Erbium-doped tunable fiber laser

The Erbium doped fiber laser (EDFL) has demonstrated to be the ideal source for optical communications due to its operating wavelength at 1550 nm. Such wavelength matches with the low-loss region of silica optical fiber. This fact has caused that the EDFL has become very important in the telecomm industry. This is particularly important for Dense Wavelength Division Multiplexing (DWDM) which demands the use of single emission sources with different emission wavelengths. In the long run, this increases the capacity of transmission of information without the necessity to increase the infrastructure, which makes tunable laser sources an important component in DWDM applications. Many techniques for tuning have been demonstrated in the state of the art and we can mention, for example, the ones using birefringence plates, bulk gratings, polarization modified elements, fiber Bragg gratings, and very recently the use of multimode interference (MMI) effects. The MMI consists in the reproduction of single images at periodic intervals along the propagation direction of a multimode optical fiber, taking into account that these single images come from a single mode fiber optic. Here, a compact, tunable, erbium-doped fiber laser is experimentally demonstrated. The mechanism for tuning is based on the multimode interference self-imagining effect, which results in a tunable range of 12 nm and optical powers of 1mW within the region of 1549.78-1561.79nm.