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arxiv: 2605.20307 · v1 · pith:SQGAP7J2new · submitted 2026-05-19 · ⚛️ physics.optics

Design and Fabrication of Coaxial Dual Core Optical Fiber Fan-in Device

Yuhong Ma , Shitai Yang , Libo Yuan This is my paper

Pith reviewed 2026-05-21 01:32 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords coaxial dual-core fiberfan-in deviceV-groove substrateinsertion lossoptical fiber fabricationspace-division multiplexingcold processingmulti-core fiber
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The pith

Cold mechanical alignment on a V-groove substrate produces a coaxial dual-core fiber fan-in device with measured losses of 1.25 dB and 2.15 dB.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper shows how to build a fan-in device that links a coaxial dual-core optical fiber to separate single-core fibers. The design uses a V-groove substrate and cold processing only, skipping any fusion or heating steps. This makes it easier to handle fibers with a central core and an outer ring core of different sizes. Tests at 980 nm wavelength found average insertion losses of 1.25 dB in the central core and 2.15 dB in the ring core. Such a device supports space-division multiplexing to increase data capacity in optical networks and aids fiber sensing applications.

Core claim

The authors demonstrate that a fan-in device for coaxial dual-core fibers can be fabricated by placing the fiber on a V-groove substrate and aligning it mechanically to output fibers using cold processing techniques alone. This results in a functional device where light from the central core and ring core couples to separate paths with average insertion losses of 1.25 dB and 2.15 dB respectively at 980 nm, without needing thermal treatments.

What carries the argument

V-groove substrate providing mechanical alignment for the coaxial dual-core fiber and the fan-out single-core fibers.

If this is right

  • Enables reliable interconnection between coaxial dual-core fibers and single-core fiber arrays for multi-core transmission systems.
  • Supports applications in particle trapping, signal emission, and spectral analysis using the unique structure of coaxial dual-core fibers.
  • Simplifies fabrication by avoiding fusion splicing and thermal processing.
  • Achieves insertion losses low enough for practical use in communication and sensing.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This cold-processing approach may lower production costs for fan-in devices compared to methods requiring heating.
  • It could be extended to other types of multi-core fibers with varying core diameters for broader multiplexing uses.
  • Performance at different wavelengths or under varying environmental conditions remains to be fully explored in follow-up tests.

Load-bearing premise

Precise mechanical alignment on a V-groove substrate using only cold processing can achieve stable, low-loss optical coupling between cores of differing diameters without any thermal treatment or active alignment feedback.

What would settle it

A measurement showing insertion losses much greater than 2 dB or observing misalignment when the device is subjected to vibration or temperature variation would challenge the effectiveness of the cold-processing alignment method.

read the original abstract

With the rapid development of information and communication technologies in recent years, the transmission capacity of single-core optical fibers has nearly reached its physical limit. Space-division multiplexing based on multi-core fibers offers an effective solution to this bottleneck. Multi-core fibers feature high integration and large transmission capacity, and their unique structural characteristics also give them special value in fiber-optic sensing applications. Among various types of multi-core fibers, coaxial dual-core fibers (CDCFs) have shown promising performance in particle trapping, signal emission, and spectral analysis. To enable reliable interconnection between different types of multi-core fibers and single-core fiber arrays, this paper presents the design and fabrication of a fan-in device for coaxial dual-core fibers with different core diameters. The proposed method relies solely on cold-processing techniques and does not require any fusion splicing or thermal processing. The device is implemented on a V-groove substrate. Through structural design, fabrication, and experimental characterization, the average insertion loss of the ring core and the central core at a wavelength of 980 nm is measured to be 2.15 dB and 1.25 dB, respectively, demonstrating the successful fabrication of a coaxial dual-core fan-in device.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 3 minor

Summary. The manuscript presents the design and fabrication of a coaxial dual-core fiber (CDCF) fan-in device using only cold-processing techniques on a V-groove substrate, without fusion splicing or thermal treatment. Experimental characterization at 980 nm yields reported average insertion losses of 2.15 dB for the ring core and 1.25 dB for the central core, which the authors interpret as demonstrating successful fabrication for space-division multiplexing and fiber sensing applications.

Significance. If the passive V-groove alignment can be shown to be repeatable and tolerant for mismatched core diameters, the cold-processing approach would offer a practical, low-damage method for interconnecting multi-core fibers, with potential value in high-capacity optical communications and specialized CDCF sensing. The avoidance of thermal steps is a methodological strength that could preserve fiber properties.

major comments (3)
  1. [Experimental characterization] Experimental characterization section: The reported average insertion losses of 2.15 dB (ring) and 1.25 dB (central) are presented without error bars, standard deviations, number of devices or measurements, or repeatability statistics. This directly limits verification of the central performance claim and fabrication success.
  2. [Fabrication method] Fabrication and alignment description: The method relies on precise mechanical placement of a single-mode fiber against the CDCF cores of differing diameters using only cold V-groove alignment, yet supplies no tolerance budget, mode-field diameter overlap calculation, or measured alignment statistics. Any unquantified lateral or angular offset would increase loss, making this assumption load-bearing for the low-loss results.
  3. [Results] Results section: No measurements of inter-core crosstalk or temporal stability of the coupling are provided. These data are necessary to substantiate that the device functions as a reliable fan-in component rather than a one-time low-loss connection.
minor comments (3)
  1. [Abstract] The abstract refers to 'average' losses without stating the sample size or wavelength-specific measurement conditions.
  2. [Introduction] Additional citations to prior V-groove or cold-processed fan-in devices for multi-core fibers would better situate the contribution.
  3. [Figures] Figure captions describing the device layout and loss measurement setup could include more detail on scale and alignment procedure.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We have carefully considered each major comment and provide point-by-point responses below. Where appropriate, we will revise the manuscript to incorporate additional details and analysis.

read point-by-point responses

  1. Referee: Experimental characterization section: The reported average insertion losses of 2.15 dB (ring) and 1.25 dB (central) are presented without error bars, standard deviations, number of devices or measurements, or repeatability statistics. This directly limits verification of the central performance claim and fabrication success.

    Authors: We agree with the referee that including statistical details would enhance the credibility of our results. In the revised manuscript, we will update the Experimental characterization section to specify the number of devices fabricated and characterized, provide the standard deviations for the insertion loss values, and include error bars in the relevant figures or tables. This revision will allow for better assessment of the repeatability and reliability of the fabrication process. revision: yes

  2. Referee: Fabrication and alignment description: The method relies on precise mechanical placement of a single-mode fiber against the CDCF cores of differing diameters using only cold V-groove alignment, yet supplies no tolerance budget, mode-field diameter overlap calculation, or measured alignment statistics. Any unquantified lateral or angular offset would increase loss, making this assumption load-bearing for the low-loss results.

    Authors: The referee raises a valid point regarding the need for quantitative analysis of the alignment process. We will revise the Fabrication and alignment description to include a tolerance budget for the V-groove alignment, calculations of the mode-field diameter overlap between the single-mode fiber and the CDCF cores, and any measured alignment statistics from our fabrication trials. This will provide a more rigorous justification for the achieved insertion losses. revision: yes

  3. Referee: Results section: No measurements of inter-core crosstalk or temporal stability of the coupling are provided. These data are necessary to substantiate that the device functions as a reliable fan-in component rather than a one-time low-loss connection.

    Authors: We acknowledge the importance of crosstalk and stability measurements for validating the device as a reliable fan-in component. The primary focus of this work was on the design and cold-processing fabrication method, with characterization limited to insertion losses at 980 nm. In the revised manuscript, we will include any available data on inter-core crosstalk from our experiments and discuss the expected temporal stability due to the absence of thermal processing. If these measurements were not fully conducted, we will clarify this and suggest it as an area for future investigation. revision: partial

Circularity Check

0 steps flagged

No circularity: purely experimental fabrication and characterization report

full rationale

The manuscript presents a design, cold-processing fabrication on V-groove substrate, and direct experimental measurement of insertion losses (1.25 dB central core, 2.15 dB ring core at 980 nm). No equations, fitted parameters, predictive models, or derivations appear in the provided text. All load-bearing claims rest on measured data rather than any reduction to prior inputs or self-citations. This is a standard experimental report whose results are externally falsifiable by replication and therefore self-contained.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work rests on standard assumptions of optical fiber alignment and coupling efficiency from prior multi-core fiber literature; no new free parameters, axioms, or invented entities are introduced beyond conventional V-groove mechanical positioning.

axioms (1)
  • domain assumption Mechanical V-groove alignment can achieve sub-micron core positioning accuracy sufficient for low-loss coupling at 980 nm
    Invoked implicitly in the structural design and experimental characterization sections of the abstract.

pith-pipeline@v0.9.0 · 5741 in / 1323 out tokens · 46221 ms · 2026-05-21T01:32:14.024925+00:00 · methodology

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Reference graph

Works this paper leans on

21 extracted references · 21 canonical work pages

  1. [1]

    static trapping

    In the optical tweezer system constructed using a CDCF, after a microscale target is stably trapped in the potential well by the focused annular beam, the CC can serve as a power channel to introduce a Gaussian beam. By utilizing the axial radiation pressure, the particle can be controllably propelled away from the fiber tip. Through dynamic regulation of...

    work page

  2. [2]

    Furthermore, owing to the physical characteristics of fine diameter and high flexibility17, the CDCF exhibits excellent potential for minimally invasive in vivo diagnosis and treatment, enabling in situ sensing deep within blood vessels or natural cavities18. In practical operation, the AC not only serves as the trapping channel for particle capture but a...

    work page

  3. [3]

    Grier, D. G. A revolution in optical manipulation. Nature 424, 810–816 (2003)

    work page 2003

  4. [4]

    Taylor, R. S. & Hnatovsky, C. Particle trapping in 3-D using a single fiber probe with an annular light distribution. Opt. Express 11, 2775–2782 (2003)

    work page 2003

  5. [5]

    Liu, Y. et al. Side-viewing axicon-integrated miniature fiber probe for extended depth of focus and ultrahigh lateral resolution endoscopic imaging. Microsyst Nanoeng 11, 235 (2025)

    work page 2025

  6. [6]

    Liu, Z. et al. Optical funnel for living cells trap. Opt. Commun. 431, 196–198 (2019)

    work page 2019

  7. [7]

    Deng, H. et al. Highly focused conical optical field for pico-newton scale force sensing. J. Lightwave Technol. 33, 2486–2491 (2015)

    work page 2015

  8. [8]

    Liu, Z. et al. Single fiber optical trapping of a liquid droplet and its application in microresonator. Opt. Commun. 381, 371–376 (2016)

    work page 2016

  9. [9]

    Liu, Z. et al. Single-fiber tweezers applied for dye lasing in a fluid droplet. Opt. Lett. 41, 2966–2969 (2016)

    work page 2016

  10. [10]

    Deng, H. et al. Fiber-based optical gun for particle shooting. ACS Photonics 4, 472–475 (2017)

    work page 2017

  11. [11]

    Jess, P. R. et al. Dual beam fibre trap for Raman micro-spectroscopy of single cells. Opt. Express 14, 5779–5791 (2006)

    work page 2006

  12. [13]

    Hua, X. et al. A fan-in fan-out device for seven-core ten-mode fiber based on commercial multi-mode fiber tapering. CLEO: Appl. Technol. JW2A.82 (2024)

    work page 2024

  13. [14]

    Zhao, E. et al. A wavelength division multiplexer based on a cocentric core fiber. Proc. SPIE 8421, 84218Z (2012)

    work page 2012

  14. [15]

    & Yuan, L

    Yang, S. & Yuan, L. Connecting technologies for coaxial dual core optical fiber. J. Lightwave Technol. 38, 6629–6634 (2020)

    work page 2020

  15. [16]

    Uematsu, T. et al. Optical coupling technique based on fiber side-polishing without service interruption. IEEE Photon. Technol. Lett. 34, 1042–1045 (2022)

    work page 2022

  16. [17]

    Yuan, L. et al. A non-contact single optical fiber multi-optical tweezers probe: design and fabrication. Opt. Commun. 285, 4068–4071 (2012)

    work page 2012

  17. [18]

    Du, J. et al. Capillary fiber-based optical machine gun for micro particle continuous shooting. Opt. Express 33, 11489–11499 (2025)

    work page 2025

  18. [19]

    & Mahadevan-Jansen, A

    Pence, I. & Mahadevan-Jansen, A. Clinical instrumentation and applications of Raman spectroscopy. Chem. Soc. Rev. 45, 1958–1979 (2016)

    work page 1958

  19. [20]

    Komachi, Y. et al. Micro-optical fiber probe for use in an intravascular Raman endoscope. Appl. Opt. 44, 4722–4732 (2005)

    work page 2005

  20. [21]

    Motz, J. et al. Optical fiber probe for biomedical Raman spectroscopy. Appl. Opt. 43, 542–554 (2004)

    work page 2004

  21. [22]

    Liu, Z. et al. Twin-core fiber SPR sensor. Opt. Lett. 40, 2826–2829 (2015)

    work page 2015