission. An unbroken FDDI network can run to 100 km with nodes up to 2 km apart on multimode fiber, and 10 km apart on single-mode fiber. However, a copper standard exists, known as a copper distributed data interface, or CDDI, although it is restricted to distances of only 100 m. Any one ring, copper or fiber, may contain as many as 500 nodes. FDDI's niche is high reliability, the result of its counter-rotating ring topology illustrated in Figure 6. A dual-attached station connects the two paths via Port A, the primary path, and Port B, the secondary path. Port A may also have a number of M ports which attach to single-attached stations such as computer workstations. Information is passed around the FDDI ring via a token generated by the main station. The token moves around the ring until a requires access to the network. When a station needs to transmit information, it takes control of the token, and transmits in an FDDI frame, after which it releases the token, signaling that it has completed its transmission. Each FDDI frame contains the address of the station or stations that need to receive this frame. All nodes read the frame, but only to verify this address. If the node address and the FDDI frame address match, the station extracts the data from the frame and then retransmits it to the next node on the ring. When the frame returns to the originating station, that station strips the frame, and the network remains quiet until a node captures the token. 6
Marine Applications- Figure 6 : Dual Counter-rotating Ring Topology Submarine fiber optic cables are undoubtedly the optimal communication infrastructure to carry digital payloads, which are then used to carry telephone traffic as well as Internet and private data traffic between nations. The total carrying capacity of submarine cables is in the terabits per second, while the alternative satellites infrastructure typically offers only megabits per second and displays higher latency. With the constant rise in demand for highspeed communications, there is a constant surge in demand for more submarine fiber optics infrastructures. In addition, due to the constant rise in maritime work performed, for example for placing gas pipes, existing submarine fiber optic cables need repositioning, repairing and maintenance. Rotal Networks offers extensive experience in designing, building, and maintaining existing and new shallow water submarine fiber optic cables. With our state of the art equipment and skilled personnel Rotal can provide rapid response to damaged cables by rapidly locating the two ends of the damaged cable, reconnecting the fibers and cable, and then testing the cable, while providing comprehensive documentation. Military fiber optics The U.S. military uses fiber optic technology for a wide variety of air, sea, ground, and space applications. Fiber optic technology has already been implemented in the FiberSTAR project for Lockheed Martin s LM-STAR avionics test equipment module. The LM-STAR is used in the ground support system for the F-35 Joint Strike Fighter (JSF). Agencies utilize high-reliability fiber optic connectors in its military fiber optics to produce precision alignment of optical fibers. Connectors with polarization keys and keyways are manufactured to exacting tolerances to reduce radial misalignment and insertion loss. 7
Broadcast Fiber Optics Broadcast media utilizes outside plant, ruggedized and harsh environment fiber optic products to support a variety of connectivity and communication requirements. These broadcast fiber optics are designed to provide multiple channel, high-bandwidth links and, in some cases, power (electrical) connections to and from cameras, trucks, and satellite links. With the increasing demand for HDTV programming, broadcasters are implementing more fiber to support HDTV signal capture and transport at live sports, music, and entertainment events. Fiber is also rapidly becoming the data transmission method of choice for stadiums, arenas, and venues allowing these facilities to supply highdefinition content for HDTV, video-on-demand, and broadband networks. CONCLUSION This paper has taken a detailed look at the technological advantages of a fiber optic telecommunication Network and its applications. A huge amount of development can be made by making further research and work on fiber optics. We need it for a faster and more sophisticated infrastructure which would be the prime demand of the ever growing population of tomorrow. At present there are many optical fiber communication links throughout the world without using optical solutions. When we introduce optical solutions as light pulses through the fibers, we can achieve high quality telecommunication at a lower cost. We can expect a great revolution in optical fiber communication within a few years by means of solutions. 8
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