Range extension of the optical delay line in white light interferometry

Area of Science:

• Optical Engineering
• Interferometry
• Metrology

Background:

• Optical delay lines are crucial for various applications, but their continuous range is often limited.
• Existing methods for extending delay range can be complex or introduce performance degradation.

Purpose of the Study:

• To propose and demonstrate an effective method for extending the continuous range of optical delay lines.
• To improve delay precision and reduce insertion loss in extended-range optical delay lines.
• To enable self-calibration without specialized measurement instruments.

Main Methods:

• Combining switchable fixed delays with a continuous-scanning stage in one interferometer arm.
• Utilizing a fiber ring with a fiber coupler in the other arm for self-calibration.
• Experimentally demonstrating a setup with 16 parallel fixed delay paths.

Main Results:

• Achieved an extended delay range of 37.2 m without a blind zone.
• Maintained low insertion loss (average 1.45 dB ±0.15 dB) and high delay precision (10.21 μm ±0.08 μm).
• Demonstrated that range extension does not compromise original stage performance or delay precision.

Conclusions:

• The proposed method effectively extends the continuous range of optical delay lines.
• The technique offers significant advantages for practical applications requiring long optical delays.
• The system's scalability and maintained performance make it highly adaptable for future advancements.