1. A system for detecting optical characteristics of a sample, comprising: an interferometer for mixing light collected from the sample with reference light for interfering therewith, the interferometer comprising: a first optical coupler having two input ports connected for receiving reference light and light collected from the sample, and at least three output ports; a first differential detector having two input optical ports coupled to a first two of the at least three output ports of the optical coupler for providing a first electrical signal having a first interferometric component; and, a second differential detector having two input optical ports coupled to a second two of the at least three output ports of the optical coupler for providing a second electrical signal having a second interferometric component; wherein the first optical coupler is such that the first and second interferometric components have a relative phase shift therebetween that is not an integer multiple of π, so as to provide information separately characterizing real and imaginary components of a complex interferometric signal related to the sample.