Optical Fiber

Prepared By AbdulRahman AlKhayyat Mohamed Felimban

An optical fiber is a glass or plastic fiber designed to guide light along its length by total internal reflection Optical fibers are widely used in communication, which permits digital data transmission over longer distances and at higher data rates than electronic communication. General View

So it is the technology that uses glass (or plastic) threads (fibers) to transmit data General View Road maintenance for fiber cables

The idea of optical fibers was first demonstrated in Victorian times, and then developed to satisfy the demands in the 1950's History then it was developed in 1970 to match the communications purposes, which is the most used today for optical fiber

The first commercial fiber optic communication system was developed, which operated at a wavelength around 0.8 µm, and at a bit rate of 45 Mb/s with repeater spacing of up to 10km History The second generation of fiber optic communication was developed for commercial use in the early 1980’s, operated at 1.3 µm

The third generation of fiber optic systems operated at 1.55 µm and had loss of about 0.2-dB/km History The fourth generation of fiber optic communication systems used optical amplification to reduce the need for repeaters and wavelength-division multiplexing to increase fiber capacity

The fifth generation of fiber optic communications is on extending the wavelength range over which a big systems can operate History In the late 1990s through 2000, the fiber optic communication became apart of the internet facilities

Fiber optic cables have a much greater bandwidth than metal cables Features This means that they can carry more data Data can be transmitted digitally rather than analogically

Fiber optic cables do not conduct electricity; they are glass or plastic therefore safer Features They are particularly suitable for use in areas that might have spark or electrical hazard restrictions

The fifth generation of fiber optic communications is on extending the wavelength range over which a big systems can operate Features In the late 1990s through 2000, the fiber optic communication became apart of the internet facilities

Second Part of Optical Fiber Components of the Transmission System Components of the Transmission System – Transmitters – Receivers – Transmission Medium Performance Performance – Attenuation – Interference Conclusion Conclusion The Fiber Optic Data Communication System

I. The Fiber Optic Data Communication System A model of this System is shown in the figure The illustration indicates the Source-User pair, Transmitter & Receiver It also clearly shows the Transmission Medium. Fiber Optic communication systems generally include: - A Transmitter - Transmission Medium including amplifiers and repeaters - A Receiver

II. Components of the Transmission System Transmitter to convert an electrical signal into an optical signal serves two functions: A light emitter A light emitter – works as a source of the light coupled into the fiber optic cable A regulator A regulator – to modulate this light to represent the binary data it receive

II.1. Transmitters: Optical Source Component 3. high efficiency in coupling the light into the fiber optic cable 4. sufficient linearity to prevent the generation of harmonics & inter-modulation distortionto prevent the generation of harmonics & inter-modulation distortion if such interference is generated it is extremely difficult to removeif such interference is generated it is extremely difficult to remove this would cancel the interference resistance benefits of the fiber optic cablethis would cancel the interference resistance benefits of the fiber optic cable 5. Should be easily modulated with an electrical signal & capable of high-speed modulation 6. The usual requirements of small size, low weight, low cost and high reliability There are some requirements for the transmitter that should be met 1. physical dimensions must be compatible with size of the fiber optic being used emit light in a cone within cross sectional diameter 2. optical source must be able to generate enough power desired BER should be met

II.1. Transmitters cont’d LD's advantages over LED's : - can be modulated at very high speeds - produce greater optical power - higher coupling efficiency to the fiber optic cable Types of Diodes that can be used as an optical source of the Transmitter: - laser diode (LD) - light emitting diode (LED) LED's advantages over LD's : - higher reliability - better linearity - lower cost

II. Components of the Transmission System Receivers to recover the signal as an electrical signal serves two functions: A sensor to detect the light coupled out of the fiber optic cable then convert the light into an electrical signal A demodulator demodulate this light determine the identity of the binary data that it represents

II.2. Receivers cont’d receiver performance is generally characterized by a parameter called the Sensitivity usually a curve indicating the minimum optical power that the Receiver can detect versus the data rate, in order to achieve a particular BER

II.3. Transmission Medium The Transmission distance is limited by fiber attenuation & fiber distortion Solution: i. repeaters convert the signal to an electrical signal send the signal again at a higher intensity high complexity & needing to be installed once every 20km = very high cost Solution: ii. optical amplifiers amplifies the optical signal directly without converting the signal into the electrical domain Amplifiers have largely replaced repeaters in new installations

III. Performance The more light that can be coupled into the core the more light will reach the Receiver and the lower BER The lower attenuation in propagating down the core the more light reaches the Receiver & the lower BER The less time realized in propagating the faster the signaling rate and the higher the end-to-end data rate from Source- to-User

III. Performance cont’d Attenuation Caused by a combination of material absorption, Raleigh scattering, Mie scattering, and connection losses Is about 1000 db/km in modern fiber Other causes of attenuation are physical stresses to the fiber, microscopic fluctuations in density, and imperfect splicing techniques.

III. Performance cont’d Interference a key concern is the problem of interference Presence of high current equipment results in the propagation of electromagnetic pulses that interfere with the data communications links In the past UTP copper cable was the transmission medium choice Using Fiber optic cables as the Transmission Medium great interference protection is simply not affected by the electromagnetic interference Has been slow in coming to the industrial environment due to cost however, this is changing as the price of fiber optic cable steadily decreases

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