optical multiplexing

1. O P T I C A L T E L E C O M M U N I C A T I O N N E T W O R K S
Optical Multiplexing & Demultiplexing:
Phillip B. Oni (u96761)
AUTO3160 – OPTICS & SPECTROSCOPY
VAASA, Spring 2012.

2. Outline
 Introduction
 Multiplexing / Demultiplexing
 Optical Multiplexing
 Components of Optical Mux/Demux
 Application
 Advantages
 Shortcomings/Future Work
 Conclusion
 References

3. 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.

4. 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.

5. Multiplexer
http://en.wikipedia.org/wiki/File:Telephony_multiplexer_system.gif

6. Multiplexing Example
 MATLAB simulation example:
 Sampled in time:
 Quantization
 Digitization
0 10 20 30
-10
-5
0
5
10
Sinusoidal Signal
Amplitude--->
Time--->
0 10 20 30
0
2
4
6
8
Triangular Signal
Amplitude--->
Time--->
0 10 20 30
-10
-5
0
5
10
Sampled Sinusoidal Signal
Amplitude--->
Time--->
0 10 20 30
0
2
4
6
8
Sampled Triangular Signal
Amplitude--->
Time--->

7. 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
8
TDM Signal
Amplitude--->
Time--->
0 5 10 15 20 25 30
-10
-5
0
5
10
Recovered Sinusoidal Signal
Amplitude--->
Time--->
0 5 10 15 20 25 30
0
2
4
6
8
Recovered Triangular Signal
Amplitude--->
Time--->

8. Recovered Signal
0 5 10 15 20 25 30
-10
-5
0
5
10
Recovered Sinusoidal Signal
Amplitude--->
Time--->
0 5 10 15 20 25 30
0
2
4
6
8
Recovered Triangular Signal
Amplitude--->
Time--->

9. 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

10. 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

11. Optical Multiplexing and Filtering
Credit: [LYNX Technik Inc.www.lynx-technik.com]

12. Components of Optical Multiplexer
 Combiner
 Tap Coupler
 ADD/DROP
 Filters
 Prisms
 Thin film
 Dichroic
 Splitter
 Optical fiber
Credit: [LYNX Technik Inc.www.lynx-technik.com]

13. 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.

14. 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.

15. 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)

16. 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.

17. 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.

18. 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.

19. THANK YOU
KIITOS

20. 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