SFP-1.25G-CWDM-XX-40KM is the most commonly used medium to long distance gigabit CWDM SFP module. The biggest advantage is the ability to fully utilize all 18 wavelengths (1271nm-1611nm) of CWDM. Due to the shortened transmission distance to 40 km, it has great flexibility in wavelength selection and is the absolute mainstay of CWDM expansion solutions.
The “XX” in the model must be replaced with a specific wavelength code (e.g. 47=1470nm, 49=1490nm). In a CWDM wavelength division system, 1 Gb SFP modules with identical wavelengths must be used at both ends of the link for normal communication which uses DFB (distributed feedback) laser and PIN photodiode. The emitted optical power is between -5dBm and 0dBm, and the receiving sensitivity is usually -24dBm or lower. The calculated optical power budget is approximately 19dB to 21dB. When deploying the project, it is necessary to ensure that the total loss of the entire fiber optic link (fiber length, fusion points, connectors, etc.) is less than this budget, and to retain a certain amount of redundancy.
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