A multi-mode 9XXnm-wavelength laser diode was developed to optimize the divergence angle and reliable ex-facet power. Lasers diodes were assembled into a multi-emitter pump package that is fiber coupled via spatial and polarization multiplexing. The pump package has a 135μm diameter output fiber that leverages the same optical train and mechanical design qualified previously. Up to ~ 270W CW power at 22A is achieved at a case temperature ~ 30ºC. Power conversion efficiency is 60% (peak) that drops to 53% at 22A with little thermal roll over. Greater than 90% of the light is collected at < 0.12NA at 16A drive current that produces 3.0W/(mm-mr)<sup>2</sup> radiance from the output fiber.
Long-period fiber gratings (LPFG’s) find applications in optical fiber communication systems and fiber sensor systems. Among others, it can be used as gain flattening filters (GFF’s) in the communication systems. Depend on the amplifier design, the GFF’s need to be either athermal, or have specific temperature sensitivities. The temperature sensitivity requiement sometimes can be very stringent. It has been known that the temperature and strain sensitivity are dependent on the fiber parameters and the order of the cladding modes it is used. In this paper we will describe the general method for finding suitable cladding mode in a specific fiber for specific requirements. We found that the polarization dependent losses (PDL) in high sensitivity modes are remarkably higher than the ones in common LPFG’s. In those high sensitivity filters achieved by the UV-beam side illuminating, the birefringence-related resonant wavelength separation (RWS), which is the central wavelength separation corresponding the slow and fast axis state of polarizations (SOP), can be in the range of 5 nm, which is remarkably larger than the reported values in other LPFG’s. There are two sources of birefringence which lead to PDL: fiber core ovality induced birefringence, which is intrinsic, and the anisotropic UV-beam exposure induced birefringence. We proposed methods to deal with those birefringence sources. The leads to almost complete remove of the RWS in the high sensitivity LPFG’s.
Because of the variation of the reflection coefficient, the measuring accuracy is greatly affected with the reflected optical fiber displacement sensor (OFDS). In this presentation, the author presents a new kind of sensing scheme which can correct the reflection coefficient in real time and make it possible to realize on-line measurement.