Instrument Design Of Polarization Optical Time Domain Reflectometry

Polarization optical time domain reflectometry(POTDR)is a kind of distributed optical fiber sensors(DOFS).POTDR is developed from Optical Time Domain Reflectometry(OTDR)and has advantages of simple construction,high sensitive to external events,long sensing range and so on.The state of polarization(SOP)of light wave in fiber is very sensitive to external perturbations,based on which the polarization time domain reflectometer(POTDR)can realize distributed sensing to bending,vibration,et al.along the sensing fiber.POTDR has shown great potential in many areas,like perimeter security monitoring,intruder detection of important places,PMD measurement and vibration sensing.Although POTDR has many advantages comparing with traditional sensor,the development of its instrumentation design is at a low level.Most POTDR systems are built in laboratory in separate components with poor portability and software in host computer for instrument control,data acquisition and signal analysis are not complete.Based on the factor above,we are going to design an instrumented POTDR system,which can combine POTDR sensing system with data acquisition and signal analysis.The instrument design of POTDR includes both hardware and software and some improvements are carried out.Besides,some research on ability of anti-interference are done for POTDR property optimization and experiments are designed for verifying the feasibility of the anti-interference scheme.The acritical is main about two aspects.(1)Deign optical structure and choose key device for POTDR refer to actual situation.We install the sensing device,DAQ device and PC together in 4U crate by customizing molds with the help of SolidWorks.The scheme will improve the portability and integrality of POTDR.Software design must be close to users.Its interface is friendly and its function is perfect.Software can control device like laser and DAQ card.The sensing data like the distance of disturbance,frequency of vibration and etc.will be presented to users directly by shown in interface.When the installation of instrumented POTDR is done,testing result meet our expectation.(2)We also present a structure for improving the ability of anti-interference for POTDR.Theoretical and experimental research are both carried out to verify the feasibility of this scheme.This structure guarantees that the disturbance in connection fiber and pigtail will not influence the state of polarization of sensing light wave.This scheme can effectively improve the ability of anti-interference of POTDR.It can also be used in monitoring multiple perimeters and has great expectation in sensing area.