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We report the development and demonstration of a long-period grating refractometer. The principle of operation is based on the using of a long-period grating that is structurally induced by a CO 2 laser, and where the resonance wavelengths are shifted as the refractive index of medium surrounding the cladding of the long-period grating. The different concentrations for three types of solutions (ethylene glycol, salt, and sugar) were experimentally measured, and results show that, as a refractometer, this fiber-based device not only can differentiate chemicals based on their refractive index, but it can also become a concentration indicator of a particular chemical solution, and applied in the oil and petroleum industry.

Splicing between single-mode fiber (SMF) and photonic crystal fiber (PCF) using a conventional electric-arc splicer is not easily achieved. It is reported, for the first time, that the condensation within the capillaries resulted in a bubble developed at the fiber ends in the midst of splicing. A novel and effective splicing technique using a CO/sub 2/ laser has successfully eliminated this limitation and a complete splicing process is achieved within 3-5 s. The splice losses have been recorded to be in the range of 1.3-2.8 dB; the high splice losses are possibly due to the field-mode discrepancy of the sampled PCF with a diameter of 100 /spl mu/m.

Silica photonic crystal fiber (PCF) is a new type of fiber that has an array of microscopic air holes running along its length. Splicing PCF to standard single-mode fiber (SMF) is a challenging task, but it is also important because of the potential broad applications. Proper splicing of SMF to PCF is imperative in order to avoid collapsing of the PCF on the air holes; however, the two types of fiber require different laser powers for melting. A laser splicing system is developed to demonstrate its effectiveness at splicing between the large-mode-area PCF and SMF with low splice loss.

An extremely short long-period grating (LPG) with strong resonance has been developed in a large-mode-area photonic crystal fiber (PCF) by use of the heat source of a CO2 laser. We believe that such a LPG in pure silica PCF is the first example to be obtained with the point-by-point technique. The fabrication method is simple and repeatable. The resulting LPG has 8 periods, written by a CO2 laser, within a 2.8-mm length of fiber, which yields a deep notch of core-cladding mode coupling of -31.5 dB at the telecommunication wavelength of 1529.2 nm, with a FWHM of approximately 0.7 nm. The principal advantages of this LPG are that it is practical, cost effective, and compact.