Multi-gigabit optical OFDM

What is it?

We are developing the first optical OFDM transceiver operating at 10 Gbit/s using real-time DSP.

Background

Multicarrier modulation (MCM) schemes such as orthogonal frequency division multiplexing (OFDM) are being adopted for wireless applications (e.g. WiFi) and are attracting increasing attention for optical interconnects. Transmitting on N carriers simultaneously reduces the symbol rate to one Nth of the original symbol rate of the serial data, reducing the impact of fiber dispersion and other bandwidth limitations.

However, real-time digital signal processing (DSP) for OFDM at multi-gigabit/s data rates has not yet been developed or shown to be feasible. Our goal is to dbuild such a system that demonstrates a throughput > 10 Gbit/s.

The diagram shows the basic system. OFDM is a MCM scheme in which adjacent subcarriers are separated in frequency by 1/T, where T is the symbol period. The optical signal waveform is generated using an inverse fast Fourier transform (IFFT). Adjacent subcarriers overlap, but are orthogonal, and can be recovered at the receiver using FFT.

The bottleneck is the forward and inverse FFT. These FFTs are provided by the Spiral DFT IP generator.

Team

This work is a collaboration between a research group at the University College London, Intel Lab Pittsburgh, and the CMU Spiral group. Specifically:

References