Optical fibres with arrays of FBG: Properties and application

Abstract

Optical fibres (OF) with inscribed arrays of fibre Bragg gratings (AFBG) are interesting for different types of fibre devices such as a fibre sensors and fibre lasers and optical signal management. The most advanced method of manufacturing such AFBG is to write them directly in-line during the fibre drawing process. This gives the possibility of making a huge number of fibre Bragg gratings (FBG) in a single OF. The parameters of these AFBG could be constant or variable along the OF length. We present results of an investigation AFBG produced during fibre drawing process. Typical parameters of such AFBG are: working wavelength into 1550 nm band, spectral width 0.2mm (3dB level), reflective contrast (excess to Rayleigh backscattering level) up to 45 dB. We use polymer or aluminum as AFBG coating. AFBG can be written either in single or multi core preforms. OF with fibre Bragg gratings A(FBG) arrays written over a long length and in-line metal coating have been made for the first time. The optical parameters of the FBG arrays are tested by the optical frequency domain reflectometer method in a wide temperature range, demonstrating no degradation in reflection at heating up to 600C for a fibre with Al coating. Moreover, array of metal coated FBG can not be erased thermally. The mechanical strength of the developed fibre is practically the same as for “ordinary” OF with similar coating, showing the absence of the influence of FBG writing process on fibre strength. Some possibilities of the developed AFBG use in advanced sensor systems with special resolution about 10 mm, Brillouin random fibre laser with linewidth less 40 kHz are considered.