A Coherent Homodyne TO-Can Transceiver as Simple as an EML

The introduction of low-cost coherent signal reception is one of the great challenges in optical telecommunications since its opto-electronic sub-systems are associated with a high degree of complexity. In this work, we propose a disruptive approach: the re-use of widely deployed direct-detection technology for simultaneous coherent homodyne reception and transmission. We first show that an externally modulated laser (EML) is sufficient to perform both, coherent reception and transmission functionality. Second, we prove that homodyne detection applies to the EML-based scheme in virtue of an injection-locked local oscillator, which for low input power levels is pulled to the optical carrier frequency of the incident data signal. The proposed methodology for coherent reception enables a greatly simplified transceiver as optical layer hardware. As we will demonstrate, it just requires single fiber access, a single radio frequency port, and can be implemented in a transistor-outline package. Full-duplex transmission with coherent homodyne reception is experimentally validated, showing 2.5 Gb/s transmission over 27.5 km reach and a loss budget of 28 dB, and coherent Gigabit Ethernet connectivity-without the use of optical layer digital signal processing functions.