INTRODUCTION TO OPTICAL COMMUNICATION TECHNOLOGY

Table of Content The learning outcomes Elements in Telecommunication System Optical Communication System Components Light : The characteristic and behavior The advantages of optical communication

The Learning Outcomes At the end of the module, student should able to : Explain the basic elements of optical communication Explain the behavior of light Describe the advantages optical communication technologies Application of optical communication

Elements in Telecommunication the part where the message is processed, modulated and sent as signal. Transmitter where the signal sent through Transmission Medium the part where signal is received, demodulated and converted to original message. Receiver Transmitter Receiver Medium

Optical Communication System Light source The transmitter Optical Fiber @ Fiber Optic Transmission medium Photodetector The receiver Light source Photodetector Optical Fiber

What is Light? Light is electromagnetic radiation that can be detect by the human eye (400-650nm). In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. Wavelength Range (nanometers) Perceived Color 340-400 Near Ultraviolet (UV; Invisible) 400-430 Violet 430-500 Blue 500-560 Green 560-620 Yellow to Orange 620-700 Orange to Red Over 700 Near Infrared (IR; Invisible)

Understanding of light Near Infrared Frequency Wavelength 1.6 229 1.0 0.8 µm 0.6 0.4 1.8 1.4 UV (vacuum) 1.2 THz 193 461 0.2 353 Longhaul Telecom Regional Telecom Local Area Networks 850 nm 1550 nm 1310 nm CD Players 780 nm HeNe Lasers 633 nm

Characteristics of Light Speed: 3x108 m/s Power (Watts,dBm) or Energy (Joules) Wavelength (m) or Frequency (Hz) Spectrum bandwidth (nm,Hz) Beam profile (shape) Phase (angle: degree or radiance) Polarization (angle: degree)

Understanding Light: The Behavior significant technologies sdn bhd Understanding Light: The Behavior An EM wave with quantized energy Travels in straight line Transmits through media Reflects off different media Chargeless - does not interact with other light- can go through each other Interact with materials (media) Can be visible/invisible 2-Dimesional; carries image

When a light wave hits an object, what happens to it depends on the: Energy Frequency at which electrons vibrate in the material Strength with which the atoms in the material hold on to their electrons. Based on these three factors, four different things can happen when light hits an object: Reflected or scattered Absorbed Refracted Pass through

TOTAL INTERNAL REFLECTION When the critical angle is exceeded for a particular light wave, it exhibits total internal reflection back into the medium. Usually the higher index medium is considered the internal medium, because air (having a refractive index of 1.0) is in most cases the surrounding, or external medium If the incident angle increases past a specific value (dependent upon the refractive index of the two media), it reaches a point at which the angle is so large that no light is refracted into the medium of lower refractive index, as illustrated in Figure 1. In this figure, individual light rays are represented by either red or yellow colored arrows moving from a medium of higher refractive index (n(2)) to one of lower refractive index (n(1)). The angle of incidence for each individual light ray is denoted by the value i and the angle of refraction by the variable r. The four yellow light rays all have an angle of incidence (i) low enough to allow them to pass through the interface between the two media. However, the two red light rays have incident angles that exceed the critical angle of reflection (approximately 41 degrees for the water and air examples) and are reflected either into the boundary between the media or back into the higher refractive index medium.

Total Internal Reflection Apply for light propagation inside fiber optic

Advantages for Communications Low cost/bandwidth High Speed Low Power Operations No Electromagnetic Interference (EMI) No Grounding Secure Simple Modulation and Detection Real Full Duplex transmission (bi-directional)

Communication Link Performance

Advantages of Optical communication Immunity to EMI High bandwidth Immunity to crosstalk Low attenuation Safety Size and capacity Immunity to EMI Because it carries light rather than electrical signals, it cannot be affected by electromagnetic interference from power, radio or microwaves sources. High bandwidth Increase information carrying capacity over long distance. Fiber optic – 10 Gb/s for 300 meters Copper – 1 Gb/s for 100 meters Immunity to crosstalk The structure of optical fiber is such that the light energy is essentially completely constrained within the core of the fiber and, hence signals cannot couple between fibers in a cable. Low attenuation Attenuation is proportional to cable length, hence, fiber’s lower attenuation enables much longer link distances than copper. Safety Fiber does not conduct electricity, hence no lightning strikes. Size & Capacity A single fiber can replace several copper conductors. Fiber: Capacity of a 1/2 inch diameter cable (144fibers) = 65,000 simultaneous conversations on each fiber…..9.36 million total calls on the entire cable Copper: Capacity of a 4 1/2 inch diameter cable = 40,300 calls (and for shorter distances ) Weight Fiber: A typical single-fiber cable weighs 9 lbs./1000 feet Copper: A comparable coaxial cable weighs 80 lbs./1000 feet

Copper VS Optical Fiber

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Next Module : Optical Fibers and Cables Termination and Connectors Measurements and test gears Optical Cable Installation