Kadhim, Shehab A., et al. “Tunable Optical Wavelength Interferometer Heterodyne System from Single Laser Source Using Fiber Bragg Grating”. International Journal of Engineering & Technology, vol. 7, no. 4, Sept. 2018, pp. 3086-9, https://doi.org/10.14419/ijet.v7i4.21544.