A five-degree-of-freedom heterodyne grating interferometry system comprises: a single-frequency laser for emitting single-frequency laser light, the single-frequency laser light can be split into a reference light beam and a measurement light beam; an interferometer lens set and a measurement grating for converting the reference light and the measurement light into a reference interference signal and a measurement interference signal; and multiple optical fiber bundles respectively receiving the measurement interference signal and the reference interference signal, wherein each optical fiber bundle has multiple multi-mode optical fibers respectively receiving interference signals at different positions on the same plane. The system is not over-sensitive to the environment, is small and light, and is easy to arrange. Six-degree-of-freedom ultra-precision measurement can be achieved by arranging multiple five-degree-of-freedom interferometry systems and using redundant information, thereby meeting the needs of a lithography machine worktable for six-degree-of-freedom position and orientation measurement.

A displacement detection device is capable of stably and accurately detecting an amount of displacement. A polarization maintaining fiber has a length not to be equal to a length obtained by dividing, a product of an integral multiple of twice a length of a resonator times a refractive index of the resonator and a beat length obtained from a difference between propagation constants of two polarization modes, by a wavelength of the light source, is selected from a range including a length equal to the above length. The polarization maintaining fiber includes multiple polarization maintaining fibers fitted to each other by removable connectors.

An opto-magnetic rotary position encoder includes a polarization optical encoder and a magnetic encoder, both configured for on-axis placement and operation with respect to a rotational axis of a rotating component. A polarization sensor digital control block and a magnetic sensor digital control block are configured and operative to combine polarizer channel position data and magnetic channel position data in a manner providing for one or more of (1) redundancy, (2) calibration, (3) monitoring performance of one channel in relation to the other channel, or (4) compensation or correction of one channel based on the other channel.

The disclosure relates to a lower display sensor. The lower display sensor includes: a light sensor, including a light irradiation portion that irradiates an induction light used for sensing an object located outside a display, and a light receiving portion that detects a reflected light reflected by the induction light from the object; a first sensor polarizing layer, disposed on an upper portion of the light sensor and having a polarizing axis inclined at a first angle; and a first sensor delay layer, disposed on an upper portion of the sensor polarizing layer and having a slow axis inclined at a first angle with respect to the polarizing axis.

An optical fiber includes multiple optical waveguides configured in the fiber. An interferometric measurement system mitigates or compensates for the errors imposed by differences in a shape sensing optical fiber's response to temperature and strain. A 3-D shape and/or position are calculated from a set of distributed strain measurements acquired for a multi-core optical shape sensing fiber that compensates for these non-linear errors using one or more additional cores in the multicore fiber that react differently to temperature changes than the existing cores.

One embodiment described herein provides a system for distributed fiber sensing. The system can include a plurality of network elements (NEs) in an optical transport network (OTN) and a control-and-management module coupled to the NEs. A respective network element (NE) can include a first wavelength coupler configured to separate an optical supervisory channel (OSC) signal from a data-carrying signal received from a fiber span, a polarization-measurement unit configured to perform a polarization measurement on the OSC signal, and a transmitter configured to transmit an outcome of the polarization measurement to the control-and-management module, thereby facilitating distributed fiber sensing based on the outcome of the polarization measurement.

The present application discloses a fiber distributed acoustic sensing system, including a forward pump source, a wavelength division multiplexer, an active phase-shifted grating array, a backward pump source, and a data demodulation and processing device. The active phase-shifted grating array includes several active phase-shifted gratings engraved on a same fiber, each active phase-shifted grating having a same excitation light wavelength. The active phase-shifted grating array is configured to receive a forward pump pulse and a backward pump light pulse incident from the backward pump source, so that a forward excitation light and a backward excitation light are generated in each active phase-shifted grating, and two adjacent active phase-shifted gratings are enabled to generate excitation light self interference within a same pulse duration. The data demodulation and processing device is configured to perform interference detection on a fiber phase between two adjacent active phase-shifted gratings to detect an acoustic signal acted on the fiber. According to the system in the present application, the passive reflected light interference is replaced with active excitation light interference, thus the excitation light signal has great strength and high stability, and environmental adaptability is high.

The invention pertains to a contactless measurement method for detecting rotation of an object over an axis coinciding with an optical axis of a probe beam. The probe beam is comprised of two monochromatic wavelengths with circular polarizations of opposite chirality, having a frequency difference for providing a heterodyne probe beam. A neutral beam splitter is provided that directs a reflected beam via a polarizer filter towards a first photodetector and that directs a transmitted beam toward a quarter wave plate attached to a rotatable object. A mirror reflects the probe beam, via the same quarter wave plate, back into the neutral beam splitter, which directs the reflected beam via a polarizer filter toward a second photodetector. The rotation is derived from the relative phase difference between the first and second photodetector signals.

A grating displacement measuring device based on conical diffraction, including a laser diode configured to emit a measuring beam, a collimating lens, a polarizing beam splitter, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, a fourth reflecting mirror and a phase shift measuring unit. A grating displacement measuring method based on conical diffraction is also provided.

One embodiment described herein provides a system for distributed fiber sensing. The system can include a plurality of network elements (NEs) in an optical transport network (OTN) and a control-and-management module coupled to the NEs. A respective network element (NE) can include a first wavelength coupler configured to separate an optical supervisory channel (OSC) signal from a data-carrying signal received from a fiber span, a polarization-measurement unit configured to perform a polarization measurement on the OSC signal, and a transmitter configured to transmit an outcome of the polarization measurement to the control-and-management module, thereby facilitating distributed fiber sensing based on the outcome of the polarization measurement.