There is no difference in meaning between fiber and fibre. Fiber is the preferred spelling in American English, and fibre is preferred in all major non-U.S. varieties of English, including Australian, British, Canadian, Indian, and Irish English.
Examples
For example, these American publications use fiber:
Daimler AG doubled down on efforts to develop lightweight carbon-fiber auto-body parts … [Wall Street Journal]
A meatless dish, packed with protein, fiber and flavor, Moroccan Chickpea and Sweet Potato Tagine is bold and intriguing. [Daily Republic]
The Nutrition Keys will list nutrients such as potassium, fiber, vitamin A, vitamin C, vitamin D, calcium, iron or protein. [Chicago Sun-Times]
And these non-American publications prefer fibre:
Namibia’s undersea telecoms fibre-optic cable laid along the West African coast went live on Tuesday … [Sydney Morning Herald]
On the upside, you did leave me some socks and that nice carbon-fibre video-camera tripod. [Globe and Mail]
Indeed, Egypt is today one of the major crossing points for the underwater fibre-optic cables that interconnect the regions of the globe. [The Guardian]
