5G Mobile Networks use much higher radio frequency bands, Massive MIMO and Beamforming technologies which require bringing Remote Radio Unit (RRU) closer to the end users and therefore much denser RRU distribution. Centralized Radio Access Networks (CRAN) are favored by many Mobile Network Architects, where remote BBU farms are built in centralized equipment rooms from where services are provided to many RRUs. Such approach fastens the 5G roll-out, reduces space requirements and rental costs in remote sites, improves maintenance and significantly simplifies transport network architecture.

Passive CWDM (Coarse Wavelength Division Multiplexing) is a cost efficient approach which can be used in 5G CRAN design to interconnect BBU farms to RRUs. Passive CWDM solution consists of colored optical transceivers which are used together with CWDM filters. CWDM eCPRI 25G SFP28 optical transceivers use a CWDM channel plan defined by ITU-T G.694.2 (For 25G eCPRI it’s possible to use 12 from 18 ITU-T defined wavelengths with 20 nm spacing) and with help of passive CWDM filters we can aggregate/separate different wavelength (nm) connections:

With Passive CWDM approach we can design up to 12 Channel CWDM eCPRI double fiber connection or up to 6 Channel CWDM eCPRI single fiber connection between BBU farm and RRU units.

CWDM eCPRI 25G modules support latest 5G Fronthaul bit rate requirements and such applications as CPRI Option 10 (24.33 Gbps), CPRI Option 9 (12.165 Gbps), CPRI Option 8 (10.138 Gbps) and CPRI option 7 (9.830 Gbps) at the same time our CWDM CPRI 25G SFP28 optical transceivers are backwards compatible with older generation 4G/3G Mobile Base Stations.

For optical module use under harsh environments, like mobile base station towers, unheated outdoor cabinets, we recommend to use Industrial Temperature product versions which support -45 to 85 Celsius operating temperature range.