A novel optical coding scheme employing parallel Sagnac-loops is proposed for all-optical analog-to-digital converters based on soliton self-frequency shift effect. The proposed coding scheme is numerically demonstrated in a 5-bit SSFS-based all-optical ADC with a wavelength range of 1 601 nm to 1 707 nm, where the results show that the maximum differential nonlinearity error and the integral nonlinearity error are 0.088 and 0.482 Least Significant Bit (LSB), respectively. Compared with other wavelength coding counterparts, the proposed optical coding scheme has a simple architecture and a broad operation wavelength range, and is easy to achieve a larger coding bit.