Fibre light acceptance for modified near field technique

Irving, D. H.; Donaghy, F. A.; Sabine, P.V.H.

doi:10.1049/el:19810177

Cited by 4 publications

(2 citation statements)

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“…However, in practice, larger errors occur at the edge of the cladding due to the leaky mode and the diffraction in that region [25,26]. For SMFs, when the fiber is illuminated by a source with reduced NA [27], the coating is removed along the entire sample, exposing the cladding to air.…”

Section: The Modified Near Field Methodsmentioning

confidence: 99%

“…Sabine et al later modified the near field method, enabling accurate measurement of the RIP when the refractive index of the coating is lower than that of the cladding. This modification made the method suitable for both the core and cladding of multimode fibers [25][26][27]. Additionally, they constrained the numerical aperture (NA) of the source to be smaller than that of the optical fibers, obtaining the near field intensity of SMFs, with geometrical parameters to calculate the RIP [28].…”

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A Modified Near Field Method for Measuring the Refractive Index Profile and Geometrical Parameters of Multi-Core Fibers

Ma,

Huang,

Yan

2024

J. Lightwave Technol.

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A modified near field (MNF) method is proposed for measuring the refractive index profile (RIP) and geometrical parameters of multi-core fibers. The near field method is based on the near field intensity at the end face of optical fibers that are illuminated by a Lambertian source to get the RIP, but the methods proposed before require a leaky-mode correction factor or additional geometrical parameters to correct the measurement results. The MNF method presented in this paper offers a simplified approach, when the power of the source is constant, the distance between the source and the incident end face of optical fibers is given, and the near field intensity distribution is linear to the RIP of the de-coated optical fibers. By using SMF-28e+® as a sample to obtain the linear coefficient, the proposed method is validated by measuring the RIP of SMF-28R with an accuracy reaching 𝟏𝟎 −𝟒 . Finally, the RIP of 4-core fiber and 7-core fiber are measured by the MNF method accurately and effectively. Also, the geometrical parameters of optical fibers can be extracted through edge extraction and ellipse curve fitting for the distribution of near field intensity. Index Terms-geometrical parameters, multi-core fiber, near field method, optical fiber measurements, refractive index profile. I. INTRODUCTIONITH the continuous reform and innovation of Internet technology, the capacity of traditional single-mode fibers (SMFs) transmission systems can no longer meet the increasing demand for data volume [1,2]. As a solution to the capacity limitation of current optical communication systems, multi-core fibers (MCFs) have gained significant attention because of their unique core distribution and mode field characteristics [3,4]. MCFs are widely used not only in optical communication but also in areas such as sensors [5], measurements [6], and biological fields [7]. Accurate measurements of refractive index profile (RIP) and geometrical parameters play crucial roles in evaluating the capacity of MCFs, as they determine insertion losses, propagation modes, and bandwidths [8][9][10]. Therefore, developing a simple and accurate method for measuring the RIP and geometrical parameters of MCFs is essential, and it is significant for the design and optimization of MCFs, as well as for quality monitoring [11][12][13].Methods for measuring parameters of optical fibers mainly

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Section: The Modified Near Field Methodsmentioning

confidence: 99%

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confidence: 99%