Nippon Telegraph and Telephone Corporation

Fumihiko Ito

Keiji Okamoto

Yusuke Koshikiya

Xinyu Fan

Hiroshi Takahashi

Kenichi Kitayama

A test pulse is generated from a first and a second test light beam pulse with different wavelengths, with a predetermined time difference applied between the first and the second test light beam pulse. A circulator inputs the test pulse to a trunk fiber of a measurement target fiber line. A reflected light is extracted which is output from an input end of the trunk fiber. A filter extracts stimulated Brillouin backscattered light. A receiver receives and converts the scattered light into an electrical signal. A processing device carries out the signal to determine in which of N branched fibers the stimulated Brillouin scattered light is generated, while varying a time difference between the first and the second test pulse.

Optical fiber line characteristic analysis apparatus and analysis method thereof

Light to be measured L and sampling pulse light Lare each split into M beams, and a time delay of 0, T, 2T, . . . , (M&#x2212;1)T is given to each of the M-split sampling pulse light beams. The M-split light beams to be measured are then respectively multiplexed with M optical 90-degree hybrids, and M electrical field amplitudes per time T are determined for the light beam to be measured, based on M sets of output currents received at a balance light receiving element that receives light emitted from each of the optical 90-degree hybrids. The amplitudes of the respective wavelength optical signals contained in the light beam to be measured are calculated through Fourier transformations of the field electrical amplitudes. Pulsed light with a spectral width that covers the total frequency bandwidth of the light to be measured is used as the sampling pulse light. Where the total frequency bandwidth of the light to be measured is &#x394;f, and the frequency interval of the optical signals contained in the light to be measured is &#x394;f, T&#x2266;1/&#x394;fand 1/(MT)&#x2266;&#x394;f are set.

Wavelength-multiplexed optical signal measurement device and the method thereof

An object of the invention is to provide an optical reflectometry and an optical reflectometer, in which accurate measurement can be performed irrespective of a measurement distance. In the optical reflectometry and optical reflectometer according to the invention, in which a distribution of backscattered light intensity from a measurement target in an optical propagation direction is measured using Optical Frequency Domain Reflectometry (OFDR), a coherence monitor unitthat monitors a coherence property of a frequency sweep light sourceis provided, and measurement result of a measuring unitis corrected based on the monitor result of the coherence monitor unit

Optical reflectometry and optical reflectometer

The invention is to provide a wavelength dispersion measuring method for an optical fiber capable of measuring a wavelength dispersion in a section extending from an incident end of the optical fiber to an arbitrary point along the way by using a scattering phenomenon in which a scattering coefficient at a local point on the optical fiber is independent of time. Incident light having a known spectral density function S(&#x3c9;) is caused to be incident on the optical waveguide, and a wavelength dispersion of the section extending from the incident end of the optical waveguide to the arbitrary point along the way by a correlational function between a signal being proportional to a scattered light amplitude generated at a first halfway point and a signal being proportional to a scattered light amplitude generated at a second halfway point.

Method, apparatus, and program for measuring wavelength dispersion of optical waveguide

The optical sampling system performs by detecting the interference effect which is a linear correlation between the signal lights and the optical pulses, so that both the signal lights and the optical pulses can have relatively low intensities, and the reception sensitivity is high. Also, the pulse width of the optical pulses and the amount of delay given to the optical pulses are the only factors that limit the time resolution, so that it is possible to provide the optical sampling system with excellent time resolution and power consumption properties, and it is possible for the optical sampling system to monitor not only the intensity of the signal lights but also the frequency modulation component as well.

Optical sampling system for simultaneously monitoring intensity modulation and frequency modulation

An optical receiver for receiving tile optical signals with high speed modulation at a high sensitivity. In this optical receiver, a local beam synchronized with a carrier of the optical signal is generated, and multi-frequency local beam components obtained from the local beam are spatially resolved to obtain spatially resolved beams with mutually different frequencies. Then, the optical signal and the obtained spatially resolved beams are entered into the photo-detector element array simultaneously to obtain an interference fringe pattern. The received optical signal is then reconstructed by Fourier analyzing the interference fringe pattern obtained by the photo-detector element array.

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Tsukuba, Japan

Fumihiko Ito