For G657 fiber FTTH selection, compare the three actual supplier references rather than ranking grade names alone. The listed G.657.A1, A2 and B3 products all specify ≤ 0.210 dB/km attenuation at 1550 nm. Their bend limits use different arrangements: A1 specifies a 15 mm radius with ten turns, A2 a 7.5 mm radius with one turn, and B3 a 5 mm radius with one turn at 1550 nm. Coating options also differ. These are source-specific bare-fiber conditions, not finished-cable minimum bend radii or a universal substitution approval. Choose against the cable design, required wavelengths, joining criteria and production qualification. Follow the product links for the full listed values and request the actual offered specification before approving a grade.
Reference specification comparison
Values below are the same supplier reference data shown on the product pages. Different test conditions occupy separate rows; “Not listed” means the cited product table does not provide that entry.
| Parameter / condition | G.657.A1 | G.657.A2 | G.657.B3 |
|---|---|---|---|
| Attenuation at 1310 nm | ≤ 0.350 dB/km | ≤ 0.350 dB/km | Not listed in reference |
| Attenuation at 1550 nm | ≤ 0.210 dB/km | ≤ 0.210 dB/km | ≤ 0.210 dB/km |
| Cladding diameter | 125 ± 0.7 μm | 125 ± 0.7 μm | 125 ± 0.7 μm |
| Coating diameter | 245 ± 10 μm / 200 ± 10 μm | Not listed in reference | 242 ± 7 μm |
| Cable cut-off wavelength | ≤ 1260 nm | Not listed in reference | Not listed in reference |
| Macrobend: 15 mm radius, 10 turns, 1550 nm | ≤ 0.25 dB | Not listed in reference | Not listed in reference |
| Coating diameter (table value) | Not listed in reference | 242 ± 7 μm / 200 ± 10 μm | Not listed in reference |
| Mode field diameter at 1310 nm | Not listed in reference | 8.6 ± 0.4 μm | 8.6 ± 0.4 μm |
| Macrobend: 7.5 mm radius, 1 turn, 1550 nm | Not listed in reference | ≤ 0.40 dB | Not listed in reference |
| Macrobend: 5 mm radius, 1 turn, 1550 nm | Not listed in reference | Not listed in reference | ≤ 0.15 dB |
| Macrobend: 5 mm radius, 1 turn, 1625 nm | Not listed in reference | Not listed in reference | ≤ 0.45 dB |
Read three bend specifications without creating a false ranking
The comparison table keeps each radius, turn count and wavelength on its own row. The A1 limit is ≤ 0.25 dB at 15 mm radius, ten turns and 1550 nm; the A2 limit is ≤ 0.40 dB at 7.5 mm radius, one turn and 1550 nm. B3 specifies ≤ 0.15 dB at 5 mm radius, one turn and 1550 nm, plus ≤ 0.45 dB under the same radius and turns at 1625 nm.
These are specified limits, not measurements from one shared experiment. The smaller dB number is not independently a better result when the arrangement changes. If the design specifies another wavelength or radius, request applicable evidence; do not interpolate an unlisted limit or treat a blank cell as zero loss.
Compare coating and geometry alongside attenuation
A1 lists 245 ± 10 μm or 200 ± 10 μm coating; A2 lists 242 ± 7 μm or 200 ± 10 μm; B3 lists 242 ± 7 μm. The site gives 125 ± 0.7 μm cladding for all three. A2 and B3 each list 8.6 ± 0.4 μm mode field diameter at 1310 nm. The A1 summary does not list that field, so request it when needed rather than copying the A2 value.
A1 and A2 list ≤ 0.350 dB/km at 1310 nm. The B3 product summary does not publish a 1310 nm attenuation entry. All three list the same 1550 nm attenuation limit, but that does not make their full specifications identical. Confirm every wavelength required by the system against the offered datasheet.
Choose a grade for the defined FTTH design
Review A1 where its published conditions meet the access-cable requirements. Review A2 when its tighter-radius reference is relevant to the specified design. Review B3 where the project needs its documented 5 mm test condition, while checking geometry, joining and the complete qualification scope. A smaller test radius alone is not a reason to change an already qualified material.
ITU-T G.657 distinguishes category A from category B; do not extend a general G.652.D compliance statement to every B3 offer. The standard provides category context, while approval of an actual product requires the complete supplier specification and any project-specific joining evidence. The table here does not establish automatic interchangeability.
Keep bare-fiber tests separate from finished-cable limits
The cable maker must define buffering, strength members, jacket and any connectors, then provide the handling and installation requirements for that construction. A fiber test at a 5 mm or 7.5 mm radius does not authorize bending a finished cable to that radius during pulling or service.
The fiber designation also does not establish PON capacity, subscriber count, network reach or completed cable fire classification. Record those as system or finished-product requirements. Keep the optical budget and environmental qualification connected to the actual construction and interfaces.
Move from the comparison to a product-specific RFQ
Open the linked A1, A2 and B3 product pages to check the reference source and listed values. Identify the required grade, exact coating and any missing parameter in the inquiry. Add total fiber-km, preferred continuous reel length, destination and required batch documents.
Use the FTTH cable manufacturing guide for the design review and the procurement guide for reel allocation and acceptance planning. If more than one grade is allowed, list the approval criteria for alternatives rather than asking for a universal cheapest or best FTTH fiber.
What to confirm
- A1, A2 and B3 compared under complete stated conditions
- Coating and geometry confirmed for the offered grade
- Missing fields requested rather than assumed
- Finished-cable limits and material substitution approved separately
Frequently asked questions
Is G.657.B3 always the best FTTH fiber?
No. Its listed tighter-radius tests may be relevant to a defined design, but coating, optical requirements, joining and the finished cable qualification still need review.
Can I compare 0.25 dB, 0.40 dB and 0.15 dB directly?
No. These site references use different radii and turn counts. Keep radius, turns and wavelength with each limit, or request results under a common required condition.
Does the B3 summary establish a 1310 nm attenuation value?
No. That entry is not listed in the current product summary. Request the offered datasheet; do not infer the A1 or A2 value for B3.
Sources & reference context
This guide is published by OpticFiberHub and summarizes the supplier literature identified below with editorial purchasing guidance. Product values describe the source grade, not a measured result or a conformity guarantee for a new order.
- G.657.A1 reference specifications — BendCom G.657.A1 Bending Insensitive Single-mode Optical Fiber datasheet, pages 1–2.
- G.657.A2 reference specifications — Jiangsu Nanfang Optical Fiber Product Manual, pages 7–8.
- G.657.B3 reference specifications — Jiangsu Nanfang Optical Fiber Product Manual, pages 9–10.
Application references
- ITU-T G.657: bend-insensitive single-mode fiber — Category and terminology reference. The supplier values on this page are not a complete reproduction of the Recommendation.
Quality & technical resources explains source selection, translated documents and the limits of historical batch records. Request the current specification and applicable records for the actual offered material.
Further terminology reference: The Fiber Optic Association: optical fiber fundamentals.
Single-mode standard references: ITU-T G.652 and ITU-T G.657. Supplier reference values above must not be mistaken for a reproduction of every requirement in those Recommendations.
