  Data centers, the engines of the global Internet, are supported by massive
high-speed optical interconnects. In optical fiber communication, the classic
direct detection obtains only the intensity of the optical field, while the
coherent detection counterpart utilizes both phase and polarization diversities
at the expense of beating with a narrow-linewidth and high-stable local
oscillator (LO). Herein, we propose and demonstrate a four-dimensional Jones
space optical field recovery (4-D JSFR) scheme without LO. The information
encoded on the intensity and phase of both polarizations can be captured by the
polarization-diversity full-field receiver structure and subsequently extracted
through deep neural network-aided field recovery. It achieves similar
electrical spectral efficiency as standard intradyne coherent detection. The
fully recovered optical field can extend the transmission distance beyond the
power fading limitation induced by fiber chromatic dispersion. Furthermore, the
LO-free advantage makes 4-D JSFR suitable for monolithic photonic integration,
offering a spectrally efficient and cost-effective candidate for large-scale
data center applications. Our results could motivate a fundamental paradigm
shift in the optical field recovery theory and future optical transceiver
design.
