An optical aperture multiplier includes a first optical waveguide (10) having a rectangular cross-section and including partially reflecting surfaces (40) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide (20), also including partially reflecting surfaces (45) at an oblique angle, is optically coupled with the first optical waveguide (10). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.

Techniques for reducing interference with sensor (light) signals and measurement in polarimetric fiber optic sensors from undesired effects of current and vibrations on light signals carried in fiber optic cables are presented. A sensor system comprises a first depolarizer associated with a fiber optic cable and in proximity to a light source that provides a light signal to such cable. First depolarizer depolarizes the light signal to produce a first depolarized light signal output to another portion of the fiber optic cable that can be wrapped around or associated with a conductor cable or ground cable. To reduce undesired polarizing effects on the first depolarized light signal due to current or vibrations from the conductor cable or ground cable, the system comprises a second depolarizer that depolarizes the (re)polarized light signal to produce a second depolarized light signal suitable for use in sensing current or voltage after additional processing.

Optical polarization control devices that include two pairs of squeezing plates oriented in mutually perpendicular directions are described. Compressive forces exerted by the two pairs of plates onto an optical fiber can be configured for low polarization mode dispersion. Various methods and systems in which the polarization control devices can be employed are also described.

An apparatus for sensing a value of a property includes: an optical sensor having a single mode optical fiber responsive to the property; an optical interrogator having a tunable laser to transmit polarized light to the optical sensor, a photo-detector to receive sensor light, and a controller configured to process the received light and output the value of the property; and a passive random depolarizer disposed between the tunable laser and the single mode optical fiber and having (i) a first polarization maintaining (PM) optical fiber of length L1 having a first fast optical axis and a first slow optical axis and (ii) a second PM optical fiber of length L2 having a second fast optical axis and a second slow optical axis rotationally spliced to the first PM optical fiber in which the second fast and slow optical axes are offset from the first fast and slow optical axes.

A polarization scrambler using a retardance element (RE) is disclosed. The polarization scrambler may include an optical fiber input to transmit an optical signal, and a beam expander to receive and expand the optical signal to create an expanded optical signal. The polarization scrambler may include a retardance element (RE) to cause a polarization scrambling effect on the expanded optical signal and to create a scrambled expanded optical signal. The polarization scrambler may include a beam reducer to receive and reduce the scrambled expanded optical signal to create a scrambled optical signal. The polarization scrambler may include an optical fiber output to receive scrambled optical signal. The optical fiber output may transmit the scrambled optical signal to one or more downstream optical components.

A depolarizer for a broadband optical source to split the source beam by power, not by polarization state, and route the components into respective light paths. A polarization rotator arranged in one of the light paths rotates the polarization state of that beam component to make it orthogonal to that of the other. The components are then recombined by a combiner and output. A variable optical attenuator is arranged in one of the light paths, which during operation is adjusted by a controller to maintain power equalization between the light paths and hence depolarization performance. The controller receives power measurements from the light paths and from after the combiner via respective sensors. With this feedforward design reminiscent of a Mach-Zehnder interferometer the light from a light source which generates highly polarized light can be depolarized in theory with zero insertion loss and in practice with losses of about 1 dB.

Techniques for reducing interference with sensor (light) signals and measurement in polarimetric fiber optic sensors from undesired effects of current and vibrations on light signals carried in fiber optic cables are presented. A sensor system comprises a first depolarizer associated with a fiber optic cable and in proximity to a light source that provides a light signal to such cable. First depolarizer depolarizes the light signal to produce a first depolarized light signal output to another portion of the fiber optic cable that can be wrapped around or associated with a conductor cable or ground cable. To reduce undesired polarizing effects on the first depolarized light signal due to current or vibrations from the conductor cable or ground cable, the system comprises a second depolarizer that depolarizes the (re)polarized light signal to produce a second depolarized light signal suitable for use in sensing current or voltage after additional processing.

An optical aperture multiplier includes a first optical waveguide (10) having a rectangular cross-section and including partially reflecting surfaces (40) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide (20), also including partially reflecting surfaces (45) at an oblique angle, is optically coupled with the first optical waveguide (10). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.

A photonic integrated circuit comprises an input interface adapted for receiving an optical input signal and splitting it into two distinct polarization modes and furthermore adapted for rotating the polarization of one of the modes for providing the splitted signals in a common polarization mode. The PIC also comprises a combiner adapted for combining the first mode signal and the second mode signal into a combined signal and a decohering means adapted for transforming at least one of the first mode signal and the second mode signal such that the first mode signal and the second mode signal are received by the combiner in a mutually incoherent state. A processing component for receiving and processing said combined signal is also comprised.

A polarization scrambler using a retardance element (RE) is disclosed. The polarization scrambler may include an optical fiber input to transmit an optical signal, and a beam expander to receive and expand the optical signal to create an expanded optical signal. The polarization scrambler may include a retardance element (RE) to cause a polarization scrambling effect on the expanded optical signal and to create a scrambled expanded optical signal. The polarization scrambler may include a beam reducer to receive and reduce the scrambled expanded optical signal to create a scrambled optical signal. The polarization scrambler may include an optical fiber output to receive scrambled optical signal. The optical fiber output may transmit the scrambled optical signal to one or more downstream optical components.