Patent ID: 7466422

Claim:
A method of interrogating sensor interferometers of an optical network comprising multiple optical pathways from a transmitter unit to a receiver unit, wherein pairs of optical pathways form the sensor interferometers, each sensor interferometer having a sensor imbalance, the method comprising: defining a plurality of transmission time intervals; dividing the plurality of transmission time intervals into a sequence of time-division multiplexing (TDM) repetition periods; defining a plurality of transmission time slots, wherein each transmission time slot comprises one of the transmission time intervals from each TDM repetition period located at the same position relative to the start of each TDM repetition period, the plurality of transmission time slots comprising pulse transmission time slots and dark transmission time slots located at the same positions within each TDM repetition period; transmitting optical signals from the transmitter unit, wherein optical pulses are transmitted during the pulse transmission time slots and no optical pulses are transmitted during the dark transmission time slots for the sequence of TDM repetition periods; and modulating a phase of the optical signals between at least one of the pulse transmission time slots and the dark transmission time slots such that unwanted interference signal components reaching the receiver unit are distributed to frequency bands that do not affect a demodulated sensor signal.