Study On The Fractional-order Optical Temporal Differentiator Based On The Asymmetric Twin-core Fiber Coupler

The processing speed of electronic devices couldn,t meet the ever-increasing demand,and all-optical signal processing emerges.The all-optical processing refers to the direct processing of signal in the optical domain.Since it avoids the usage of electronic devices,thereby avoiding the speed limit in the electrical domain,and has become one of the hot technologies that break through the speed limit of the signal processing in the electrical domain.The optical temporal differentiator is a key component of the all-optical signal processing circuits.It can perform differential calculation on the signal in the optical domain,and it has advantages of high operation speed,resistance to electromagnetic interference,and compactness.The fractional-order optical temporal differentiators based on asymmetric twin-core fiber couplers are studied in this paper.The main research contents can be summarized as follows:(1)On the basis of the coupled-mode theory,the coupling properties of symmetric and asymmetric twin-core fiber couplers are analyzed.The influence of the structural parameters of the couplers on the coupling properties is discussed.(2)The differential characteristic of symmetric twin-core fiber couplers is analyzed from the perspective of frequency domain.The influence of the structure parameters of the coupler on the performance of the differentiator is studied.The influence of input pulse width and the length deviation of the coupler on the performance of the differentiator is analyzed.(3)The differential characteristic of symmetric twin-core fiber couplers is studied from the perspective of time domain,revealing that the all-optical differential characteristic is a kind of special case of the modal dispersion effect in the essence.(4)The fractional-order optical temporal differentiator based on asymmetric twin-core fiber coupler is proposed.Optical temporal differentiators with fractional orders of 0.47,0.78,1.1 based on the asymmetric twin-core fiber couplers are designed and analyzed,of which the processing error are 10.04%,6.11%,22.24%,and the energetic efficiency are 20.61%,19.62%,20.93%,respectively.The relationship between the structural parameters of the coupler and the differential order is analyzed.The influence of input pulse width and the length deviation of the coupler on the performance of the differentiator is analyzed.