Wavelength referencing in passive optical networks

A method is demonstrated that uses the HDWDM (high-density wavelength-division-multiplexing) channels transmitted from a head-end as a reference comb for upstream transmission. A dual-purpose, grating-based tunable optical filter simultaneously selects the required downstream wavelength channel and automatically generates an identical wavelength as part of a tunable ring laser. This enables all customers to employ identical amplifiers, without requiring a set of distinct laser wavelengths to be accurately manufactured.<>