A system comprises an electromagnetic radiation source, a polarizing element, a mode converter, an optical fiber, and a measurement device. The polarizing element receives electromagnetic radiation produced by the electromagnetic radiation source and outputs linearly-polarized electromagnetic radiation having a linear polarization angle .sub.1. The mode converter converts the linearly-polarized electromagnetic radiation to an orbital angular momentum (OAM) mode of linearly-polarized electromagnetic radiation with topological charge L.sub.i. The OAM mode of linearly-polarized electromagnetic radiation is a superposition of first and second OAM modes with topological charges L.sub.i and opposite circular polarizations. The optical fiber supports propagation of the first and second OAM modes with an absolute effective index difference n.sub.eff greater than or equal to 510.sup.5, such that linearly-polarized electromagnetic radiation with linear polarization angle .sub.2 is emitted by the optical fiber. The measurement device is configured to determine a property of the electromagnetic radiation based on the polarization angle .sub.2.

An optical apparatus is comprising an optical imaging arrangement generating either an image of the original object field or the field of the original sample at the pupil plane which consist of both amplitude and phase information. The apparatus is further comprising a digital adaptive optics arrangement with a wave front sensor and a computing unit, which is adapted to generate at least one orthogonally translated digital copy of the original sample object field at the spatial Fourier or pupil plane and to analytically calculate a wave front error based on the phase difference between the original sample wave front and its digital copy or copies.

A system and method for phase-readout/control and active stabilization on arbitrary interferometric phase in the optical interferometer platform is disclosed. The method makes use of a bi-colored polarization-multiplexed reference laser scheme. The disclosed scheme is based on two phase-locked reference signals with different frequencies that together remove the phase ambiguity. The two signals are polarization-multiplexed (either in free-space or optical fiber implementations) to enable easy separation and combining of these two signals through the use of polarization beam-splitters. The disclosed scheme provides a one-to-one map between phase and feedback signal levels, and enables phase-readout and stabilization even when one of the feedback-signals is at a maximum/minimum.

An optical module includes an LD that emits laser beam; a carrier that mounts the LD and thermistor thereon; a photodetector detecting the laser beam output from the LD; a TEC that mounts the carrier and the photodetector thereon; a chassis having a box-shape demarcated by walls that form a space for enclosing the LD, the TEC, and the photodetector therein, wherein at least of the walls has a window, and the thermistor arranged between the LD and the photodetector.

Method and apparatus for determining the wavelength of a light beam are provided. An input light beam is received, and light from the input light beam is distributed to multiple channels. At a first pair of interferometer cavities that has a first free spectral range, two of the multiple channels of light are received. The intensity of light reflected from the first pair of cavities is measured, and a first estimate of the wavelength or optical frequency of the input light beam is determined based on measurements of interference signals from the first pair of cavities and an initial estimate of the wavelength or optical frequency. At a second pair of cavities that has a second free spectral range smaller than the first free spectral range, another two of the multiple channels of light are received. The intensity of light from the second pair of cavities is measured, and a second estimate of the wavelength or optical frequency of the input light beam is determined based on the first estimate and measurements of interference signals from the second pair of cavities, in which the second estimate is more accurate than the first estimate.

An optical apparatus is comprising an optical imaging arrangement generating either an image of the original object field or the field of the original sample at the pupil plane which consist of both amplitude and phase information. The apparatus is further comprising a digital adaptive optics arrangement with a wave front sensor and a computing unit, which is adapted to generate at least one orthogonally translated digital copy of the original sample object field at the spatial Fourier or pupil plane and to analytically calculate a wave front error based on the phase difference between the original sample wave front and its digital copy or copies.

An interferometer for use in remote sensing systems includes a beam splitter that separates an input wave into a reflected wave, which travels along a first optical path within an upper interferometer arm, and a transmitted wave, which travels along a second optical path within a lower interferometer arm. The reflected and transmitted waves are subsequently recombined by the beam splitter for imaging onto a sensor. A highly dispersive element is incorporated into at least one of the pair of interferometer arms. Due to anomalous dispersion, a frequency shift in a wave transmitted through a dispersive element changes the optical path length within its corresponding arm. As a result, the recombined wave produces an interference pattern with a measurable phase change that can be utilized to calculate the original frequency shift in the input wave with great precision and potential sub-Hertz sensitivity.

Disclosed is a method for producing an optical fiber coil including the following steps: a. symmetrical winding of an optical fiber around a shaft, the winding forming a pattern including a same number N of layers of each half of the optical fiber, one layer including a set of turns of optical fiber and spaces between adjacent turns, the winding forming a sectored arrangement including a regular stacking area including at least one continuous sealing surface between two layers of adjacent turns, and an overlap area where portions of optical fiber linking different turns cross each other; b. infiltration of a glue through an external surface of the overlap area in such a way that the glue infiltrates into the spaces located between adjacent turns in the regular stacking area.

Apparatus and associated methods relate to determining the wavelength of a narrow-band light beam. The narrow-band light beam is passed through an optical filter. The optical filter has complementary and monotonically-varying transmission and reflection coefficients within a predetermined band of wavelengths. The predetermined band of wavelengths includes the wavelength of the narrow-band light beam. A first photodetector detects amplitude of a first portion of the narrow-band light beam transmitted by the optical filter. A second photodetector detects amplitude of a second portion of the narrow-band light beam reflected by the optical filter. The wavelength of the narrow-band light beam is determined, based on a ratio of the determined amplitudes of the first and second portions of the narrow-band light beam transmitted and reflected, respectively.

An illustrative interferometric system with high-fidelity optical phase demodulation includes a receiver having a fiberoptic coupler that produces optical interferometry signals having mutual phase separations of 120 and balanced photo-detectors that each produce an electrical difference signal based on a respective pair of said optical interferometry signals. The system further includes circuitry that converts the electrical difference signals into measurements of an interferometric phase.