Yokogawa Electric Corporation

The University of Tokyo

Other

Mitsubishi Heavy Industries Limited

Japan Aviation Electronics Industry, Limited

Hotate, Kazuo

Kazuo Hotate

Yoshihiro Kumagai

Takashi Yari

Zuyuan He

Kwang Yong Song

Aritaka Ohno

Rodrigo Kendy Yamashita

Kazushi Oishi

Masahito Ishioka

Shinji Motohara

Motokatsu Kannou

Masato Kishi

There are proposed an optical fiber property measuring device and an optical fiber property measuring method which can enhance spatial resolution more than before. In the present invention, in synchronization with frequency modulation applied to x-polarized light, intensity modulation is also applied to the x-polarized light by an intensity modulation means. This makes it possible to increase or decrease the intensity of the x-polarized light at a specific frequency, thereby allowing the effective length of a Brillouin dynamic grating formed by the x-polarized light to be adjusted. As a result, the shape of the reflection spectrum obtained when y-polarized light is reflecting by the Brillouin dynamic grating can also be adjusted optimally, which leads to enhancement of spatial resolution with the y-polarized light.

Optical fiber property measuring device and optical fiber property measuring method

Provided is an optical fiber characteristics measurement device that is provided with: a light source for emitting laser light modulated by a specified modulation frequency; an incident means for receiving the laser light from the light source as continuous light and pulse light from one end and the other end of an optical fiber, respectively; and a light detector for detecting light emitted from the optical fiber, the optical fiber characteristics measurement device measuring the characteristics of the optical fiber using the detection results of the light detector, wherein the optical fiber characteristics measurement device is characterized in being provided with a synchronous detector that extracts, from among the detection signals output from the light detector, detection signals obtained by detecting the light in the vicinity of a measurement point set in the optical fiber, and synchronously detects the extracted detection signals using a synchronization signal having a specified period.

Optical fiber characteristics measurement device and method

An optical fiber characteristic measuring device of the present invention includes: a light source which emits laser light modulated at a predetermined modulation frequency; an incident section which causes the laser light from the light source as continuous light and pulsed light to be incident from one end and other end of an optical fiber respectively; a timing adjuster which causes light emitted from the optical fiber to pass therethrough at a predetermined timing; and a light detector which detects the light which passes through the timing adjuster, and measures a characteristic of the optical fiber by using a detection result of the light detector, and the device includes: a synchronous detector which synchronously detects the detection result of the light detector by using a synchronization signal having a predetermined frequency; and a frequency setter which changes the frequency of the synchronization signal in a case where the modulation frequency at the light source is an integer multiple of the frequency of the synchronous signal.

Optical fiber characteristic measuring device and method

A measurement precision is improved and a measurement range is extended by efficiently suppressing a noise level of integrated unnecessary components from non-correlation positions. Measuring meansdetects the Brillouin gain of a probe light output from a measurement-target optical fiber FUT while sweeping a frequency difference between the pump light and the probe light, and measures the distribution of strains of the measurement-target optical fiber FUT. An optical intensity modulatorperforms intensity modulation on output light in synchronization with frequency modulation performed on a light source. Accordingly, the spectrum distribution with respect to the frequency of light from the light sourcecan be adjusted arbitrarily, and a noise spectrum shape generated at a position other than a correlation peak position and spreading over a frequency axis can be adjusted, and the peak frequency of a Lorentz spectrum generated at the correlation peak position can be measured precisely. Moreover, a measurement range dcan be extended.

Optical-fiber-characteristic measuring device and optical-fiber-characteristic measuring method

A measurement range is extended while maintaining the spatial resolution high by completely separating the increment of a probe light from noises. Modulations are performed on both probe light and pump light to differentiate both lights. Using the modulations, only the change in the probe light necessary for measuring the characteristic of a measurement-target optical fiber FUT can be separated. Accordingly, unlike the conventional technology, an optical wavelength filter becomes unnecessary. Further, in a case where an amplitude &#x394;f of the frequency modulation of a light sourceis made wide to some extent to make the measurement range wide while maintaining a spatial resolution &#x394;z high, the amplitude &#x394;f does not affect to detection of the change in the probe light. Therefore, the increment of the probe light can be completely separated from noises, thereby extending the measurement range while maintaining the spatial resolution &#x394;z high.

Optical-fiber-characteristic measuring apparatus and optical-fiber-characteristic measuring method

A light source produces laser beams that are subjected to frequency modulation whose frequency can be adequately set or varied. A light modulator modulates laser beams with respect to the center wavelength, so that the lower sideband is used as probe light input into one end of the measured optical fiber. A pulse modulator produces laser pulses based on laser beams as pump light, which is input into the other end of the measured optical fiber, along which correlation peaks emerge at different positions. The output light is extracted from the other end of the measured optical fiber and is supplied to a timing adjuster, which adjusts a transmission timing to allow transmission of light proximate to a measuring point in the measured optical fiber therethrough. Thus, it is possible to reliably measure characteristics of the measured optical fiber entirely over the relatively long distance with high spatial resolutions.

Apparatus and method for measuring characteristics of optical fibers

An optical fiber coil in a fiber optic gyro is formed by a single mode optical fiber and two polarization retaining optical fibers of the same length connected respectively to both ends of the single mode optical fiber. The polarization retaining optical fibers and an optical fiber coupler are connected, and clockwise and counterclockwise light beams are distributed and supplied by the optical fiber coupler to the optical fiber coil, and the two light beams having returned to the optical fiber coupler are thereby caused to interfere with each other. The lengths of the X-axis and Y-axis components of light are displaced apart in phase to such an extent as not to interfere with each other, by the birefringent property induced in the coil of the single optical fiber and the birefringent property of the polarization retaining optical fibers themselves.

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Tokyo, Japan

Kazuo Hotate