The New Solar Telescope (NST) project at Big Bear Solar Observatory (BBSO) now has all major contracts for design and fabrication in place and construction of components is well underway. NST is a collaboration between BBSO, the Korean Astronomical Observatory (KAO) and Institute for Astronomy (IfA) at the University of Hawaii. The project will install a 1.6-meter, off-axis telescope at BBSO, replacing a number of older solar telescopes. The NST will be located in a recently refurbished dome on the BBSO causeway, which projects 300 meters into the Big Bear Lake. Recent site surveys have confirmed that BBSO is one of the premier solar observing sites in the world. NST will be uniquely equipped to take advantage of the long periods of excellent seeing common at the lake site. An up-to-date progress report will be presented including an overview of the project and details on the current state of the design. The report provides a detailed description of the optical design, the thermal control of the new dome, the optical support structure, the telescope control systems, active and adaptive optics systems, and the post-focus instrumentation for high-resolution spectro-polarimetry.

A new and innovative single-mode fiber interferometer is proposed for the wave-front test of the adaptive optics (AO) system. It is based on a modified Mach-Zehnder interferometer with the two arms replaced by optical fibers. It avoids the difficulty of fringe interpretation of the conventional Mach-Zehnder interferometer. As fibers are used, the whole instrument is compact, flexible, and suitable for the AO on-site test. Furthermore, as minimum optical components are used, the interferometer is free of calibration and has high measurement accuracy. The operation of the interferometer is also very simple, and wave front can be tested quickly. We discuss the working principle, experiment setup, fringe analysis, and its application for an existing AO system. The interferometer can also be used to test wave aberrations of a single lens or an optical system.