Optical Fiber Communication

Type of optical fiber

            When we are selecting optical fiber for a specific application we have two types of optical fibers. They are Single mode and multi mode. The mode structure depends on the wavelength of the light used, so that this fiber actually supports a small number of additional modes at visible wavelengths. Multi-mode fiber is a type of fiber optic cable which is thick enough for light to follow several paths through the code. Multi-mode fiber is best suited for use in short lengths, such as those used in Local Area Networks (LANs). But single modes are standard choice for high data rates or long distance telecommunications which use laser diode based fiber optic transmission equipment. 

Dispersion

When we discuses about dispersion of fiber. Ever fiber has Inter modal or chromatic dispersion. Multi mode dispersion only occurs in multimode fibers. . But single mode fibers are having lower dispersion than multi mode fibers. Therefore we can use single mode fibers for long haul repeater/amplifier less optical communication links. 

Fiber non linearity

In this system it is difficult to maintain a linear fiber connection. The system has bending losses and signal transmitting distance may reduce. So, it is important to try to design a linear fiber optic transmission system as possible.

Operating wavelength

When we are selecting a suitable wave length for optical fiber communication we have to analyze the Optical window graph. In optical window there are three windows. We have  820 nm to 900 nm(1^st window), 1280 nm to 1350 nm (2^nd  window), and 1450 to 1650 nm(3^rdwindow) But 3^rd window is enhanced for long distance communication for the reason that, the attenuation is varying 0.15 - 0.25 dB/Km which is very low compare to other two windows.

Transmitting power

Operation of semiconductor laser Amplifier

Operation of semiconductor laser Amplifier

Hi this stuff describes about semiconductor laser Amplifiers, and I think you will get idea about its operation.

These SLA (semiconductor laser Amplifier) are based on semiconductor laser diode (SLD). This figure shows us a semiconductor laser amplifier with length l, thickness. This active region is having excited electrons and when they force to come to ground level, amplification process occurs. Here facet reflectivity is in between 30% and 35%. We can generalize the structure of a SLA by an embedded active region with two end-facets for the input and output of light signals. The end-facets with power reflection coefficients (R₁ and R₂₎ are responsible for providing optical feedback into the amplifier. These finite reflections arise because of the discontinuities of the refractive index between the semiconductor and air. When the signal passes through active region of gain G, it will boost up.

Advantages of integrated optical amplifiers

Integrated optical amplifiers have the advantage of integrating with other guided wave devices such as power dividers leading to compensation of waveguide losses.

And also optical switches associated with integrated optical amplifiers are capable of providing loss less switching and it will reduce the cross talk.

Integrated optical amplifiers are much smaller in length than fiber amplifiers


    Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you.