Nortel Networks Corporation

Andy Rowland

Franz Li Mok

Simon P Parry

Eric Maniloff

Tom M Luk

Wolfgang W Oberhammer

Gary Mak

Anant Grewal

Sevgui Hadjihassan

Symbol decoding errors at a receiver utilising a flash analog to digital converter (ADC) can be reduced by adjusting a reference voltage level of the ADC where a decoding error rate at the reference voltage level exceeds a threshold.

Flash ADC receiver with reduced errors

Provided by the invention is a fast, continuously variable AGC that can be used to control the gain of an optical amplifier. The AGC is designed around a controller having control coefficients that may be dynamically adjusted according to operating conditions. According to an embodiment of the invention provided is an AGC that can operate at much higher speeds in comparison with prior art AGC designs that have fixed control coefficients, while simultaneously maintaining stability over all operating conditions.

Fast, continuously variable automatic gain control for optical amplifiers

In a method and apparatus for tracking dynamic characteristics of an optical amplifier, optical signal probes are used to determine the gain and the corner frequency of the optical amplifier. A first optical probe having a predetermined modulation frequency above an expected corner frequency of the amplifier is used to estimate the gain of the optical amplifier. A second optical probe signal having a second predetermined modulation frequency at or below the expected corner frequency of the amplifier is used to estimate the corner frequency. These parameters can be used to optimize gain control of an optical amplifier.

Optical amplifier gain control monitoring

A radio transceiver system uses a single variable local oscillator frequency source which is used in mixing both before and after a band-pass filter. This causes a reduction in band-pass filter bandwidths. In an all-band transceiver for PCS for example the effect of this reduced bandwidth requirement is to increase the spacing between the transmit bands and the receive bands and thereby enable a reduction in transmission noise interfering with the reception bands.

Transceiver bandwidth extension using double mixing

A self balancing matrix amplifier is provided in which a plurality of input signals are divided with an input transform matrix, amplified by a number of amplifiers, and recombined with an output transform matrix to form amplified versions of the input signals. One of the inputs is set aside as a monitor input, and this is connected to the characteristic impedance of the system. The output corresponding to this input is monitored for gain imbalances which should be zero if the entire matrix amplifier is perfectly balanced. Then, on the basis of the monitored phase and gain imbalances, attenuators and phase adjusters in series with each of the amplifiers are iteratively controlled so as to insert phase shift or gain/loss so as to reduce the monitored phase and gain imbalances.

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Kanata, Canada

Andy Rowland