OSSB modulation of tunable optical carrier-to-sideband ratio with FBG-based acousto-optic tunable filter

Abstract

Abstract In this paper, we experimentally fabricated a fiber Bragg grating based acousto-optic tunable filter (FBG-AOTF) and illustrated its further application in OSSB modulation with continuously tunable optical carrier-to-sideband ratio (OCSR). Based on the numerical results, a conclusion can be drawn that the OCSR can be continuously tuned from −20.12 dB to 29.04 dB under certain modulation index of the modulator and certain modulation depth of FBG-AOTF refractive index. Under certain modulation index of the modulator, with the change of modulation depth of FBG-AOTF refractive index, the range of the OCSR tunability can be enlarged. The FBG-AOTF with a specific spectrum was then applied in an OSSB modulation scheme with tunable OCSR. By simply adjusting the acoustically induced strain, the OCSR can be continuously tuned from 13.96 dB to 0.47 dB which is very close to the optimum value and can improve the receiver sensitivity by around 3.7 dB.