Correlation-based multiplexing of spectral channels and fiber-optic sensors using unmodulated continuous-wave...

In this Letter, we demonstrate a method for the multiplexing of spectral channels and fiber-optic sensors. The method makes use of the correlation-based demultiplexing technique. In our approach, each light source has an inherent phase noise which we propose to use as a "fingerprint" for correlation-based recognition and demultiplexing of spectral channels as well as signals from different sensors in each spectral channel. The proposed method requires for its implementation an extremely simple and robust scheme and can be attractive for budget-sensitive applications. As active elements, it uses only two standard free-running CW distributed feedback (DFB) diode lasers. No modulators or optical filters are required for operation. Results of proof-of-concept experiments are presented for the interrogation of several ultra-weak fiber Bragg gratings (FBGs) with reflectivity of 0.05% in a 4-km-long fiber for temperature measurements with the resolution of 0.1°C.