RESUMEN
A photonic integrated circuit performing simultaneous mode and wavelength demultiplexing for few-mode-fiber transmission is demonstrated for the first time. The circuit is realized on an InP-based technological platform; it can handle up to eight mode- and wavelength-division-multiplexed (MDM/WDM) channels and allows all-optical multiple-input-multiple-output processing to unscramble mode mixing generated by fiber propagation. A single arrayed waveguide grating is used to demultiplex the WDM channels carried by all the propagating modes, optimizing circuit complexity, chip area, and operational stability. Combined with an integrated wideband mode multiplexer the circuit is successfully exploited for the transmission of 10 Gbit/s on-off-keying non-return-to-zero channels with a residual cross talk of about -15 dB.
RESUMEN
Spatial division multiplexing in multi-mode fibers allows to largely enhance transmission capacity compared to single-mode links. Photonic integrated circuits can provide solutions for mode multiplexing at the transmitter and demultiplexing at the receiver but have to generally face high losses and inter-modal cross-talk issues. Here a photonic circuit for efficient mode multiplexing and demultiplexing in few-mode fibers is presented and demonstrated. Two 10 Gbit/s channels at the same wavelength and polarization are simultaneously transmitted over modes LP01 and LP11a of a few-mode fiber relying only on integrated mode MUX and DEMUX. The proposed Indium-Phosphide-based circuits have a good coupling efficiency with fiber modes and mode-dependant loss smaller than 1 dB. Measured mode excitation cross-talk is as low as -20 dB and a channel cross-talk after propagation and demultiplexing of -15 dB is achieved. An operational bandwidth of the full transmission system of at least 10 nm is demonstrated. Both mode MUX and DEMUX are fully reconfigurable and allow a dynamic switch of channel routing in the transmission system. These results enable fully-integrated fiber mode handling for high-bandwidth flexible optical networks.