Bend-insensitive bismuth-doped P2O5-SiO2 glass core fiber for a compact O-band amplifier

For the first time, we report on the fabrication of a bend-insensitive single-mode bismuth (Bi)-doped P 2 O 5 − S i O 2 fiber having a depressed cladding design and study its gain characteristics at a spectral region of 1.3–1.4 µm. It was shown that the obtained Bi-doped fiber can efficiently operate in the spectral band even at a bend radius of 1.5 cm. In addition, it was shown that this type of fiber has a smaller mode-field diameter in comparison with a step-index single-mode Bi-doped P 2 O 5 − S i O 2 fiber with Δ n ≈ 0.006 that resulted in a decrease of saturation power and, as a consequence, in a reduction of the total pump power required to a high-level-gain operation. The laser and gain experiments show the possibility of the construction of a compact high-performance optical amplifier for O-band based on the depressed-cladding Bi-doped fiber.