ABSTRACT
The group refractive-index difference of cladding modes excited by a long-period fiber grating is characterized by use of the technique of optical low-coherence reflectometry, with a precision of <10(-4) . Very good agreement between theoretical and experimental results is demonstrated.
ABSTRACT
The mechanical resistance of single-mode fibers containing fiber Bragg gratings inscribed with cw UV laser irradiation is almost identical to that of pristine fiber. The median breaking strength of the gratings' Weibull distribution is more than 5 GPa, and the m value is of the order of 70. Based on a dynamic fatigue model, a Bragg grating lifetime of 50 years with a failure probability of 0.001 is predicted, assuming a constant applied stress of 0.96 GPa.
ABSTRACT
New measurements of the birefringence induced in ultralow-birefringence fibers by a succession of orthogonally polarized UV side exposures show the reversibility of the process. Moreover, it is shown that the birefringence growth depends on two parameters, the total irradiation dose and the nature of the successive polarized UV side exposures. These observations indicate that geometric asymmetry is not the major cause of the birefringence and confirm a model of birefringence growth based on dipole alignment.
ABSTRACT
A simple, flexible method of postfabrication positioning of resonance wavelengths of long-period cladding-modecoupled gratings is proposed. This method is based on changing the outer fiber diameter. Reducing the diameter by etching the fiber in HF acid shifts the loss peaks to higher wavelengths. A shift as large as 130 nm after 5 min of HF etching was observed for our strongest grating peak, corresponding to the cladding mode HE19. The experimental results are in excellent agreement with model calculations.
