Simple laser transmitter pair as polarization-independent coherent homodyne detector

Coherent optical reception promises performance gains for a wide range of telecom applications and photonic sensing. However, the practical implementation and the particular realization of homodyne detection is by no means straight-forward. Local oscillator requirements and polarization management need to be cost-effectively supported for accurate signal detection at high sensitivity, preferably without relying on digital processing resources. Towards this direction we propose a conceptually simple, laser-based homodyne receiver. We exploit the injection locking of a pair of externally modulated lasers that simultaneously serve as optically synchronized local oscillators and photodetectors in a polarization-diversity analogue coherent receiver arrangement. We demonstrate signal detection at 2.5 Gb/s over an optical budget of 35 dB and a dynamic range of >20 dB. Long-term measurements over field-installed fiber confirm the correct operation independent of the polarization state of light. Stability considerations for the injection locking process are drawn in view of even higher loss budgets.