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

Juan Clement1, Haroldo Maestre2, Germán Torregrosa3

  • 1Engineering Research Center (I3E), Department of Communications Engineering, Universidad Miguel Hernández de Elche, Av. Universidad s/n, 03202 Elche, Spain. jclement@umh.es.

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This study introduces a novel fiber-optic sensor system using homodyne electro-optic downconversion for incoherent optical frequency-domain reflectometry (I-OFDR). The new approach eliminates the need for vector network analyzers (VNAs), enabling high-resolution sensing with simpler, more compact interrogators.

Keywords:
Rayleigh backscatteringfiber Bragg gratingfrequency-shifted interferometryincoherent optical frequency-domain reflectometryoptical fiber sensingreflectometry

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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.