Optical Fiber Technology

Presented by –Rajen Kumar Maji

Rumpa MallickAnkita KunduSayani Sarkar

IntroductionAn Optical fiber is a flexible, transparent fiber made of high quality glass(silica) or plastic.It either functions as a waveguide or light pipe that transmits light between two ends of the fiber or fiber cable.Optical fibers are widely used in fiber-optic communication which permits transmission over long distances at higher bandwidths.Fibers are used instead of metal wires because signal travels along them less loss & also safe to electromagnetic interference.

Optical Fiber – Types & Construction

Fiber types- Single mode & multimode According to refractive index, there are

three types of fiber : Multimode step index fiber Multimode graded index fiber Single mode step index fiber

Cable construction - There are basic two cable designs are :

• Tight buffer tube cable• Loose buffer tube cable

Installation of optical fiber cables

• Installation of cables in underground ducts.• Installation of fiber cables with trenchless

technique.• Installation of fiber cables with mini trench

technique.• Installation of fiber cables with micro

trench technique.• Installation of Aerial cables.• Installation of Buried cables.• Installation of fiber cables over power lines.• Installation of underwater cables.• Installation of Indoor cables.

Optical Fiber SplicingThere are three types of splicing -

•Adhesive splicing or Glue splicing : This is the oldest splicing technique use in fiber splicing.•Mechanical splicing : This splicing is mainly used for temporary splicing in case of emergency repairing.• Fusion splicing : This is the most popular technique used for achieving low splice loss.

Fiber Optic Cable – Splicing Procedure

Strip fiber cable jacket.Strip fiber tubes.Clean cable gel.Secure cable tubes.Strip first splicing fiber.Place the fusion splice protection sleeve.Clean the bare fiber.Fiber cleaving. Prepare second fiber being spliced.

Fusion splicing.Heat shrinks the fusion splice protection sleeve.Place splice into splice tray.Perform OTDR test.Close the splice tray.Bidirectional OTDR test(or power meter test).Mount the splice enclosure.

Connectors in Optical Fiber Technology• D4 connector• SC fiber optic connector• ST connector• FC connector• LC connector• FDDI connector• ESCON connector

OTDR is a fiber optic tester that is used to detect, locate and measure events at any location in the fiber link. Components of OTDR—Printer jack , Pigtail jack, RS232 jack, Display monitor, Cursor, Start/LASER switch , Select switch, Function key.It operates as a one-dimensional radar system & generates geographic information.It works on back scattering principle.

OTDR(OPTICAL TIME DOMAIN REFLECTOMETER)

DEAD ZONEWhen a strong reflection occurs, the power received by the photodiode can be more than

4,000 times higher than the backscattered power, saturating the photodiode. The

photodiode requires time to recover from its saturated condition. During this time, it will not

detect the backscattered signal accurately. The one at the start of the fiber where the signal

is being launched is called the launch dead zone.

WORKING PRINCIPLE OF OTDR

Optical Power Meter & Measurement • It is a device used to measure the power in an optical signal. The term usually refers to a

device for testing average power in fiber optic systems.

• The procedure to measure the optical loss in the fiber optic cable using power meter :

• Connect a short fiber jumper cable between the light source & the power meter.

• Make note of the power level , in dBm as Reading A• Connect the fiber cable under test to the output of

the source• Connect the power meter, set the same

wavelengths as the power source, to the far end of the fiber cable under test

• Make note of power level, in dBm as Reading B• Optical loss = Reading A – Reading B

AttenuatorsOptical attenuators use several different principles in order to accomplish the desired power reduction

•Gap-loss Principle• Absorptive Principle• Reflective Principle

Types of Attenuators :• Stepwise variable attenuators• Continuously variable attenuator

Optical Power BudgetThe optical power budget in a fiber-optic communication link is the allocation of available optical power among various loss producing mechanisms such as launch coupling loss, fiber attenuation, splice losses, and connector losses, in order to ensure that adequate strength is available at the receiver. The optical power budget is usually specified or expressed in dB.Power budget is the difference between :

The minimum(worst case) transmitter output power

The maximum (worst case) receiver input required