Patent ID: 8396363

Claim:
A measurement system comprising: a plurality of channels, each of the channels transmitting a unique wavelength signal; a tone generator for generating a plurality of tones, each tone having a unique frequency, and for providing a unique sequence of the tones for each respective channel; a modulator for modulating the unique wavelength signal of each channel with the unique sequence of the tones provided for each respective channel; a transmitter for transmitting the modulated signals for each channel; and a detector for detecting the modulated signals for each channel; wherein each channel includes a lock-in amplifier that performs lock-in on the detected signal during a lock-in time period, the lock-in time period includes at least one repetition of the unique sequence of the tones for each respective channel, an inphase multiplier and quadrature multiplier, a 90 degree phase shifter for phase shifting the unique sequence of the tones, and the inphase multiplier and quadrature multiplier multiply the detected signal with both the unique sequence of the tones and the 90 degree phase shifted unique sequence of the tones respectively to produce inphase and quadrature components.