Long period fiber grating (LPFG) can be used as active gain controlling device in EDFA. However, LPFGs fabricated in the standard telecom fiber only have a typical temperature sensitivity of 3-10nm/100 degree(s)C, which may not be sufficient for implementing tuneable filters capable of wide tuning range and high tuning efficiency. In this paper, we report a theoretical and experimental investigation of thermal properties of LPFGs fabricated in B/Ge co-doped optical fiber. We have found that the temperature sensitivity of the LPFGs in the B/Ge fiber is considerably increased compared with those produced in the standard fiber. The LPFGs written in the B/Ge fiber have achieved, on average, one order of magnitude higher sensitivity than that of the LPFGs produced in the standard telecom fiber. We have also identified that the thermal response of LPFG is strongly dependent on the order of the coupled resonant cladding mode. The maximum sensitivity of 1.75nm/ degree(s)C achieved by the 10th cladding mode of the 240micrometers LPFG is nearly 24 times that of the minimum value (0.075nm/C) exhibited by the 30th mode of the 34micrometers LPFG. Such devices may lead to high-efficiency and low-cost thermal/electrical tunable loss filters or sensors with extremely high temperature resolution.
[1]
A. Vengsarkar,et al.
Optical fiber long-period grating sensors.
,
1996,
Optics letters.
[2]
Robert S. Windeler,et al.
Widely tunable long-period fibre gratings
,
1999
.
[3]
C.G. Atherton,et al.
Resonance conditions of long-period gratings in temperature sensitive polymer ring optical fibers
,
2000,
IEEE Photonics Technology Letters.
[4]
B.J. Eggleton,et al.
Electrically tunable efficient broad-band fiber filter
,
1999,
IEEE Photonics Technology Letters.
[5]
D. Hall,et al.
An introduction to optical waveguides
,
1982,
Proceedings of the IEEE.
[6]
John E. Sipe,et al.
Long-period fiber gratings as band-rejection filters
,
1995
.