Research On Compensation Techniques For Light Source In Measurement Of Low-loss Parameter

The paper was based on "the comprehensive test instrument for testing ultra-low loss of the optical components ". The equipment was mainly used for measuring integral scattering rate of low-loss optical components. Due to the scattering signal of the low-loss optical components is very weak, the measurement results can be seriously affected or even submerged by the error caused by fluctuation of light source. Therefore, on the basis of the original test system, the error generated by the fluctuation of light source would be eliminated by using the compensation techniques for the light source in this paper, and the measurement results of a higher precision were obtained.He-Ne laser light source of the original test system was modulated by the mechanical chopper, which was not conducive to the integration of test instrument and the invested cost was high. In order to overcome the shortcomings of the original system, He-Ne laser light source was replaced by the semiconductor laser (LD) light source which did have the advantages of small size, low price and impact resistant. LD laser would be directly driven and modulated by the generated signal of the D/A output card controlled by the computer, reducing research costs and facilitating instrument integration effectively. The system hardware part is mainly composed of light path system, acquisition and controlling of signal and the hardware circuit design. The light path system realized the election of light source and the light splitting. The acquisition and controlling of signal realized the extraction of the weak optical signal in the strong noise. The hardware circuit design realized the laser driver and the optical power signal monitoring and amplification. The feasibility of circuit was verified by the simulation and actual measurement of two circuits. The signal modulation module, synchronous data acquisition module and light compensation module were added in the system software design based on Lab VIEW platform. A method of high precision measurement of optical power was proposed in the process of researching this topic. According to the measurement of two different kinds of laser power, the power error range of two kinds of laser is±1.60 and ± 2.25%, respectively.In order to eliminate the error of the light source fluctuation, a light compensation algorithm was proposed. The rationality of the algorithm was verified by simulation and actual measurement of signal. This kind of light compensation technology can also be used for measurement of other weak optical signal.