Laser &Laser & OpticalOptical FibersFibers

Prepared by : Prepared by : Deepti JainDeepti Jain

ContentsContents Fiber Laser Fiber Laser Advantages of Fiber Laser Advantages of Fiber Laser Disadvantages of Fiber Laser Disadvantages of Fiber Laser Design and manufactureDesign and manufacture Fiber Disk LasersFiber Disk Lasers Optical fibersOptical fibers Use of Optical fibers Use of Optical fibers Advantages of Optical fibersAdvantages of Optical fibers Disadvantages of Optical fibersDisadvantages of Optical fibers

Fiber Laser Fiber Laser A A fiber laserfiber laser or or fibre laserfibre laser is a is a

laser in which the active gain laser in which the active gain medium is an optical fiber medium is an optical fiber

doped with rare-earth elements doped with rare-earth elements such as erbium, ytterbium, such as erbium, ytterbium, neodymium, dysprosium, neodymium, dysprosium,

praseodymium, and thulium. praseodymium, and thulium. They are related to doped fiber They are related to doped fiber amplifiers, which provide light amplifiers, which provide light amplification without lasing. amplification without lasing. Fiber nonlinearities, such as Fiber nonlinearities, such as

stimulated Raman scattering or stimulated Raman scattering or four-wave mixing can also four-wave mixing can also

provide gain and thus serve as provide gain and thus serve as gain media for a fiber laser. gain media for a fiber laser.

Advantages of Fiber Advantages of Fiber LaserLaser• High Power: ease of cooling in long High Power: ease of cooling in long

fiber fiber • High Stability: spliced wave guiding High Stability: spliced wave guiding

fibers fibers • High Reliability: operate 24/7 for High Reliability: operate 24/7 for

decades decades • Lower total cost of ownership Lower total cost of ownership • Low jitter and low amplitude noise Low jitter and low amplitude noise

• Compact form factor Compact form factor • Immune to tough environmental Immune to tough environmental

changes changes • Turn-key OperationTurn-key Operation

Disadvantages of Disadvantages of Fiber Laser Fiber Laser

• Pulse pedestals from non-ideal optical spectrum for higher energy pulses.

• Undesired nonlinear optical effects at high pulse energy, such as self-phase modulation and Raman scattering.

Design & Design & ManufactureManufacture 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.

Double-clad Double-clad fibersfibersMany 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."

Power ScalingPower ScalingRecent 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 .

Fiber disk lasersFiber disk lasers

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.

Optical Optical FiberFiber

Optical FiberOptical Fiber 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

      Uses of Optical Uses of Optical FibersFibers

  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.  

Advantages of Optical Advantages of Optical Fibers Fibers

•Capacity Capacity •Size and Weight•Running Costs •Security

CapacityCapacityOptical 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.

Size and Size and WeightWeight

Optical fiber cables are Optical fiber cables are much lighter and thinner much lighter and thinner

than copper cables with the than copper cables with the same bandwidth. This same bandwidth. This means that much less means that much less

space is required in space is required in underground cabling ducts. underground cabling ducts.

Also they are easier for Also they are easier for installation engineers to installation engineers to

handlehandle..

SecuritySecurity 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.

Running CostsRunning Costs 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.

Disadvantages of Optical Disadvantages of Optical fiber fiber1. Enormous Bandwidths

2. Low transmission loss3. Immunity to cross talk 4. Small size and weight 5. Signal security6. Electrical Isolation 7. Ruggedness and flexibility 8. Low cost and availability9.  Reliability