1. Simultaneous Wavelength Conversion and
Signal Detection in a Traveling-wave
Electroabsorption Modulator
Hsu-Feng Chou and John E. Bowers
Department of Electrical and Computer Engineering
University of California, Santa Barbara
Chip-Scale WDM Program
University of California
Santa Barbara
04/25/2003

2. Objective
» Investigate integration of traveling-wave electroabsorption
modulator (TW-EAM) into InP platform
 Integrated SOA for total loss compensation
 Integrated mode-converter for coupling loss reduction
» Investigate wavelength conversion using TW-EAM with
electrical monitoring capability
 Adding monitoring capabilities to the two-stage SOA-IWC
» Investigate integration of traveling-wave electroabsorption
modulator (TW-EAM) into InP platform
 Integrated SOA for total loss compensation
 Integrated mode-converter for coupling loss reduction
» Investigate wavelength conversion using TW-EAM with
electrical monitoring capability
 Adding monitoring capabilities to the two-stage SOA-IWC
Chip-Scale WDM Program
University of California
Santa Barbara 1

3. Two-Stage SOA-IWC 2 University of California Chip-Scale WDM Program
Santa Barbara 2

4. TW-EAM as 1st stage WC with electrical monitoring capability
Two-Stage SOA-IWC
TW-EAM as 1st stage WC with
electrical monitoring capability
Chip-Scale WDM Program
University of California
Santa Barbara 2

5. Traveling-Wave Electroabsorption Modulator (TW-EAM)
» Traveling-wave Electrodes:
-Overcome RC Limitation
-Longer Device, Higher Extinction
Ratio, Lower Driving Power
-Flexible Microwave Design
» Characteristics:
> 20 dB/V Between 0V and 2V
> 47 dB Maximum Extinction Ratio
< 1 Vpp Driving Voltage for 10 Gb/s
Active Waveguide Length: 300 mm
Chip-Scale WDM Program
University of California
Santa Barbara 3

6. Prior Art of Wavelength Conversion Using Lumped-Element EAM
» Utilize Cross-Absorption Modulation (XAM) induced by photo-
generated carriers through screening of the external electrical field
and band filling
» High input power (16~20dBm) required to saturate < 100 mm device
» Extracted RF signal was demonstrated to recover electrical clock*
*T. Miyazaki et al., OFC’99, paper WM53-1
Chip-Scale WDM Program
University of California
Santa Barbara 4

7. Photocurrent-Assisted Wavelength Conversion in TW-EAM
New Mechanism
» Problems of Prior Art:
 High input power is required to saturate absorption (XAM)
 Electrical monitoring of signal was not demonstrated
» New Mechanism for WC:
 Saturation is not required for XAM (lower input power)
 Capability of electrical signal monitoring
» Problems of Prior Art:
 High input power is required to saturate absorption (XAM)
 Electrical monitoring of signal was not demonstrated
» New Mechanism for WC:
 Saturation is not required for XAM (lower input power)
 Capability of electrical signal monitoring
Photocurrent-Assisted
Wavelength Conversion in TW-EAM
NEW
Chip-Scale WDM Program
University of California
Santa Barbara 5

8. Photocurrent-Assisted Wavelength Conversion
Principle of Operation
Photocurrent-Assisted
Wavelength Conversion
Chip-Scale WDM Program
University of California
Santa Barbara 6

9. How can it be possible? 7 » Typical Values Input NRZ Power: 10 mW
Responsivity: 0.4 A/W
Impedance: 25 Ohm
Modulation Efficiency: 24 dB/V
» Extinction = 10 mW * 2 * 0.4 A/W
* 25 Ohm * 24 dB/V
= 200 mV * 24 dB/V
= 4.8 dB
Chip-Scale WDM Program
University of California
Santa Barbara 7

10. 2.5 Gb/s NRZ Conversion: Configurations
(Sampling Scope)
= -0.45V
Open
Open Termination
50 Ohm Termination
Chip-Scale WDM Program
University of California
Santa Barbara 8

11. 2.5 Gb/s NRZ from LiNbO3 modulator
2.5 Gb/s NRZ Conversion: Input Eye Diagram
2.5 Gb/s NRZ from LiNbO3 modulator
Chip-Scale WDM Program
University of California
Santa Barbara 9

12. 2.5 Gb/s NRZ Conversion: Output Eye Diagram
Chip-Scale WDM Program
University of California
Santa Barbara 10

13. Summary and Future Work
» Integration of TW-EAM into InP platform and adding
electrical monitoring capability to two-stage SOA-IWC
» Preliminary result shows proof of principle of photo-
current-assisted wavelength conversion in TW-EAM
at 2.5 Gb/s
» Issues and future works:
 Improve efficiency and extinction ratio
 Reduce pattern dependence
 Investigate fundamental limitations
 BER measurements at 2.5 Gb/s RZ and NRZ
 Analog performance testing
Chip-Scale WDM Program
University of California
Santa Barbara 11