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Today, 25G optical transceivers are quite common in 5G front-haul networks. Preferably, 25G WDM modules are used in such applications to save resources. It should be mentioned that 25G WDM modules are much more expensive compared to other 25G transceivers (such as 25G SFP28 BiDi, SFP28 SR, SFP28 LR modules). This is where 25G SFP28 LWDM transceivers come into play - a robust alternative that enables multi-channel transmissions over a single fiber. On top of that, these transceivers are significantly less expensive than 25G WDM transceivers. The characteristics such as flexibility and cost efficiency of the 25G SFP28 LWDM transceiver make it an ideal solution for demanding and extensive networks as well as for 5G front-haul networks.
What makes 25G SFP28 LWDM transceivers suitable for 5G front haul networks?
Full compatibility with the 40/100Gb/s standard (IEEE802.3ba) opens the door for a move from 25G Ethernet networks to single channel 50G networks or even 100G networks in the future. The 25G SFP28 LWDM has 12 O-band wavelengths, of which 8 are standard wavelengths with 800Hz spacing between them. The remaining 4 wavelengths can be multiplexed by the 25G SFP28 LWDM transceiver with 25G SFP28 CWDM transceivers, i.e. 1269.23nm, 1291.10nm, 1332.41nm, and 1313.73nm wavelengths. The 25G LWDM module can multiplex numerous wavelengths onto a single fiber strand using WDM technology. This brings some savings in terms of power and lines.
As has already been listed, the 25G LWDM (Light Wavelength Division Multiplexing) module serves channels within a 4nm wide span, which is much narrower than 25G SFP28 CWDM modules. Consequently, a jump to a different wavelength range is inevitable. Generally, the operating temperature of 25G LWDM transceivers is -40°C to 85°C. A 1°C change in operating temperature is sufficient to cause an offset of 0.1nm at the wavelength. For stable transmission, the TEC (Temperature Control) takes over an important task for 25G LWDM modules. The affiliation of a suitable TEC enables 25G LWDM modules to provide precise and stable data transmissions in demanding networks. For more detailed information about the general characteristics of 25G SFP28 LWDM transceivers, please refer to the table below.
25G LWDM modules provide multiplexing over multiple wavelengths as is the case with 25G DWDM and CWDM transceivers. With this module, multiple wavelengths can be multiplexed onto a single fiber. Remarkable is the price, which is much lower for 25G SFP28 LWDM modules than for 25G CWDM/DWDM transceivers, because they are equipped with cheaper PIN receivers. This is in contrast to the expensive APD receivers in 25G CWDM/DWDM transceivers. Furthermore, 25G SFP28 LWDM transceivers use inexpensive DML lasers, whereas 25G CWDM/DWDM transceivers use expensive PIN lasers. Thus, 25G SFP28 LWDM modules are a low-cost alternative to 25G CWDM/DWDM transceivers for 5G front-haul transmissions.
Build a network with 25G SFP28 LWDM transceiversn
25G LWDM transceivers and CWDM/DWDM modules offer similar types of connections. However, a set of LWDM Mux/Demux (multiplexer/demultiplexer) must be used if 25G SFP28 LWDM transceivers are to be used.
Following are some guidelines that contain important information for designing a network with 25G SFP28 LWDM transceivers.
8 25G SFP28 LWDM modules are required. 4 in the first 25G switch and 4 in the second 25G switch.
Now two sets of 25G LWDM modules are connected to LWDM Mux/Demux, which in turn are connected via singlemode fiber.
Conclusion:
A 25G SFP28 LWDM transceiver uses a single optical fiber for multi-channel transmissions. The ability to avoid the high cost of 25G CWDM and DWDM modules makes the 25G LWDM transceiver a viable and effective alternative for 5G front-haul networks. The 25G LWDM transceiver offers reliable, cost-effective and stable performance in demanding network applications.
