Abstract: A method and apparatus are provided for detecting a frequency of an optical signal within a communications channel having a plurality of optical carriers separated by a predetermined frequency spacing. The method includes the steps of locking an optical carrier frequency to an axial mode of an optical resonator of known free spectral range; providing an additional optical resonator as a reference having a known free spectral range that differs from that of the first optical resonator; locking an optical reference signal to a closest axial mode of a reference optical resonator producing an optical reference signal that is spectrally offset from said optical carrier frequency by a spectral quantity less than the known free spectral range; mixing the optical carrier frequency with the reference optical signal frequency thus generating a difference signal as a beat frequency; and measuring a frequency of a difference signal.

Abstract: A method and apparatus are provided for transmitting and receiving multiple RF/microwave subcarriers on a single optical wavelength over an optical link. The method includes the steps of modulating a plurality of RF/microwave subcarrier frequencies with a respective communication signal and modulating an optical carrier wave with the plurality of modulated RF/microwave subcarrier frequencies.

Abstract: A method of the present invention includes exposing a structure to first electromagnetic radiation including at least one wavelength absorbed by a predetermined substance that is to be detected. Such substance can be water, a water-soluble substance, or fungi, the presence of which can be a significant problem in a structure such as a house or building. The method includes sensing second electromagnetic radiation from the structure, the second radiation based on the first radiation. The method also includes determining whether the substance is present in the structure, based on the sensed second radiation. If the substance to be detected is water and the determining step reveals a water-suspect area in the structure, the method can include testing the water-suspect area of the structure to determine whether water is present therein. If water is confirmed by the determination to be present in the structure, the method can include a step of determining the source of the water.

Abstract: A method of the present invention includes exposing a structure to first electromagnetic radiation including at least one wavelength absorbed by a predetermined substance that is to be detected. Such substance can be water, a water-soluble substance, or fungi, the presence of which can be a significant problem in a structure such as a house or building. The method includes sensing second electromagnetic radiation from the structure, the second radiation based on the first radiation. The method also includes determining whether the substance is present in the structure, based on the sensed second radiation. If the substance to be detected is water and the determining step reveals a water-suspect area in the structure, the method can include testing the water-suspect area of the structure to determine whether water is present therein. If water is confirmed by the determination to be present in the structure, the method can include a step of determining the source of the water.