A new side pumping method based on the diffractive properties of a planar grating which is directly written into the
inner cladding of a double-clad fiber (DCF) is proposed. This technique assumes that the inner cladding of the DCF is
highly photosensitive and its diameter is large enough. Then a planar grating with a proper thickness can be written into
the inner cladding. The principles, characteristics and coupling efficiencies of the proposed scheme are described and
simulated by coupled wave theory. The simulating results show that the coupling efficiencies can achieve over 98% for
TE-, TM- and un-polarized incident pump lights simultaneously. And the average coupling efficiencies can still achieve
80% regardless of TE or TM polarization even when the pump wavelength ranges from 974 to 978nm and the incident
angle ranges from −0.8° to 0.8°. The fabrication tolerances of the planar grating and the leakage of pump powers for
multi-point side-pumping are also analyzed. The advantages of the proposed scheme include: (1) no risk of damaging the
DCF; (2) no index-matching optical adhesive; (3) high temperature sustainability; (4) simple, stable and compact. It
provides an effective way to scale the output power of DCF lasers or amplifiers to a high level.
A moiré interferometer system based on single metrology grating (SMG) that can achieve nanometer resolution is presented. By properly selecting the diffraction beam, different resolution can be realized with different diffracting orders. The measuring principle is described in detail. A new moiré fringes subdividing method is developed. This method can accurately deal with input signals which deviate from the orthogonal state by dynamically tracing the joints of input signals. So the stringent requirement for orthogonality of input signals is loosen. With the combination of the SMG and new subdividing method, the system can easily achieve nanometer resolution. A displacement measuring system, which resolution is 1nm and measure range is 400mm, is set up. And the experiment results of the system are given. It shows that the system has better anti-jamming ability to the orthogonal error of input signals than conventional systems.
A new kind of distributed fiber optic sensor is described in the paper. On the basis of mode coupling between two orthogonal fundamental modes of HiBi polarization- maintaining fiber, a new method is developed to locate the mode coupling point caused by external pressure applied on the fiber.