Single-mode fibre: G.652.D and G.657
Most telecom, FTTH and long-distance links use single-mode fibre to ITU-T G.652.D. In the reference construction from public datasheets, the cladding is 125.0 um with a manufacturer tolerance of plus or minus 0.7 um, and the coating is 242 plus or minus 7 um, about 250 um once coloured; a reduced 200 um coating is offered for high-count cables. Mode field diameter at 1310 nm is per datasheet, typically 8.6-9.2 um. Attenuation is stated per datasheet for the fibre and per cable specification for the finished cable; ask for the maker's figures rather than a generic number.
G.657 fibres tolerate tighter bends. ITU-T sets the minimum bend radius at 10 mm for G.657.A1, 7.5 mm for A2 and B2, and 5 mm for B3, and the A category is compatible with G.652.D, so A1 and A2 can be spliced into G.652.D networks. G.657.A1 or A2 is the usual choice for FTTH drop cable and indoor routing; see G.652.D vs G.657.
Multimode fibre: OM3, OM4 and OM5
Multimode fibre, 50/125 um, serves short links in buildings and data centres with lower cost optics. Grades are set by effective modal bandwidth at 850 nm.
| Type | Key parameter | Typical use |
|---|---|---|
| G.652.D single-mode | 125 um cladding, 242 um coating (datasheet) | Backbone, outdoor, FTTH feeder |
| G.657.A1 | Minimum bend radius 10 mm | Drop and indoor cable |
| G.657.A2 / B2 | Minimum bend radius 7.5 mm | Tight indoor routing |
| G.657.B3 | Minimum bend radius 5 mm | Very tight routing in premises |
| OM3 | EMB at least 2,000 MHz.km at 850 nm | Data centre links |
| OM4 | EMB at least 4,700 MHz.km at 850 nm | Longer data centre links |
| OM5 | As OM4, plus 2,470 MHz.km at 953 nm | Short wavelength multiplexing |
For 10G over OM4, the commonly quoted reach is 400 m (IEEE 10GBASE-SR). Attenuation for multimode is per the applicable standard and datasheet.
Cable constructions around the fibre
- Tight-buffered indoor cable: 0.9 mm buffered fibres, aramid yarn and a PVC or LSZH jacket; the reference 12-core distribution cable is about 6.0-6.3 mm overall and 33-41 kg/km. See indoor fibre cables.
- Loose tube outdoor cable: gel-filled tubes stranded round a central strength member, water blocking, a PSP or APL tape and a PE sheath; the reference GYTS 24-core cable is about 10 mm overall, with weight that varies by maker, 76-116 kg/km per datasheet.
- ADSS aerial cable: central FRP, loose tubes and aramid yarn under a PE or AT sheath, to IEEE 1222-2019 and IEC 60794-4-20. The span must be stated with weather loading; OPGW is a different product under IEEE 1138-2021.
- FTTH drop cable: flat 2.0 x 3.0 mm GJXFH type with one or two G.657 fibres, FRP or steel strength members and an LSZH jacket.
Telcordia GR-20 covers outdoor cable requirements and GR-409 indoor cable. In the EU, fibre cable permanently installed in buildings falls within EN 50575; in the US, indoor fibre carries OFNR or OFNP ratings under NEC Article 770. Fibres and tubes follow the TIA-598 colour order; see fibre colour codes.
Link budgets and connectors
For planning, older TIA-568 values give cabled attenuation of 3.5 dB/km at 850 nm and 1.5 dB/km at 1300 nm for multimode, 1.0 dB/km indoor and 0.5 dB/km outdoor for single-mode, 0.75 dB per mated connector pair and 0.3 dB per splice. These are older TIA-568 planning values; use the cable maker's specification where available. For patch cords, IEC 61753-1 sets single-mode insertion loss Grade B at 0.12 dB mean, with 97 percent at or below 0.25 dB, and Grade C at 0.25 dB mean; return loss Grade 1 (APC) is at least 60 dB and Grade 2 (UPC) at least 45 dB.
Tests, price and lead time
Each fibre is checked by OTDR before shipment, with traces supplied per drum; patch cords carry IL and RL results per connector. Fibre type, core count and construction drive price: the fibre grade sets the glass cost, while armour tape, aramid yarn, strength members and the number of tubes add material and process time. A 24-core GYTS and a 24-core ADSS carry the same fibres but very different builds, so compare quotes construction by construction, not by core count alone. Wuhan supplies preform, fibre and cable, with over 25 percent of the international market according to the Wuhan municipal government, and Qidu in Wujiang is a national torch programme base for optical and electric cable. Lead time follows fibre and tube scheduling and is confirmed in writing for each order; see MOQ and lead time or send your build through the quote form.