Equivalent phase shift in a fiber Bragg grating achieved by changing the sampling period

It is proposed and demonstrated experimentally for the first time to achieve the desired phase shifts within one channel of a sampled Bragg grating by changing the sampling period. Only ordinary phase masks and submicrometer precision are needed, leading to improved flexibility, repeatability, and cost-effectiveness in fiber Bragg grating design and fabrication especially when multiple and mutable phase shifts are required. Based on this method, a π-shift and two bipolar encoders for direct-sequence optical code-division multiple-access systems are obtained experimentally, which are in good agreement with simulation.