Abstract
Optical fiber sensors have evolved over the years in many different directions. One particular direction dictated by necessity is miniaturization and the creation of micro- and nano-optical fiber sensors. Many techniques now exist that allow the micro-structuring of optical fiber. One in particular is focused ion beam technology. This chapter aims to introduce this technique and present the latest work on the application of focused ion beam to optical fiber micromachining, more specifically, the fabrication of optical fiber microstructure sensors such as micro-gratings and micro-cavities.

Abstract
The effect of an erbium-doped fiber amplifier (EDFA) placed inside the fiber ring of a cavity ring down (CRD) configuration is studied. The limitations and advantages of this configuration are discussed, and the study of the ring-down time as a function of the current applied and gain to the EDFA is also presented. In this case, the power fluctuations in the output signal are strongly dependent on the cavity ring-down time with the EDFA gain.

Abstract
A projection apparatus was bought in 1909 by the Physics Cabinet of the Polytechnic Academy (predecessor to the University of Porto's Faculty of Science) in order to present various physics experiments, mostly in the realm of Optics, to a large student audience. A stout and impressive mahogany and brass piece, with a voltaic arc lighting system, it was manufactured by the firm E. Leybold's Nachfolger, based in Chemnitz (Germany), already with a worldwide reputation as a supplier of teaching instruments and equipment to superior schools and universities. It was sold along with an extensive set of accessories, allowing for demonstrations in geometrical optics, spectrum analysis, interferometry, diffraction, polarization and double refraction. Two extra attachments, one for projecting microscopic objects, and the other for the projection of gypsum preparations in polarized light, added to the versatility of this lantern, appropriately dubbed of universal use. Both apparatus and accessories are presently to be found in the collection of the Museum of Science of our University. On studying them, we have come to the conclusion that many classical experiments in Optics may be displayed, without great effort and in an attractive manner. The adaptation to present day usage takes no more than the replacement of the lantern's voltaic arc by a suitable and safer light source. It so happens that a hundred-year old projection apparatus, fitted with a set of purposely designed add-ons, becomes so effective as its modern counterparts.

Abstract

Abstract
In this work, the authors propose a new configuration for an intensity vibration sensor based on a Raman fiber laser. The linear cavity of the Raman fiber laser relies on the combination of a distributed Rayleigh mirror and fiber Bragg gratings, which are used as the sensing element and intensity filter. The sensor was able to measure vibrations with frequencies of up to 350 Hz with more than 50 dB of signal-to-noise ratio (SNR) and also the amplitude of the vibrations with a sensitivity of up to 0.57 +/- A 0.07 dB/mu I mu for vibrations with a maximum strain variation of up to 35 mu I mu. The main advantages of the proposed configuration are the simple scheme with high SNR for remote sensing and the easy possibility of multiplexing.

Abstract
The emergence of optical fiber tapers allowed for the development of new sensing heads to measure physical and external parameters. In the last five years, investigation became more intense with the rapid development of new types of fiber such as microstructured fiber. This chapter aims to present the latest work based on tapers: single tapers, interferometers based on tapers, tapers combined with other structures such as Bragg gratings or surface plasmon resonance. Finally, it also describes new taper geometries and tapers in microstructured fiber. © 2013 by Nova Science Publishers, Inc.