Apparatus, systems, and methods of operating a fiber laser having polarization-preserving fibers can be applied as a sensor to detect a physical quantity. In various embodiments, polarization-preserving fibers can provide a laser cavity having an interferometer disposed in the laser cavity. In various embodiments, a fiber optical parametric oscillator can include an interferometer disposed in the cavity of the optical parametric oscillator. Additional apparatus, systems, and methods are disclosed.

Disclosed are a testing apparatus and a testing method. When the testing apparatus is used to test a sample (11) to be tested, a first detection apparatus (21) and a second detection apparatus (22) can be switched by means of an objective lens switching apparatus (20), so as to acquire height information and structure information of the sample (11) to be tested. In the process, the sample (11) to be tested does not need to be transferred between testing apparatuses, thus, not only is pollution potentially created in the process of transferring the sample (11) to be tested avoided, and the probability of the sample (11) to be tested being polluted in the testing process reduced, but also a region to be tested of the sample (11) to be tested does not need to be determined repeatedly, improving the testing speed for the sample (11) to be tested.

An OCT device includes a light source that outputs light including a plurality of wavelengths; a division unit that divides light output from the light source into reference light and measurement light; a measurement arm that forms a light path of the measurement light with which a measurement target is irradiated and reflected light from the measurement target, which is generated by the measurement light; a reference arm that forms a light path of the reference light; and a measurement unit that measures the measurement target based on interference light between the reflected light and the reference light. At least one of the measurement arm and the reference arm includes a dispersion unit that disperses light into lights of each wavelength and a dispersed light path portion that forms light paths of dispersed lights, the light paths having a light path length different for each wavelength.

An OCT device includes a light source that outputs light including a plurality of wavelengths; a division unit that divides light output from the light source into reference light and measurement light; a measurement arm that forms a light path of the measurement light with which a measurement target is irradiated and reflected light from the measurement target, which is generated by the measurement light; a reference arm that forms a light path of the reference light; and a measurement unit that measures the measurement target based on interference light between the reflected light and the reference light. At least one of the measurement arm and the reference arm includes a dispersion unit that disperses light into lights of each wavelength and a dispersed light path portion that forms light paths of dispersed lights, the light paths having a light path length different for each wavelength.

A fiber optic sensor arrangement is disclosed that includes a plurality of optical fiber based sensor elements, the sensor elements configured to modify an associated optical carrier signal in accordance with changes in a sensed quantity at a location of the sensor element and a phase modulation arrangement for phase modulating each optical carrier signal in accordance with respective uncorrelated pseudorandom binary sequence signals. The sensor arrangement also includes an interferometer module for receiving each of the phase modulated optical carrier signals, the interferometer module operable to convert a change in the phase modulated optical carrier signals to a change in optical intensity of the corresponding optical carrier signal to generate a combined modulated optical intensity signal, an optical intensity detector for measuring the combined modulated optical intensity signal and generating a time varying electrical detector signal and an analog to digital convertor to convert the time varying electrical detector signal to a time varying digitized detector signal. Also included in the sensor arrangement is a decorrelator arrangement for decorrelating the time varying digitized detector signal against the respective uncorrelated pseudorandom binary sequence corresponding to each of the optical carrier signals to recover each of the modulated optical carrier signals and a demodulator for demodulating each of the modulated optical carrier signals to recover the respective optical carrier signal to determine the changes in the sensed quantity at the location of the sensor element.

A temperature measurement technology includes generating an input optical signal at a wavelength using an optical signal generator, splitting the input optical signal into a first beam and a second beam, optically transmitting the first beam through the first arm of an interferometer, transmitting the second beam through a second arm of the interferometer that introduces a phase shift in the second beam relative to the first beam, combining at least a portion of the transmitted first beam and the transmitted phase-shifted second beam to produce an output optical signal, measuring an optical signal intensity of the output optical signal, and correlating the measured optical signal intensity with a temperature to produce a measured temperature. Alternatively, the input optical signal may be transmitted through two or more interferometers.

An apparatus comprising: a double path interferometer comprising a sample path for an object and a reference path; a source of linearly polarized light for the double path interferometer, a phase plate positioned in the sample path; means for superposing the sample path and reference path to create a beam of light for detection; means for spatially modulating the beam of light to produce a modulated beam of light; means for dispersing the modulated beam of light to produce a spatially modulated and dispersed beam of light; a first detector, a second detector, and means for splitting the spatially modulated and dispersed beam of light, wherein light of a first linear polarization is directed to the first detector and light of a second linear polarization, orthogonal to the first linear polarization, is directed to the second detector.

A high-resolution phase detection method and system based on a plane grating laser interferometer. The method uses a dual-frequency interferometer to measure the displacement, and the measurement signal processing comprises an integral part and a decimal portion, a phase equation set of a displacement measurement signal is constructed according to a measurement optical path principle of a heterodyne plane grating laser interferometer; a non-linear equation set for which the unknowns are instantaneous phase, interval phase and signal amplitude is established; and the equation sets above are solved by using the least squares method, so as to realize phase discrimination, thereby realizing precise displacement measurement. The method can solve the problems in the traditional time measurement-based phase detection technology, such as low measurement accuracy, and failing to satisfy small measuring range measurement. The measurement method can be applied to systems such as precision manufacturing equipment and lithography machine.

A method includes receiving a representation of an N-mode interferometer and a representation of at least one imperfection associated with the N-mode interferometer at a processor, N being a positive integer value. The processor identifies multiple two-mode interferometers and multiple phases based on the representation of the N-mode interferometer and the representation of the at least one imperfection. The multiple two-mode interferometers and the multiple phases are configured to apply a unitary transformation to an input signal. The method also includes sending a signal to cause at least one of storage or display of a representation of the multiple two-mode interferometers and a representation of the multiple phases.

A method includes receiving a representation of an N-mode interferometer and a representation of at least one imperfection associated with the N-mode interferometer at a processor, N being a positive integer value. The processor identifies multiple two-mode interferometers and multiple phases based on the representation of the N-mode interferometer and the representation of the at least one imperfection. The multiple two-mode interferometers and the multiple phases are configured to apply a unitary transformation to an input signal. The method also includes sending a signal to cause at least one of storage or display of a representation of the multiple two-mode interferometers and a representation of the multiple phases.