Low-complexity real-time coherent TX/RX prototype for UD-WDM access networks

A coherent TX-RX prototype is presented including a real-time polarization-independent coherent receiver (PI-RX) with analog processing (no DSP). The prototype, realised by means of common DFBs and commercially available RF electronic ICs, is targeted for use on a 6.25 GHz Ultra Dense Wavelength Division Multiplexed (UD-WDM) grid and features up to 50 dB of loss budget. Robustness of the PI-RX against crosstalk from coexistent adjacent channels is demonstrated. Using two such prototypes, bidirectional transmission in a 8x1.25G UD-WDM system configuration with 6.25 GHz frequency spacing and 45 dB ODN loss is shown with channel selection by means of thermal tuning of the local oscillator.