Predistorter for high frequency optical communications devices

A signal distorting circuit for providing a pre-distorted signal to an output device, and comprising:

• an input terminal;
• a first filter that alters both phase and amplitude in a frequency dependent manner and is connected to the input terminal and having an output terminal;
• a linearizer circuit connected to the output terminal of the first filter and having an output terminal;
• and
• a second filter connected to the output terminal of the linearizer circuit, and having an output terminal.

A method of predistorting a signal to be transmitted by an output device, comprising the steps of:

• splitting the signal into first and second parts;
• transmitting the first part to a combiner;
• filtering the second part, altering both phase and amplitude of the second part in a frequency dependent manner;
• distorting the filtered part;
• then, again filtering the filtered part;
• and
• then, combining the filtered part with the first part at the combiner.

A method of fabricating a predistorter circuit for providing a signal to a transmission device, comprising the steps of:

• measuring nonlinear properties of the transmission device;
• connecting a first filter, a linearizer, and a second filter in that order and in series wherein the first filter alters both the phase and amplitude of a signal input to the first filter in a frequency dependent manner;
• and
• setting the first and second filter to produce a linear signal output from the transmission device from the signal passed through the first and second filters and the linearizer wherein the step of setting comprises setting both a phase and amplitude effect of the first and second filters relative to frequency.

A method of predistorting a signal, comprising the steps of:

• filtering the signal in both phase and amplitude in a frequency dependent manner;
• distorting the filtered signal;
• and
• again filtering the distorted signal.