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Properties and applications of fiber gratings

We evaluate the mode-coupling mechanisms for short- and long-period gratings based on the propagation constant differences between the various spatial modes of the optical fiber. The properties of these photoinduced devices such as strain and temperature response and spectral behavior are also reviewed. Short-period fiber gratings have applications to adding and dropping WDM channels, flattening the grain spectrum of optical amplifiers and compensating chromatic dispersion. The applications of long-period gratings to gain equalization, ASE suppression and sensor are summarized.