Abstract: The present invention provides an off-axis rotary joint for optical signal transfer. An annular waveguide has optical discontinuity means, such as a plurality of circumferentially equally spaced apart notches directed inwardly thereof, which discontinuities intercept a light beam emanating from a light source near the waveguide. The discontinuities direct light into the waveguide, along which it travels until it meets an internal reflecting member which, in turn reflects the travelling light out of the waveguide to a suitable detector. The light source and the waveguide/reflector/detector are relatively rotatable so that the signal strength at the detector is an indication of the position of the light source relative to the waveguide. The invention has practical applicability in apparatus, such as turrets and CT scanners, in which the central shaft or axis area must be occupied by equipment or personnel rather than componentry of the rotary joint.

Abstract: The invention is a rotary joint for singlemode optical fibers, having a fixed and a rotating part to permit the transmission of optical signals across a rotational interface (such as a winch or turret) with minimal insertion loss and, in particular, low reflections (good return loss). There is no need of conversion to electrical signals; the device is passive. It may be use an oil of refractive index matched to that of the glass fibers and to that of fiber tapers or lenses used to expand the beam emitted from one fiber and contract it for transmission into the other fiber. The device is bidirectional. By use foil, through precision techniques for building and mounting the optical and mechanical components, and by use of advanced bearings, both the insertion loss and unwanted reflections (return loss) can be minimized, thereby making it suitable for use with singlemode fiber.

Abstract: A fibre optic sensor, particularly for ascertaining fluid levels, utilizes two cylindrical lightguides with regular perturbations to emit and/or accept light in a radial direction. Each waveguide is coupled to one (or more) light source and/or to one (or more) light detector. A light source such as a light emitting diode or laser diode is coupled to the lightguide which emits radially, illuminating a planar dielectric surface, which in the presence of a fluid with a low index of refraction, e.g. air, behaves as a mirror, coupling light via total internal reflection to the lightguide which accepts this light radially and channels the light to a light detector. In the presence of a fluid with a high index of refraction, for example water, at the planar dielectric surface the fluid dielectric interface becomes primarily transmissive, with relatively little light being coupled to the lightguide which accepts light radially.

Abstract: A fibre optic sensor, particularly for ascertaining fluid levels, utilizes at least two optical fibres having at least a portion thereof embedded in a transparent substrate material of similar refractive index. One of the fibres is coupled to a light source, the other to a light detector. The source fibre illuminates the interior of the substrate so that light exiting the source fibre is coupled to the detector fibre when total internal reflection at the substrate/fluid interface occurs in the presence of a first fluid. In the presence of a second fluid of higher refractive index than the first fluid, there will be no coupling, due to the loss of light into the fluid by refraction. The mechanism for coupling light into the detector fibre is fluorescence within that fibre causing it to provide a light signal which varies with the level of the second fluid. Several different embodiments, to achieve continuous level sensing or the sensing of other parameters, are disclosed.