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Rise of optical technology

In modern-day communication systems, electromagnetic waves play a very important role. Communication with microwaves, radio waves are well known examples [2]. Optical fibers carry electromagnetic signals in the form of light waves. The wavelengths of these light waves ranges generally from $ 0.4 \,\mu$m to $ 1.6 \,\mu$m. Unlike in the conventional copper wires, where electromagnetic signals are carried by electrons, in the optical fibers the signals are carried by photons.

This fundamental difference offers several advantages for the use of optical fibers in place of copper cables [3]. Compared to copper cables, optical fibers have much lower line loss and smaller dispersion per unit length. Moreover, optical fibers support a broad bandwidth permitting multiplexing to further increase the transmission capacity. Copper cables are prone to electromagnetic interference causing high error rates, and also they are sensitive to eavesdropping, whereas optical fibers are immune to these problems. As a result, optical fibers soon became one of the essential components of communication networks.

As most processing/transmission devices (e.g. computers, routers, amplifiers, etc.) are at present based on electronics, data to be processed or transmitted is typically available in the form of electrical signals. To send these signals over optical fiber networks, these signals first have to be converted from the electrical domain to the optical domain. At amplifier/receiver units, the data have to be converted back to electrical signals. This signal conversion from the electrical domain to the optical domain, and vice versa, involves losses. And also the realization introduces additional costs [4].

With the use of optical fibers, even though the signal transmission is improved significantly, the ultimate performance of combined electronic-optical transmission systems is determined by the processing speed of the electronic devices. Microelectronic devices are also getting faster, but their switching speed is not at par with the transmission capacity of optical networks [5,6]. This is inevitable, because the underlying physical mechanisms for the transfer of electrons and photons are quite different. Also there are technological limitations for the extreme miniaturization of the electronic circuits [7]. To accommodate the increasing demand of faster information processing, there is a need to develop a new technology. The potential shown by the optical fibers drew attention to optics.

The field of optics has made huge progress from the time of seminal work of Huygens (1629-1695), Newton (1643-1727) and Maxwell (1831-1879). The invention of lasers in 1958 rejuvenated the interest in optics. The next stepping stone for optics was the use of optical fibers in telecommunication networks. This growing interest in optics led to the establishment of new fields like ``optronics'', ``photonics''1.1.

A main concern of the field of modern optics is the generation, manipulation, guidance, and detection of light for communication and information processing applications. Thus the communication networks are evolving from mere cost effective optical signal transport in networks based on electronic devices to full-fledged optical networks. In an advanced stage, such optical networks will as far as possible avoid the expensive conversion of electrical signals into optical signals, and vice versa. Apart from optics based light sources, detectors, and signal carriers (i.e. waveguides), essential building blocks of such networks are optics based amplifiers, modulators, switches, and filters [8]. Successful demonstration and realization of these functional components will lead to ``all-optical-processing'' systems.


next up previous contents
Next: Next generation Active Integrated Up: Introduction Previous: Introduction   Contents
Kirankumar Hiremath 2005-09-23