Optical channel regulator and method

Abstract

An optical channel regulator (46) is provided. The optical channel regulator (46) includes a tapped optical coupler (60) receiving an optical line carrying an optical signal. The tapped optical coupler (60) provides substantially all of the optical signal as an output. An electrically variable optical attenuator (64) receives the output of the tapped optical coupler (60) and attenuates the optical signal responsive to a feedback control signal. A second tapped optical coupler (66) receives an output of the attenuator (64). The second coupler (66) provides substantially all of the received optical signal as an output and provides a remaining portion of the optical signal as a tapped output. An optical detector (68) then receives the tapped output and provides an output signal representing the optical signal. A comparator (70) receives the output signal of the optical detector (68) and a reference signal. The comparator (70) compares the output signal and the reference signal and provides the feedback control signal to the attenuator (64) responsive to the comparison. As part of a multi-channel communication system, the regulator is used to adjust the levels of each channel for automatically maintaining channel balance and equalization.

Description

[0001]This application claims priority under 35 U.S.C. 119(e) to Provisional Application No. 60 / 060,526 filed Sep. 30, 1997.<?insert-end id="INS-S-00001" ?>TECHNICAL FIELD OF THE INVENTION[0002]This invention relates in general to optical communication systems, and more particularly to an optical channel regulator and method.BACKGROUND OF THE INVENTION[0003]In multiple channel wavelength division multiplexed (WDM) communication systems, optical amplifiers are used to boost signal powers to provide for longer transmission spans. When using optical amplifiers in such systems, it is important to balance the channels at the input to the amplifiers to assure that the available amplifier output power is shared equally among the channels. If the channels are not balanced across each amplifier input, the weaker signals reduce the transmission span distance.[0004]Another problem faced is that optical amplifiers used in multiple channel wavelength division multiplexed communication syst...

AI Technical Summary

Benefits of technology

[0007]The present invention provides an optical channel regulator method that substantially eliminates or reduces disadvantages and problems associated with previously developed optical channel regulation schemes.

[0009]The present invention provides an important technical advantage by eliminating the need for manual measurement and selection of fixed attenuators required for balancing the channels.

[0010]The present invention provides another technical advantage by solving the problem of balancing the power levels at bi-directional line amplifiers using a single amplifier.

Problems solved by technology

Another problem faced is that optical amplifiers used in multiple channel wavelength division multiplexed communication systems often do not have uniform gain across all of the optical channels.

This creates some channel imbalance.

In other systems where optical amplifiers are used as repeaters, the cascade of the amplifiers results in signal inequalities even when they are well balanced at the head end.

Other problems relate to the configuration of a bi-directional line amplifier (BDLA) which uses a single amplifier.

Further, significant power level imbalances between channels at the end of a cascade of amplifiers may require attenuation of the strong channels to keep the signal level to the receiver at an acceptable level.

However, the selection or the adjustment of the attenuators requires manual measurement of each optical channel, since the source transmitter power level for each channel varies and is not precisely known beforehand.

Furthermore, when the source transmit power changes, due to aging or module replacement, the attenuator adjustment process has to be repeated.

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