Optical fiber couplers for precision spaceborne metrology

Area of Science:

• Optical Engineering
• Space Instrumentation

Background:

• Fiber couplers are critical components in optical systems, requiring precise control of beam parameters.
• The LISA Pathfinder mission necessitated robust fiber couplers with stable beam pointing for its interferometer.

Purpose of the Study:

• To design, construct, and test a pair of matched, spaceflight-qualified fiber couplers.
• To meet specific requirements for collimated beam waist size and position for two couplers.
• To ensure tight limits on relative beam curvature for minimal noise in interferometric applications.

Main Methods:

• Detailed optical and mechanical design of fiber couplers.
• Implementation of a construction philosophy for spaceflight qualification.
• Rigorous testing including environmental stress (vibration, shock, thermal vacuum).

Main Results:

• Achieved beam waist sizes and positions meeting or exceeding mission targets.
• Measured beam matching of λ/33 peak-valley over the central 1 mm.
• Demonstrated pointing stability of 3 μrad/°C over a 50°C temperature range.
• Couplers withstood environmental testing without performance degradation.

Conclusions:

• The developed fiber couplers are spaceflight-qualified and meet stringent performance requirements.
• The design is suitable for various ground and space-based applications requiring robust, well-controlled fiber coupling.
• The successful testing validates the design's reliability and stability in harsh environments.