Softel adopts unique bandwidth extension techniques (asymmetric craft) for the tri-windows couplers to change the characteristic of the wavelength and make tri-windows at 1310/1490/1550nm wavelength meet the precision requirements of the coupling ratio. This unit specially applies for the low-cost solution of " 3 in 1 network" and tri-wavelength bi-direction transmission with a single fiber in FTTx network.