For longer spans—between buildings or across cities—single-mode fiber is used, operating at either 1310 nm or 1550 nm. The 1310 nm window offers low dispersion, while the 1550 nm band provides ultra-low loss and supports optical amplification, making it ideal for long-haul. Our fiber optic couplers can be integrated into a ruggedized housing with 3 mm reinforced Kevlar fiber jackets. Contact Tech Sales for details. Our couplers can be packaged in an aluminum housing such as the one shown here for a 1550 nm coupler. 1 Each. Light in optical fiber travels in the near-infrared region, far beyond visible light, and choosing the right transmission wavelengths is fundamental for minimizing loss and maximizing bandwidth. Need a product customized? We can customize our products to fit your requirements. Although. Optical fiber communication systems use specific wavelength windows in the electromagnetic spectrum to transmit data over fiber optic cables. The. Notes: All the data are tested without connectors. Insertion loss of one pair of connector is less than 0.