Lightwave Communications Systems Research University of Kansas TISL

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Lightwave Communications Systems Research at the
University of Kansas
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Objectives and Benefits to Sprint

• Development of techniques and identification of
  tradeoffs for increasing Sprints network
  capacity while maintaining reliability
• Identifying and evaluating long-range technology
  trends
• Evaluating the feasibility of new technologies
  for Sprints network
• Resource of graduates educated in state of the
  art lightwave communication systems

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Laboratory Infrastructure

• Started Jan. 96
• 600 ft2 laboratory space
• Key test equipment includes
• Lucent FT-2000 WDM system
• Ciena 16? system
• Soliton generator (built at KU)
• Recirculating loop (built at KU)
• Optical Clock Recovery (built at KU)

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Participants

• Faculty

Ken Demarest (WDM Systems, modeling) Chris Allen
(WDM and coherent systems) Rongqing Hui (WDM
systems, devices) Victor Frost (ATM, SONET,
networking)

• Postdoctoral Fellows
• 1

• Students

6 Graduate, 3 undergraduate
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Major Results and Technology Transfer

• 1 Patent and 2 patent applications
• 11 Papers in major photonics journals
• Development of soliton generator and circulating
  loop testbed
• WDM modeling software and measurements
• PMD compensation and measurement techniques
• Subcarrier modulation

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Current Activities

• WDM Modeling/measurements
• Subcarrier modulation
• PMD compensation
• Link quality monitoring

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The KU Soliton Source
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All-Optical Clock Recovery

• Goal
• To make optical networks optically transparent by
  performing clock recovery without electronics
• What we accomplished
• Developed an all-optical clock recovery device
  compatible with WDM
• Patent application

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All-Optical ClockRecovery Using SBS
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WDM Clock Recovery
Input
Output
?1.557 ?m
10 Gbps 27-1 prbs
?1.556 ?m
100 ps/div
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Modeling and Measurements

• Goal
• Model fiber link and network performance for
  dense wavelength division multiplexed operation
• What weve done
• Developed high fidelity model for fiber transport
• Applied model to address WDM over DSF issues
  raised by Sprint
• What were doing
• Increasing the capabilities of this model to
  handle hundreds of optical channels
  simultaneously.
• Modeling legacy network performance at 40 Gb/s

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WDM Simulator
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NEC WDM System on DSF/SMF

• Two OC-48, WDM system configurations

Dispersion SMF 16 ps/km-nm, DSF 0 ps/km-nm
Expectations System 2 has better performance
(less dispersion) Reality System 1 error free,
System 2 mass errors
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NEC WDM System on DSF/SMF

• What we found
• Strong cross phase modulation (XPM ) in the DSF
  caused spectral broadening
• High dispersion in the SMF caused pulse-width
  broadening

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NEC WDM System on DSF/SMF
Bandwidth Expanding Factors in DSF and SMF
1.45
1.4
DSF
Spectral expanding factor for100 km DSF and 100
km SMF
1.35
1.3
1.25
Bandwidth Expanding Factor
1.2
1.15
SMF
1.1
1.05
1
0
10
20
30
40
50
60
70
80
90
100
Distance (km)
Calculated eye-diagrams
Bit Rate 2.5 Gb/s Channel Number 4 Number of
Samples/bit 64 Channel Wavelength 1553.50 nm
Bit Rate 2.5 Gb/s Channel Number 4 Number of
Samples/bit 64 Channel Wavelength 1553.50 nm
30
30
25
25
System 2
System 1
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20
Pulse intensity (mW)
Pulse intensity (mW)
15
15
10
10
5
5
0
0
100
200
300
400
500
600
700
800
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Subcarrier Modulation Techniques

• Goal
• Increase fiber link capacity and flexibility by
  multiplexing several digital signals on a single
  optical carrier
• What weve done
• Modeled optical subcarrier modulation systems
• Constructed and tested a 2-channel system
• What were planning to do
• Construct and test a 4-channel system
• Determine the commercial feasibility of optical
  subcarrier systems for digital applications on
  long links.

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Optical single-sideband technique
Advantage of optical SSB 1. Better bandwidth
utilization 2. Possibility of moving
dispersion compensation to electronics
domain
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PMD Compensation

• Goal
• Increase fiber link data rates by reducing the
  effects of polarization mode dispersion (PMD)
• What weve done
• Developed a scheme for compensating first order
  PMD
• Demonstrated a prototype
• What were planning to do
• Measure the PMD on a Lawrence-K.C. link
• Test our compensation scheme on this link

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PMD Compensation
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Current Thrusts

• PMD Compensation
• Dense WDM modeling
• Subcarrier modulation