Single-mode optical modules have a typical center wavelength of 1310 nm or 1550 nm, and are used with single-mode fibers. That value determines whether the module is designed for multimode fiber (MMF) or single-mode fiber (SMF), how much attenuation the signal will experience, how dispersion behaves over distance, and. Gigabit single-mode fiber optic module Common parameters of optical modules 1. Center wavelength 1) 850nm (MM, multi-mode, low cost, but short transmission distance, usually only 500M); 2) 1310nm (SM, single mode, large loss during transmission, small dispersion, generally used for transmission. A CWDM SFP module is an optical transceiver that uses Coarse Wavelength Division Multiplexing (CWDM) technology to transmit multiple data channels over a single strand of single-mode fiber, helping networks expand capacity without deploying additional fiber. In practical terms, CWDM SFP modules are. An optical module usually consists of an optical transmitting device (TOSA, including a laser), an optical receiving device (ROSA, including a photodetector), functional circuits,main control circuit board (PCBA), housing and optical (electrical) interface and other components.