Optical Single-Sideband Modulation Using a Fiber-Bragg-Grating-Based Optical Hilbert Transformer

An all-optical approach to realizing optical single-sideband (OSSB) modulation based on optical Hilbert transform implemented using a fiber Bragg grating (FBG) is proposed and demonstrated. In the proposed approach, an optical double-sideband (ODSB) signal is divided equally into two channels with the output at one channel being the in-phase (I) component and that at the other being the quadrature phase (Q) component. An FBG-based optical Hilbert transformer (HT) is incorporated in the Q channel, making the two sidebands out of phase at the output of the HT. The combination of the two optical signals from the two channels leads to the cancellation of one sideband, thus an OSSB signal is generated. An experiment is performed. An OSSB signal with a frequency from 6 to 15 GHz and a sideband suppression ratio (SSR) as large as 20 dB is generated. The transmission of the OSSB signal over a single-mode fiber of 45.6 km is also studied.