It depends: some companies identify their wavelengths off the color of the clasp on the optic. ex: Gray 1470nm, Violet 1490nm, Blue 1510nm, yellow 1550nm, etc. Generally, plastic optical fiber runs between 650-850nm, MM fiber requires 850-1300nm, and SMF runs between 1300-1625. It's usually labeled directly on the optic, and on any cabling, to avoid confusion.