System and method for polarization multiplexed optical communications
A transmitter modulates a first polarization signal at a wavelength with a first data signal using intensity modulation. The transmitter modulates a second polarization signal at the same wavelength with a second data signal using intensity modulation. The transmitter combines the modulated, polarization signals and generates an output signal. A receiver includes a photodetector that receives the output signal and generates an electrical output signal including components of both modulated, polarization signals. A signal processing circuit implements correlation techniques or matching filters to recover the first and second data signal from the electrical output signal.
1. An apparatus comprising an optical receiver, the optical receiver comprising:
a photodetector configured to output a single electrical signal by direct detection of an optical input signal received in the optical receiver; and
an electrical processor circuit connected to produce from the single electrical signal first data signals and second data signals in response to the optical input signal including a first polarized signal modulated with the first data signals and a second polarized signal modulated with the second data signals; and
wherein the first and second polarized signals are in a same wavelength channel and are independently modulated with data.
2. The apparatus of claim 1 , wherein the electrical processor circuit comprises:
an electrical splitter configured to split the single electrical signal into first and second portions; and
a first correlation circuit configured to filter the first portion of the single electrical signal using a first base signal to generate the first data signal.
3. The apparatus of claim 2 , wherein the electrical processor circuit comprises a second correlation circuit configured to filter the second portion of the single electrical signal using a second base signal to generate the second data signal.
4. The apparatus of claim 1 , wherein the photodetector is polarization insensitive such that the single electrical signal includes components from a plurality of polarization states of the optical input signal.
5. An apparatus comprising an optical receiver, the optical receiver comprising:
a photodetector configured to output a single electrical signal by direct detection of an optical input signal received in the optical receiver; and
an electrical processor circuit that comprises:
a first circuit connected to filter the single electrical signal using correlation techniques and a first base signal to obtain first data signals in response to the optical input signal including a first polarized signal modulated with the first data signals; and
a second circuit connected to filter the single electrical signal using correlation techniques and a second base signal to obtain second data signals in response to the optical input signal including a second polarized signal modulated with the second data signals; and
wherein the first and second polarized signals are in a same wavelength channel and are independently modulated with data.
6. The apparatus of claim 5 , wherein, in the optical input signal, a polarization state of the first polarized signal is orthogonal to a polarization state of the second polarized signal.
7. The apparatus of claim 5 , wherein the photodetector is polarization insensitive such that the single electrical signal includes components from a plurality of polarization states of the optical input signal.
8. The apparatus of claim 1 , wherein the electrical processor circuit comprises first and second matched filters for recovering the first data signals and the second data signals based on respective temporally orthogonal base signals.