Dispersion compensating fiber and optical transmission system including the same

Inactive Publication Date: 2003-04-22
SUMITOMO ELECTRIC IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

A dispersion compensating optical fiber according to the present invention is optically connected to the conventional optical fiber (an optical transmission line being a compensated object), so as to compose an optical transmission system. It is, therefore, an object of the present invention to provide a dispersion compensating fiber enabling the long-distance and high-bit-rate optical communication by optically connecting the dispersion compensating fiber according to the present invention to the conventional optical fiber transmission line in respectively appropriate lengths, thereby improving the overall chromatic dispersion and dispersion slope of the optical transmission line in the 1.55 .mu.m wavelength band (i.e., making absolute values of chromatic dispersion and dispersion slope closer to zero), and to provide an optical transmission system comprising it.
Further, the dispersion compensating fiber according to the present invention preferably has such characteristics for the 1.55 .mu.m band light that the chromatic dispersion thereof is not less than -20 ps / km / nm and not more than -5 ps / km / nm and that the dispersion slope thereof is not less than -0.4 ps / km / nm.sup.2 and not more than -0.13 ps / km / nm.sup.2. This setting of chromatic dispersion and dispersion slope allows the whole of the optical transmission system including the dispersion compensating fiber (and including the dispersion shifted fiber the zero-dispersion wavelength of which is set in the wavelength range of 1450 to 1650 nm, preferably in the range of 1450 to 1550 nm) to be compensated more suitably (which means that the absolute values of chromatic dispersion and dispersion slope of the whole can be made closer to zero).
Further, the dispersion compensating fiber according to the present invention, together with another optical fiber (compensated object) optically connected to the dispersion compensating fiber and forming a part of the optical transmission line, constitutes an optical transmission system (see FIG. 1). The optical transmission system including the dispersion compensating fiber preferably has the dispersion slope not less than -0.02 ps / km / nm.sup.2 and not more than 0.05 ps / km / nm.sup.2 for the 1.5 .mu.m-band light. Such an optical transmission system permits long-distance and high-bit-rate optical transmission and particularly, in realizing the optical communication utilizing multi-wavelength light by the WDM method, it permits much longer-distance and higher-bit-rate optical communication.
In addition, the optical transmission system comprising the dispersion compensating fiber and the dispersion shifted fiber as a compensated object as described above may further comprise an optical fiber amplifier forming a part of the optical transmission line. This optical fiber amplifier comprises at least an optical fiber for amplification a core region of which is doped with the erbium element, an excitation light source for outputting exciting light for exciting the erbium element in the optical fiber, to the optical fiber, and an optical coupler for optically coupling the excitation light source with the optical fiber. Since the length of the optical fiber for amplification inserted in this optical transmission system is far shorter than the length of the dispersion shifted fiber or the whole optical transmission line including the dispersion shifted fiber, contribution thereof to the chromatic dispersion and dispersion slope to be compensated for as the whole of optical transmission line is negligible.
Accordingly, the optical transmission system comprising the dispersion compensating fiber the core region of which is doped with the erbium element comprises the dispersion compensating fiber according to the present invention, another optical fiber (compensated object) optically connected to the dispersion compensating fiber and forming a part of the optical transmission line, an excitation light source for outputting exciting light for exciting the erbium element in the dispersion compensating fiber, to the dispersion compensating fiber, and an optical coupler for optically coupling the excitation light source with the dispersion compensating fiber. According to this configuration, the optical transmission system comprising the dispersion compensating fiber, as the whole of optical transmission line, has the dispersion slope not less than -0.02 ps / km / nm.sup.2 and not more than 0.05 ps / km / nm.sup.2 for the 1.5 .mu.m-band light. The optical transmission system of this type enables longer-distance, higher-bit-rate, and low-loss optical communication.

Problems solved by technology

This would be a problem in the case of communication by the wavelength division multiplexing (WDM) system for multiplexing signal light components of mutually different wavelengths in order to further raise the transmission speed to higher rates.
However, the dispersion=flattened fibers need to be fabricated with extremely precise control of the size, such as the core diameter, and the refractive index profile and are hard to fabricate, thus not coming to the stage of practical application yet.

Method used

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  • Dispersion compensating fiber and optical transmission system including the same
  • Dispersion compensating fiber and optical transmission system including the same
  • Dispersion compensating fiber and optical transmission system including the same

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first embodiment

(First Embodiment)

.[.FIG. 4 is a drawing.]. .Iadd.FIG. 4 and FIG. 4A are drawings .Iaddend.to show the cross-sectional structure and index profile of the first embodiment (having the double cladding structure) of the dispersion compensating fiber according to the present invention.

As shown in this FIG. 4, the dispersion compensating fiber 100a (first embodiment) having the double cladding structure is a single-mode optical fiber the main ingredient of which is silica glass, which has a core region 110 having predetermined refractive indices, an inside cladding region 111 being a glass region provided on the periphery of the core region 110 and having a lower refractive index than the core region 110, and an outside cladding region 112 provided on the periphery of the inside cladding region 111 and having a higher refractive index than the inside cladding region 111 and a lower refractive index than the core region 110.

A ratio Ra (=2a / 2b) of the outer diameter 2a of the core region 1...

second embodiment

(Second Embodiment)

.[.FIG. 5 is a drawing.]. .Iadd.FIG. 5 and FIG. 5A are drawings .Iaddend.to show the cross-sectional structure and index profile of the second embodiment (having the triple cladding structure) of the dispersion compensating fiber according to the present invention.

As shown in this FIG. 5, the dispersion compensating fiber 100b (the second embodiment) having the triple cladding structure is a single-mode optical fiber the main ingredient of which is silica glass, which comprises a core region 120 having predetermined refractive indices, an inside cladding region 121 being a glass region provided on the periphery of the core region 120 and having a lower refractive index than the core region 120, an intermediate cladding region 122 provided on the periphery of the inside cladding region 121 and having a higher refractive index than the inside cladding region 121 and a lower refractive index than the core region 120, and an outside cladding region 123 provided on the...

third embodiment

(Third Embodiment)

.[.FIG. 6 is a drawing.]. .Iadd.FIG. 6 and FIG. 6A are drawings .Iaddend.to show the cross-sectional structure and index profile of the third embodiment (having the triple cladding structure) of the dispersion compensating fiber according to the present invention. This third embodiment is different from the second embodiment described above in that the radial index profile of the intermediate cladding region is of the graded-index type (whereas the radial index profile of the intermediate cladding region in the second embodiment was of the step-index type).

As shown in this FIG. 6, the dispersion compensating fiber 100c (the third embodiment) having the triple cladding structure is a single-mode optical fiber the mean ingredient of which is silica glass, which has the structure similar to that of the second embodiment described above. The dispersion compensating fiber 100c has a core region 130 having predetermined refractive indices, an inside cladding region 131 b...

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Abstract

The present invention relates to a dispersion compensating fiber for improving a transmission system with it in total chromatic dispersion and dispersion slope in the 1.55 mum wavelength band. The dispersion compensating fiber according to the present invention is characterized by having the following characteristics for light in the 1.55 mum wavelength band: chromatic dispersion not less than -40 ps / km / nm and not more than 0 ps / km / nm; dispersion slope not less than -0.5 ps / km / nm2 and not more than -0.1 ps / km / nm2; transmission loss not more than 0.5 dB / km; polarization mode dispersion not more than 0.7 ps.km-½; mode field diameter not less than 4.5 mum and not more than 6.5 mum; cut-off wavelength not less than 0.7 mum and not more than 1.7 mum in the length of 2 m; and bending loss at the diameter of 20 mm, not more than 100 dB / m. The dispersion compensating fiber is optically connected with a dispersion shifted fiber as a compensated object at a ratio of appropriate lengths, which can improve the system including the dispersion compensating fiber in the total chromatic dispersion and dispersion slope of the system in the 1.55 mum band.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a dispersion compensating fiber and an optical transmission system including the same, which are applied to an optical fiber transmission network capable of long-distance and high-bit-rate optical communication utilizing the 1.55 .mu.m-band wavelength-multiplexing signal light.2. Related Background ArtFrom social needs based on the coming of advanced information society, research and development has been conducted vividly heretofore as to high-bit-rate high-speed communication such as video communication and long-distance communication such as international communication utilizing the optical fiber transmission network.In the case of the optical fiber transmission network to realize such long-distance and high-bit-rate optical communication, first, its transmission lines need to be optical fibers that permit only single-mode propagation. It is because mode dispersion (represented by dispersion due t...

Claims

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Application Information

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IPC IPC(8): C03B37/014G02B6/34H01S3/067H01S3/30
CPCC03B37/014C03B2203/22C03B2203/36G02B6/02004G02B6/02261G02B6/0228G02B6/02285G02B6/0281G02B6/0283G02B6/0286G02B6/03611G02B6/03627G02B6/03644G02B6/29377H01S3/06729H01S3/302
InventorONISHI, MASASHIKANAMORI, HIROONISHIMURA, MASAYUKIKASHIWADA, TOMONORIKOYANO, YASUSHI
OwnerSUMITOMO ELECTRIC IND LTD