Tapered multi-core fiber for lensless endoscopes

Tapered multi-core fiber for lensless endoscopes


El Moussawi, F., Hofer, M., Labat, D., Cassez, A., Bouwmans, G., Sivankutty, S., ... & Andresen, E. R. (2022). Tapered multi-core fiber for lensless endoscopes. arXiv preprint arXiv:2204.03320.


  • tapered multi-core fiber (MCF)
  • lensless endoscopes
  • two-photon imaging
  • memory effect
  • point-scanning
  • power delivery
  • coupled-mode theory (CMT)
  • cross-talk
  • Strehl ratio
  • fabrication
  • characterization


A new tapered multi-core fiber (MCF) component is designed to address low power delivery in MCF-based lensless endoscopes, resulting in a two-photon signal yield increase by a factor of 6.0 while keeping the point-scanning ability of the memory effect, and a factor of 8.9 when sacrificing it.


This article presents a novel fiber-optic component called a "tapered multi-core fiber (MCF)" for use in ultra-miniaturized endoscopes. The tapered MCF improves upon existing MCF-based lensless endoscopes by addressing the issue of power delivery, which is crucial for two-photon imaging.
The authors outline the design, fabrication, and application of a tapered MCF optimized for two-photon imaging with 920 nm pulsed excitation. The tapered MCF aims to address the conflicting requirements of lensless endoscopes for both dense and sparse core layouts by incorporating three segments: injection, transport, and imaging. The segments are joined by conical tapers.

Key Findings:

  • A six-fold increase in two-photon signal yield was achieved experimentally by using a tapered MCF with optimal design parameters. This design maintained the ability to point-scan using the memory effect.
  • Sacrificing the memory effect allowed the researchers to further enhance the two-photon signal yield by a factor of 8.9.
  • The researchers developed a fast numerical model based on coupled-mode theory (CMT) to predict the essential properties of an arbitrarily tapered MCF from its structural parameters.
  • They validated the CMT model with a finite-element beam propagation method (FE-BPM) model.
  • The study demonstrated the fabrication of the target tapered MCF designs using a CO2 laser-based glass processing and splicing system.
  • The researchers characterized the optical properties of the fabricated tapered MCFs using a filtered super-continuum laser source.

The article highlights the potential of tapered MCFs to improve two-photon lensless endoscopy by significantly increasing two-photon yield, offering a promising avenue for minimally invasive, high-resolution imaging in biological tissues.

Origin: https://browse.arxiv.org/pdf/2204.03320v1

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