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The single-mode fiber provided by YOFC inc is employed for spiral processing by commercial welding machine. It can clearly see the periods structure under the light, but there is no obvious deformation of the fiber core, cladding and surface morphology under a microscope. There is an obvious resonant peak near 1560 nm, half peak width is about 25 nm, the depth of the resonant peak closed to –26 dB, when the period is about 411 μm. It agrees with theoretical calculation results according to the long-period fiber grating coupled-mode theory. The resonance wavelength is caused by coupling between the fundamental mode and the LP14 mode. The responsivities of the helically twisted long-period fiber gratings (H-LPFG) for the temperature is measured, the resonance wavelength is linear with temperature, the slope is 86 pm/℃. Because it is easy to inscribe by commercial welding machine, and has a strong resonance peak, it has potential applications as the temperature sensor.

The solid complexes of rare earth nitrates Perchlorates and thiocyanates with 2,2′-bipyridine-N,N′-dioxide (bipyO 2 ) have been reported [1–6] . However, the corresponding complexes of other rare earth chlorides have not been investigated except lanthanum, cerium and yttrium [7–9] . As an extension of our previous work on the synthesis of complexes of praseodymium and neodymium chlorides with bipyO 2 , [10] we have now prepared fluorescent solid complexes of samarium, europium, gadolium and terbium chlorides with bipyO 2 , using methanol as a reaction medium. The new synthesized compounds have been identified by means of elemental analysis, infrared spectrometry, conductometry, differential thermal analysis (DTA), thermogravimetry(TG) and X-ray powder diffraction. The main results are as follows.