Modern distributed temperature control systems are used today everywhere, in particular, in the telemetry of oil and gas wells. Thus, when creating a distributed fiber-optic temperature sensor based on Raman scattering (DTS) for these purposes, the problem of improving its metrological characteristics always remains urgent. They are in turn determined by the known SNR (signal-to-noise ratio, SNR from English Signal-to-Noise Ratio). To achieve this goal, it is proposed to use a promising method of increasing the SNR in the DTS based on encoding the probing sensor signal by the Hadamard code sequences (simplex coding). For this purpose, a numerical experiment is carried out to implement this coding method using the DTS model and taking into account the noise of the photodetector device. The article presents the simulation results, confirms the effectiveness of the coding method, and summarizes the results of the simulation.

Keywords: distributed fiber optic temperature sensor, Raman scattering, photodetector device, noise, signal-to-noise ratio, optical pulse encoding, Hadamard code, simplex coding

In this paper, it is shown that the noise of the photodetector device (PD) is the dominant factor limiting the metrological characteristics in real distributed fiber-optic temperature sensors based on Raman scattering (RDTS), which contribute significantly to the process of signal noise using the example of the RDTS taking into account the noise of the PD, which was chosen as the avalanche photodiode (APD). The analysis of the main types of noise in the model of an APD in the model, including both basic PD noise, and characteristic for APDs, for example, their influence on the signal-to-noise ratio (SNR). The graphs of the dependence of the influence of noise on the RDTS, derived from the SNR ratio, are given and conclusions are drawn about the predominance of some noise over others under different conditions, based on their.

Keywords: distributed fiber optic temperature sensor, avalanche photodiode, shot noise, dark noise, thermal noise, amplitude noise, signal-noise ratio, random number distribution law