Incoherent Optical Frequency-Domain Reflectometry Based on Homodyne Electro-Optic Downconversion for Fiber-Optic...

Area of Science:

• Photonics and Optical Engineering
• Sensing Technologies
• Fiber Optics

Background:

• Incoherent optical frequency-domain reflectometry (I-OFDR) offers stable interference and high signal-to-noise ratio (SNR) for fiber-optic sensors.
• Conventional I-OFDR systems require high-frequency detectors and vector network analyzers (VNAs), limiting resolution and system complexity.
• There is a need for simplified I-OFDR architectures that reduce hardware requirements while maintaining high performance.

Purpose of the Study:

• To develop and demonstrate a VNA-free I-OFDR architecture using homodyne electro-optic downconversion.
• To achieve high-resolution sensing with reduced hardware complexity for optical fiber sensors.
• To validate the performance of the proposed system in measuring fiber optic sensor parameters.

Main Methods:

• Implementation of two C-band I-OFDR systems utilizing synchronized modulators for homodyne electro-optic downconversion at 25.5 kHz.
• Employing low-bandwidth, high-sensitivity receivers instead of VNAs for signal detection.
• Testing the systems with different modulation frequency ranges to achieve varying resolutions and sensitivities.

Main Results:

• The first system achieved centimeter resolution with a sensitivity of -90 dB using a 3.2–14.2 GHz modulation frequency range.
• The second system successfully measured Rayleigh backscattering in standard single-mode fiber with 6 m resolution and -83 dB sensitivity using a 10.1–30.1 MHz range.
• Demonstrated the feasibility of VNA-free I-OFDR for compact interrogator designs.

Conclusions:

• Homodyne electro-optic downconversion significantly simplifies I-OFDR systems by eliminating the need for VNAs.
• The developed systems offer a practical and cost-effective solution for distributed and quasi-distributed optical fiber sensing.
• This approach paves the way for more compact and accessible fiber-optic sensor interrogators.