Improvement Of DOFS Performance With Simplexs Coding

The distributed optical-fiber sensor detects the temperature or strain in the continued space.Comparing with traditional optical-fiber sensor,it has many advantages: immune to electromagnetic effects,strong environmental adaptability,large area detecting,high sensitivity…So it attracts wide attention.But there is a conflict between the spatial resolution and the sensitivity in the system.Increasing pulse width of the probe pulse improves the signal to noise ratio(SNR) of the detected signal,and degrades the spatial resolution.In order to overcome this conflict between the SNR and the spatial resolution,people want to overcome it by using codes techniques.By simplex code,we can improve the SNR,but don't increase the pulse width and pulse range of the probe pulse,and the same number of acquired traces.In this paper,we validate the effects of simplex codes in the raman distributed optical-fiber sensor and brillouin distributed optical-fiber sensor in theory.Then a 7-bit simplex-coded is used in the raman distributed optical-fiber sensor experiment.The output signal fluctuation becomes smaller.So the resolving power of system is improved.