Security–orientated Plastic Optical Fiber sensor in Modalmetric Configuration

The article describes the operation's rule of the fiber optic sensor in the modalmetric configuration. This type of sensor is described by comparatively simple construction, while retaining other features of fiber-optic sensors such as high sensitivity. A modalmetric fiber optic sensor [1] , whose scheme is shown in Fig. 1, comprises a multimode sensor fiber, a light source for launching light into the multimode fiber to produce a multimode speckle pattern of light at an end of the fiber, a single mode fiber to receive light from the multimode speckle pattern and a detector connected to the single mode fiber to detect the received a partial light from the multimode speckle pattern. Any disturbance to the fiber which can cause a change in any one of the phase, polarization and distribution of the modes, will cause the speckle pattern to change. By measuring this change, a physical perturbation to the fiber such as a vibration or strain can be detected. This gives a very high potential application. In the paper presents, for example, possible application of the modalmetric sensor to protection of works of art and museum collections. The advantage of its use is the ability to tie the fiber in structure of material. Moreover, the advantage of such type a sensor compared to existing solutions of security sensors is the reaction for vibration and touch. The paper presents the concept and results of the system optimization.