Electrically Programmable All-Fiber Structured Second Order Optical Temporal Differentiator

We propose and experimentally demonstrate an electrically programmable second order optical temporal differentiator (OTD) based on linearly chirped fiber Bragg grating (LCFBG) and digital thermal print head (TPH). For the high-speed optical signal with 25-GHz repetition rate, an efficient second-order OTD has been achieved for arbitrary wavelength and bandwidth with the software-defined TPH configurations. By optimizing the thermooptic effect induced optical phase change in the LCFBG, the central wavelength of the differentiator can be reconfigured flexibly from 1543.5 to 1561.7 nm, with a step size of 0.114 nm. By dynamically controlling the heating elements bonded with the LCFBG, optical pulses with 0.55- and 0.8-nm 3-dB bandwidths have been successfully processed with acceptable deviation compared with the theoretical calculations.