Laser & Optical Fibers Prepared by : Deepti Jain
Contents <ul><li>Fiber Laser </li></ul><ul><li>Advantages of Fiber Laser </li></ul><ul><li>Disadvantages of Fiber Laser </li></ul><ul><li>Design and manufacture </li></ul><ul><li>Fiber Disk Lasers </li></ul><ul><li>Optical fibers </li></ul><ul><li>Use of Optical fibers </li></ul><ul><li>Advantages of Optical fibers </li></ul><ul><li>Disadvantages of Optical fibers </li></ul>
Fiber Laser A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. They are related to doped fiber amplifiers, which provide light amplification without lasing. Fiber nonlinearities, such as stimulated Raman scattering or four-wave mixing can also provide gain and thus serve as gain media for a fiber laser.
Advantages of Fiber Laser <ul><li>High Power: ease of cooling in long fiber </li></ul><ul><li>High Stability: spliced wave guiding fibers </li></ul><ul><li>High Reliability: operate 24/7 for decades </li></ul><ul><li>Lower total cost of ownership </li></ul><ul><li>Low jitter and low amplitude noise </li></ul><ul><li>Compact form factor </li></ul><ul><li>Immune to tough environmental changes </li></ul><ul><li>Turn-key Operation </li></ul>
Disadvantages of Fiber Laser <ul><li>Pulse pedestals from non-ideal optical spectrum for higher energy pulses. </li></ul><ul><li>Undesired nonlinear optical effects at high pulse energy, such as self-phase modulation and Raman scattering. </li></ul>
Design & Manufacture <ul><li>Unlike most other types of lasers, the laser cavity in fiber lasers is constructed monolithically by fusion splicing different types of fiber ; fiber Bragg gratings replace conventional dielectric mirrors to provide optical feedback. Another type is the single longitudinal mode operation of ultra narrow distributed feedback lasers where a phase-shifted Bragg grating overlap the gain medium. Fiber lasers are pumped by semiconductor laser diodes or by other fiber lasers. </li></ul>
Double-clad fibers <ul><li>Many high-power fiber lasers are based on double-clad fiber. The gain medium forms the core of the fiber, which is surrounded by two layers of cladding. The lasing mode propagates in the core, while a multimode pump beam propagates in the inner cladding layer. The outer cladding keeps this pump light confined. This arrangement allows the core to be pumped with a much higher-power beam than could otherwise be made to propagate in it, and allows the conversion of pump light with relatively low brightness into a much higher-brightness signal. As a result, fiber lasers and amplifiers are occasionally referred to as "brightness converters." </li></ul>
Power Scaling <ul><li>Recent developments in fiber laser technology have led to a rapid and large rise in achieved diffraction-limited beam powers from diode-pumped solid-state lasers. Due to the introduction of large mode area (LMA) fibers as well as continuing advances in high power and high brightness diodes, continuous-wave single-transverse-mode powers from Yb-doped fiber lasers have increased from 100 W in 2001 to >50 kW. Single mode lasers have reached 10 kW in CW power . </li></ul>
Fiber disk lasers <ul><li>Another type of fiber laser is the fiber disk laser. In such, the pump is not confined within the cladding of the fiber (as in the double-clad fiber), but pump light is delivered across the core multiple times because the core is coiled on itself like a rope. This configuration is suitable for power scaling in which many pump sources are used around the periphery of the coil. </li></ul>
Optical Fiber <ul><li>An optical fiber is a flexible, transparent fiber made of very pure glass (silica) not much wider than a human hair that acts as a waveguide, or "light pipe", to transmit light between the two ends of the fiber . Optical fiber typically consists of a transparent core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by total internal reflection </li></ul>
Uses of Optical Fibers <ul><li> Optical fibers offer huge communication capacity. A single fiber can carry the conversations of every man, woman and child on the face of this planet, at the same time, twice over. The latest generations of optical transmission systems are beginning to exploit a significant part of this huge capacity, to satisfy the rapidly growing demand for data communications and the Internet. </li></ul>
Advantages of Optical Fibers <ul><li>Capacity </li></ul><ul><li>Size and Weight </li></ul><ul><li>Running Costs </li></ul><ul><li>Security </li></ul>
Capacity <ul><li>Optical fibres carry signals with much less energy loss than copper cable and with a much higher bandwidth . This means that fibres can carry more channels of information over longer distances and with fewer repeaters required. </li></ul>
Size and Weight Optical fiber cables are much lighter and thinner than copper cables with the same bandwidth. This means that much less space is required in underground cabling ducts. Also they are easier for installation engineers to handle .
Security <ul><li>Optical fibers are much more difficult to tap information from undetected; a great advantage for banks and security installations. They are immune to Electromagnetic interference from radio signals, car ignition systems, lightning etc. They can be routed safely through explosive or flammable atmospheres, for example, in the petrochemical industries or munitions sites, without any risk of ignition. </li></ul>
Running Costs <ul><li>The main consideration in choosing fiber when installing domestic cable TV networks is the electric bill. Although copper coaxial cable can handle the bandwidth requirement over the short distances of a housing scheme, a copper system consumes far more electrical power than fibre, simply to carry the signals. </li></ul>
Disadvantages of Optical fiber <ul><li>Enormous Bandwidths </li></ul><ul><li>Low transmission loss </li></ul><ul><li>Immunity to cross talk </li></ul><ul><li>Small size and weight </li></ul><ul><li>Signal security </li></ul><ul><li>Electrical Isolation </li></ul><ul><li>Ruggedness and flexibility </li></ul><ul><li>Low cost and availability </li></ul><ul><li> Reliability </li></ul>
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