HIGH-ACCURACY WAVELENGTH-CHANGE MEASUREMENT SYSTEM BASED ON A WOLLASTON INTERFEROMETER, INCORPORATING A SELF-REFERENCING SCHEME

A novel wavelength-difference measurement scheme with a Wollaston pris m is presented. By using a suitable reference wavelength, a small vari ation in the signal wavelength can be converted into a relatively larg er change in the modulated wavelength, as a result of the so-called fr inge beating effect, resulting in enhanced measurement sensitivity by use of autocorrelation and Gaussian filtering techniques. From the res ults of a simulation carried out. we observed a wavelength variation o f 0.01 nm over 15 nm or 0.1 nm over 60 nm for a typical pair of laser diodes with wavelengths of 785 and 810 nm, and wavelength variations o f 0.5 nm over 40 nm or 1 nm over 110 nm for 671 -and 785-nm wavelength s. These results were partially verified by the experimental results o btained for which a resolution of 0.01 nm over a range of 2.5 nm for t he first pair and 0.5 nm over 4 nm for the second pair of laser diodes was seen. The results have applications to the determination of wavel ength variations in a wavelength-division multiplexing system or measu rement of the wavelength changes induced in a range of optical sensors . (C) 1997 Optical Society of America.