Patent ID: 8913888

Claim:
A method comprising: receiving a user data frame comprising user data from an upstream node; intentionally creating line patterns with significant single frequency tones used to implement an optical frequency domain reflectometry (OFDR) system, wherein the line patterns with significant single frequency tones are used as a test signal data pattern; encapsulating the test signal data pattern in a test signal data frame that does not comprise the user data, and transmitting the test signal data frame and the user data frame into an optical fiber toward a downstream node using time division multiplexing (TDM), wherein a transmitter is used as a delta-sigma modulator and a digital waveform is generated for use as the test signal data pattern by modulating fractions of 0's and 1's sent in a certain period, and wherein a sinusoidal function is approximated by the sequence of 0's and 1's.