Improved Modal Reconstruction for Spatially and Spectrally Resolved Imaging $({\rm S}^{2})$

Abstract

Spatially and spectrally resolved imaging (S2) is a very sensitive, robust and elegant method to measure the power of excited modes in a fiber. For the common reconstruction technique an approximation is necessary, which is based on dominant fundamental mode content. In this work we present several algorithms that significantly improve the accuracy of modal reconstruction for weak excited fundamental mode content. We show that in some cases general analytical solutions exist that can completely overcome the former limitation. In addition, we introduce an iterative procedure to improve the mode modal reconstruction independent of the specific used algorithm.Index Terms-Optical fiber applications, optical fibers, sensor phenomena and characterization.

Flexible cross-correlated (C^2) imaging method for the modal content characterization in a broad range of wavelengths

“…However, time consumption for the raster-scanning approach,for example, and the requirement of one propagating mode being dominant for both approaches, limit the method. Several reported theoretical algorithms [7] can help to overcome S 2 limitation, but for the present they are not confirmed experimentally.…”

“…A technique for modal content analysis which is robust and easy in implementation is highly desired and a beneficial diagnostic tool for characterization of fiberbased systems. Among up-to-date developed methods of fiber mode detection interference-based imaging techniques have already contributed significant results [6][7][8][9][10][11][12].…”

Invited paper: Characterization of few mode fibers and devices

“…In our measurements, the broadening of the peaks of the Fourier spectrum is further due to the wavelength dependent response of the camera used. As described in [32] and [36], the slowly varying DC term I DC (x, y, λ)…”

“…The above analysis works well as long as the power of the dominant modes is 10 to 12 dB higher than the other modes. Here, for the case of two modes, a modified version of the method of Otto et al [36] is proposed to relax the requirement for a dominant mode. Otto suggest for the case of only two modes to use the exact solution:…”

“…analyzing algorithm has been proposed by Otto et al [36] and Sévigny et al [37]. The Otto algorithms has, as far as we know, not been implemented for practical use, and the Sévigny methods are for cases with more than two modes.…”