Self-Seeded DWDM Solution for Fronthaul Links in Centralized-Radio Access Network

One of the requirements for the fronthaul segment in the Centralized-Radio Access Network architecture, is the capability to multiplex several fronthaul links on the same fiber by means of wavelength division multiplexing (WDM). In the self-seeded solutions, each transceiver creates its own wavelength carrier to form the transmitter source. Thus, this scenario seems suitable for fronthaul applications as there is no longer requirement to provide wavelength specific sources. Each transceiver automatically creates a laser field that tunes to the connection port of the optical multiplexer. An optical cavity is established between an optical reflector (Faraday Rotator Mirror) and the Reflective Semiconductor Optical Amplifier. Achieving a colorless transceiver would solve the inventory management problem for wavelength assignment that appears in the traditional WDM fronthaul systems. However, to our knowledge, no study has been done yet to show the performances of this technique on a real fronthaul link. In this paper we study and verify the compatibility of a self-seeded DWDM solution with the most critical fronthaul requirements: the data rate, the bit error rate, the jitter, the round trip delay and the radio frequency accuracy budget. Moreover, the quality of the end to end long term evolution (LTE) signal is measured in terms of error vector magnitude (EVM). The experiments are carried out for transmission up to 30 km, for different cavity lengths and different LTE modulation signals (QPSK, 16-QAM, 64-QAM).