The low-loss ion exchanged (IOX) waveguide disclosed herein includes a glass substrate having a top surface and comprising an alkali-aluminosilicate glass with between 3 and 15 mol % of Na2O and a concentration of Fe of 20 parts per million (ppm) or less. The glass substrate includes a buried Ag—Na IOX region, wherein this region and a surrounding portion of glass substrate define the IOX waveguide. The IOX waveguide has an optical loss OL≤0.05 dB/cm and a birefringence magnitude |B|≤0.001. The glass substrate with multiple IOX waveguides can be used as an optical backplane for systems having optical functionality and can find use in data center and high-performance data transmission applications.