Aspects herein describe an optical delay controller which introduces a desired delay into an optical signal. To do so, the optical delay controller includes multiple reflective surfaces (e.g., mirrors) that establish a closed loop on which an input signal propagates. The optical delay controller includes an output interface that outputs a delayed version of the input optical signal where the delay corresponds to the circumference of the closed loop. For example, the optical delay loop may use a Brewster window as the output interface which permits the optical signal propagating in the closed loop to exit the loop. Moreover, the optical delay loop may include one or more actuators that move the reflective surfaces forming the closed loop relative to each other. Changing the distance between two mirrors changes the delay introduced by the optical delay loop.