Interrogator unit for multi-span distributed acoustic sensing

A method for monitoring an optical transmission path in an optical transmission system, the optical transmission system includes a distributed acoustic sensing (DAS) interrogation unit having a single DAS transmitting device and a plurality of DAS receiving devices, the method comprising:

• generating, by the single DAS transmitting device, one or more optical signals for determining a status of one or more portions of an optical communication path;
• modulating, by the single DAS transmitting device, the one or more optical signals using one or more measurement pulses and generating one or more modulated optical signals;
• transmitting, by the single DAS transmitting device, the one or more modulated optical signals to the one or more portions of the optical communication path;
• receiving, by the plurality of the DAS receiving devices, one or more reflected signals in response to the one or more modulated optical signals reflected by the one or more portions, wherein each DAS receiving device in the plurality of DAS receiving devices receives at least one of the one or more reflected signals in accordance with a predetermined wavelength of signals that the DAS receiving device is configured to receive;
• and
• determining, by plurality of DAS receiving devices, the status of the one or more portions of the optical communication path based on the one or more reflected signals.