Nortel Networks Corporation

Avid E Lemus

James St Harley

Richard A Habel

Gregory Dean May

Marc Veilleux

James St Leger Harley

Marc Gagnon

Gen G Ribakovs

An accurate method for characterizing optical fiber using a modest enhancement to equipment that is already in place for other purposes within an optical transmission system is thereby disclosed. In particular, optical amplifier light sources already embedded in transmission equipment are used to provide accurate characterization information in addition to their conventional purpose. Therefore, the invention permits fiber characterization at little additional cost over the optical amplifier light sources already present in a system. Furthermore, the need of going out to the field, disconnecting the transmission equipment and performing the field measurements with separate test equipment is eliminated.

Out of band fiber characterization using optical amplifier light sources

A method and apparatus for embedding control information in an optical signal transporting optical data, consisting of encoding the control information as a control signal having an amplitude proportional to a controllable modulation depth. The optical signal is then optically modulated in accordance with the amplitude of the control signal. The control signal is subsequently detected and the control information is decoded. A major feature of the invention lies in determining a level of similarity between the encoded and decoded control information and varying the modulation depth according to this level of similarity. Hence, the modulation depth yielding a given bit-error rate (BER) or signal-to-noise ration (SNR) can be minimized, in order to reduce the degradation of the optical channel data. The invention also provides a means for modulating the control information about a carrier frequency, and varying this carrier frequency if the SNR is below a certain tolerance value. This is useful in countering the periodic interference spectrum of framed data signals, which may be unknown or time-varying. Furthermore, the bit rate of the control signal can be adjusted to carry a required amount of information, so as to meet the system's evolving control requirements.

Robust variable-bit-rate optical channel overhead

In WDM systems, each wavelength travels over a different optical paths, thus having different reflections within the path. This method for detecting reflections in bidirectional multichannel communication systems uses a unique signature attached to each signal. This allows to isolate reflections within each optical path, by measuring the optical power of a signal and of the reflection, by measuring the power of the signal and the power of the reflection. The location of the reflection is determined by calculating the relative delay between the signal and the respective reflection.

Wavelength specific optical reflection meter/locator in signatured

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Ottawa, Canada

Avid E Lemus