Tunable laser action has been obtained in Nd
3+- and Er
3+-doped single-mode fiber lasers. In the case of the Nd
3+-doped fiber, an extensive tuning range of 80 nm has been achieved. Tunable CW lasing also has been observed for the first time in an Er
3+-doped fiber laser, which has an overall tuning range of 25 nm in the region of

m.