We design and investigate a triple-band plasmonic metamaterial absorber (PMA) for sensor application. The underlying mechanism is investigated theoretically and numerically. Three characteristic absorption peaks are demonstrated to be induced by different plasmonic modes which lead to different responses for the plasmonic sensor. These modes show great improvement for the sensitivity and accuracy of the plasmonic sensors. This triple-band plasmonic metamaterial optical absorber has great potential to improve the performance in practical applications.

The vibration signal is essential for accurate event recognition along submarine cables. However, rapid and concise identification still poses challenges for prompt recognition and classification of events in harsh environments. For such reasons, this article proposes a developed hybrid model combining the modern power spectrum estimation (MPSE) and improved gradient neural networks (IGNNs), to identify and organize events instantaneously. Three different categories of data are selected as data samples, collected using the phase-sensitive optical time-domain reflectometry ( $\Phi $ -OTDR) device. The signal characteristics of the power distribution are extracted in the frequency and time domains. These characteristics together form the eigenvector, used in a multiclass IGNN classifier, to initiate the extent and position of collision events on the cable. The results demonstrate that the proposed hybrid model has a better identification rate, compared to the existing schemes used for the same purposes. It is verified that the accuracy rate of identification has expanded by almost 1%; confirming the validity and reliability of the proposed hybrid model.

The ampacity of photoelectric composite cables largely depends on the temperature of their conductors, which in turn is related to other internal and external factors of the cable. Due to the thermal degradation associated with these factors, the cable can be damaged, regardless of its quality. To avoid this damage, an iterative parameter correction method (IPCM) is proposed and developed to correct the parameters of the cable before determining its ampacity based on the fitting function. Different optical fiber temperatures of the cable are collected using Brillouin Optical Time-Domain Analysis; together with the material parameters of the cable, they are modeled in ANSYS, which is a finite element modeling engineering software. Then, the IPCM is performed before determining the corrected ampacity. After conducting experiments on multiple groups of data, the results show that the calculation error is within the engineering error range. The mean error obtained with the proposed method is less than that obtained by the finite element method; it shows that the engineering adaptability improved by about 0.41%.