Research On Fiber Optical Interferometer Using Digital Tunable Laser

Non-contact, high-accuracy absolute distance measurement has important theoretical valueand practical significance in the field of industrial application and measurement science,therefore distance measurement technology based on the principle of absoluteFrequency-scanning interferometry has been widely studied. Existing ranging system based onthe principles they use to scan back and forth continuously tunable laser as a light source and theinterference optic path is built by lens. An additional wavelength locator is needed to realize highprecision measurement. So these systems have shortcomings such as large body, high opticalalignment requirements, measured target need to install mirrors and so on.To solve these problems, a fiber optical interferometry rangefinder using digital tunablelaser based on the analysis of the Frequency-scanning interferometry principle of absolutedistance ranging technology and data processing methods is designed. The rangefinder consistsof digital tunable laser, fiber optical interferometer, signal acquisition circuit and PC. Thefrequency of the digital tunable laser output can be set and the positioning is very accurate. Highprecision measurement can be realized without an additional wavelength locator. Single-modeoptical fiber and related devices are used to build the optical interferometer, a kind of integratedfiber optical sensor with reflective surface is designed. This sensor realizes absolute distancemeasurement to the non-smooth surface and reduces the measuring optical path of alignmentrequirements by using fiber’s spatial filtering characteristics and light’s diffuse reflectioncharacteristics. Signal acquisition circuit includes8-channel acquisition board and ARM controlboard. The8-channel acquisition board realizes the photoelectric conversion and AD acquisition.The ARM control board selects STM32F103as main chip, achieves tunable laser control andsends the date of AD acquisition to PC through Ethernet. The LabVIEW program is designed torealize Interference signal data analysis and distance calculation.The fiber optical interferometry rangefinder prototype is experimented and tested.Experimental results show that the rangefinder has30mm range and repeat deviation value ofmeasurement is less than0.002%. The rangefinder can realize directly measuring to thenon-smooth surface of metal, plastic etc., and allows the measuring optical path in an angular deviation. The rangefinder also has the advantages of high integration, small size, multi-channelmeasurement and remote measurement, this has a good prospect in field of industrial automaticproduction.