An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

A Mach-Zehnder Interferometer (MZI) includes a first arm having one or more first delay sections and respective first undercuts beneath the first delay sections, the first delay section(s) having a total first length and a first width. A second arm includes one or more second delay section(s) and respective second undercuts beneath the second delay section(s), the second delay section(s) having a total second length and a second width. The total first length is longer than the total second length, and the first width is less than the second width. The first width and the second width are selected to be less than a threshold width. For widths above the threshold width, variations in index-to-width tolerance are anticorrelated with respective variations in index-to-thickness tolerance and index-to-temperature tolerance. For widths below the threshold width, variations in index-to-width tolerance are correlated with respective variations in index-to-thickness tolerance and index-to-temperature tolerance.

A measurement system for use in measuring parameters of a patterned sample, the system including a broadband light source, an optical system configured as an interferometric system, a detection unit, and a control unit, where the interferometric system defines illumination and detection channels having a sample arm and a reference arm having a reference reflector, and is configured for inducing an optical path difference between the sample and reference arms, the detection unit for detecting a combined light beam formed by a light beam reflected from the reflector and a light beam propagating from a sample's support, and generating measured data indicative of spectral interference pattern formed by spectral interference signatures, and the control unit for receiving the measured data and applying a model-based processing to the spectral interference pattern for determining one or more parameters of the pattern in the sample.

A signal processing device includes a controller which acquires an output signal output from a single light receiver that receives a plurality of interference beams in which a light beam that is output from a single light source and traces a sample arm toward a measurement target and a light beam that is output from the light source and traces a reference arm that is different from the sample arm interfere with each other, the plurality of interference beams each having a different wavelength dispersion characteristic difference between the sample arm and the reference arm traced by the light beams interfering with each other; and extracts an extraction signal that is a signal for each of the interference beams on the basis of the output signal acquired and a correction signal obtained by applying wavelength dispersion correction processing to the output signal.

A self-referencing interferometric microscope uses near-common-path, common component beam separators to produce two beams that illuminate the sample at different angles. Two return beams collected from the sample interfere at the image plane to produce an interferometric image of the sample comprising fringes across the image. The image can be processed to determine the topography of the sample.

An optical measuring device includes a measuring head with an imaging optical unit and an evaluation unit, wherein the measuring head is connected to the evaluation unit by way of two light-guiding fibers, wherein the evaluation unit includes a light source whose light is guided through the first light-guiding fiber into the measuring head and wherein light reflected by the measurement object is guided back through the measuring head and into a second light-guiding fiber by means of a beam splitter, in such a way that outgoing and returning light are separated, wherein the fiber ends are in mutually conjugate positions, wherein the beam splitter and the fiber ends are arranged together in a connector that is separably connected to the measuring head.

An optical measuring device includes a measuring head with an imaging optical unit and an evaluation unit, wherein the measuring head is connected to the evaluation unit by way of two light-guiding fibers, wherein the evaluation unit includes a light source whose light is guided through the first light-guiding fiber into the measuring head and wherein light reflected by the measurement object is guided back through the measuring head and into a second light-guiding fiber by means of a beam splitter, in such a way that outgoing and returning light are separated, wherein the fiber ends are in mutually conjugate positions, wherein the beam splitter and the fiber ends are arranged together in a connector that is separably connected to the measuring head.

A measurement apparatus for measuring a thickness of a semiconductor wafer includes: an optical system configured to perpendicularly irradiate a sample wafer and a reference wafer with light, and receive interference signals of the light reflected on front and back surfaces of the respective wafers; a signal processor configured to perform frequency analysis of the interference signals received by the optical system to obtain peak positions of a point spread function of the respective wafers; and a calculator configured to calculate a thickness tsample of the sample wafer based on the peak position x of the sample wafer and the peak position y of the reference wafer obtained by the signal processor, and a thickness treference of the reference wafer.

An interferometer system for measuring the displacement of a location of a test surface includes a reflective beamsplitter having a through-hole through which light enters into and exits from a reference arm and having a second through-hole through which a portion of light from the measurement arm of the interferometer passes through the beamsplitter and is incident on a position sensing device (PSD). The output of the PSD is then used as an indicator of the amount and direction of tilt of the surface under test so that systemic errors of the interferometer induced by the tilt of the test surface can be determined and removed from the displacement measurement.

An interferometer system for measuring the displacement of a location of a test surface includes a reflective beamsplitter having a through-hole through which light enters into and exits from a reference arm and having a second through-hole through which a portion of light from the measurement arm of the interferometer passes through the beamsplitter and is incident on a position sensing device (PSD). The output of the PSD is then used as an indicator of the amount and direction of tilt of the surface under test so that systemic errors of the interferometer induced by the tilt of the test surface can be determined and removed from the displacement measurement.