According to examples, a fiber-optic testing source for testing a multi-fiber cable may include a laser source communicatively coupled to a plurality of optical fibers connected to a connector. The fiber-optic testing source may include at least one photodiode communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement a communication channel between the fiber-optic testing source and a fiber-optic testing receiver. The communication channel may be operable independently from a polarity associated with the multi-fiber cable. The fiber-optic testing receiver may include a plurality of photodiodes communicatively coupled to a plurality of optical fibers. The fiber-optic testing receiver may include at least one laser source communicatively coupled to at least one of the plurality of optical fibers by at least one corresponding splitter to implement the communication channel between the fiber-optic testing receiver and a fiber-optic testing source.

Described are systems and techniques for characterizing optical fibers. Disclosed systems and techniques employ optical metrology, functional metrology, or both to characterize microstructured optical fibers and determine fiber characteristics, errors, and quality control metrics. The characteristics, errors, and quality control metrics are useful for improving the manufacturing of optical fibers.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

Devices, systems and techniques for measuring optical polarization-related parameters in optical materials and devices such as polarization maintaining (PM) fiber links based on polarization crosstalks that spatially distribute over a length of a material such as a PM fiber link.

A method and structure are provided for testing photonic circuits with integrated optical mixers having idle ports. A test port is provided for coupling test light into one or more idle ports of the mixer. Light exiting output ports of the mixer may be measured with photodetectors. Phase errors of optical hybrids may be determined by using waveguides of different lengths to inject test light into two input ports of the mixer and scanning the test wavelength. The method and structure may be used for on-wafer and off-wafer measurements of integrated photonic circuits implementing coherent optical receivers.

The nondestructive determination of core size of a hollow-core photonic bandgap fiber (HC-PBF) using Fabry-Perot (FP) interference is performed with an apparatus including a tunable laser source (TLS), a 12 single-mode (SM) coupler, an SM collimator, a six-axis translation stage, an optical detector, and an oscilloscope. The light from the TLS passes through the 12 SM coupler and the SM collimator to perpendicularly enter two parallel air-SiO.sub.2 interfaces of the core of the fiber and is reflected, while the TLS is tuned from one wavelength to another. Then the reflected spectrum is guided to the optical detector, where its interference intensity is converted into voltage intensity to be displayed at the oscillator and fitted with a least-squares method to obtain the distance between the two air-SiO.sub.2 interfaces. The core size of the fiber can be obtained by rotating the fiber and repeating the procedure at multiple angular positions.

Apparatus and methods are disclosed for measuring polarization properties and phase information, for example as can be used in microscopy applications. According to one example of the disclosed technology, an apparatus includes a light source, an interferometer configured to receive light generated by the light source and split the received light into two split beam outputs. The split beam outputs including combined, interfering light beams. Two light sensors, each including a polarization-sensitive focal plane array receive a respective one of the split beam outputs from the interferometer. Thus, some examples of the disclosed technology allows for simultaneous or concurrent measurement of properties of light including intensity, wavelength, polarization, and phase. The polarization-sensitive focal plane array includes a number of macropixels, each of which includes superpixels having different polarization filtering properties, each of which includes one or morepixels, which comprise filters for different colors.