Signal and data processing of wavemeter with Michelson interferometer

Laser wavemeter with a Michelson interferometer is a high-precision instrument. The signal and data processing is so important to this wavemeter. It includes an optoelectronic conversion module, an amplifying and comparator circuit, a PLL unit, a counter, serial communications between the MCU and the computer. S1223 photodiodes are selected as the detectors. PLL unit including NE564 and 74LS193 is used to multiply frequency. The timing capacitor, loop gain coefficient, and the locking range of PLL are calculated. The counter is used to measure the number of interference fringes of the reference laser and the number of interference fringes of an unknown laser. Finally, the wavelength of an unknown laser is calculated and displayed on LCD. The signal and data processing of the wavemeter meets its accuracy of seven-bit significant figure.