The Suppression Of Stray Interference Peak And The Device Testing In Fiber Optical White Light Interferometer

The measurement system of optical fiber white light interferometry has the advantage of distributed measurement,which is widely used in distributed sensing,measuring of optical element and optical polarimetric device.With the continuous improvement of dynamic range of optical fiber white light interferometer,the stray interference peaks caused by discontinuous points is the major factor which influences the measuring property.The stray interference peaks appear in interference spectrum that influence the dynamic range and inducing terrors during measurement.Consequently,the accuracy can’t guarantee for measurement system.There is a great significance to design a larger dynamic range system which has no stray interference peaks.The paper takes the several discontinuous points as research object.The residual light and stray interference peaks were defined and classified.We proposed three methods: optical path mismatch(OPM)method and polarization mismatch(PM)method and Optimal structure designing method to suppress or eliminate these stray interference peaks.The optical path mismatch(OPM)method is realized by using a fiber whose length is known to prevent the residual light interferences during the optical delay line scanning,while the main beam can intervene to form the main interference peak.Three rulers of this method as follow:(a)The minimum optical path difference caused by the last period of fiber in interferometer two arms is longer than the scanning distance of the optical delay line.(b)The optical path difference of arbitrary two joints in two arms of interference is larger than scanning distance of the optical delay line.(c)The optical path difference of arbitrary two points that exist at each arm is larger than the scanning distance of the optical delay line.The polarization mismatch(PM)method is changing the polarization state of light by adjusting polarization controller.The interference peak is restrained because the polarization state of residual light can’t satisfy the condition of interference.The improvement of device structure can also restrain interference peaks.We designed a measurement system of the optical fiber white light interference which has no interference peaks.It is used to detect the part optical devices,such as photoelectric detector,circulator,Faraday rotation mirror,and Y-waveguide.We obtained the extinction ratio of higher high-performance Y-waveguide whose extinction ratio is 90.5 dB.