JPH04371931A - Multichannel optical communication system - Google Patents

Abstract

PURPOSE:To amplify light beams of many channels equally by doping an optical waveguide with metal ions of Al<3+>. CONSTITUTION:This optical communication system is equipped with signal light sources 21 and 22 which emit light signals a and b differing in wavelength, a coupler 3 which couples the light signals 'a and b, an isolator 4 which prevents oscillation due to the reflection of the light signals a and b, an exciting light source 5, a multiplexer 6 which couples the light signals with exciting light, and a rare earth doped optical waveguide 1; and the light signal a whose wavelength is nearby a 1.55mum band and the light signal b having different wavelength are amplified by the rare earth doped optical waveguide 1. The rare earth doped optical waveguide 1 is doped with metal ions of Al<3+>, etc., preferably by >=300ppm. Consequently, many channels can easily and equally be amplified.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multichannel optical communication system for transmitting two or more signal lights of different wavelengths, and more particularly to a multichannel optical communication system using a rare earth doped optical waveguide as an amplifier.

0002

2. Description of the Related Art In recent years, research has been actively conducted on optical amplification devices that utilize the optical amplification effect of fluorescent substances such as rare earth elements mixed into silica fibers during optical excitation. As an example of an optical amplifier using a rare earth element-doped optical fiber (fiber-type optical amplifier), one that can amplify light in the 1.55 μm band using an Er-doped quartz optical fiber has been confirmed. Such fiber-type optical amplifiers have high gain and low noise, so they can be applied to various optical communication systems. In particular, it is suitable for application to multi-channel optical communication systems, taking advantage of its wide gain bandwidth and large saturation output.

0003

When a rare earth element-doped optical fiber is used as an optical amplifier in a multi-channel optical communication system, the optical amplifier must be able to uniformly amplify each channel. However, until now, it was not possible to design a system that could evenly amplify each channel because the channel arrangement and optical amplification device selection methods were unknown.

0004

OBJECTS OF THE INVENTION An object of the present invention is to realize a multi-channel optical communication system that can uniformly and easily amplify the light of all channels.

[0005]

[Means for Solving the Problems] A multi-channel optical communication system according to claim 1 of the present invention, as shown in FIG. In this multi-channel optical communication system, the optical waveguide 1 is amplified by a rare earth-doped optical waveguide 1 which operates in a saturated state, and the optical waveguide 1 is co-doped with metal ions such as Al3+. The multi-channel optical communication system according to claim 2 of the present invention is characterized in that the multi-channel optical communication system according to claim 1
It is characterized in that the amount of 3+ added is 300 ppm or more. The multi-channel optical communication system of the present invention may be other than that shown in FIG. 1, and for example, three or more channels of light may be used. In addition to rare-earth doped optical fibers, the optical waveguide 1 may be YAG or YL.
It is also possible to use an optical waveguide in which rare earth elements or transition metal ions are mixed in oxide or fluoride crystals such as F.

[0006]

[Embodiment 1] In FIG. 1 showing an embodiment of the multi-channel optical communication system of the present invention, 21 and 22 are signal light sources that generate signal lights of different wavelengths, and 3 is both signal light sources 21.
, 22 is a coupler that combines the signal lights a and b generated from the signal lights a and b, 4 is an isolator for preventing oscillation due to reflection of the signal lights a and b, 5 is an excitation light source, and 6 is the signal light and the excitation light. 1 is a rare earth doped optical waveguide (optical amplifier). In this embodiment, the two signal light sources 21
, 22 was used for two-channel amplification. In this case, the wavelength of one signal light source 21 was fixed at 1.552 μm (channel 1), and the wavelength of the other signal light source 22 was varied from 1.53 μm to 1.56 μm (channel 2). Signal level is -4.5dB for both channels
It was m. In addition, as the rare earth doped optical waveguide 1, Er
A Ge/Er doped optical fiber with a concentration of 77 ppm and a length of 160 m, an Er concentration of 260 ppm, and an Al concentration of 5
Two types of Ge/Al/Er-doped optical fibers with 000 ppm and a length of 40 m were used. Excitation light source is 1.48μm
The excitation power was approximately 23 mW. The results of this example are shown in FIG. In a Ge/Er doped fiber, the gain of the two channels fluctuates greatly as shown in Figure 4, making it impossible to obtain uniform amplification, but in the present invention, which uses an Al co-doped fiber, both channels have a relatively large gain as shown in Figure 2. Equal amplification was obtained.

[0007]

[Embodiment 2] The configuration of this embodiment is basically the same as that of the first embodiment, and each parameter is also the same as that of the first embodiment. However, here, a fiber with an Al concentration of 300 ppm was used. The results of this example were as shown in FIG. Almost the same results as in Example 1 were obtained.

[0008]

According to the multichannel optical communication system of the present invention, as is clear from the results of the above embodiments (FIGS. 2 and 3), a large number of channels can be easily and evenly amplified.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a multi-channel optical communication system of the present invention.

FIG. 2 is an explanatory diagram of wavelength-gain characteristics of an embodiment of the optical communication system of the present invention.

FIG. 3: Wavelength of another embodiment of the optical communication system of the present invention.
An explanatory diagram of gain characteristics.

FIG. 4 is an explanatory diagram of wavelength-gain characteristics of a conventional optical communication system.

[Explanation of symbols]

1 Rare earth doped optical waveguide 21, 22 Signal light source 3 Coupler 4 Isolator 5 Excitation light source 6 Multiplexer a, b Signal light

Claims (2)

[Claims] [Claim 1] Signal light a whose wavelength is near the 1.55 μm band
In a multi-channel optical communication system in which a rare earth-doped optical waveguide 1 operates in a saturated state and amplifies signal light b having a different wavelength from that of the signal light b, the optical waveguide 1 is co-doped with metal ions such as Al3+. A multi-channel optical communication system characterized by: [Claim 2] The amount of Al3+ added is 300 ppm.
2. The multichannel optical communication system according to claim 1, wherein the multichannel optical communication system is as follows.