Polarization-division multiplexing based on power encoding of different polarization channels

A system, comprising:

• a transmitter which includes:
• a laser to produce an optical carrier wave at a carrier wavelength,
• a first polarization element to separate said optical carrier wave into a first carrier wave of a first polarization and a second carrier wave of a second polarization which is different from said first polarization,
• a first optical modulator to modulate said first carrier wave in response to a first control signal representing a first channel of binary data to produce a first modulated wave of first high and low power levels,
• a second optical modulator to modulate said second carrier wave in response to a second control signal representing a second channel of binary data to produce a second modulated wave of second high and low power levels, and
• a second polarization element to combine said first and said second modulated waves to produce a polarization multiplexed wave whose power has possible four distinct power levels to represent said first and said second channels of binary data;
• and
• a receiver to produce two output signals respectively representing said first and second channels of binary data according to a power of said polarization multiplexed wave with respect to said four distinct power levels, without recovering said first and said second polarizations.

A system, comprising:

• a wavelength division multiplexing (“WDM”) transmitter to produce a WDM signal having a plurality of optical signals at different wavelengths, said WDM transmitter including:
• a plurality of polarization division multiplexing (“PDM”) transmitters to respectively produce said optical signals, and
• a multiplexer to combine said optical signals to produce said WDM signal,
• wherein each PDM transmitter is operable to combine first and second optical beams of different polarizations modulated to respectively carry first and second channels of binary data to produce a respective optical signal which has unequal power contributions from said different polarizations to have four possible distinct power levels to represent said first and second channels of binary data;
• and
• a WDM receiver which includes:
• a demultiplexer to receive and separate said WDM signal into a plurality of received optical signals at said different wavelengths;
• and
• a plurality of PDM receivers, respectively corresponding to said PDM transmitters in said WDM transmitter and processing said received optical signals, to recover said first and second channels in each received optical signal,
• wherein each PDM receiver produces two output signals respectively representing said first and second channels of binary data according to a power level of a respective received optical signal with respect to said four distinct power levels, without recovering said different polarizations.

A method, comprising:

• producing two optical waves of a common carrier wavelength which are polarized along two different directions;
• modulating power levels of said two optical waves to respectively carry two different channels of binary data;
• combining said two optical waves to produce a polarization multiplexed wave which is a weighted linear combination of said two optical waves and has four possible distinct power levels to represent information of said two different channels of binary data;
• transmitting said polarization multiplexed wave over an optical transmission medium;
• receiving said polarization multiplexed wave to measure a power level of the received polarization multiplexed wave, without recovering polarization states of said two optical waves;
• and
• comparing said measured power level to said four distinct power levels to retrieve said two different channels of binary data.

A method, comprising:

• producing different optical waves of a common carrier wavelength which are polarized along different directions, wherein power levels of said optical waves are modulated to respectively carry different channels of binary data;
• combining said optical waves to produce a polarization multiplexed wave which is a weighted linear combination of said optical waves and has at least four possible distinct power levels to represent information of said different channels of binary data;
• and
• receiving said polarization multiplexed wave, after transmission through an optical transmission medium, to measure a power level of the received polarization multiplexed wave, without recovering polarization states of said different optical waves prior to said combining, to retrieve said different channels of binary data.