Real Time Assessments of DML and EML with 25G-class APD for Higher Speed PONs

This paper aims at assessing two types of optical transmitters as potential candidates to realize transmissions at 50 Gbit/s in the context of Higher Speed Passive Optical Networks (HS-PON). A Receiver Optical Sub-Assembly (ROSA) with a high bandwidth (25 GHz) Avalanche Photodiode with a Transimpedance Amplifier (APD-TIA) is proposed to achieve high optical budget required for this application. Thus, we demonstrate, real time transmission for HS-PON at 25 and 50 Gbit/s, performed with a Directly Modulated Laser (DML) composed of a Distributed Feedback laser (DFB), or an External Modulation Laser (EML) composed of a DFB, integrated with an Electro-Absorption Modulator (EAM) and optionally a Semiconductor Optical Amplifier (SOA). The transmission is realized with reduced complexity of equalization (pre-emphasis 3-taps in emission + Finite Impulse Response (FIR) filter 6-taps at the reception). A sensitivity of -29.4 dBm is obtained with a DML and 25 km of fiber at 25 Gbit/s and -22.7 dBm at 50 Gbit/s. The EML-SOA achieved a sensitivity of -27.8 and -24.4 dBm at 25 and 50 Gbit/s respectively. The results obtained open a perspective on the feasibility of HS-PON with DML at the emitter side, as a low-cost alternative to EML.