An object of the present invention is to provide an optical fiber test method, an optical fiber test apparatus, and a program, capable of detecting a boundary of an optical fiber line facility regardless of a change in a noise amount. A change amount (a differential value) of an OTDR waveform increases toward a distal end due to noise effects, making it difficult to determine a boundary of the optical fiber using the change amount. Therefore, in the present invention, a dispersion of the OTDR waveform, which increases toward a distal end due to noise effects, is also used to determine the boundary of the optical fiber. In other words, in the present invention, the noise amount is expressed by the dispersion, and the dispersion is compared with the change amount such as a differential value as a threshold, to determine the boundary of the optical fiber. For this reason, when noise increases, the threshold increases together with an increase in the change amount, and therefore, the boundary of the optical fiber can be determined regardless of noise.

A method for selecting wide-band multimode optical fibers from a single wavelength, the method comprising the following steps of, for each multimode optical fiber obtaining a first DMD plot using a measurement of DMD carried out at a first single wavelength, obtaining from the first DMD plot, a first multimode fiber specification parameter; and for each fiber: obtaining from the first DMD plot, a curve representative of a radial offset delay, called ROD curve, as a function of the radial offset value; applying a linear fit on the ROD curve for at least two radial offset value ranges; obtaining from the linear fit and for each radial offset value range, an average radial offset delay slope, called ROD slope; selecting the multimode optical fibers meeting a first predetermined specification criterion for the first multimode fiber performance parameter, and for which the at least two computed ROD slopes meet a predetermined slope criterion.

There is provided a method of measuring the PMD of an optical fiber under test (FUT). A polarization-sensitive optical time domain reflectometer (POTDR) is used to inject into the FUT and from a proximal end thereof, a test signal comprising a series of repeated light pulses and detecting a corresponding polarization-analyzed return light signal coming back from the optical fiber and representing back-reflected light from a light reflector connected to a distal end of the FUT, said return light signal comprising repeated reflected light pulses. The plurality of polarization-sensitive acquisitions defines at least one pair of acquisitions performed with mutually different but closely-spaced wavelengths and substantially the same state of polarization (SOP), a center of said wavelengths defining a center wavelength for said at least one pair. The process may be repeated for a plurality of pairs of acquisitions performed with at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarization (SOP). For each said acquisitions, respective amplitudes of at least part of the repeated reflected light pulses are averaged so as to obtain an averaged reflected power. The PMD is obtained by, for each said pairs of said acquisitions, computing a value of a difference between the two averaged reflected powers corresponding to said pair, followed by the mean-square value of computed values of difference over said at least one of a plurality of mutually-different center wavelengths and a plurality of mutually-different states of polarizations (SOPs) and, from said mean-square value, calculating a value of the PMD for the optical fiber under test.

Systems and methods for correcting chromatic dispersion in a remote distributed sensing application are disclosed. A remote distributed sensing system includes an interrogation subsystem configured to transmit an optical pulse and receive a reflection from the optical pulse. The remote distributed sensing system also includes a transit optical fiber coupled to the interrogation subsystem and having chromatic dispersion of a first slope at a frequency of the optical pulse, and an optical fiber under test being located in a remote location apart from the interrogation subsystem. The remote distributed sensing system additionally includes a chromatic dispersion compensator coupled in-line with at least one of the transit optical fiber and the optical fiber under test to adjust chromatic dispersion on the optical pulse in a direction of a second slope having an opposite sign from the first slope.

A dispersion measurement apparatus includes a pulse forming unit, a correlation optical system, a photodetection unit, and an operation unit. The pulse forming unit forms a light pulse train including a plurality of light pulses having time differences and center wavelengths different from each other from a measurement target light pulse output from a pulsed laser light source. The correlation optical system receives the light pulse train output from the pulse forming unit and outputs correlation light including a cross-correlation or an autocorrelation of the light pulse train. The photodetection unit detects a temporal waveform of the correlation light output from the correlation optical system. The operation unit estimates a wavelength dispersion amount of the pulsed laser light source based on a feature value of the temporal waveform of the correlation light.

Examining a light optical element (LOE) may include placing a first slit optically between a projector configured to emit light and the LOE's first major surface and placing a second slit optically between the LOE's second major surface and a detector. Facet parallelism between two facets may be deduced based on a shift of the image reflected from the first facet to the second facet relative to light transmitted normal to the first and second major surfaces through a portion of the substrate not including a facet. Facet refractive index homogeneity or deviation may be deduced based on the light transmitted through the facet relative to light transmitted normal to the first and second major surfaces through a portion of the substrate not including a facet.

A dispersion measurement apparatus includes a pulse forming unit, a correlation optical system, a photodetection unit, and an operation unit. The pulse forming unit forms a light pulse train including a plurality of light pulses having time differences and center wavelengths different from each other from a measurement target light pulse output from a pulsed laser light source. The correlation optical system receives the light pulse train output from the pulse forming unit and outputs correlation light including a cross-correlation or an autocorrelation of the light pulse train. The photodetection unit detects a temporal waveform of the correlation light output from the correlation optical system. The operation unit estimates a wavelength dispersion amount of the pulsed laser light source based on a feature value of the temporal waveform of the correlation light.

Examining a light optical element (LOE) may include placing a first slit optically between a projector configured to emit light and the LOE's first major surface and placing a second slit optically between the LOE's second major surface and a detector. Facet parallelism between two facets may be deduced based on a shift of the image reflected from the first facet to the second facet relative to light transmitted normal to the first and second major surfaces through a portion of the substrate not including a facet. Facet refractive index homogeneity or deviation may be deduced based on the light transmitted through the facet relative to light transmitted normal to the first and second major surfaces through a portion of the substrate not including a facet.