Quantum information theory has come a long way in defining several fundamental quantum-limited bounds on the performance of optics-based information processing systems, with applications ranging across communications, sensing and computation. Examples of such bounds are the Holevo bound on communications capacity, the Chernoff Bound on the error exponent for binary state discrimination with repeated interrogation, the quantum Cramer-Rao bound on the variance of an estimate of a parameter, and the Helstrom bound on the probability of error of discriminating between a set of quantum states. In several instances, quantum information theory has succeeded in not only finding these ultimate performance bounds, but also in developing rigorous proofs of the achievability of the bounds. However, most such proofs have been existential, and have evaded the issue of finding structured schemes to realize optimal quantum measurements using familiar optical components, such as mirrors, beamsplitters, phase-shifters, parametric amplifiers, etc., whose performance could approach the quantum-limited performance bounds. Measurements are ubiquitous, and lie at the heart of quantum mechanics and all applications thereof. But we are still far from a complete understanding of the realizability of general measurements permitted by the laws of quantum physics. In this talk, we will present a brief unified review of recent developments in our understanding of structured optical realizations of quantum measurements, both in the context of optical communications and sensing, and will present several difficult open questions that lie ahead.