A novel upgrade path for transparent optical networks based on wavelength reuse

Passive optical networks (PONs) provide an economical method of delivering a wide variety of services to a small number of customers. Using optical fibre amplifiers, PONs can be aggregated to form transparent optical networks (TONs) serving a very large customer base. However, the effective bandwidth per user is limited, particularly in the upstream direction. In the future, customers will demand increasingly high bandwidth services requiring TONs to be regularly upgraded. A WDM TON upgrade is proposed based on a novel wavelength reuse scheme in which information is routed passively using optical filters without the need for electronic switching, buffering, wavelength conversion or network synchronisation. Wavelengths are dynamically allocated to customers, enabling bandwidth to be offered on demand