Research On Wavelength Measurement And Its Applications Based On Optical Rotatory Dispersion Effect

With the continuous improvement of the modern science and technology level and emergence of new technologies, wavelength measurement range of applications is throughout the production, life, military, scientific and other fields. Convenient measurement of wavelength is also becoming a pressing demand. At present wavelength measurements are mainly divided into three types including dispersion-type, interference-type and filter-type. The dispersion-type is based on dispersive elements (diffraction grating or prism) which are used to separate the polychromatic light, and then the intensity of each spectral line element is detected to determine the wavelength. The wavelength measurement in interference-type is to detect the interference intensity of all line elements simultaneously, then to obtain the spectrum by carrying on the inverse Fourier transformation of the interference figure. Filter-type wavelength measurement uses tunable filter to determine wavelength. These wavelength measurement methods have advantages and disadvantages when used in different applications. A new method of wavelength measurement based on optical rotatory dispersion effect of quartz is investigated in this paper. Wavelength can be determined by detecting the rotation angle of plane polarized light. Experimental results show that the wavelength range of this system is greater than 1000nm, and wavelength measurement resolution is better than 0.1pm, wavelength absolute accuracy is better than±2pm, which is now at the best level of wavelength measurement.We propose and design a measurement system by using tunable laser and double-beam testing technique, with which we have measured the optical rotatory dispersion properties of quartz crystal at three low loss wavebands in optical fiber communication. We get the optical rotatory dispersion curves and the fitting formula at the three wavebands. Using the optical rotatory dispersion curves, we measure the rotatory power of quartz crystal at 850nm,1310nm and 1550nm waveband accurately. From the experimental data we also calculate the coefficients in Sellmeier equation, and then constructe Sellmeier equation in near-infrared waveband. Optical rotatory dispersion plots from the constructed equation are well coincide with the experimental results in all the three wavebands, and furthermore the calculated rotatory power at 1342nm from the equation are completely consistent with that in optics handbook. These results show that the optical rotatory dispersion test system proposed by us provides a reliable means of detecting the optical rotatory dispersion characteristics of optical materials.At 850nm,1310nm and 1550nm waveband, we obtain the continuous rotation rate of quartz crystal in the whole wavelength range of tunable lasers. Up to now there is no literature to give the relative information. We also investigate the temperature effect of the optical rotation of quartz crystal at 1310nm waveband. The relation of Sellmeier equation's coefficient to temperature is calculated. These data have practical significance to the further development and application of quartz crystal in the near-infrared waveband.A new method of calibrate wavelength of Fabry-Perot tunable filter based on optical rotatory dispersion effect has been investigated. With this method wavelength calibration of Fabry-Perot tunable filter in the whole scanning range can be realized. We can readout the wavelength directly through the optical rotatory dispersion curve. The reported methods, such as grating array method, Fabry-Perot semiconductor lasers method, gas absorption method and other methods, can only calibrate wavelength in their comb characteristic peaks, and then the non-linear relationship curves between wavelength and voltage of Fabry-Perot tunable filter are fitted, they can not achieve a real-time and wide range wavelength calibration. We carry out the wavelength calibration of optical fiber Fabry-Perot tunable filter at 1550nm band. Experimental results show that the wavelength scanning resolution of this system is better than lpm, wavelength scanning accuracy is better than±2pm, it is at the best level of wavelength calibration methods that have been reported.A new method of building wavemeter based on rotatory dispersion effect is proposed. The wavelength of near-infrared waveband is measured by using the existing conditions of laboratory. We measure the wavelength of fiber Bragg grating and tunable laser, and analyzed the error in detail. The absolute error between experimental values and display value of tunable laser is less than±10pm, the relative error is less than±2x10-6. Because there are no precision mechanical scanning system and no use of interferometer; the system machinery stability, temperature stability and repeatability can be improved. Also from the point of price, the cost of this testing method is far less than the price of same accuracy equipment. Therefore, this wavelength measurement method is very competitive in the core parameter, stability, reliability and cost, it has good prospects for practical application.