A shape sensor employs light guide technology to determine a degree, positioning, and direction of curvature of a flexible substrate to which the shape sensor is applied. The shape sensor includes a flexible two-dimensional lattice of a plurality of first light guides that extend in a first direction and a plurality of second light guides that extend in a second direction that intersects with the first direction; each of the light guides of the two-dimensional lattice including a light source at a first end of the light guide and a photodetector at a second end of the light guide opposite from the first end; and a flexible cladding material in which the two-dimensional lattice of first and second light guides is embedded. Each of the light guides of the two-dimensional lattice includes a core having a refractive index that is greater than a refractive index of the cladding material. The first light guides and the second light guides intersect at intersecting core regions at which crosstalk of light travel occurs between the first light guides and the second light guides. The shape sensor may be connected in signal communication to a controller configured to transmit excitation control signals to the light sources and read output signals from the photodetectors. The controller further is configured to determine a curvature of the shape sensor based on the output signals read from the photodetectors.

An optical fiber distributed acoustic sensor system makes use of a specially designed optical fiber to improve overall sensitivity of the system by a factor in excess of 10. This is achieved by inserting into the fiber weak broadband reflectors periodically along the fiber. The reflectors reflect a small proportion of the light from the DAS incident thereon back along the fiber, typically in the region of 0.001% to 0.1%. To allow for temperate compensation to ensure that the same reflectivity is obtained if the temperature changes, the reflection bandwidth is relatively broadband. The reflectors are formed from a series of fiber Bragg gratings, each with a different center reflecting frequency, the reflecting frequencies and bandwidths of the gratings being selected to provide the broadband reflection. The reflectors are spaced at the desired spatial resolution of the optical fiber DAS.

An optical fiber sensor includes a first single mode fiber, a second single mode fiber, and a multimode fiber positioned between, and coupled to, the first single mode fiber and the second single mode fiber. The multimode fiber includes a graded-index core with an outer diameter between about 35 m and about 45 m. A numerical aperture of the core is between about 0.15 and about 0.25. The multimode fiber includes a cladding with an outer diameter between about 70 m and about 90 m. A coupling strength of an LP.sub.01 mode of the first single mode fiber to each of an LP.sub.02 mode and an LP.sub.03 mode of the multimode fiber is at least about 0.25.

Sensor bearing unit providing at least two bearings stacked one relative to the other and each having an inner ring and an outer ring, the sensor bearing unit having a sleeve radially surrounding the bearings and having a radial projection in axial contact with one of the bearings, an annular flange having a radial portion in axial contact with the other bearing and an axial portion radially surrounding the sleeve and connected to the sleeve, and a wire carrier configured to support at least one wire and at least one connector, the wire carrier includes at least one fastening element mounted on the bearing.

Aspects of the present disclosure describe optical fiber sensing systems, methods and structures disclosing a distributed fiber sensor network constructed on an existing, live network, data carrying, optical fiber telecommunications infrastructure to detect temperatures, acoustic effects, and vehicle trafficamong others. Of particular significance, sensing systems, methods, and structures according to aspects of the present disclosure may advantageously identify specific network locations relative to manholes/handholes and environmental conditions within those manholes/handholes namely, normal, flooded, frozen/iced, etc.

Disclosed herein is an optical cable comprising a support; flexible protective tubes helically wound around the support, each flexible protective tube comprising an optical fiber comprising an optical core; a cladding disposed on the core; and a primary coating external to the cladding; and a deformable material surrounding the optical fiber; an outer jacket surrounding the flexible protective tubes; wherein each optical fiber is about 0.5% to about 1.5% longer than its respective flexible protective tube; wherein an allowable strain on the optical cable with substantially zero stress on the optical fibers is determined by equations (1) and (2) below:

[00001]$\begin{array}{cc}\mathrm{.Math.}=\underset{\_}{\sqrt{{{}^2\left(D+\frac{d}{2}\right)}^2+p^2}}.Math..Math.\underset{\_}{\sqrt{{{}^2\left(D-\frac{d}{2}\right)}^2+p^2}}.Math..Math.\underset{\_}{{}^2.Math.\mathrm{dD}}-\underset{\_}{10.Math..Math.\mathrm{dD}};& \left(1\right)\\ \mathrm{.Math.}100=\mathrm{Percent}.Math..Math.\mathrm{elongation}.Math..Math.\mathrm{or}.Math..Math.\mathrm{contraction};& \left(2\right)\end{array}$

where d is the amount of optical fiber clearance for free movement within the flexible protective tube, D is an average helical dia

A sensor for detecting micro-movements is provided herein. In various embodiments, the sensor includes a looped structure formed of a continuous multi-mode optical fiber arranged into a plurality of loops disposed substantially in a plane. Each loop within the looped structure is partially overlapping yet laterally offset from neighboring loops. The sensor further includes a light source coupled to a first end of the looped structure, a receiver coupled to a second end of the looped structure, and one or more control and processing modules. Related methods of manufacture and use are also disclosed.

A distributed sensing optical fiber cable is proposed. An optical fiber is positioned at the center of the cable and includes a core region, at least one cladding layer surrounding the core region, a protective coating covering the at least one cladding layer, and a tight buffer of elastomeric thermoplastic material disposed to surround the protective coating. The remainder of the cable structure includes a pair of strength members disposed longitudinally on either side of the optical fiber (the strength members formed of a glass-based, memory-less material) and a hard plastic jacket formed to encase the optical fiber and the pair of strength members, the plastic jacket preferably exhibiting an essentially rectangular profile.

A DPTSS fiber optic cable includes an optical fiber sheathing cylindrical metal tube accommodating a pressure sensor optical fiber and having a plurality of through holes formed therein; and pressure blocking sections formed at intervals in the axial direction of the cable.

A vibration sensing optical fiber cable is provided. The cable includes at least one optical fiber embedded in the cable jacket such that vibrations from the environment are transmitted into the cable jacket to the optical fiber. The cable is configured in a variety of ways, including through spatial arrangement of the sensing fibers, through acoustic impedance matched materials, through internal vibration reflecting structures, and/or through acoustic lens features to enhance sensitivity of the cable for vibration detection/monitoring.