The advantage of optical fiber grating sensors are easily implemented multiplexing by using broadband light source.
Erbium doped fiber (EDF) are important as a gain media, because it affects the performance of light sources. We
demonstrated tunable fiber ring laser using Bi2O3-based Erbium doped fiber (BIEDF) and a tunable filter with bandwidth
of 1 nm. We show the BIEDF fiber length dependence, pump power dependence and also show the its spectra. By
increasing fiber lengths of BIEDF, the tunable range changes toward longer wavelengths with varying tunable range. By
using 0.7 m of BIEDF as a gain media, the tunable range reached over 110 nm with just pump power of 100 mW at 1480
nm. Tunable range was insensitive to pump power in this experiment. Also we show the laser spectra. BIEDF laser
shows high optical signal-to-noise ratio (OSNR) higher than 55 dB at over 110 nm tunable range, and 70 dB for 99 nm
(1530 - 1629 nm) tunable range. This means that BIEDF has potential for broad band fiber sensor sources, especially for
fiber grating sensors.
We have developed novel bismuth-based photonic crystal fiber which exhibits high nonlinearity γ ~ 780W-1km-1
and relatively low group-velocity-dispersion D ~ -25 ps/nm/km at 1560 nm. The new fabrication process was
also developed for this novel photonic crystal fiber with 6-fold symmetric structure. The core diameter 2.7 μm
of this fiber was designed to have modelately decreased normal dispersion and high nonlinearity. Spectral broadening
induced by self-phase-modulation by 1550 nm fs-pulse propagation shows that the high nonlinearity and dispersion reduction is simultaneously achieved.
Bismuth oxide based highly nonlinear fiber (Bi-NLF) enabled by glass composition and small core fiber design was successfully fabricated. There's much expectation for the development of high nonlinearity optical devices along with the large volumetric and speed increase of the information traffic in recent years. In order to achieve higher nonlinearity, it is necessary to enlarge the nonlinear refractive index n2 and make the effective core area Aeff smaller, as g is γ=2πn2/(λAeff). Much effort has been put into the development of small-Aeff holey fiber, as its high nonlinearity and dispersion can be controlled to a certain extent. However, holey fiber has issues such as large propagation loss, high connection loss with silica single-mode-fiber (SMF) because of their particular structure, and higher fabrication cost. We performed the fabrication of a conventional step-index-type SMF with high nonlinearity and low propagation loss using Bi2O3-based glass. First, we fabricated Bi2O3-based glass with high refractive index of >2.2 at 1550 nm by a conventional melting method. This glass exhibited extreme thermal stability for fiber drawing. Then in order to make Aeff smaller, cladding glass composition was designed so that the difference with the refractive index of the core glass must be large. Finally the core diameter was controlled to satisfy the single mode condition, and fiber drawing was performed. Typical Aeff of this fiber is less than 5 um2. The nonlinearity g of the fiber can be estimated to be >600 W-1km-1, as large as the value reported in holey fibers using non-silica glass. Bi-NLF with step-index-type structure would become the best candidate for short length and highly nonlinear optical devices.