25  Gbit/s per User Coherent All-Optical OFDM for Tbit/s-Capable PONs

Abstract

We propose and test a coherent all-optical orthogonal frequency-division multiplexing (AO-OFDM) system, based on all-optical (de)multiplexing and coherent detection, for multiterabit per second (multi-Tbit/s) passive optical networks (PONs). The proposed approach allows us to greatly increase the downstream data rate per user and extend the standard single-mode fiber reach for future long-reach applications. The compliance with a next-generation PON layout is guaranteed thanks to the exploitation of cyclic arrayed waveguide gratings. Five-user transmission with 12.5 Gbaud quadrature phase shift keying modulation per user (125 Gbit/s downstream capacity per wavelength) over a more than 40 km link has been successfully demonstrated.

Enhancing the Anti-Dispersion Capability of the AO-OFDM System via a Well-Designed Optical Filter at the Transmitter

“…Due to higher spectrum utilization and more flexible carrier allocation strategies, the AO-OFDM system can be regarded as one of the core technologies of the next generation of optical networks with more flexibility and elasticity [1][2][3][4][5][6]. At present, AO-OFDM systems typically use optical arrayed waveguide gratings (O-AWGs) and wavelength-selective switches (WSSs) based on liquid crystal on silicon (LCoS) as the core components for generating orthogonal sub-carriers [7][8][9][10][11][12]. The WSS is a key component of a reconfigurable optical adding/dropping multiplexer and a key all-optical routing element in a wavelength-reconfigurable network.…”

“…It can provide almost meshless switching and carrier assignment functions. The AO-OFDM system based on WSS can demodulate the carrier while separating and redirecting the subcarrier to a certain corresponding output port from the overlapping supercontinuum spectrum when performing carrier allocation through wavelength-selective switching [10][11][12]. Although there are other optical devices that can be used to implement AO-OFDM, such as AWG, multi-fiber Bragg gratings, and circuits with trees of delay line interferometers, these solutions still rely on the use of WSSs for subcarrier separation and flexible allocation [13,14].…”

“…At the same time, Ref. [11] also reported that the AO-OFDM system based on AWG was applied to passive optical networks far exceeding Tbit/s. It should be pointed out that AO-OFDM systems, whether applied to large-capacity longdistance transmission or large-capacity passive optical networks, rely heavily on dispersion compensation.…”

Single Radio-Over-Fiber Link and RF Chain-Based 60 GHz Multi-Beam Transmission

“…In this work, a low cost and low complexity technique for multi-user transmission is presented which makes use of a Subcarrier Multiplexing (SCM) composite signal to carry data for multiple users and the beamsteering characteristics of a frequency-selective Leaky-Wave-Antenna (LWA) to generate multiple beams. The use of Subcarrier Multiplexing (SCM) [13]- [17] with a single RoF transport link can provide high system capacity and support for large numbers of users [18], [19]. The LWA is a steerable directive antenna which operates in the 60GHz-band [20] and requires only a single feed input port.…”

FDM exploitation for next access and data networks

“…Orthogonal frequency division multiplexing (OFDM) [1,2] and its directly-modulated version discrete multitone (DMT) modulation provide a high spectral efficiency thanks to the partial subcarrier overlapping. Moreover, bit loading allows to minimize the penalty due to signal-to-signal beating interference.…”