Abstract: Apparatus (FIG. 1) receives electrical input potentials (11A-11D) representing components, e.g. coefficients (zero or one), of weighted digital input data, and provides analog optical output (12) proportional to the sum of the weighted digital values in the input data. An electrooptic waveguide (13) has four adjacent electrooptic diffractive means (14A-14D), each responsive to a separate component of the digital input data and comprising a first electrode (15A-15D) and a second electrode (16A-16D) on the waveguide (13) for temporarily changing the index of refraction when different electrical potentials are present thereon, and thus forming a Bragg grating therein with a direction of Bragg incidence in the same input direction (17) and a direction of Bragg diffraction in the same output direction (18). A coupling prism (21) directs light from a laser (20) to enter into each diffractive means (14A-14D) in the input direction (17).