Arc-Induced Long Period Gratings in Phosphorus-Doped Fiber

Phosphorus-doped fibers have been reported and discussed in extensive works, as well as the radiation effects on their guiding features in different spectral ranges. However, the assessment of a technique enabling the fabrication of grating devices in this fiber is still an open issue. Here, for the first time to the best of our knowledge, we report on the fabrication of long period gratings (LPGs) in P-doped optical fiber by means of electric arc discharge technique (EAD). LPGs having periods of
$500~\mu \text{m}$
and of
$700~\mu \text{m}$
were presented, achieving the coupling up to LP
₀₆
cladding mode, attenuation bands with depth up to 35 dB, power losses lower than 0.5 dB, and devices length less than 20 mm. The results being also compared with numerical simulations. Moreover, the sensitivity characteristics to surrounding refractive index (SRI) and temperature changes of LPGs in P-doped fibers were also investigated. The SRI sensitivity of LP
₀₆
for SRI = 1.437 was about −478 nm/RIU, slightly higher than in standard fiber. Whereas, differently from standard Ge-doped fibers, a negative temperature response was found (−116 pm/°C) opening the possibility of new applications, for example for temperature compensation solutions.