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Optical Multiplexing . optical telecommunication networks. Outline. Introduction Multiplexing Optical Multiplexing Components of Optical Mux Application Advantages Shortcomings/Future Work Conclusion References. Introduction.
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Optical Multiplexing optical telecommunication networks
Outline • Introduction • Multiplexing • Optical Multiplexing • Components of Optical Mux • Application • Advantages • Shortcomings/Future Work • Conclusion • References
Introduction • Optical transmission uses pulses of light to transmit information from one place to another through an optical fiber. • The light is converted to electromagnetic carrier wave, which is modulated to carry information as the light propagates from one end to another. • The development of optical fiber has revolutionized the telecommunications industry. • Optical fiber was first developed in the 1970s as a transmission medium. • It has replaced other transmission media such as copper wire since inception, and it’s mainly used to wire core networks. • Today, optical fiber has been used to develop new high speed communication systems that transmit information as light pulses, examples are multiplexers.
Multiplexing • Multiplexing • What are Multiplexers? • Multiplexers are hardware components that combine multiple analog or digital input signals into a single line of transmission. • And at the receiver’s end, the multiplexers are known as de-multiplexers – performing reverse function of multiplexers. • Multiplexing is therefore the process of combining two or more input signals into a single transmission. • At receiver’s end, the combined signals are separated into distinct separate signal. • Multiplexing enhances efficiency use of bandwidth.
Multiplexing Example • MATLAB simulation example: • Sampled in time: • Quantization • Digitization
Multiplexing Example • Multiplexed Signals • Separation of signals • Using time slots.
Laser 1 Laser 2 Multiplexer Optical Fiber De-multiplexer Laser 3 Laser 4 Regenerator + Receiver Optical Multiplexing • Optical multiplexer and de-multiplexer are required to multiplex and de-multiplex various wavelengths onto a single fiber link. • Each specific I/O will be used for a single wavelength. • One optical filter system can act as both multiplexer and de-multiplexer
Optical Multiplexing • Optical multiplexer and de-multiplexer are basically passive optical filter systems, which are arranged to process specific wavelengths in and out of the transport system (usually optical fiber). • Process of filtering the wavelengths can be performed using: • Prisms • Thin film filter • Dichroic filters or interference filters • The filtering materials are used to selectively reflect a single wavelength of light but pass all others transparently. • Each filter is tuned for a specific wavelength
Components of Optical Multiplexer • Combiner • Tap Coupler • ADD/DROP • Filters • Prisms • Thin film • Dichroic • Splitter • Optical fiber
Optical Multiplexing Techniques • There are different techniques in multiplexing light signals onto a single optical fiber link. • Optical Multiplexing Techniques • Optical Time Division Multiplexing (OTDM) • Separating wavelengths in time • Wavelength division multiplexing (WDM) • Each channel is assigned a unique carrier frequency • Channel spacing of about 50GHz • Coarse Wavelength Division Multiplexing (CWDM) • Dense Wavelength Division Multiplexing • Uses a much narrower channel spacing, therefore, many more wavelengths are supported. • Code Division Multiplexing • Also used in microwave transmission. • Spectrum of each wavelength is assigned a unique spreading code. • Channels overlap both in time and frequency domains but the code guide each wavelength.
Applications • The major scarce resource in telecommunication is bandwidth – users want transmit at more high rate and service providers want to offer more services, hence, the need for a faster and more reliable high speed system. • Reducing cost of hardware, one multiplexing system can be used to combine and transmit multiple signals from Location A to Location B. • Each wavelength, λ, can carry multiple signals. • Mux/De-Mux serve optical switching of signals in telecommunication and other field of signal processing and transmission. • Future next generation internet.
Advantages • High data rate and throughput • Data rates possible in optical transmission are usually in Gbps on each wavelength. • Combination of different wavelengths means more throughput in one single communication systems. • Low attenuation • Optical communication has low attenuation compare to other transport system. • Less propagation delay • More services offered • Increase return on investment (ROI) • Low Bit Error Rate (BER)
Shortcomings • Fiber output loss + dispersion • Signal is attenuated by fiber loss and distorted by fiber dispersion • Then regenerator are needed to recover the clean purposes • Inability of current Customer Premises Equipment (CPEs) to receive at the same transmission rate of optical transmitting systems. • Achieving all-optical networks • Optical-to-Electrical conversion overhead • Optical signals are converted into electrical signal using photo-detectors, switched and converted back to optical. • Optical/electrical/optical conversions introduce unnecessary time delays and power loss. • End-to-end optical transmission will be better.
Future Work • Research in optical end user equipment • Mobile phones, PC, and other handheld devices receiving and transmitting at optical rate. • Fast regeneration of attenuated signal • Less distortion resulting from fiber dispersion. • End-to-end optical components • Eliminating the need for Optical-to-Electrical converter and vise versa.
Conclusion • Optical multiplexing is useful in signal processing and transmission. • Transporting multiple signals using one single fiber link • The growth of the internet requires fiber optic transmission to achieve greater throughput. • Optical multiplexing is also useful in image processing and scanning application. • Optical transmission is better compare to other transmission media because of its low attenuation and long distance transmission profile.
