Coherence has been used as a resource for optical commu- nications since its earliest days. It is widely used for the multiplexing of data, but not for the encoding of data. Here we introduce a coding scheme, which we call mutual coher- ence coding, to encode information in the mutual coherence of spatially separated light beams. We describe its implemen- tation and analyze its performance by deriving the relevant figures of merit (signal-to-noise ratio, maximum bit-rate, and spectral efficiency) with respect to the number of trans- mitted beams. Mutual coherence coding yields a quadratic scaling of the number of transmitted signals with the num- ber of employed light beams, which might have benefits for cryptography and data security.ISSN:0146-9592ISSN:1539-479
