OPTICAL RECEIVER FOR QUADRATURE-PHASE-SHIFT-KEYING AND QUADRATURE-DUOBINARY SIGNALS

摘要

We disclose an optical receiver that can receive PDM-QDB and PDM-QPSK signals without hardware changes. In an example embodiment, the optical receiver includes a MIMO equalizer configured to perform electronic polarization de-multiplexing and ISI compensation. The constant modulus algorithm that controls the configuration of the MIMO equalizer also causes the MIMO equalizer to output signal samples corresponding to the QPSK modulation format regardless of whether the received optical signal is QDB-modulated or QPSK-modulated. A QPSK-to-QDB constellation converter processes the signal samples generated by the MIMO equalizer to convert them into the QDB modulation format. A QDB decoder coupled to the constellation converter then recovers the data encoded in the received optical signal by mapping the processed signal samples onto the QDB constellation. Differential encoding used at the corresponding remote transmitter enables the decoder to correctly recover the encoded data both when the received optical signal is QDB-modulated and QPSK-modulated.

主权项

1. An apparatus comprising:
a front-end circuit configured to mix an optical input signal and an optical reference signal to generate a first plurality of electrical digital measures of the optical input signal; and a digital processor configured to
process the first plurality of electrical digital measures in a manner that enables the digital processor to recover data encoded in the optical input signal both for a case that the optical input signal is QPSK-modulated and for a case that the optical input signal is QDB-modulated; wherein the digital processor comprises an equalizer configured to perform equalization processing in a manner that causes equalized signal samples generated by the equalizer to be located substantially on a single constant radius on a complex plane regardless of whether the optical input signal is QPSK-modulated or QDB-modulated; and wherein the digital processor is configured to recover the data using the equalized signal samples.