Archived — Fiber Optic Cable

The effect of nonlinearities can be reduced by designing a fiber with a large effective area. Non-Zero Dispersion Shifted fibers (NZ-DSF) have a small value of the chromatic dispersion in the 1550nm band to minimize the effects of chromatic dispersion. Unfortunately, such fibers also have a smaller effective area. Recently, an NZ-DSF with a larger effective area – over 70 μm2 – has been developed by both Corning (LEAF) and Lucent (TrueWave XL). This compares to about 50 μm2 for a typical NZ-DSF and 85 μm2 for standard single mode fiber. These fibers thus achieve a better trade-off between chromatic

In this tutorial, we will discuss the maximum distance that a fiber cable can transmit without an amplifier or repeater. This distance is limited by the fiber’s attenuation (loss) and dispersion (pulse widening). In practice, fiber link distance can be extended by using fiber amplifiers and dispersion compensators. >> Fiber Distance Limit by Attenuation For a practical fiber optic communication link, the Bit Error Ratio (BER) must be less than 10-9. Based on this BER requirement, there must be a minimum number of photons per bit of information. Let’s assume this minimum number is Np, then for a bit rate

1. Light Pulse Dispersion and the Reasons In digital communication systems, information is encoded in the form of pulses and then these light pulses are transmitted from the transmitter to the receiver. The larger the number of pulses that can be sent per unit time and still be resolvable at the receiver end, the larger is the capacity of the system. However, when the light pulses travel down the fiber, the pulses spread out, and this phenomenon is called Pulse Dispersion. Pulse dispersion is shown in the following figure. Pulse dispersion is one of the two most important factors that

The attenuation of an optical fiber measures the amount of light lost between input and output. Total attenuation is the sum of all losses. Optical losses of a fiber are usually expressed in decibels per kilometer (dB/km). The expression is called the fiber’s attenuation coefficient α and the expression is where P(z) is the optical power at a position z from the origin, P(0) is the power at the origin. For a given fiber, these losses are wavelength-dependent which is shown in the figure below. The value of the attenuation factor depends greatly on the fiber material and the manufacturing

1. Light is an Electromagnetic Wave Fundamentally, light wave is an electromagnetic wave which is described by Maxwell’s Equations. It is composed of electric and magnetic fields. These two fields are perpendicular to each other and to the direction in which the light travels. This is shown in the following figure. The electric and magnetic field amplitude varies with time as a sine wave, just like a since function in trigonometry. Wavelength: Wavelength is the distance between two nearest amplitude positive peaks. The amplitude rises from 0 to a positive peak, goes through 0, goes to negative peak, then returns