Abstract: An optical cable (31) includes: a stress wave detection optical cable (30) having an optical fiber (7) and a plurality of first steel wires (8) which are helically wound so as to surround the optical fiber (7) and which are surrounded by a flexible material (9); and second steel wires (32) different from the first steel wires (8). The stress wave detection optical cable (30) and the plurality of second steel wires (32) are helically wound to form one annular body as a whole, and a winding angle (?) of the stress wave detection optical cable (30) with respect to the axis is determined by a property value prescribed by Lamé constants of the flexible material (9).

Abstract: A magnetic field measurement cable (10) of the present disclosure includes an electric cable (1) provided at an axial part, and an outer circumferential cable (2) provided on the outer side of the electric cable (1) and helically formed by a plurality of steel wires helically wound and a magnetic field measurement optical cable (3) having an optical fiber cable (3a).

Abstract: An optical fiber for measuring pressure comprising a core for guiding optical signals along a length of the core and a cladding layer including a plurality of stress applying parts disposed around the core. The plurality of stress applying parts are disposed parallel to and symmetrically around the core to induce intensified symmetric shear stress upon application of external pressure while preventing birefringence. The optical fiber provides improved strain sensitivity compared to a standard single-mode optical fiber.

Abstract: An optical cable includes: an optical fiber for sensing deformation of hydrocarbon absorbing resin having a property of expanding by absorbing hydrocarbon in oil; a strand provided so as to surround the outer circumference of the optical fiber; and hydrocarbon absorbing resin filling a space between the optical fiber and the strand. The optical cable configured as described above is installed along the depth direction of a well that is a measurement subject, over the entire range thereof, and a backscatter light frequency shift signal from the optical fiber is measured by a backscatter light measurement device, to detect presence/absence of leakage of oil from the well over the entire range in the depth direction of the well.

Abstract: This optical fiber distribution measurement system of distributed optical fiber sensing type includes: a tunable wavelength distributed feedback LD (1) for obtaining a DTSS signal through frequency shift analysis; an external resonance laser (2) for obtaining a DAS signal through phase shift analysis; a pulse compression coding circuit (4) including an intensity modulator (4a) and an phase modulator (4b); an acousto-optic switch (5); an erbium doped optical fiber amplifier (6); a circulator (7); a diversity device (8); a digitizer (11); a CPU (12); and a serial transfer interface (13). Through calculation on discrete signals sent from the digitizer (11), the CPU (12) converts an analyzed Rayleigh frequency shift signal obtained as the DTSS signal, to phase error, and corrects an analyzed phase signal obtained as the DAS signal, by the phase error.

Abstract: An optical cable (31) includes: a stress wave detection optical cable (30) having an optical fiber (7) and a plurality of first steel wires (8) which are helically wound so as to surround the optical fiber (7) and which are surrounded by a flexible material (9); and second steel wires (32) different from the first steel wires (8). The stress wave detection optical cable (30) and the plurality of second steel wires (32) are helically wound to form one annular body as a whole, and a winding angle (?) of the stress wave detection optical cable (30) with respect to the axis is determined by a property value prescribed by Lamé constants of the flexible material (9).

Abstract: A magnetic field measurement cable (10) of the present disclosure includes an electric cable (1) provided at an axial part, and an outer circumferential cable (2) provided on the outer side of the electric cable (1) and helically formed by a plurality of steel wires helically wound and a magnetic field measurement optical cable (3) having an optical fiber cable (3a).