Spectrum of Bragg grating reflection coefficient (RC) in optical fiber.

Some of the optical devices work on the basis of Light extension in the dielectric environment with refractive index as a periodical function. The following devices belongs to such class: interference filters on reflection(1), deep holograms (2), optic waveguides with Bgagg gratings imprinted in the fiber core(3), etc. Interference filters belong to the classic optical devices and are well known (1). Deep holograms have no wide application at present time except holographic optic elements 2, and are studied for the application in holographic memory devices with high density of recording and storage of information in the volume unit of storage environment(4). Optical fibers with Bragg gratings wide created and applied in 1992-1997 (3,5,6) now find their application in sensors, in-line Bragg reflectors, optical amplifiers, filters, laser sources, etc. But on the RC dependence on wave length spectrum we can see side maximums near the main one. Amplitude of these side tops is less than main top. These tops will deteriorate optical characteristics of devices because they becomes noise sources. Question arises: can we remove or decrease essentially their amplitude? In the theory of filters on the surface acoustic waves where we met the same problem this question was solved (9) by the way of electrodes apodization. It was to be expected that provided apodization of space grating will show the same results. Under space grating apodization we understand that grating amplitude is not stable but changes according to the definite functional dependence along one of the axis.