In-service line monitoring of a colourless wavelength division multiplexed passive optical network

A multi-wavelength tuneable OTDR is realized and tested for in-service monitoring of a colourless WDM PON. The instrument regenerates the probe optical pulse by modulating, through an acousto-optic modulator, the continuous wave emission of a tuneable telecommunication laser. This setup reduces at the same time the spontaneous emission noise and the coherent Rayleigh noise. The absence of interference between the signal transmission and the monitoring is demonstrated also performing BER measurements of the upstream communication in an RSOA-based reflective PON.