An optical time domain reflectometer (OTDR) operates in a gated mode, enabling a predetermined width of an optical fiber to be analyzed. The OTDR may test only a desired position on the fiber. Data obtained along different lengths of the fiber may be combined together, providing a thorough representation of the fiber characteristics. Alternatively, specific regions of the fiber may be analyzed. The OTDR measures the backscattered signal using photon-counting techniques, and improves the accuracy...

The present invention relates to a method for interpreting data obtained by measuring a length of optical fiber using an optical time domain reflectometer (OTDR), and comparing that measurement to a reference measurement. The technique uses statistical inference to determine a whether a reference trace is valid by comparing that trace to a more recent test trace. The reference trace may be replaced or an alarm may be transmitted under certain conditions.

A method and apparatus sense attributes of reflected signals in an optical sensing system. In one embodiment, a method for sensing in an optical sensing system comprising an interrogator coupled to a Bragg grating sensor by an optical cable includes the steps of producing a first optical signal, coupling the first optical signal to an optical cable, receiving a first reflected signal from a Bragg grating sensor within the optical cable, resolving a wavelength of first reflected signal, producing...

An optical time domain reflectometry apparatus for sensing a parameter in a region of interest is characterized in that the optical fiber includes a first section into which optical radiation at the probe wavelength is launched and a second section deployed in the region of interest. The first section has a higher intensity threshold for the onset of non-linear effects than the second section. The source launches the optical radiation into the first section at an intensity lower than the non-lin...

A method for measuring non-circularity of a core portion of an optical fiber base material includes a distribution measuring step of (i) moving the optical fiber base material in a direction parallel to a central axis of the core portion while light is irradiated, in a direction perpendicular to the central axis, to the optical fiber base material which is immersed in the matching oil, and (ii) recording a variation in a width of a portion of the irradiated light which transmits through the core...

Methods and apparatus for detecting defects, such as air lines, in optical waveguide fibers are provided. The methods and apparatus employ scattered light interference signals produced by a fiber clad measurement system that transversely illuminates a fiber with a laser beam. Defects in the fiber produce characteristic peaks in the frequency spectrum of the scattered light signal. By filtering the scattered light signal to remove (a) the components associated with the fiber clad measurement syst...

This invention is applied to an optical amplifier evaluation method of modulating by an optical modulator 23 light output from a light source 1 into a rectangular optical signal which is enabled/disabled in a predetermined period, then applying the optical signal to an optical fiber amplifier 2 to be measured, and obtaining the gain and noise figure of the optical fiber amplifier from the light intensities in the ON and OFF periods of an optical signal output from the optical fiber amplifier and...

The present invention aims to provide apparatus to measure the beat length, the correlation length, the polarization mode dispersion and other characteristics of single mode optical fibers related to the two polarization modes of the fiber at different positions along the length of the fiber. The present invention also aims to provide apparatus for the measurement of characteristics of an optical fiber with access to only one end of the fiber.

The present invention provides a seismic sensing system having at least one sensor, transducer, optical source and detection unit, optical fiber and measurement unit. The sensor responds to a seismic disturbance, for providing a sensor signal containing information about the seismic disturbance. The sensor may be a geophone that detects vibrations passing though rocks, soil etc, and provides an electrical voltage sensor signal. The transducer responds to the sensor signal, for providing a transd...

The present invention relates generally to an image tracking device in an optical communication system, and in particular, to a device and method for measuring the transverse characteristics, including the refractive index or residual stress of an optical fiber or a fiber preform.