OPTICAL TELECOMMUNICATION NETWORKS Optical Multiplexing & Demultiplexing: Phillip B. Oni (u96761)...
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Transcript of OPTICAL TELECOMMUNICATION NETWORKS Optical Multiplexing & Demultiplexing: Phillip B. Oni (u96761)...
OPTICAL TELECOMMUNICATION NETWORKS
Optical Multiplexing & Demultiplexing:
Phillip B. Oni (u96761)
AUTO3160 – OPTICS & SPECTROSCOPY
VAASA, Spring 2012.
Outline
IntroductionMultiplexing / DemultiplexingOptical MultiplexingComponents of Optical Mux/DemuxApplicationAdvantagesShortcomings/Future WorkConclusionReferences
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 & Demultiplexing
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
http://en.wikipedia.org/wiki/File:Telephony_multiplexer_system.gif
Multiplexing Example
MATLAB simulation example: Sampled in time:
Quantization Digitization
0 10 20 30-10
-5
0
5
10Sinusoidal Signal
Am
plitu
de--
->
Time--->0 10 20 30
0
2
4
6
8Triangular Signal
Am
plitu
de--
->
Time--->
0 10 20 30-10
-5
0
5
10Sampled Sinusoidal Signal
Am
plitu
de--
->
Time--->0 10 20 30
0
2
4
6
8Sampled Triangular Signal
Am
plitu
de--
->Time--->
Multiplexing Example
Multiplexed Signals Separation of signals Using time slots.
0 10 20 30 40 50 60-8
-6
-4
-2
0
2
4
6
8TDM Signal
Am
plitu
de--
->
Time--->
0 5 10 15 20 25 30-10
-5
0
5
10Recovered Sinusoidal Signal
Am
plitu
de---
>
Time--->
0 5 10 15 20 25 300
2
4
6
8Recovered Triangular Signal
Am
plitu
de---
>
Time--->
Recovered Signal
0 5 10 15 20 25 30-10
-5
0
5
10Recovered Sinusoidal SignalA
mpl
itude
--->
Time--->
0 5 10 15 20 25 300
2
4
6
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-multiplexer
Laser 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
Credit: [LYNX Technik Inc.www.lynx-technik.com]
Components of Optical Multiplexer
CombinerTap Coupler
ADD/DROPFilters
Prisms Thin film Dichroic
SplitterOptical fiber
Credit: [LYNX Technik Inc.www.lynx-technik.com]
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 delayMore services offeredIncrease 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 signalLess 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.
THANK YOU
KIITOS
References
Russell Steve. (2010) “The CWDM Fiber Primer” LYNX Technik Inc. <www.lynx-technik.com> 8/05/2012
Indumathi. T. S et al. (2009) "Evaluating Wavelength Routing Power of Dynamic ROADM Networks (cat-I)" International Conference on Advanced Information Networking and Applications Workshop.
Saleh Bahaa E. A., Malvin Carl Teich. (1991) Fundamentals of photonics. Wiley: New York. pg 799 – 832
Watanabe, Shigeki. (2012) "All-Optical Data Frequency Multiplexing on Single-Wavelength Carrier Light by Sequentially Provided Cross-Phase Modulation in Fiber." IEEE Journal of Selected Topics in Quantum Electronics, Vol. 18, No. 2.
Deng Lei. et al. (2012) "Fiber Wireless Transmission of 8.3 Gb/s/ch QPSK-OFDM Signals in 75-110-GHz Band." IEEE Photonics Technology Letters, Vol. 24, NO. 5