Abstract: Thermally compensated waveguides are disclosed herein. According to one aspect, the present disclosure proposes new ways to combine negative TOC (NTOC) material layers within the waveguides. NTOC materials can be implemented in one or more of a cladding layer, a core rib/channel waveguide, a horizontally segmented waveguide, a vertically segmented waveguide, a sub-wavelength grating structure, and/or in various other waveguide structure implementations including arbitrary core or cladding shapes. The integration of NTOC materials improves the temperature dependence of the waveguide spectrum. The need for fast and efficient optical-based technologies is increasing as Internet data traffic growth rate is overtaking voice traffic, pushing the need for optical communications.