Electro-optic modulator with improved harmonic performance

An electro-optic modulator comprising:

• a 1:N splitting section, for splitting a received optical signal into N sub-signals, N greater than or equal to 3, wherein the 1:N splitting section includes an adjustable splitter;
• N transmission legs, each leg coupled to receive one of the N sub-signals from the 1:N splitting section;
• an RF phase-shifig section for phase shifting at least two of the sub-signals in the N transmission legs by an amount proportional to a received RF signal;
• a DC phase-shifting section for phase shifting at least two of the sub-signals in the N transmission legs by a DC phase relative to a reference one of the transmission legs;
• and
• an N:1 combining section coupled to received the RF phase-shifted and DC phase-shifted sub-signals from the N transmission legs for combining said sub-signals into a modulated optical signal.

A modulator system comprising:

• an optical source for producing an optical signal;
• an electro-optic modulator coupled to the optical source for modulating the optical signal, said electro-optic modulator including:
• a 1:N splitting section, for splitting the optical signal into N sub-signals, N greater than or equal to 3;
• N transmission legs, each leg coupled to receive one of the N sub-signals from the 1:N splitting section;
• an RF phase-shifting section for phase shifting at least two of the sub-signals in the N transmission legs by an amount proportional to a received RF signal;
• a DC phase-shifting section for phase shifting at least two of the sub-signals in the N transmission legs by a DC phase relative to a reference one of the transmission legs;
• and
• an N:1 combining section coupled to received the RF phase-shifted and DC phase-shifted sub-signals from the N transmission legs for combining said sub-signals into a modulated optical signal;
• and
• linewidth broadening means for broadening a linewidth of the optical signal.

A modulator system comprising:

• an electro-optic modulator, said electro-optic modulator including:
• a 1:N splitting section, for splitting a received optical signal into N sub-signals, N greater than or equal to 3;
• N transmission legs, each coupled to receive one of the N sub-signals from the 1:N splitting section, at least two of the transmission legs including electro-optic material;
• exactly one RF electrode for receiving an RF signal to create RF electric fields in the electro-optic material of at least two of the transmission legs, whereby the sub-signal in said transmission legs are phase shifted by an amount proportional to said RF signal;
• and
• an N:1 combining section coupled to received the RF phase-shifted sub-signals from the N transmission legs for combining said sub-signals into a modulated optical signal.

A method for modulating an optical signal comprising:

• receiving an optical signal;
• splitting the received optical signal into exactly three sub-signals;
• phase shifting each of at least two of the three sub-signals by an amount proportional to a received RF signal;
• phase shifting each of at least two of the three sub-signals by a DC phase relative to the third sub-signal;
• and
• combining the RF phase-shifted and DC phase-shifted sub-signals into a modulated optical signal.

A method for modulating an optical signal comprising:

• receiving an optical signal;
• adiustably splitting the received optical signal into N sub-signals, N greater than or equal to 3;
• phase shifting at least two of the sub-signals by an amount proportional to a received RF signal;
• phase shifting at least two of the sub-signals by a DC phase relative to a reference sub-signal;
• and
• combining the RF phase-shifted and DC phase-shifted sub-signals into a modulated optical signal.

A method for modulating an optical signal comprising:

• receiving an optical signal;
• splitting the received optical signal into N sub-signals, N greater than or equal to 3;
• broadening a hnewidth of the received optical signal and/or one of the sub-signals;
• phase shifting at least two of the sub-signals by an amount proportional to a received RF signal;
• phase shifting at least two of the sub-signals by a DC phase relative to a reference sub-signal;
• and
• combining the RF phase-shifted and DC phase-shifted sub-signals into a modulated optical signal.

A method for designing an electro-optic modulator, wherein the modulator includes a 1:N splitting section for splitting a received optical signal into N sub-signals, N greater than or equal to 3;

• N transmission legs, each leg coupled to receive one of the N sub-signals from the 1:N splitting section;
• an RF phase-shifting section for phase shifting at least two of the sub-signals by an amount proportional to a received RF signal;
• a DC phase-shifting section for phase shifting at least two of the subsignals by a DC phase relative to a reference one of the sub-signals;
• and an N:1 combining section coupled to received the RF phase-shifted and DC phase-shifted sub-signals for combining said sub-signals into a modulated optical signal;
• the method comprising:
• selecting a desired harmonic performance for an output of a system including the electro-optic modulator;
• identifying design parameters for the electro-optic modulator;
• deriving a mathematical expression which expresses the output of the system including the electro-optic modulator as a function of the design parameters;
• series expanding the mathematical expression for the output;
• applying the desired harmonic performance to the series expansion;
• and
• solving for the design parameters.

A method for designing an electro-optic modulator comprising:

• identifying a desired harmonic performance for an output of an electro-optic modulator;
• identifing design parameters for the electro-optic modulator;
• determining an output of the electro-optic modulator in terms of the design parameters;
• series expanding the output;
• applying the desired harmonic performance to the series expansion;
• and
• selecting values for the design parameters to maximize a signal strength.