Melanie N. Ott Sigma Research and Engineering / NASA Goddard Space Flight Center Component Technologies and Radiation Ef

1. Characterization of Integrated Fiber Optical Modulators for Space Flight Melanie N. Ott Sigma Research and Engineering / NASA Goddard Space Flight Center Component Technologies and Radiation Effects Branch Melanie.ott@gsfc.nasa.gov 301-286-0127 URL: http://misspiggy.gsfc.nasa.gov/tva/authored/fo_photonics.htm The Team: Dr. Carl Magee, Juan Vela, Harry Shaw, Patricia Friedberg, Matthew Dodson NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

2. Outline • Objectives • Approach • Failure modes • Failure modes vs. testing • Telecordia standards • Modulator characterization parameters • Typical test for aging • Innovative test method for failure modes and characterization. • Criteria for modulators in survey • Survey of modulators • Summary • Planned work NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

3. Objectives • To enable the usage of commerical off the shelf optical fiber modulator technology for space flight use. • To develop innovative test methods to make the path to usage quicker and less expensive. • To provide information on test plans, methods, and candidates that are appropriate for typical environments. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

4. Approach • Failure modes study. • Standards and tests identification. • Evaluation of testing plans. • Identify innovative test methods. • Survey for candidates based on failure modes and space flight requirements. • Validate best candidates through innovative test plan. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

5. Failure and Degradation Modes 200mj/cm2 damaged the coupling material. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

6. Failure Modes NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

7. Telecordia Tests X cut devices do not require hermetic packages NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

8. Characterization Parameters • S11, VSWR • S21, Frequency response • Vrf • Vdc • Phase, shift away from quadrature, • non bias devices • Optical Loss, insertion loss • Return Loss, Pin/Preflected • Extinction Ratio, Opticalmax/Opticalmin More efficient method of characterizing the functionality and predicting performance; system approach, by monitoring BER and optical insertion loss. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

9. Typical Reliability Test System Approach Accelerated aging at high temperature • 2000 to 10,000 hours. • > 70°C usually 85°C or 100°C. The higher the temp, the larger the Vdc swing. • Maximum modulation rate. • Titanium waveguides (bias devices: X or Z cut), two tests required, • constant quadrature, monitor Vdc/Vi, insertion loss, BER • constant voltage, monitor phase, insertion loss, BER. • Proton waveguides (no bias, X cut), • monitor BER, phase, insertion loss NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

10. Innovative Test Methods • Thermal cycling for aging and to bring out a majority of failure modes, • To device specifications, example -45°C to +85°C. • Long soak of 40 min at extremes 1°C/min ramp rate. • Not less than 100 cycles. • Monitor pseudo random binary sequence (PRBS) extinction ratio “eye pattern” instead of the BER. Integrates intrinsic parameters in to one extrinsic parameter. (NIST method for 2.5 Gb/s devices). • Monitor insertion loss. To stress RF electrodes, can use RF sine wave at specified frequency and voltage. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

11. Criteria for Survey • 10 Gb/s devices, • that can operate at 1 Gb/s. • Telecordia qualified. • Mitigated failure modes. • Low power requirements. • Low insertion loss. • High extinction ratio. • Large input power limit. • Wide optical bandwidth NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

12. Survey Summary Optical Power Extinction Ratio Insertion Loss Return Loss Device Vπ VRF l NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

13. Environmental Test Plan • Materials analysis and test, • System analysis and test • Vibration testing, • Random vibration to protoflight levels, • Verify survival during launch using typical launch parameters ~ 14.1 grms total for protoflight small box components. • 3 minutes per axis, 20 grms total • Thermal cycling aging, • long dwell at extremes, 1 °C/min to extent of specification, -45°C to +85 °C for 100 cycles, 40 minute soak. Monitor insitu “eye pattern” and insertion loss. Stress RF electrodes. • Radiation analysis and test. • Space flight environments from GSFC are less than 1 rad/min and more typically less than .1. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

14. Summary • System approach • Method to mitigate failure modes, design choice • X cut devices do not require hermetic packaging. • Still needs to be verified. • Proton waveguides, no bias requirement, drift reduction. • Proposed method to test for reliability and for failure modes using “eye pattern”. NEPP Workshop 2002: Optical Fiber Modulators for Space Flight

15. Planned Work • Space flight requirements. • Formulate space flight test plan. • Additional tests. • Sample size. • Lower data rate, then higher data rate. • Testing using innovative methods. • Document all information. http://misspiggy.gsfc.nasa.gov/tva/authored/fo_photonics.htm http://www.nepp.nasa.gov/ This work is funded by NEPP Parts Program NEPP Workshop 2002: Optical Fiber Modulators for Space Flight