US 6,323,994 B1Granted

WDM system equalization with EDFA optical amplifiers

AssigneeNortel Networks Limited

InventorsJinghui Li, Suet Yuen

Life of this patent

Estimating the term…

Loading patent…

Abstract

An in-line repeater implemented within a Wavelength Division Multiplexed (WDM) optical fiber communication system is shown that includes an attenuator. The communication system includes a WDM multiplexer that transmits a WDM signal including a series of WDM channels, via the in-line repeater, to a demultiplexer that separates the WDM channels into a series of output signals. Within the in-line repeater, the attenuator is coupled between two stages of a single amplifier in order to aid in the power equalization of the WDM channels at the demultiplexer. The addition of the attenuator results in the powers and OSNR of the individual WDM channels becoming closer in value, hence reducing the time and the dynamic range of transmitter power adjustments required for traditional methods to equalize the channels' powers.

Claims21

Dependent claims

An amplifying apparatus comprising:

a first amplifying module comprising a first coupler that is operable to receive a first signal comprising a plurality of first Wavelength Division Multiplexed (WDM) channels from a first optical fiber, a first amplifier having an input coupled to the first coupler, and a second amplifier having an output coupled to the first coupler;
a second amplifying module comprising a second coupler that is operable to receive a second signal comprising a plurality of second WDM channels from a second optical fiber, a third amplifier having an output coupled to the second coupler, and a fourth amplifier having an input coupled to the second coupler;
a first attenuator coupled in series between an output of the first amplifier and an input of the third amplifier;
and
a second attenuator coupled in series between an output of the fourth amplifier and an input of the second amplifier;
whereby the first attenuator adjusts an input signal power to the third amplifier relative to a pump power of the third amplifier to reduce a difference in gain experienced by the first WDM channels;
and
whereby the second attenuator adjusts an input signal power to the second amplifier relative to a pump power of the second amplifier to reduce a difference in gain experienced by the second WDM channels.

5 more elements

A Wavelength Division Multiplexed (WDM) optical fiber communication system comprising:

a multiplexer that is operable to receive a plurality of input signals and to output a signal comprising a plurality WDM channels that correspond to the plurality of input signals;
a demultiplexer that is operable to receive a signal comprising a plurality of WDM channels and to output a plurality of output signals corresponding to the WDM channels;
at least one amplifying apparatus;
a first optical fiber coupled between the multiplexer and the amplifying apparatus;
a second optical fiber coupled between the amplifying apparatus and the demultiplexer;
a signal power detector coupled to each of the output signals to measure a power characteristic corresponding to each the output signals;
and a power adjuster coupled to each of the input signals for adjusting the transmission power of the input signals based upon the corresponding detected power characteristics in order to equalize the power characteristics;
wherein the amplifying apparatus comprises:
a first amplifier having an input coupled to the first optical fiber;
an attenuator coupled to an output of the first amplifier;
and
a second amplifier having an input connected to an output of the attenuator and an output connected to the second optical fiber.

9 more elements

Dependencies are inferred from the claim text.