OPTIC FIBRE

• Optical fibres, composed of thin cylindrical strands of glass, have transformed the world of communication. With diameters close to that of a human hair, these remarkable fibres carry information, including text, images, voices, videos, telephone calls, and anything that can be encoded into digital data, across vast distances at nearly the speed of light.
• Receiving text messages and making phone calls have become commonplace in our daily lives, often taken for granted. However, optical fibres play a crucial role in enabling these modern communication technologies. By transmitting massive amounts of data at incredible speeds, optical fibres form the backbone of the internet and telecommunications networks that connect us globally.
• Despite their delicate appearance, ultra-thin fibres, when manufactured correctly as long threads encased in protective layers, prove to be remarkably durable. They are strong, lightweight, and flexible, making them ideal for underground burial, underwater deployment, or coiling around spools.
• Nearly 60 years ago, physicist Charles Kao proposed that glass fibres could surpass copper wires as the primary medium for telecommunication. Initially met with scepticism, his prediction has become a reality, earning him a share of the 2009 Nobel Prize in Physics for his groundbreaking contributions to fibre optic communication.

• Light, an electromagnetic wave with a vast spectrum of frequencies, encompasses visible light, X-rays, radio waves, and even thermal radiation (heat).
• We perceive the world around us through sunlight, but it took us centuries to harness and guide light through fibre optic cables, also known as "light pipes," to send encoded signals over long distances.
• When a beam of light encounters a glass surface, it partially passes through while the rest is reflected.
• As the light enters the glass, its path bends due to the difference in the refractive index of air and glass.
• The refractive index is a property of a medium that determines how fast light travels through it.
• Interestingly, when the light beam travels in the reverse direction, from glass to air, it may not escape the glass altogether.
• Instead, it undergoes complete reflection, bouncing back within the glass. This phenomenon, known as total internal reflection, is the key to guiding light across long distances without significant loss of optical power.
• With precise adjustments, the light can be kept bouncing within the glass, with minimal escape to the outside environment.

3.1. The Mechanism of Optical Fiber Communication

Optical fibre communication systems consist of three main components

1. The transmitter encodes information into optical signals, typically in the form of rapidly blinking light pulses representing zeros and ones.
2. The optical fibre acts as the transmission medium, carrying the encoded signal to its destination.
3. The receiver decodes the information from the encoded signal, reproducing the original data.

3.2. Advantages of Optical Fiber Communication

Optical waves offer several advantages over traditional copper-based communication methods:

• Optical fibres can transmit massive amounts of data at incredible speeds, reaching up to several terabits per second in a single fibre.
• Unlike radio or copper-cable-based communication, fibre cables are immune to external electromagnetic interference, such as lightning strikes or bad weather conditions.
• Optical fibres are inherently more secure than electrical cables, as they are less susceptible to eavesdropping or signal tampering.

4. The development of fibre optic cables

• Jean-Daniel Colladon and Jacques Babinet demonstrated that light could be guided through curved glass rods.
• Clarence Hansell and John Logie Baird developed methods for transmitting images through glass fibres, while doctors began using fibre bundles for internal examinations and surgical illuminations.
•  Harold Hopkins and Narinder Singh Kapany successfully transmitted images through a bundle of over 10,000 optical fibres, and Lawrence E. Curtiss developed glass-clad fibres, paving the way for long-distance data transmission. Kapany also coined the term "fibre optics."
• Theodore Maiman's invention of the laser in 1960 boosted optical communication research. However, signal attenuation remained a major challenge, with fibres losing 99% of their power after a few meters.
•  Charles Kao and his colleagues discovered that signal attenuation was primarily caused by impurities in the glass, not light scattering. They proposed using high-purity fused silica to reduce attenuation below 20 decibels per kilometre (dB/km).
• Corning Glass Works successfully produced a cable with an attenuation of 20 dB/km, marking a significant milestone in fibre optic technology.
• Today, optical fibres are manufactured using the fibre-drawing technique, which involves heating a high-purity glass rod and drawing it into a thin, long fibre. The drawn fibre is then coated with a protective layer for enhanced strength and durability.

5. The Future of Fiber Optic Cables

• Fibre optic technology, with its remarkable ability to transmit massive amounts of data at incredible speeds, has revolutionized communication, medicine, laser technology, and sensing. As we look towards the future, the possibilities of fibre optics continue to expand, reaching new horizons in quantum communication and beyond.
• Recognizing the immense potential of fibre optics, the Indian government has taken a proactive approach to foster its development. In the Union Budget of 2020, a national mission titled "National Mission on Quantum Technologies and Applications" was announced, with a proposed budget of Rs 8,000 crore over five years. This mission aims to secure communication networks, promote quantum science, and accelerate the adoption of fibre optic technologies across various sectors.
• Quantum optics, the intersection of quantum mechanics and optics, promises to transform fibre optic communication by enabling secure and encrypted data transmission. By harnessing the principles of quantum entanglement, scientists are developing quantum communication networks that are immune to eavesdropping and hacking.
• Fibre optics is poised to enter our homes, bringing with it a new era of connectivity and convenience. Fiber-to-the-home (FTTH) connections are rapidly expanding, offering ultra-high-speed internet access, seamless video streaming, and enhanced gaming experiences.
• Fibre optic communication, coupled with quantum optics, stands on the cusp of a new era, brimming with untapped potential. As research and development continue, we can anticipate advancements in quantum computing, ultra-secure communication networks, and even teleportation, all powered by the remarkable capabilities of fibre optics.

6. Conclusion

The future of fibre optic cables is bright and expansive. With its ability to deliver secure, high-speed data transmission, fibre optics is poised to revolutionize communication, science, and our everyday lives. As we embrace the possibilities of quantum optics and fibre-to-the-home technologies, we stand at the threshold of a new era of connectivity and innovation.