Optical Fiber Cables Sizing in FTTH Network

Optical Fiber Cables Sizing in FTTH Network: Three types of optical fiber cable sizes are used to build up FTTH networks. These are Feeder cable,Distribution Cables and Drop Cables. Feeder Cables are connecting the OLT at CO to the Remote splitters/FDT/FDH. Feeder optical cable laid in Point-to-point or ring topology. Single mode, loose tube available from 12F-288F; as standard practice the feeder cable size has to be 288 fiber optic.The only lose tube approved structure have to used 12 fiber per tube.

Distribution Optical fiber Cables- Distribution Optical fiber Cables connecting the Splitters in the FDTs to the FATs.They are laid in P2P/Star topology from FDT/Splitter location.Single mode, loose tube available from 12F-144F. The distribution cables leaving the FDT can only be 144F or 96 fiber optic.Drop Fiber Cables-Drop Fiber Cables cables used in last mile from FATs to FTBs and from FTBs to FOB/ATBs (customer premises).Bending radius in drop cable must be maintained at radius 15mm. Single mode, center or loose tube available in 8, 12 and 24F.

Cable sizing in FTTH network

Optical Fiber Cables Sizing in FTTH Network

Feeder Cables Sizing

The Feeder network covers the link Exchange (OLT, ODF or FDF) - FDT (splitter point). It usually presents the highest networks distances, as the exchange may be far away from the FDT covered area. The fiber cost is far less than the duct space cost. Hence the provision of the Feeder cables will mandatorily cover the ultimate demand determined in a Fundamental Plan for the area.

The total number of splitters per cabinet shall be based on the corresponding Fundamental Plan, and particularly on the DWU count per FDT. The FDTs will have 30% splitter spare capacity to cover potential future demand.

For FTTH projects only 288F feeder cables shall be used (144F cables are to be used only in exceptional cases where there is no further FTTH deployment foreseen in the area). 

The 288F cables will be terminated on the exchange using OSP HD-ODF. HD-ODFs accommodate up to 7 feeder cables (x288 fibers/cable=2016 connections).

Feeder Cable Assignment

Fibers 1 to 216 will be used to feed different FDTs,its also depend upon the telecom operator plan of optical fiber network. Fibers 217 to 240 telecom operators can be reserved for other services e.g. splitters in MHs, Point-to-point connections, etc.

Telecom operators can keep Fibers 241 to 288  spare for future use (i.e. FTTM).Multiples of 12F will be spliced in MH to match the total number of fibers in the FDT feeder cable.

Distribution Cables & Drop cables Sizing

Distribution cables go from the splitter 1:32 located in the FDT to the FAT, FTB (SDU), ODB (MDU) or indoor optical splitter box (OSB). Loose tube fiber cables of sizes 144F or 96F shall be used depending upon the grouping of villas and number of FATs.

The FAT closures accommodate up to 24 drop cables (144 F.O. max).The max. number of splices inside the FAT should not exceed 96 Fibers.The drop cables / termination box to be used are:

➤For 1 to 2 DUs per parcel: 8 fiber optic cable / TB (TBs with 8 ports will be specified).
➤For 3 to 8 DUs per parcel: 12 fiber optic cable / ODB
➤For 9 to 16 DUs per parcel: 24 fiber optic cable / ODB
➤More than 16 DUs per parcel: OSBs. The no. of fiber strands to the OSB may go from 4 to 12 depending on the Medium Business and Key Account in the MDU (potential P2P services).

All drop cable fibers will be spliced at TB/ODB/OSB side. Only required fibers should be spliced at FAT. For Examples (Its not universal standard):

➤For SDU: 8F spliced at the TB and 2F spliced inside the FAT
➤For MDU serving 14 DWUs: 24F spliced at the ODB and 14F spliced inside the FAT.

The distribution cable shall be labeled as 144F/96F(80) S1+S2:1-10+S17-S18 and drop cables as 8F(2) or 12F/24F(7). In case of single villas (SFU), telecom operator will extend and terminate the drop cable up to the ONT location for Green & brown Fields.

In Green Field MDU, the building owner shall install a minimum of 2 core fiber drop cables from the main telecom room/ODF Location to the ONT location of each Flat/shop/office etc;. Installer has to leave an extra length of 3m of cable on either end for terminations.

No splices are allowed between the Telecom Room and Floors. ODBs may be used as intermediate devices if the number of flats per floor is high or the building has many floors.