Experimental Demonstration of Optical Quantizers Based on General MMI and CSS-MMI

We analyzed the optical quantizers based on cascaded step-size multi-mode interference (CSS-MMI) and general MMI. The theoretical results show that the imaging quality of CSS-MMI is better than that of general MMI because its second stage length is shorter than that of general MMI. We designed and fabricated the optical quantizers based on 9-port MMI with two structures on a commercially available 220-nm SOI platform. The experimental results show that optical quantizers based on CSS-MMI and general MMI can achieve optimal effective number of bit (ENOB) values of 4.07 bits and 3.83 bits, respectively. The average ENOB of the optical quantizer based on CSS-MMI is about 0.24 bits higher than that of the general MMI at wavelengths between 1532nm and 1556nm.