Certain embodiments described herein pertain to optical sensors, systems and methods for continuous glucose monitoring. In some embodiments, methods of preparing a layered optical sensor are disclosed. The optical sensor can be formed by laminating a plurality of sheets together to form a final sensor. In some embodiments, the sensor tip comprises a oxygen conduit, an enzymatic layer, and an sensing layer. In some embodiments, the sensor includes a plurality of waveguides configured to direct light to and from a target material, such as an oxygen sensing polymer. Systems are also disclosed for an adhesive system for attaching an optical sensor-transmitter system. Methods and systems are also disclosed for a sensor inserter system. The inserter can include a lancet tip that includes a convex feature attached to a first surface of the lancet tip.
