Temperature changes from 30℃ to 230℃ significantly affect wavelength and coupling length in directional couplers. The effective refractive index is influenced by temperature, governed by the thermo-optic coefficient (∂n/∂T). Based on the multicladding equivalent method, the coated fiber coupler was simplified to a conventional one. The directional. We offer a full line of fiber optic couplers and splitters supporting SM, MM, PM, large core, and double-clad fibers across 300–2000 nm, with power handling up to 100 W and operating temperatures up to 300°C.