A new technique of ultrafast analogue-to-digital (A-D) conversion for an all-optical data processing is proposed. This technique is based on the Kerr nonlinearity-induced cross-phase modulation in single-mode Mach–Zehnder interferometer configurations arranged in a specific way. Two schemes, capable of realizing both sequential and parallel A-D conversions of optical signals are considered. The potential for an extremely high-bit-rate processing, up to 1 THz in each converter, is due to a femtosecond time response of Kerr effect in fused silica glass. Optical schemes of proposed devices are presented and algorithmically estimated; their functional capabilities are discussed.