Measurement of Principal Modes in Few-Mode Fibers by S² Method

Abstract

Using principal modes (PMs) can avoid the inter-mode crosstalk in fiber-optic communication and reduce the complexity of digital signal processing. In this paper, a new detection method for PMs based on spatially and spectrally resolved imaging (S 2) is used to recover their intensity distributions and inter-mode dispersion parameters. This method collects the optical interference information on a two-dimensional plane at different frequencies. The collected data can be used to characterize the principal modes, including their patterns and differential mode group delays. Due to the frequency invariance of PMs even in mode coupling state, which is studied carefully, this proposed method is shown to be robust. Analyses based on a four-mode fiber show that the distributed fluctuation of the coupling coefficients break the frequency invariance of PMs. We experimentally measure the mode characteristics of a four-mode fiber with S 2 method. The results show that the mode group delays of degenerate modes can be separated in mode coupling state, which is exactly appropriate for the modified measurement method.

Few-Mode Fiber Characterization System Based on the Spatially and Spectrally Imaging Technique

“…The S 2 testing technique also can be regarded as a kind of mode decomposing method [31], which can be used to measure the content of the principal mode [32]. Therefore, it also can be applied in the sensing field.…”

Arising 2D Perovskites for Ionizing Radiation Detection

“…In general, 2D perovskites display a low dark current due to the limited conductivity of the organic molecular layer, with high resistivity and suppressed ion migration, making them potential candidates for radiation detectors. [49][50][51] Additionally, layered 2D brominated perovskites exhibit large exciton binding energy, high photoluminescence quantum yield (PLQY), and ample light yield, as excellent scintillator detectors. [52,53] This review focuses on the development of 2D ionizing radiation detectors, mainly including 2D semiconductors and scintillator X-ray detectors.…”

Modified S2 schemes for estimating differential mode group delay in polarization-maintaining few-mode fiber

“…A typical characterization method is spatially and spectrally resolved imaging (S 2 ), where the characteristic parameter of the DMGD is extracted according to the beat frequency generated between each mode [5,6]. Using this method, the DMGD and the mode field information of the FMF can be measured accurately [7][8][9]. The polarizationmaintaining fiber (PMF) is one branch of special optical fibers which can maintain the state of the polarization [10].…”