JP2001069081A - Wavelength division multiplexed optical fiber communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength division multiplexed optical fiber communication system where wavelength multiplex processing is attained with an optional wavelength for a wavelength band of 1.3-1.6 μm so as to attain high speed transmission. SOLUTION: An SM fiber (ISMF) with zero dispersion wevelength around 1.3 μm, a dispersion shift fiber (2DSF) with zero dispersion wavelength around 1.6 μm, and a dispersion compensation fiber (3DCF) with non-zero dispersion at a desired wavelength are connected in a way that the total dispersion is nullified to attain high speed transmission at an optical wavelength for a wavelength band of 1.3-1.6 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion-compensated wavelength division multiplexing (WDM) optical fiber communication system.

[0002]

2. Description of the Related Art It is important to construct a multi-channel WDM optical fiber communication system that the chromatic dispersion of the entire system is made zero at a predetermined wavelength, instead of making the local dispersion of the system zero. That is. U.S. Patent Nos. 5,448,674 and 5,361,319,
In order to use the dispersion of a normal step index type multi-mode fiber (hereinafter, referred to as SM fiber) having zero dispersion in the 1.3 μm band in the 1.55 μm band, a dispersion compensating fiber (DCF) is provided in the transmission path. Discloses a compensated system. Also, JP-A-10-2
No. 21562 discloses a code (+,
It discloses that fibers having different dispersions are connected to make the total dispersion zero, and that the dispersion slope is compensated to make the dispersion substantially zero in a target wavelength range.

[0003]

SUMMARY OF THE INVENTION Japanese Patent Laid-Open No. Hei 10-2215
No. 62 compensates for dispersion and dispersion slope in the 1.3 μm band and 1.55 μm band by applying amplification technology in each wavelength, but for all wavelengths in the 1.3 to 1.6 μm band. Not compensated. In recent years, progress in optical amplification technology has been remarkable, and it has become possible to perform amplification in a 1.3 to 1.6 μm band. Therefore, the present invention provides a method of 1.3 to 1.6 μm.
It is an object of the present invention to provide a wavelength division multiplexing optical fiber communication system capable of wavelength multiplexing at an arbitrary wavelength in a band and enabling high speed transmission.

[0004]

SUMMARY OF THE INVENTION A wavelength division multiplexing optical fiber communication system according to the present invention comprises an SM fiber having a zero dispersion wavelength near 1.3 .mu.m and a dispersion shift fiber having a zero dispersion wavelength near 1.6 .mu.m. A dispersion compensating fiber whose dispersion is not zero at a desired wavelength is connected so that the total dispersion becomes zero, thereby enabling high-speed transmission at an arbitrary wavelength in a 1.3 to 1.6 μm wavelength band. . The polarization mode dispersion value is set to 0.2 PS / km or less.

[0005] The SM fiber and the dispersion shift fiber have a V
It is desirable to use one manufactured by the AD method and having an OH peak loss of 0.3 dB / km or less at a wavelength of 1.39 μm. For long-distance transmission, polarization mode dispersion is important in addition to chromatic dispersion. However, the fiber produced by the VAD method has a polarization mode dispersion value (P
MD) There is a feature that PMD is small. When a core is manufactured by the MCVD method or the OVD method, a process of crushing (collapse) the core is included, so that the core is easily deformed and the PMD
Tends to be large. In addition, in the VAD method, a part of the core and the clad are simultaneously formed, and then dehydration is performed.
There is a feature that the H group remains very little and the loss at 1.39 μm is small, and the use of the 1.39 μm band is also possible.

In the present invention, an input signal is represented by W
The signal is input to the DM coupler and multiplexed.
After demultiplexing a signal using a coupler, dispersion compensation is performed for each wavelength band.

Normal SM having zero dispersion in 1.3 μm band
Since the fiber has a small relative refractive index difference of the core and small scattering (Rayleigh scattering) due to the refractive index fluctuation, the loss is small. Further, there is a feature that the mode field diameter (MFD) is large and is hardly affected by the nonlinear effect. Further, as shown in FIG. 1, the 1.3 μm band to 1.55 μm
Has a positive variance over the obi. Further, the SM fiber is inexpensive due to its simple structure, and its characteristics (loss, dispersion,
The dispersion (dispersion slope, MFD diameter) is also small.

A dispersion-shifted fiber (DSF) having zero dispersion in the 1.6 μm band has a more complicated structure than an SM fiber having zero dispersion in the 1.3 μm band, but as shown in FIG. It has a characteristic that it has a negative dispersion value in the band of 3 μm to 1.6 μm, and that the dispersion slope (curve slope) is almost equal to that of the SM fiber. When the SM fiber and the dispersion-shifted fiber are connected, the dispersion slope is almost uniform, so that the dispersion slope is constant and the total dispersion can be made zero at an arbitrary wavelength. Specifically, this is achieved by adjusting the length of each fiber.

In this system, a low-cost, low-loss S
Since the M-fiber and the dispersion-shifted fiber are connected, it is possible to construct a transmission line with small loss and low cost, and with zero total dispersion at a desired wavelength. Further, if dispersion compensation is performed in a desired wavelength range, it is easy to construct a system capable of WDM transmission. The desired wavelength may be appropriately selected according to the amplification wavelength of the optical amplifier, and even a system having a plurality of wavelength bands can be constructed using a WDM coupler.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the drawings based on the following embodiments, but the present invention is not limited to these.

[0011]

(Embodiment 1) As shown in FIG.
SM fiber (SMF) having zero dispersion wavelength in m band,
A dispersion-shifted fiber (DSF) having a zero-dispersion wavelength was connected to the 1.6 μm band, and a dispersion-compensating fiber (DCF) for reducing the dispersion to zero in a desired wavelength region was connected. The SM fiber and dispersion shift fiber used are V
All are manufactured by the AD method.
Was 0.1 dB / km or less, and the polarization mode dispersion value (PMD) was 0.1 PS / km or less.

Embodiment 2 Using an optical fiber similar to that used in Embodiment 1, an SM fiber (SMF) and a dispersion shift fiber (D) connected as shown in FIG.
Before and after SF), a 1.3 μm / 1.55 μm band WDM coupler was provided. 1.3 μm band optical signal and 1.
The optical signal in the 55 μm band is multiplexed by the front WDM coupler, and the original optical signal is demultiplexed by the rear WDM coupler, and then connected to a dispersion compensating fiber (DCF) to perform dispersion compensation for each wavelength band. Have been. In the optical fiber communication systems of the first and second embodiments, multiplexing and demultiplexing are easy in the entire 1.3 to 1.6 μm band, and high-speed transmission can be easily performed because the polarization mode dispersion is small. .

[0013]

The WDM optical fiber communication system of the present invention has a wide wavelength range from 1.3 μm to 1.6 μm.
Since there was no local zero-dispersion wavelength, light-wave mixing was suppressed, and signal degradation due to polarization dispersion could be prevented. Furthermore, since the total dispersion can be made zero at any wavelength and the loss in the 1.39 μm band is small, 1.
Wavelength multiplexing over the entire band of 3 to 1.6 μm can be easily performed. Since the communication system according to the present invention has small polarization mode dispersion, high-speed transmission can be easily performed. There are good fiber amplifiers in the 1.3 μm and 1.55 μm bands,
After splitting these lights and separately performing dispersion compensation, the light power can be returned to the original light power. Furthermore, since the loss of the optical fiber used is small, the power of the amplifier can be suppressed small, or the interval between the amplifiers can be lengthened, and the loss and dispersion of the optical fiber are small, so that the yield is good and the price of the optical fiber is low. For this reason, this optical fiber communication system can be constructed at low cost.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between wavelength and dispersion of an optical fiber.

FIG. 2 is a diagram showing a connection example of a communication system according to the present invention.

FIG. 3 is a diagram showing an application example of a communication system according to the present invention in a two-wavelength region.

Claims (4)

[Claims] 1. An S having a zero-dispersion wavelength around 1.3 μm.
An M fiber, a dispersion shift fiber having a zero dispersion wavelength near 1.6 μm, and a dispersion compensating fiber having a non-zero dispersion at a desired wavelength are connected so that the total dispersion becomes zero. A wavelength division multiplexing optical fiber communication system that enables high-speed transmission at an arbitrary wavelength in a 6 μm wavelength band. 2. The wavelength division multiplexing optical fiber communication system according to claim 1, wherein the polarization mode dispersion value is 0.2 PS / km or less. 3. The SM fiber and the dispersion-shifted fiber are manufactured by a VAD method, and have a wavelength of 1.39 μm.
The wavelength division multiplexing optical fiber communication system according to claim 1 or 2, wherein an OH peak loss at the time is not more than 0.3 dB / km. 4. An input signal is input to a wavelength division multiplexing coupler and multiplexed.
The wavelength division multiplexing optical fiber communication system according to any one of claims 1 to 3, wherein after M) demultiplexing the signal using a coupler, dispersion compensation is performed for each wavelength band.