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.

Example embodiments add an optical amplifier to an multi-channel, continuously swept OFDR measurement system, adjust amplified swept laser output power between rising and falling laser sweeps, and/or utilize portions of a laser sweep in which OFDR measurements are not typically performed to enhance the integrity of the OFDR measurement system, improve the performance and quality of OFDR measurements, and perform additional measurements and tests.

The present invention provides a plastic optical fiber comprising a core and a sheath consisting of at least one layer, the plastic optical fiber having a transmission loss of 120 dB/km or less as measured by a 25 m-1 m cutback method under conditions of a wavelength of 525 nm and an excitation of NA=0.45, and satisfying either one of the following conditions when a thickness of the innermost sheath layer is 0.5 m to 4.5 m, an amount of foreign matter having a size of 2 m or greater contained in the innermost sheath layer is 2000/cm.sup.3 or less, or a size X (m) of foreign matter contained in the innermost sheath layer and an amount Y of the foreign matter (number/cm.sup.3) satisfy formula (1) below: Y1200 X e.sup.(0.067X) (1). Such optical fibers have a low transmission loss of green light (in particular, light having a wavelength of 525 nm), enabling longer distance communication.

A bending measurement apparatus includes a first multimode fiber, a wavefront input apparatus, a first wavefront measurement device, and a processor. The wavefront input apparatus inputs a first wavefront to the first multimode fiber as an input wavefront. The first wavefront measurement device measures an output wavefront outputted from the first multimode fiber as a measured wavefront. The processor select correspondence information which corresponds to the measured wavefront. The correspondence information shows a correspondence relationship between the input wavefront and the output wavefront. The processor sets the bending amount corresponding to the selected correspondence information as a current bending amount of the first multimode fiber.

The present invention relates to a method of and a system for optically connecting an optical fiber sensor (12) to an optical shape sensing console (21). The optical shape sensing console (21) has a number of single optical channels (C1, C2, C3). The optical fiber sensor (12) has a number of single fiber cores (A1, A2, A3) angularly spaced with respect to one another around a longitudinal center axis of the fiber sensor (12) and a fiber sensor connection end (30) for connection to an optical coupler (32; 38) connected to the shape sensing console (21). The optical coupler (32; 38) has the optical channels (C1, C2, C3) arranged for optical connection with the fiber cores (A1, A2, A3). A number of single calibration data sets indicative of individual optical properties of the single fiber cores (A1, A2, A3) is assigned to the single optical channels (C1, C2, C3). The fiber sensor connection end (30) is connected to the optical coupler (32; 38) such that a first fiber core (A2) of the fiber cores (A1, A2, A3) is in optical communication with a first optical channel (C1) of the optical channels (C1, C2, C3). An optical response of the first fiber core (A2) is measured by optically interrogating the first fiber core (A2) while a first calibration data set of the calibration data sets is assigned to the first optical channel (C1). The first fiber core (A2) is identified among the fiber cores (A1, A2, A3) of the fiber sensor (12) on the basis of the measured optical response of the first fiber core (A2) and the calibration data sets of the fiber sensor (12). If the first fiber core (A2) is identified as not matching with the first calibration data set used hi measuring the optical response, then a second calibration data set of the calibration data sets, which matches with the identified first fiber core (A2), is reassigned to the first optical channel (C1), or the fiber sensor connection end (30) and/or the optical coupler (32; 38) are repositioned such that a second fiber core (A1) matching with the first calibration data set is in optical communication with the first optical channel (C1).

Example embodiments add an optical amplifier to an multi-channel, continuously swept OFDR measurement system, adjust amplified swept laser output power between rising and falling laser sweeps, and/or utilize portions of a laser sweep in which OFDR measurements are not typically performed to enhance the integrity of the OFDR measurement system, improve the performance and quality of OFDR measurements, and perform additional measurements and tests.

An interferometric measurement system measures a spun optical fiber sensor that includes multiple optical cores configured in the fiber sensor. A calibration machine includes a calibration fixture having known dimensions, one or more automatically controllable actuators for wrapping the fiber sensor starting at one end of the fiber sensor onto a calibration fixture having known dimensions, and an actuator controller configured to control the one or more actuators with actuator control signals. Interferometric detection circuitry, coupled to the actuator controller and to the other end of the fiber sensor, detects measured interferometric pattern data associated with each of the multiple cores when the fiber sensor is wrapped onto the calibration fixture. Data processing circuitry determines compensation parameters that compensate for variations between an optimal configuration of the multiple cores and an actual configuration of the multiple cores in the fiber sensor based on the detected measured interferometric pattern data. The compensation parameters compensate subsequently-obtained measurement interferometric pattern data for the fiber sensor.

The present disclosure provides a sensory cable (100). The sensory cable (100) includes a central strength member (106). In addition, the sensory cable (100) includes a first layer (108). The first layer (108) surrounds the central strength member (106). The first layer (108) is made of low smoke zero halogen. Further, the sensory cable (100) includes a plurality of optical units (110). Furthermore, the sensory cable (100) includes a second layer (112). The second layer (112) is made of a plurality of glass yarns. Moreover, the sensory cable (100) includes a first jacket layer (114). The first jacket layer (114) is made of either polyethylene or polypropylene. Also, the sensory cable (100) includes a second jacket layer (116). The second jacket layer (116) is made of nylon.

A fiber sensor includes an optical fiber configured for operation at a wavelength from about 800 nm to about 1600 nm. The optical fiber includes a cladding that is defined by a fiber outer diameter and a core that is surrounded by the cladding. The core of the optical fiber has a Rayleigh scattering coefficient, .sub.s, that is controlled by controlling a concentration of one or more dopants in the core. The Rayleigh scattering coefficient is tuned to be within a predetermined range of an optimum Rayleigh scattering coefficient for a given total length, L, of the optical fiber. The predetermined range is from about 70% of the optimum .sub.s to about 130% of the optimum .sub.s.

Embodiments involve optical waveguides with spongy material for cladding or layers that include compressible gas pockets. The refractive index of the porous cladding material will change when compressed, bent, or stretched. Measurements for pressure, strain, bending, etc., may be obtained by monitoring the signal degradation and/or escape of radiant energy, e.g., IR, etc., from the core and out through the spongy cladding, where it may be picked up by a neighboring core. Optical waveguides configured as fibers may be easily sewn to stretchable materials, such as athletic tape, fabrics used in umbrellas, balloons, fabrics used in clothing, etc., to meet a robust number of applications.