Brahma, Debolina, et al. “Design Characterization of Erbium-Doped Fiber Ring Laser Using a Circulator and Filter for C and L Band Amplification”. Photonics Letters of Poland, vol. 6, no. 1, Mar. 2014, pp. pp. 38-40, doi:10.4302/photon. lett. pl.v6i1.480.