The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described.

Moreover, this type of wavelength switching, provided by the fibre-intrinsic absorption, turns the grating insensitive to the external low temperature fluctuations.Another important topic in optical switching is the required optical power to switch between adjacent channels according to the ITU-T recommendation G.694.1. Table 1 shows the required optical pump power to perform all-optical switching in the different WDM systems, with the CW 1480-nm pump. Note that, when the grating is written in the doped fibre, the required pump power is more than two times lower than in the case of the FBG written in the undoped fibre. Structures based in Er-doped fibre gratings will be more viable and will achieve a higher dynamic tuning range.One of the possible applications of the device based in the technology presented herein is an OADM with wavelength selectivity, shown in Figure 6. This is a classical optical add-drop multiplexer (OADM), but with switching-enhanced capabilities. CONCLUSIONAn all-optical switch has been proposed and demonstrated. The spectral characteristics of the architecture were presented.The operation of the all-optical switch has been experimentally investigated and its performance evaluated. It was shown that the tuning range can be enhanced by using two pump laser diodes.This all-optical switching technique, apart from finding a direct application in an OADM architecture, can also be integrated in different all-optical networking devices, such as optical cross connects, optical multiplexers and demultiplexers, and other types of wavelength routers.

A magnifying fiber element with an array of sub-wavelength Ge/ZnSe pixel waveguides for infrared imaging Appl. Phys. Lett. 101, 021108 (2012) Embedded calibration system for the DIII-D Langmuir probe analog fiber optic links Rev. Sci. Instrum. 83, 10D710 (2012) Analytical analysis of modulation instability in fiber optics AIP Advances 2, 022168 (2012) Atmospheric pressure dielectric barrier microplasmas inside hollow-core optical fibers

Strong continuous three-wave mixing of 514.5-nm argon laser light in a single-mode fiber is reported. The effect, due to the third-order nonlinearity of silica, has been observed for light whose frequency spectrum consists of either a few discrete monochromatic frequency components separated by ∼1 GHz or a quasicontinuous distribution of frequencies having a spectral envelope ∼4 GHz wide. We show that the effect provides a simple and effective method for measuring the nonlinearity of silica. In the first manifestation of the effect, the nonlinearity mixes the frequency components to produce new frequencies. In the second, multiple mixing occurs that broadens the quasicontinuous spectrum. This manifestation of the effect is large; broadening by a factor of 4 has been observed with lower intensity levels than are required to produce stimulated Brillouin scattering in the same fiber. A theoretical model is presented to describe spectral broadening by three-wave mixing for the case of small broadening. The effect of three-wave mixing on the operation of continuous stimulated Brillouin and Raman oscillators is also discussed. Finally, it is noted that the presence of this effect may constrain the design of long-haul single-mode fiber optical communication trunks.

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