Parallel Optical All Pass Filter Equalisers and Implementation by Wisit Loedhammacakra Supervision t

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Parallel Optical All Pass Filter Equalisers and
ImplementationbyWisit Loedhammacakra
Supervision teamDr Wai Pang NgProf R.
CryanProf. Z. Ghassemlooy Northumbria
Communication Research Laboratories
(NCRL)Northumbria University13th June 2007
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Overview

• Long-haul communication systems
• Problem Statement
• Chromatic Dispersion
• Parallel Optical All Pass Filter Equaliser
• Conclusion

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Long-haul Communication System 1Ideal
Communication Systems

• Audio
• Video
• Data

• Quality of digital communication systems can be
• monitored from bit error rate (BER) of
  system.
• Error-free detection, BER less than 10e-9
• (Single error in one billion transmitted bits)

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Long-haul Communication System 2Evolution of
Long-haul communication systems
x
x
x
x
x
x
Source Agrawal
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Long-haul Communication System 3
Optical Communication systems
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Problem StatementSingle Mode Fibre (SMF)
?
?
Attenuation
Dispersion

• 1.31 µm chromatic dispersion (CD) is zero, but
  high attenuation is 0.5 dB/km.
• 1.55 µm has high CD of 17 ps/nm-km while
  attenuation is the lowest (0.2 dB/km).

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Chromatic Dispersion 1
Fibre
Transmitted pulse
restored pulse
Dispersed pulse
3 bits pattern of restored pulse
3 bits pattern of dispersed pulse
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Chromatic Dispersion 2
Core of fibre
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Chromatic Dispersion 3Output Pulses of
Different Lengths of SMF
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Chromatic Dispersion 4Chromatic Dispersion
Effect
Summed signal
Summed signal
Transmitted pulse
Dispersed pulse at 111 km
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Chromatic Dispersion 5 The Bit Rate-length
Product

• Doubling the bit rate (B) would reduce the
  repeater-less length (L) of optical communication
  systems by a factor of 4.
• CD is the main limiting factor for repeater-less
  length.

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Chromatic Dispersion 6Dispersion Compensation
Techniques
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Parallel optical all pass filter
equaliser (p-OAPF)
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p-OAPF Equaliser 1Compensated System by Using
OAPF
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p-OAPF Equaliser 2OAPF is Implemented With IIR
Structure
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p-OAPF Equaliser 3Compensated System by Using
p-OAPF
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Conclusion
Adjust the phase of the optical pulse back to the
phase of transmitted optical pulse
CD limits 10 Gb/s system at 30 km
Be implemented in optical domain by using IIR
structure and optical components
Capable of extending the length to 90 km in 10
Gb/s systems
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Publications
Papers
1. W. Loedhammacakra, W. P. Ng, and R. A. Cryan,
"Investigation of an Optical All Pass Filter for
a 10 Gb/s Optical Communication System,"
presented at PG-NET 2005 Proceeding, Liverpool
John Moores University, UK, pp. 170-175, 27-28
June 2005. 2. W. Loedhammacakra, W. P. Ng, and R.
A. Cryan, "An Improved Chromatic Dispersion
Compensation Technique Employing an Optical All
Pass Filter Equaliser in a 10Gb/s Optical
System," presented at The Tenth High Frequency
Postgraduate Student Colloquium, University of
Leeds, UK, pp. 105-108, 5-6 September 2005. 3. W.
Loedhammacakra, W. P. Ng, and R. A. Cryan,
"Chromatic Dispersion Compensation Using an
Optical All Pass Filter for a 10 Gb/s Optical
Communication System at 160 km," presented at
London Communication Symposium 2005, University
College London, UK, pp. 255-258, 8-9 September
2005. 4. W. Loedhammacakra, W. P. Ng, and R. A.
Cryan, Chromatic Dispersion Compensation
Employing Optical All Pass Filter by Using IIR
Structure for 10 Gb/s Optical Communication
System, presented at the IEE Photonics
Professional Network Seminar on Optical Fibre
Communications and Electronic Signal Processing,
The IEE Savoy place, London, UK, pp 17/1-17/6, 15
December 2005. 5. W. Loedhammacakra, W. P. Ng, R.
A. Cryan, and Z. Ghassemlooy, Investigation of
Optical All Pass Filter to Compensate Chromatic
Dispersion in a 10 Gb/s Optical Communication
System at 160 km, CSNDSP 2006, Patras, Greece,
pp. 454 458, 19 21 July 2006. 6. W. P. Ng,
W. Loedhammacakra, R. A. Cryan, and Z.
Ghassemlooy, Performance Analysis of the
Parallel Optical All-pass Filter Equalizer for
Chromatic Dispersion Compensation at 10 Gb/s,
under-review by Globecom 2007. 7. W. P. Ng, W.
Loedhammacakra, R. A. Cryan, and Z. Ghassemlooy,
Characterisation of a Parallel Optical All Pass
Filter for Chromatic Dispersion Equalisation in
10 Gb/s System , under-review by IET processing
on signal processing.
Posters
1. Chromatic Dispersion Compensation Technique
Employing OAPF in Optical Communication Systems,
presented at UK Grad Poster Competitive 2006,
Northumbria University, Newcastle, Aril 2006. 2.
High Speed Optical Network Need Low Dispersion,
presented at Britains Early-State Engineers on
UK Engineering research and RD, House of
Commons, London, December 2006.
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Acknowledgements
I would like to thank

• My supervision team (Dr. Wai Pang Ng, Prof. R.
  Cryan and Prof. Z. Ghassemlooy)
• OCR Group leader (Prof. Z. Ghassemlooy) for all
  of his support
• Dr Krishna Busawon and Dr Mark Leach for all of
  the useful discussions we had
• My colleague in Room E405 and E409 Especially,
  Hoa, Popoola, Sujan and Ming Feng for discussion
  and helpful.

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Thank you
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Optical All Pass Filter Equaliser 1 Phases of
SMF, Rectangular and Dispersed Pulse

• The interested bandwidth is between 193.49
  193.51 THz, which phase response of dispersed
  pulse is same as phase response of SMF.

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Optical All Pass Filter Equaliser 2Phase
Response of Ideal Equaliser and OAPF

• The phase response of the ideal equaliser is
  used as the optimisation criterion.
• The phase response of OAPF at upper frequency
  does not equalise properly.

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Optical All Pass Filter Equaliser 3Optical
Communication System
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Optical All Pass Filter Equaliser 6Output Pulses

• A dispersed pulse was equalised back to 100 ps
  at FWHM.
• The larger pulse width on the right hand side of
  compensated pulse is not properly compensated and
  resulted in higher ISI and BER.

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Optical All Pass Filter Equaliser 5Phase response

• The compensated phase is close to zero at lower
  frequency.
• At the higher frequency, the phase response is
  not properly compensated.

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Results 1Compensated Phase Response by p-OAPF
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Results 2Compensated Pulse by p-OAPF