A fiber optical sensor and methods for sensing a physical quantity such as rotation using the same. The sensor has an optical fiber supporting propagation of light that is configured as an interferometer. One or more segments of the optical fiber, where the segments may be non-contiguous, are poled in such a manner that a phase shift in light propagating through the fiber is created in response to application of a voltage to an electrode thereby inducing an electric field across a poled segment of the fiber. A phase modulator comprising multiple poled segments is additionally described. Applying phase-shifting effects differentially across poled segments of optical fibers of an array of optical fibers may also allow for steering an optical beam.

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.

A method is provided for spatially modulating electromagnetic radiation at high frequency where the modulation is phase, polarization or direction of propagation comprises a substrate carrying an ordered array of optical elements in relative motion with respect to an incident beam of electromagnetic radiation to be modulated and measuring the relative motion. The array contains at least three optical elements and at least two different types of optical elements. At least some of the optical elements are formed from and integral to the substrate material. The optical elements may be fabricated on the substrate material by a subtractive process. The electromagnetic radiation to be modulated is incident on a region of the substrate termed the active region. As the substrate moves relative to the incident electromagnetic radiation, the active region also moves and the designation of individual optical elements changes also.

Various embodiments relate to devices for measuring the state of devices and multi-stage rotary encoders as well as to associated sensors. In order to simplify the design of devices which can be read out electronically and multi-turn rotary encoders, according to some embodiments a device having at least one rotatable wheel, at least one light source and at least one polarization sensor is proposed, the wheel being at least partially transparent and polarization-maintaining, parts of the wheel being configured as pole filters, it being possible for light which exits the light source to be polarized by the pole filter and to be received by the polarization sensor.

A polarization tracking device that tracks polarization fluctuation of light using a Stokes vector, includes: an updating unit configured to express a fluctuation amount of the Stokes vector on a Poincare sphere in an xy plane perpendicular to a travelling direction of a light wave using a first and a second angles, the first angle being an angle between a direction of an electric field of the light wave and y axis, and the second angle being a phase difference between a component of the optical electric field in a direction of the y axis and a component of the optical electric field in a direction of an x axis; and an application unit configured to rotate the Stokes vector using an inverse polarization rotation matrix expressed with the first and the second angles.

An optical position-measuring device for sensing a position of two relatively movable objects includes a scale connected to one object and having a measuring graduation. A scanning unit is disposed on the other object and has optical elements. An arrangement and design of the optical elements of the scanning unit results in a scanning beam path in which split and subsequently interfered sub-beams propagate mirror-symmetrically with respect to a plane of symmetry and either impinge on and/or are reflected back from the scale in a V-shape. The plane of symmetry is tilted by a defined tilt angle relative to the scale about an axis of rotation that is oriented parallel to a surface of the scale and extends perpendicular to the graduation direction. The sub-beams that are interfered are deflected at the measuring graduation into symmetric diffraction orders. The sub-beams travel identical optical path lengths between splitting and recombination.

A deformation sensing apparatus comprises a propagation channel, a transmitter coupled to a first end of the propagation channel, a receiver coupled to a second end of the propagation channel, and a controller. The propagation channel is deformable and the controller instructs the transmitter to transmit a signal, instructs the receiver to capture one or more measurements of the transmitted signal, and determines a bend in the propagation channel based on the one or more measurements. In one embodiment, the transmitter is a light source, the propagation channel is an optical fiber, and the receiver is a photodiode. The propagation channel is made of a material that has a variation in a refractive index responsive to applied mechanical stress. The deformation sensing apparatus may also include a polarizer positioned between the transmitter and the propagation channel and a wave plate positioned between the propagation channel and the receiver.

A polarization tracking device that tracks polarization fluctuation of light using a Stokes vector, includes: an updating unit configured to express a fluctuation amount of the Stokes vector on a Poincare sphere in an xy plane perpendicular to a travelling direction of a light, wave using a first and a second angles, the first angle being an angle between a direction of an electric field of the light wave and y axis, and the second angle being a phase difference between a component of the optical electric field in a direction of the y axis and a component of the optical electric field in a direction of an x axis; and an application unit configured to rotate the Stokes vector using an inverse polarization rotation matrix expressed with the first and the second angles.

An optical position-measuring device for sensing a position of two relatively movable objects includes a scale connected to one object and having a measuring graduation. A scanning unit is disposed on the other object and has optical elements. An arrangement and design of the optical elements of the scanning unit results in a scanning beam path in which split and subsequently interfered sub-beams propagate mirror-symmetrically with respect to a plane of symmetry and either impinge on and/or are reflected back from the scale in a V-shape. The plane of symmetry is tilted by a defined tilt angle relative to the scale about an axis of rotation that is oriented parallel to a surface of the scale and extends perpendicular to the graduation direction. The sub-beams that are interfered are deflected at the measuring graduation into symmetric diffraction orders. The sub-beams travel identical optical path lengths between splitting and recombination.

An optical fiber changes a polarization state of a propagating light when at least one of a vibration and a displacement occurs. An optical transmitter inputs a first wavelength light to the optical fiber via a separator, and an optical transmitter inputs a second wavelength light to the optical fiber via a separator. The first and second wavelength lights propagated through the optical fiber in mutually opposite directions are respectively received by optical receivers (13 and 12) via the separators (18 and 17), and a fluctuation of a polarization is detected in polarization fluctuation detectors (16 and 15). A data processing device collects data indicating the fluctuation of the polarization detected by the polarization fluctuation detector and data indicating the fluctuation of the polarization detected by the polarization fluctuation detector.