JLT19 – cohTDMA
Analogue Coherent TDMA Receiver with Fast Locking to Free-Running Optical Emitters (Top-Scored Paper)
JLT, vol. 38, no. 2, pp. 379-385, Jan. 2020
B. Schrenk, and F. Karinou
As coherent reception technology continues to move downstream the optical telecommunication infrastructure, the complexity of the involved transceiver technology can quickly introduce a techno-economic roadblock. Under this umbrella, we experimentally demonstrate a conceptually simple, single-polarization and analogue coherent homodyne receiver that builds on no more than an optically locked externally modulated laser. We evaluate this coherent homodyne receiver in the context of analogue radio-over-fiber transmission – a demanding application setting, where a small degradation in signal integrity is leading to large reception penalties. We conduct a continuous-mode characterization of the locking methodology, which enables homodyne detection and hence the transparent translation of electrical signals from the optical to the electrical domain during the coherent reception process. Furthermore, the locking dynamics are being investigated for packet-level reception at a 1 MHz frame rate and two time division multiplexed channels, which are sourced by two optical emitters with free-running laser sources. The radio-over-fiber transmission performance is evaluated for 64-ary quadrature amplitude modulated, orthogonal frequency division multiplexed radio with a short guard interval of 2.7 μs between the packet radio signals. A data rate of 0.5 Gb/s over 100 MHz radio bandwidth is obtained at an optical loss budget of >35 dB between transmitter and receiver, without resorting to digital signal processing resources for the purpose of signal recovery. Moreover, a small ∼0.3% penalty in error vector magnitude between continuous- and packet-mode confirms the compatibility of the analogue coherent receiver in networks with fast locking requirements.