No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Registration of low intensity IR radiation using modal interference in an optical fiber
Abstract
A high sensitivity fiber-optic method for registration of low intensity IR radiation is proposed. The method is based on the effect of variation of the speckle pattern in the far-field of a multimode fiber. IR radiation that falls on a lateral surface of the fiber leads to variation of the speckle image. Computer processing of the speckle image provides information on the amplitude of the perturbation that hits the fiber. An algorithm has been developed for processing of the speckle image and determining of the intensity of IR radiation. The results of computer simulation correlate sufficiently well with experimental ones.
ResearchGate has not been able to resolve any citations for this publication.
A high sensitivity fiber-optic method for registration of infrared (IR) radiation is proposed. The method is based on the effect of modal interference in an optical fiber. The speckle pattern is registered in the far field of a multimode fiber and is processed by a PC for deriving the output signal. The method also can be applied for registration of temperature, mechanical vibrations, etc.
This paper describes the development of optical fibre low-coherence speckle interferometers capable of three-dimensional surface profiling with a resolution of 10–20 µm and a depth range of typically tens of centimetres. The technique is absolute, enabling the measurement of steps and through holes. The inclusion of optical fibres enables compact, flexible configurations to be realized, alleviating the experimental difficulties encountered with bulk interferometers, particularly when using long path lengths for measurements on large test objects. Sources including light-emitting and superluminescent diodes and multimode laser diodes are compared, and the use of a multimode laser diode source in pulsed mode is shown to improve depth resolution. Fibre-based systems using both single mode and polarization-maintaining fibre are described, and the results of experimental measurements on a stepped test object, a tilted plate and a coin are presented. A depth resolution of ±20 µm is obtained for the standard fibre system and ±14 µm for the system based on polarization-maintaining fibre.
The combination of speckle pattern interferometry and temporal phase unwrapping allows the measurement of large-object dynamic displacements without the propagation of spatial unwrapping errors. For retrieving phase data for whole-object displacement, the temporal Fourier transform method is a commonly used approach. As the temporal Fourier transform method can be applied with or without introducing a temporal carrier in one of the beams in an interferometer, this paper presents a comparison of both phase measurement techniques. The analysis is performed using computer-simulated speckle interferograms, an approach that allows to know precisely the original phase distribution and also to evaluate the spatial rms phase error as a function of the phase change introduced between two consecutive speckle interferograms. The performance of the temporal Fourier transform method to process experimental data modulated by a temporal carrier is also illustrated using results obtained from the study of a metal plate subjected to thermal loading.
This paper presents an overview of integrated optics routing and
coupling devices based on multimode interference. The underlying
self-imaging principle in multimode waveguides is described using a
guided mode propagation analysis. Special issues concerning the design
and operation of multimode interference devices are discussed, followed
by a survey of reported applications. It is shown that multimode
interference couplers offer superior performance, excellent tolerance to
polarization and wavelength variations, and relaxed fabrication
requirements when compared to alternatives such as directional couplers,
adiabatic X- or Y-junctions, and diffractive star couplers