Sensing with fiber specklegrams

Abstract

The fiber specklegram is highly sensitive to the relative modal phases and is of multiplexing capability. Its properties are analyzed and experimentally demonstrated.

Influence of the volume speckle on fiber specklegram sensors based on four-wave mixing in photorefractive materials

“…These sensors have been widely studied by their potential applications in several engineering fields. [2][3][4][5][6][7][8][9][10][11][12]. Holographic FSS setups have been mainly developed by recording speckle patterns on photorefractive materials and optically performing self-correlation operations [3][4][5].…”

“…Holographic FSS have shown to be more sensitivity than any non holographic FSS, and this property has been explained by the inclusion of phase information in the holographic register [4]. However, the use of photorefractive materials in FSS has been limited to crystals with a high diffraction efficiency but with a low time response, such as Ce:Fe:LiNbO 3 , which make difficult the real time performance of the sensing system [3][4][5]13]. Now well, it is well known that a speckle pattern has a volumetric distribution.…”

Improvement of the dynamic range of a fiber specklegram sensor based on volume speckle recording in photorefractive materials

“…Sensing systems based on speckle patterns obtained by modal interference in multimode optical fibers are known as fiber specklegram sensors (FSS). These sensors have been widely studied for their potential applications in several engineering fields [2][3][4][5][6][7][8][9][10][11][12]. Techniques that are non-holographic and holographic are highlighted in the literature of FSS.…”

“…This kind of detection systems is very simple and very cheap, but present low sensitivity [10][11][12]. On the other hand, holographic FSS have been mainly developed by recording speckle patterns on photorefractive materials and optically performing self-correlation operations [3][4][5]. Holographic FSS have shown to be more sensitive than any non holographic FSS and this property has been explained by the inclusion of phase information in the holographic register [4].…”

Performance evaluation of a few- and multimode fiber optic perimeter sensor with selective mode excitation

“…Various methods to detect specklegram changes have been tested such as phase conjugate mirror (PCM) [1] holographic detection [2] induced mode coupling, [3] joint-transform correlator (JTC) [4,5], mean-absolute speckle-intensity variation (MSV) using a CCD camera [6], spatial filtering technique [7] by butt-joining fibers with different core diameters, a reflection-type speckle interferometer combined with spatial mode filtering [8] as well as a sophisticated combination of threshold and frequency filtering based on fast Fourier transform [9].…”