| Photonic crystal fiber is a kind of brand-new fiber with multiple advantages,including high non-linear characteristic, color dispersion controllability, high birefringence, and infinite single-mode characteristic. In particular, as a key component, it has been applied to optical fiber gyro, high power fiber laser, and high power optical fiber amplifier, etc. In these applications, effective mode area is a major parameter among the parameters of PCF. The traditional measurement for effective mode area in fiber is not applied to a variety of structure of PCF, so this paper has a deep research on measurement technology for effective mode area.This paper gives up the traditional way of measuring round fiber core diameter, but try to calculate mode area by measuring non-round single-mode PCF core.This paper mainly includes:Firstly, with regard to topic research purpose and significance, this paper has discussed the mode field measurement, the concerned issues and the present research.Moreover, the traditional measurement for PCF mode diameter are also discussed.Secondly, in order to overcome the limitations of mode diameter measurement for non-round core PCF, the near-field scanning methodology is put forward, and the experiment scheme and the measurement system are designed.Thirdly, a noise reduction method and the effect for spot image has been discussed,which can work out the effective mode area when it is combined with OpenCV procedure. In general, three methods for mode area calculation are introduced,including the traditional Gauss fitting method, the double integral method and the CDD imaging online measurement.Finally, simulation to three PCF modes has conducted, acting as an experiment reference; mode area measurement system has been established to investigate its measurement. Proposed measurement in this paper has been tested with Corning G652single-mode fiber, with which mode area of triangle-shaped PCF and double-reflected PCF can be worked out. |
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