Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1994-11-17
1996-07-23
Boudreau, Leo
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359161, 359189, H04B 1008
Patent
active
055395570
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for receiving a repeater supervisory signal which is transmitted while being superimposed on a main optical signal in an optical amplifier repeater system.
BACKGROUND OF THE INVENTION
To transmit an optical repeater supervisory signal in an optical amplifier repeater system to the end office side, there have been proposed the following systems which superimpose the supervisory signal on the main optical signal to such an extent as not to affect the main signal.
(1) System which superimposes the supervisory signal on the envelope of the main optical signal with a low modulation depth. (For example, Japanese Pat. Laid-Open No. 119328/90, "Optical Repeater Supervisory Control System")
(2) System which superimposes the supervisory signal on the main optical signal, using an optical signal of a wavelength different from that of the main optical signal.
The repeater supervisory signal is superimposed on the main optical signal and the both signals are received simultaneously; when the supervisory signal is received at the end office, the main signal is also received. Consequently, the signal spectrum of the supervisory signal after photoelectric conversion overlaps the power spectrum of the main signal, and since the supervisory signal is superimposed on the main signal at such an extremely low level as not to exert any influence on the main signal, the main signal component becomes noise when the supervisory signal is received; hence, it is difficult to receive the supervisory signal with a sufficient signal power vs. noise power ratio (SNR).
The inventors of this application has proposed a solution to this problem in Japanese Pat. Appln. No. 337902/92, entitled "Supervisory Signal Receiving Method and Apparatus." However, the method and apparatus proposed in the prior application are defective in that the function of keeping the main signal component at minimum at all times is somewhat poor.
An object of the present invention is to provide a supervisory signal receiving method and apparatus which ensure stable and reliable supervision of repeaters by receiving the repeater supervisory signal with a higher SN ratio in the optical amplifier repeater system.
DISCLOSURE OF THE INVENTION
To solve the above problem, according to the present invention, the received repeater supervisory signal, superimposed on or combined by wavelength multiplexing with the main optical signal of the optical amplifier repeater system, is subjected to a photoelectric conversion and then branched into two electric signals, the one of which is subjected to equalizing amplification, timing extraction and discrimination and regeneration to extract only the main signal component. The thus extracted main signal component and the main signal contained in the other electric signal which is not discriminated nor regenerated are respectively subjected to required equalization, delay adjustment and amplitude adjustment so that their waveforms, phases and amplitudes match with each other. In addition, the amplitude adjustment of the main signal is automatically controlled. By differentially combining these signals to remove only the main signal component in a manner to minimize its residual value, thereby extracting the supervisory signal desired to obtain.
Thus, according to the present invention, the received optical signal having the supervisory signal superimposed on the main optical signal is differentially combined with the main optical signal component to effectively remove the main optical signal component from the received optical signal, thereby extracting the supervisory signal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the supervisory signal receiving apparatus according to a first embodiment of the present invention;
FIG. 2 is a timing chart showing variations of signals at respective parts of the supervisory signal receiving apparatus of the present invention which are caused by intensity variations of the optical input signal there
REFERENCES:
patent: 5293260 (1994-03-01), Kikawa et al.
patent: 5383046 (1995-01-01), Tomofuji et al.
Akiba Shigeyuki
Horiuchi Yukio
Wakabayashi Hiroharu
Yamamoto Shu
Boudreau Leo
Kokusai Denshin Denwa Kabushiki Kaisha
Lobato Emmanuel J.
Negash Kinfe-Michael
LandOfFree
Supervisory signal receiving method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Supervisory signal receiving method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Supervisory signal receiving method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-717652