Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-05-21
2001-07-03
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06256126
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a narrow band wavelength division multiplexed optical communication system (a NB-WDM system, hereinafter), in which the output power of optical amplifier is controlled based on the number of wavelengths of optical signals, and a method of establishing the number of the wavelengths of the same.
BACKGROUND OF THE INVENTION
In the NB-WDM system, a main optical signal and a supervisory optical signal have different signal wavelengths, and are propaged through the same optical fiber. In order to prevent the deterioration of the transmission characteristic of the main signal in a long distance transmission, it is very important that in-line amplifier stations distributed along the optical transmission line are controlled based on a correct information on the number of channels (wavelengths) of the optical signals. Accordingly, the information on the number of the wavelengths (the wavelength number information, hereinafter) of the optical signals is established on the format of the supervisory signal (the SV signal, hereinafter) and transmitted to the respective in-line amplifier stations.
However, if a fault arises in a terminal station or the in-line amplifier station, it is indicates that the wrong wavelength number information is supplied to the down-stream in-line amplifier stations. Accordingly, it is extremely desirable that the NB-WDM system is provided with the function of discriminating whether the wavelength number information is reliable or not.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention provide a NB-WDM system, which prevents deterioration of a transmission characteristic.
It is a further object of the invention to provide a method for establishing a wavelength number of a NB-WDM system, by which deterioration of the transmission characteristic can be prevented.
According to the first feature of the invention, a NB-WDM system comprises;
a terminal station connected with plural cascaded IN-LINE amplifier stations via an optical transmission line,
means allocated in the terminal station for establishing an information on a number of wavelengths of optical signals (a wavelength number information, hereinafter) on a format of a supervisory signal,
means respectively allocated in the terminal station and the IN-LINE amplifier stations for discriminating whether the wavelength number information is reliable or not, and
means respectively allocated in the terminal station and the IN-LINE amplifier stations for transmitting information on results of the discriminations to next down-stream stations.
According to the second feature of the invention, a method for establishing a wavelength number of the NB-WDM system comprises the steps of:
establishing a wavelength number information in a format of a supervisory signal of optical signals in a terminal station,
managing the wavelength number information in an IN-LINE amplifier station, and
detecting occurrence of a failure of the optical signals based on the wavelength number information in the IN-LINE amplifier station.
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“Short Slot Proposal” by Bridger, et al, dated Apr. 22-23, 1997 (Full Service Access Network—Optical Access Network) workgroup.
Japanese Office Action, dated Apr. 18, 2000, with English language translation of Japanese Examiner's comments.
Bello Agustin
McGuireWoods LLP
NEC Corporation
Pascal Leslie
LandOfFree
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