Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
2001-03-08
2003-04-29
Kim, Robert H. (Department: 2882)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
C385S123000, C385S126000
Reexamination Certificate
active
06556758
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber suitable for long-haul transmission of optical signals having wavelengths different from each other, and an optical transmission line including the same.
2. Related Background Art
In an optical communication system using an optical fiber network, long-haul and large capacity optical communication is possible. Particularly, in the recent increase in capacity, a wavelength division multiplexing (WDM) technique which enables transmission of a plurality of optical signals having wavelengths different from each other is used. This optical communication system is constituted by an optical transmitter for outputting optical signals, an optical amplifier for amplifying the optical signals, an optical fiber as an optical transmission line for transmitting the optical signals, an optical receiver for receiving the optical signals, and the like.
Among these structural elements, in the optical amplifier which is indispensable for obtaining a high S/N ratio, a wavelength band (amplification wavelength band) in which optical signals can be amplified is conventionally 1530 to 1565 nm. Thus, the other elements constituting the optical communication system have been designed so that they operate excellently in this amplification wavelength band. For example, an optical transmission line disclosed in D. W. Peckham, et al., “Reduced Dispersion Slope, Non-Zero Dispersion Fiber”, ECOC′ 98, pp. 130-140, 1998 (first document) or U.S. Pat. No. 5,684,909 (second document) is designed so that a deviation of dispersion in this amplification wavelength band, that is, a dispersion slope becomes small.
SUMMARY OF THE INVENTION
The present inventors examined the conventional optical communication system having the above structure, and consequently, found the problems as follows:
That is, as the performance of the optical amplifier is improved, the amplification wavelength band of the optical amplifier is being expanded from the foregoing wavelength band (1530 to 1565 nm) to the wavelength band of 1530 to 1620 nm including a longer wavelength side. This fact is introduced by, for example, M. Kakui, et al., “Optical Amplifications Characteristics around 1.58 &mgr;m of Silica-Based Erbium-Doped Fibers Containing Phosphorous/Alumina as Codopants”, OAA'98, TuC3, pp. 107-110, 1998 (third document). As the amplification wavelength band of the optical amplifier is expanded, it is necessary that other elements are also designed so that they operate excellently in the expanded wavelength band of 1530 to 1620 nm. However, it was impossible to say that in the conventional optical fiber and the optical transmission line including the same, the dispersion slope is sufficiently small in the expanded amplification wavelength band of 1530 to 1620 nm.
For example, let us consider an optical transmission line in which a first optical fiber having a positive dispersion and a positive dispersion slope in the wavelength band of 1530 to 1620 nm and a second optical fiber having a negative dispersion and a positive dispersion slope in the wavelength band of 1530 to 1620 nm are connected to each other at a suitable length ratio. Incidentally, in this optical transmission line, it is assumed that a dispersion in the center wavelength 1575 nm of the wavelength band of 1530 to 1620 nm is 0, and a difference between the maximum value and the minimum value of the dispersion in the wavelength band of 1530 to 1620 nm is &Dgr;D.
FIG. 1
is a graph showing the dispersion of each of the optical transmission line, the first optical fiber, and the second optical fiber, and in
FIG. 1
, a graph G
110
indicates the dispersion of the first optical fiber, a graph G
120
indicates the dispersion of the second optical fiber, and a graph G
130
indicates the dispersion (obtained by the fiber length and dispersion value of each of the first and second optical fibers) of the optical transmission line including the first and second optical fibers.
FIG. 2
is a graph showing the relation between transmission distance and accumulated dispersion with respect to the optical transmission line having the foregoing structure. In
FIG. 2
, G
210
indicates the relation between the transmission distance and the accumulated dispersion value in the case where the difference &Dgr;D is 3.6 ps
m/km, G
220
indicates the relation in the case where the difference &Dgr;D is 2.0 ps
m/km, and G
230
indicates the relation in the case where the difference &Dgr;D is 1.0 ps
m/km. Besides,
FIG. 2
shows a value (arrow A in the drawing) of the accumulated dispersion which becomes a transmission limit when the bit rate of optical signals is 10 Gb/s, and a value (arrow B in the drawing) of the accumulated dispersion which becomes a transmission limit when the bit rate of optical signals is 20 Gb/s.
In the optical transmission line disclosed in the first document, the dispersion slope in the wavelength band of 1530 to 1620 nm is 0.04 ps
m
2
/km, and the difference &Dgr;D between the maximum value and the minimum value of the dispersion in this wavelength band is 3.6 ps
m/km. Thus, in the case of the optical transmission line of the first document, as is understood from
FIG. 2
, the optical signals of a bit rate of 10 Gb/s can be transmitted only over a distance of about 550 km, and the optical signals of a bit rate of 20 Gb/s can be transmitted only over a distance of about 150 km. For reference, when the difference &Dgr;D is 2.0 ps
m/km, the optical signals of a bit rate of 10 Gb/s can be transmitted over a distance of about 1000 km, and the optical signals of a bit rate of 20 Gb/s can be transmitted over a distance of about 250 km. Further, when the difference &Dgr;D is 1.0 ps
m/km, the optical signals of a bit rate of 10 Gb/s can be transmitted over a distance of about 2000 km, and the optical signals of a bit rate of 20 Gb/s can be transmitted over a distance of about 500 km.
The present invention has been made to solve the foregoing problems, and has an object to provide an optical fiber having a structure suitable for long-haul transmission of a plurality of optical signals having wavelengths different from each other in a wavelength band of 1530 to 1620 nm, and an optical transmission line including the same.
An optical transmission line of the present invention is an optical fiber transmission line disposed in at least one of places between an optical transmitter and an optical receiver, between an optical transmitter and an optical repeater including an optical amplifier, between optical repeaters, and between an optical repeater and an optical receiving station.
The optical transmission line of the present invention includes one or more first optical fibers, and one or more second optical fibers. However, the optical transmission line may be constituted by one first optical fiber and one second optical fiber, and in the case where a plurality of first optical fibers and a plurality of second optical fibers are mutually fused and connected, the order of connection of these optical fibers may be arbitrary.
Each of the first optical fibers has a dispersion of +1.0 to +8.0 ps
m/km in a wavelength band of 1530 to 1620 nm, and a difference between the maximum value and the minimum value of the dispersion is 3.0 ps
m/km or less, preferably 2.0 ps
m/km or less. Besides, each of the second optical fibers has a dispersion of −1.0 to −8.0 ps
m/km in the above wavelength band, and a difference between the maximum value and the minimum value of the dispersion is 3.0 ps
m/km or less, preferably 2.0 ps
m/km or less. The optical transmission line is characterized in that in the above wavelength band, an average dispersion value obtained from each fiber length and each dispersion value of the first and second optical fibers is 2.0 ps
m/km or less, preferably 1.0 ps
m/km or less, more preferably 0.5 ps
m/km or less.
Incidentally, in the above structure, it is preferable that the dispersion (average dispersion value) of the whole opt
Caley Michael H
Kim Robert H.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
LandOfFree
Optical fiber and optical transmission line including the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fiber and optical transmission line including the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fiber and optical transmission line including the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076271