An apparatus for estimating a parameter, the apparatus includes: an optical fiber; a component in communication with the optical fiber and configured to interact with light at a wavelength related to the parameter; and an optical interrogator in communication with the optical fiber and configured to: illuminate the optical fiber with a series of light inputs, each light input in the series having a substantially constant unique optical wavelength and swept-frequency amplitude modulation; and receive a resulting light signal associated with each light input in the series; wherein the resulting light signals associated with the series of light inputs are used to estimate the parameter.