Optical Sigma-Delta Modulation Using Fiber Lattice Filter Structures

Modern avionics equipment, such as super resolution direction-finding systems, now require resolutions on the order of 20 to 22 bits. Oversampled analog-to-digital converter architectures offer a means of exchanging resolution in time for that in amplitude and represent an attractive approach to implementing precision converters without the need for complex precision analog circuits. Using oversampling techniques based on sigma-delta (ΣΔ) modulation, a convenient tradeoff exists between sampling rate and resolution. One of the major advantages of integrated optics is the capability to efficiently couple wideband signals into the optical domain. Typically, ΣΔ processors require simple and relatively low-precision analog components and thus are well suited to integrated optical implementations. This paper presents the design of a first-order, integrated optical ΣΔ modulator.