10-Gb/s colorless re-modulation of signal from 1550nm vertical cavity surface emitting laser array in WDM PON

High speed vertical-cavity-surface-emitting lasers (VCSELs) [1] are attractive candidates for use in future wavelength division multiplexed passive optical network (WDM-PON) systems because they may meet the stringent size, power dissipation and cost constraints of access network components. Colorless transceivers at the optical networking unit (ONU) in a WDM PON can further help reduce the costs: one approach for implementing colorless transceivers is to use a low extinction ratio non return to zero (NRZ) modulation from a VCSEL for downstream transmission and differential phase shift keying (DPSK) remodulation of the received signal in a low cost silicon photonic transceiver for upstream transmission [2]. In this paper we describe a proof-of principle implementation of such a remodulation scheme with a directly modulated VCSEL array, as shown schematically in Fig. 1. Although a discrete receiver, VCSEL array and wavelength filters were used here for implementing the transceiver at the Optical Line Terminal (OLT) (Fig 1), flip-chip mounting of the VCSEL array onto a silicon photonic integrated circuit containing the WDM multiplexer (MUX) and DPSK receivers has potential for implementing low cost multi-wavelength optical transceivers.