Apparatus for externally modulating two optical channels at the same time

A phase modulator for externally modulating two independent optical signals with first and second electrical signals, the modulator comprising:

• a first electrode receiving the first electrical signal;
• a second electrode receiving the second electrical signal;
• a first optical signal path co-propagating the first optical signal with the first electrical signal and counter-propagating the first optical signal with the second electrical signal, to generate a first modulated optical signal corresponding to the first optical signal modulated with the first electrical signal;
• and
• a second optical signal path co-propagating the second optical signal with the second electrical signal and counter-propagating the second optical signal with the first electrical signal, to generate a second modulated optical signal corresponding to the second optical signal modulated with the second electrical signal.

A Mach-Zehnder interferometer-type modulator for externally amplitude modulating first and second optical signals with first and second electrical signals, the modulator comprising:

• a first electrode receiving the first electrical signal;
• a second electrode receiving the second electrical signal;
• a first laser, coupled to a first optical signal path, for generating the first optical signal;
• a second laser, coupled to a second optical signal path, for generating the second optical signal;
• a first optical port receiving the first optical signal;
• a second optical port receiving the second optical signal;
• a first terminating resistor coupled to a second end of the first electrode;
• and
• a second terminating resistor coupled to a second end of the second electrode, wherein the first and second terminating resistors are disposed diagonally to each other.

A Mach-Zehnder interferometer-type modulator for externally amplitude modulating first and second optical signals with first and second electrical signals, respectively, the modulator comprising:

• a first dual electrode having first and second ends, the first end receiving a first electrical signal for propagation in a first direction and the second end receiving a second electrical signal for propagation in a second direction opposite to the first direction;
• a second dual electrode substantially isolated from the first dual electrode and having first and second ends, the first end receiving a third electrical signal for propagation in a third direction and the second end receiving a fourth electrical signal for propagation in a fourth direction opposite to the third direction;
• a first optical signal path for propagating a first optical signal in the first direction and the third direction to modulate the first optical signal with the first electrical signal and the third electrical signal;
• and
• a second optical signal path for propagating a second optical signal in the second direction and the fourth direction to modulate the second optical signal with the second electrical signal and the fourth electrical signal.

A phase modulator for externally modulating first and second optical signals with first and second electrical signals, respectively, the modulator comprising:

• a first dual electrode having first and second ends, the first end receiving a first electrical signal for propagation in a first direction and the second end receiving a second electrical signal for propagation in a second direction opposite to the first direction;
• a second dual electrode substantially isolated from the first dual electrode and having first and second ends, the first end receiving a third electrical signal for propagation in a third direction and the second end receiving a fourth electrical signal for propagation in a fourth direction opposite to the third direction;
• a first optical signal path for propagating a first optical signal in the first direction and the third direction to modulate the first optical signal with the first electrical signal and the third electrical signal;
• and
• a second optical signal path for propagating a second optical signal in the second direction and the fourth direction to modulate the second optical signal with the second electrical signal and the fourth electrical signal.

A wavelength division multiplexed optical transmission system, comprising a Mach-Zehnder interferometer-type modulator for externally modulating two independent optical signals with first and second electrical signals, the modulator including:

• a first electrode receiving the first electrical signal;
• a second electrode receiving the second electrical signal;
• a first optical signal path co-propagating the first optical signal with the first electrical signal and counter-propagating the first optical signal with the second electrical signal, to generate a first modulated optical signal corresponding to the first optical signal modulated with the first electrical signal;
• and
• a second optical signal path co-propagating the second optical signal with the second electrical signal and counter-propagating the second optical signal with the first electrical signal, to generate a second modulated optical signal corresponding to the second optical signal modulated with the second electrical signal.

A wavelength division multiplexed optical transmission system, comprising a phase modulator for externally modulating two independent optical signals with first and second electrical signals, the modulator including:

• a first electrode receiving the first electrical signal;
• a second electrode receiving the second electrical signal;
• a first optical signal path co-propagating the first optical signal with the first electrical signal and counter-propagating the first optical signal with the second electrical signal, to generate a first modulated optical signal corresponding to the first optical signal modulated with the first electrical signal;
• and
• a second optical signal path co-propagating the second optical signal with the second electrical signal and counter-propagating the second optical signal with the first electrical signal, to generate a second modulated optical signal corresponding to the second optical signal modulated with the second electrical signal.