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.

MULTIPLEXER

MULTIPLEXING EXAMPLE MATLAB simulation example:

Sampled in time: Quantization Digitization

0 10 20 30-10

-5

0

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10Sinusoidal Signal

Am

plitu

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->

Time--->0 10 20 30

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8Triangular Signal

Am

plitu

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->

Time--->

0 10 20 30-10

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10Sampled Sinusoidal Signal

Am

plitu

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->

Time--->0 10 20 30

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8Sampled Triangular Signal

Am

plitu

de--

->Time--->

MULTIPLEXING EXAMPLE Multiplexed Signals

Separation of signalsUsing time slots.

0 10 20 30 40 50 60-8

-6

-4

-2

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8TDM Signal

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plitu

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Time--->

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10Recovered Sinusoidal Signal

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plitu

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>

Time--->

0 5 10 15 20 25 300

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8Recovered Triangular Signal

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plitu

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Time--->

RECOVERED SIGNAL

0 5 10 15 20 25 30-10

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10Recovered Sinusoidal Signal

Am

plitu

de--

->

Time--->

0 5 10 15 20 25 300

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8Recovered Triangular Signal

Am

plitu

de--

->

Time--->

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-multiplexerLaser 1

Laser 2

Laser 3

Laser 4

Multiplexer Optical Fiber De-multiplexer

Regenerator + Receiver

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

OPTICAL MULTIPLEXING AND FILTERING

COMPONENTS OF OPTICAL MULTIPLEXER Combiner Tap Coupler

ADD/DROP Filters

PrismsThin filmDichroic

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 linkThe 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.

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