An All-Fiber Even-Order Optical Temporal Differentiator Based on the Optical Sagnac Loop
In this paper, an all-fiber optical second-order temporal differentiator (OTD) scheme using an optical Sagnac loop is proposed firstly. The optical Sagnac loop is based on a single length of polarization-maintaining fiber (PMF). Feasibility of the proposed method is verified through theory and simulation. Research results shows that, the PMF-based optical Sagnac loop can provide the second-order temporal differential processing with the bandwidth up to 6.625THz for the input optical Gaussian pulse, under the condition that only one port of the Sagnac loop has optical signal input. The performance of the proposed second-order differentiator was measured from three aspects, differential error factor D, energy efficiency E and 3dB bandwidth of the differentiator. When the input Gaussian pulse has an attenuation factor of 0.5ps, the differential error factor is only about 0.0055 and the energy efficiency is as high as 0.7534. On this basis, an even-order optical temporal differentiator based on cascaded optical Sagnac loops was proposed. The feasibilities of realizing fourth-order and sixth-order optical temporal differentiators were verified. Moreover, the performance of the proposed even-order differentiators based on cascaded optical Sagnac loops were analyzed comprehensively. It can be concluded from the research results that, the optical temporal differentiator based on cascaded Sagnac loops could achieve good even-order differential function.