In many cable TVs, because the signal transmission is to be realized, a modulator is technically used to achieve this purpose. Among many modulator technologies, distributed fiber optic sensing technology is widely used.
Because distributed optical fiber sensing technology has the ability to simultaneously acquire the measured distribution information that changes with time and space in the sensing fiber area, the PBI modulator has many advantages, and its basic features are:
① The sensing elements in the distributed optical fiber sensing system are only optical fibers;
② The measured one-dimensional distribution map in the entire optical fiber area can be obtained in one measurement, and the measured two-dimensional and three-dimensional distribution can be measured by erecting the optical fiber in a grating shape;
③ The spatial resolution of the system is generally on the order of meters, so only the average value of the measured changes in a narrower range can be observed;
④ There is generally a mutual restriction between the measurement accuracy and the spatial resolution of the system;
⑤ The detection signal is generally weak, so the signal processing system is required to have a higher signal-to-noise ratio;
⑥ Due to the need for a large number of signal addition and averaging, frequency scanning, phase tracking and other processing in the detection process, it takes a long time to achieve a complete measurement.
