الوصف

CWDM - Coarse Wavelength Division Multiplexing. WDM systems with fewer than eight active wavelengths per fiber. DWDM - Dense Wavelength Division Multiplexing. WDM systems with more than eight active wavelengths per fiber. Types of WDM Currently, there are two types of WDM in existence today: Coarse WDM (CWDM) and Dense WDM (DWDM). Backwards as it may seem, DWDM came well before CWDM, which appeared only after a booming telecommunications market drove prices to affordable lows. Whereas CWDM breaks the spectrum into big chunks, DWDM dices it finely. DWDM fits **-plus channels into the same frequency range used for two CWDM channels. CWDM is defined by wavelengths. DWDM is defined in terms of frequencies. DWDM’s tighter wavelength spacing fit more channels onto a single fiber, but cost more to implement and operate. Distinctive CWDM differences CWDM can—in principle—match the basic capabilities of DWDM but at lower capacity and lower cost. CWDM enables carriers to respond flexibly to diverse customer needs in metropolitan regions where fiber may be at a premium. However, it’s not really in competition with DWDM as both fulfill distinct roles that largely depend upon carrier-specific circumstances and requirements anyway. The point and purpose of CWDM is short-range communications. It uses wide-range frequencies and spreads wavelengths far apart from each other. Standardized channel spacing permits room for wavelength drift as lasers heat up and cool down during operation. By design, CWDM equipment is compact and cost-effective as compared to DWDM designs. Distinctive DWDM differences DWDM is designed for long-haul transmission where wavelengths are packed tightly together. Vendors have found various techniques for cramming *2, *4, or **8 wavelengths into a fiber. When boosted by Erbium Doped-Fiber Amplifiers (EDFAs)—a sort of performance enhancer for high-speed communications—these systems can work over thousands of kilometers.