System for measuring wavelength dispersion of optical fiber

Details System for measuring wavelength dispersion of optical fiber System for measuring wavelength dispersion of optical fiber

2001-04-23

2003-09-02

Font, Frank G. (Department: 2877)

Optics: measuring and testing

For optical fiber or waveguide inspection

Reexamination Certificate

active

06614512

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a wavelength dispersion measuring system for measuring wavelength dispersion of optical fibers provided in an optical communication path, and more particularly to a wavelength dispersion measuring system including: a wavelength dispersion measuring apparatus for, in a case where an optical fiber to be measured is formed of a plurality of optical fibers connected in series by at least one connecting point, measuring wavelength dispersion values of the respective optical fibers from an end of the optical fiber to be measured; an optical time domain reflectometer (hereinafter referred to as an OTDR) having such a wavelength dispersion measuring function; such an optical wavelength dispersion measuring method; and a storage medium storing such a wavelength dispersion processing program.
BACKGROUND ART
An optical fiber laid in an optical communication path has a wavelength dispersion characteristic; that is, the reflectivity of light traveling through the optical fiber varies depending on the wavelength.
Since the transmission speed of light within an optical fiber is influenced by the wavelength dispersion characteristic, it is necessary to measure the wavelength dispersion characteristic of the optical fiber.
FIG. 11
is a diagram showing a state of measurement of a wavelength dispersion characteristic according to the conventional art.
A transmitter
50
and a receiver
51
are respectively arranged at the ends of an optical fiber F laid in an optical communication path.
An optical fiber F
0
, serving as a reference, is arranged parallel to the optical fiber F to be measured.
The wavelength dispersion characteristic of the optical fiber F is measured by (1) the phase method or (2) the pulse method as will be described below by means of the transmitter
50
and the receiver
51
. (1) The Phase Method
In the phase method, a laser beam of a predetermined wavelength (hundreds of megahertz) is intensity-modulated and transmitted from the transmitter
50
. The wavelength dispersion characteristic is obtained on the basis of a phase difference between the optical fibers F and OF detected by the receiver
51
.
(2) The Pulse Method
In the pulse method, a plurality of pulse beams &lgr;
1
, &lgr;
2
, . . . of different wavelengths are transmitted from the transmitter
50
, and the pulse beams &lgr;
1
, &lgr;
2
, . . . of the respective wavelengths are detected by the receiver
51
. The wavelength dispersion characteristic is obtained on the basis of the detection times of the wavelengths (delay time).
However, in the measurement of the wavelength dispersion characteristic according to the conventional art, since the transmitter
50
and the receiver
51
must be arranged at the respective ends of the optical fiber F, the following problem arises.
A measurement operator must be located at each of the sites of the transmitter
50
and the receiver
51
. In addition, when the measurement is carried out, the measurement operators must establish communications with each other. Thus, the problem is that the measurement is inevitably complicated.
Jpn. Pat. Appln. KOKAI Publication No. 62-207927 and Jpn. Pat. Appln. KOKAI Publication No. 4-285836 disclose a wavelength dispersion measuring apparatus that measures a wavelength dispersion characteristic of an optical fiber from an end of the optical fiber by means of an OTDR.
However, the former wavelength dispersion measuring apparatus is disadvantageous in structure in that a Faraday rotation element (polarization canceling plate) is required as a structural feature.
Further, as regards the former and latter wavelength dispersion measuring apparatuses, in the case where an optical fiber to be measured is formed of a plurality of optical fibers connected in series by at least one connecting point, how to calculate the wavelength dispersion values of the optical fibers and easy calculation thereof are not disclosed.
DISCLOSURE OF INVENTION
The present invention was made to solve the above problem, and has an object to provide a wavelength dispersion measuring apparatus for, in a case where an optical fiber to be measured is formed of a plurality of optical fibers connected in series by at least one connecting point, measuring wavelength dispersion values of the respective optical fibers from an end of the optical fiber to be measured; an OTDR having such a wavelength dispersion measuring function; such an optical wavelength dispersion measuring method; and a storage medium storing such a wavelength dispersion processing program.
According to an embodiment of the present invention, there is provided a wavelength dispersion measuring apparatus comprising:
a light source (
2
) for emitting optical pulses of a plurality of wavelengths;
branching means (
3
) for transmitting the optical pulses emitted from the light source (
2
) to one end of an optical fiber to be measured and extracting reflected lights from the optical fiber to be measured;
light receiving means (
11
) for detecting the reflected lights from the branching means (
3
) and outputting them as measurement data; and
processing means (
8
) for calculating a wavelength dispersion value of the optical fiber to be measured, by detecting a time of emitting the optical pulse of each of the plurality of wavelengths from the light source (
2
) and a time of receiving the reflected light of the wavelength by the light receiving means (
11
),
wherein, in a case where the optical fiber to be measured is formed of a plurality of optical fibers connected in series by at least one connecting point, the processing means calculates wavelength dispersion values of the respective optical fibers by detecting the time of emitting the optical pulse, a time of receiving a reflected light from the connecting point and a time of receiving a reflected light from another end of the optical fiber to be measured.


REFERENCES:
patent: 4551019 (1985-11-01), Vella et al.
patent: 4893006 (1990-01-01), Wakai et al.
patent: 5179420 (1993-01-01), So et al.
patent: 62-207927 (1987-09-01), None
patent: 4-285836 (1992-10-01), None
patent: 8-5515 (1996-01-01), None
patent: 08-334436 (1996-12-01), None
patent: WO 97/46870 (1997-11-01), None

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