Wavelength division multiplexed optical communication system

Details Wavelength division multiplexed optical communication system Wavelength division multiplexed optical communication system

1998-05-14

2001-08-07

Chan, Jason (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200

Reexamination Certificate

active

06271948

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a wavelength division multiplexed (WDX, hereinafter) optical communication system, and more particularly to a WDM optical communication system which is low in price and small in size to transmit optical signals with high and equalized levels.
BACKGROUND OF THE INVENTION
Recently, a WDM optical communication system, in which plural signals with different wavelengths are multiplexed and transmitted through a single optical transmission line, is being vigorously developed as means for realizing an optical transmission system with high capacity.
In order to extend the transmission distance of the WDM optical communication system, it is important that the transmission levels of the respective optical signals are as high as possible and equal to each other. Accordingly, following methods have been adopted to achieve the aforementioned purpose until now.
The first method is that outputs of plural signal light sources of different wavelengths are multiplexed by a coupler, and the signal light sources are so adjusted that the power levels of the optical signals are equalized at the output port of the coupler.
The second method is that optical variable attenuators are respectively inserted between the signal light sources and the coupler, and the optical variable attenuators are so adjusted that the power levels of the optical signals are equalized at the output port of the coupler.
The third method is that optical fiber amplifiers are respectively inserted between the signal light sources and the coupler, and the gains of the optical fiber amplifiers are so adjusted that the power levels of the optical signals are equalized at the output port of the coupler.
However, in the first and second methods, since the power levels of the optical signals are adjusted based on the minimum power level of them, so that the high transmitting power levels cannot be obtained.
According to the third method, since each of the signal light sources are respectively provided with the optical fiber amplifier, the system is magnified and high-priced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a low-priced and small-sized optical communication system, which transmits optical signals with high and equalized levels, by classifying optical signals into plural groups of plural optical signals.
It is an further object of the invention to provide a low-priced and small-sized optical communication system, which transmits optical signals with high and equalized levels, by classifying optical signals into one or more individual optical signals and one or more groups of plural optical signals.
According to the first feature of the invention, a WDM optical transmission system comprises:
plural signal light sources for respectively generating optical signals with different wavelengths,
wherein the optical signals are classified into plural groups of the plural optical signals,
plural first stage optical couplers for respectively multiplexing the plural groups of the plural optical signals,
plural optical amplifiers for respectively amplifying outputs of the plural first stage optical couplers, and
a second stage optical coupler for multiplexing outputs of the plural optical amplifiers.
According to the second feature of the invention, a WDM optical transmission system comprises;
plural signal light sources for respectively generating optical signals with different wavelengths,
wherein, the optical signals are classified into one or more individual optical signals and one or more groups of optical signals,
one or more first stage optical couplers for respectively multiplexing the one or groups of the optical signals,
plural optical amplifiers for respectively amplifying the one or more individual optical signals and outputs of the one or more first stage optical couplers, and
a second stage optical couplers for multiplexing outputs of the plural optical amplifiers.


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patent: 4-101124 (1992-04-01), None
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Japanese Office Action, dated Apr. 18, 2000, with English language translation of Japanese Examiner's comments.

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