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US 2003/0190166 A1Published application
Gain tilt compensators and their systems
AssigneeHitachi, Ltd.
InventorKenro Sekine
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AssigneeHitachi, Ltd.
InventorKenro Sekine
Estimating the term…
In the variable gain compensating apparatus, input power of optical amplifiers employed in respective optical repeaters is monitored, and the monitored input power is transferred to a down-stream side by using supervisor (SV) light. In a repeater equipped with a variable gain tilt compensator, input power monitor information of the optical amplifiers employed in the respective repeaters provided on the upper stream side is acquired from a supervisor signal. While utilizing a linear relationship established between a gain tilt of an optical amplifier and input power of the optical amplifier, the acquired input power monitor information is compared with a reference power value so as to calculate gain tilt amounts of the respective optical amplifiers. Then, the optimum gain tilt compensation amount of the variable gain tilt compensator is determined based upon the calculated gain tilt amounts.
In a WDM (wavelength division multiplexing) transmission system constituted by either one or plural sets of optical repeaters and a variable gain tilt compensator, in which said variable gain tilt compensator is installed on the side of a down stream from at least an optical repeater installed on the uppermost stream side among said either one or plural sets of optical repeaters,
In a WDM (wavelength division multiplexing) transmission system constituted by either one or plural sets of optical repeaters and a variable gain tilt compensator, in which said variable gain tilt compensator is installed on the side of a down stream from at least an optical repeater installed on the uppermost stream side among said either one or plural sets of optical repeaters,
In a WDM (wavelength division multiplexing) transmission system constituted by either one or plural sets of optical repeaters and a variable gain tilt compensator, in which said variable gain tilt compensator is installed on the side of a down stream from at least an optical repeater installed on the uppermost stream side among said either one or plural sets of optical repeaters,
Dependencies are inferred from the claim text.
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In a multiwavelength system, e.g. gain equalisation: transient power control, e.g. due to channel add/drop or rapid fluctuations in the input power
Using a supervisory or additional signal: performance monitoring and measurement of transmission parameters
For the reduction or elimination of distortion or dispersion: using spectral equalisation, e.g. spectral filtering
Power control, e.g. to keep the total optical power constant: by gain equalization
Term end not estimated
1. Field of the Invention
The present invention generally relates to a gain tilt compensator capable of compensating gain differences among wavelengths in wavelength division multiplexing (WDM) transmissions, and to a transmission system using the gain tilt compensator. More specifically, the present invention is directed to a control method of a variable type gain tilt compensator and to a transmission system using this variable type gain tilt compensator.
2. Description of the Related Art
FIG. 1 is a diagram for schematically indicating an arrangement of a transmission system according to a first embodiment of the present invention.
FIG. 2 is a graphic representation of an example of an output characteristic of an EDFA.
FIGS. 3(a) and 3(b) schematically indicate the monitors of the conventional gain tilt.
A first embodiment of the present invention will now be described with reference to FIG. 1. That is, a transmission system according to the first embodiment, shown in FIG. 1, is arranged by a repeater 9, an optical fiber 10, and a repeater 17 equipped with a gain tilt compensator.
In the repeater 9, both SV light (supervisor light) and WDM signal light are demultiplexed by a WDM demultiplexer 1 for supervisor signal, this SV light is converted into an electric signal by a photodiode 5 for supervisor light, and then, this electric signal is transferred to a supervisor circuit 7. Signal power of a portion of the WDM signal which has transmitted the WDM demultiplexer 1 for supervisor signal is split by an optical power splitter 2, and the split signal power is converted into an electric signal by a monitor photodiode 6. In other words, information P1 outputted from the monitor photodiode 6 corresponds to a signal which is direct proportional to an input power amount of an optical amplifier 3. The input monitor information P1 is transferred to the supervisor circuit 7. The supervisor circuit 7 adds the input monitor information P1 of the optical amplifier 3 to the information which is transferred from the upstream repeater, namely the output information from the above-described photodiode 5 for supervisor signal so as to form a new supervisor information signal, and sends out a new supervisor signal (supervisor light) from a laser diode 8 for supervisor signal. In a WDM multiplexer 4 for supervisor signal, the supervisor signal is multiplexed with the signal outputted from the optical amplifier 3. The multiplexed signal is outputted from the repeater 9.
Subsequently, in each of the repeaters 9, input monitor information P2, P3, - - - of the optical amplifier 3-are detected by the monitor photodiode 6, this detected input monitor information is superimposed on the supervisor signal, and then the superimposed monitor information signal is sent out to the down-stream repeater 9 in a manner similar to the above-described manner.