G.657.A1 vs G.657.A2 for FTTH: A Segment-by-Segment Procurement Strategy

1. What G.657.A1 and G.657.A2 Actually Change

The current ITU-T G.657 Recommendation (08/2024) classifies A1 and A2 as Category A bend-loss-insensitive single-mode fibers. Category A requirements are a subset of G.652.D, preserving the transmission and interconnection characteristics needed in access links that also contain G.652.D fiber.

The principal difference is the small-radius macrobending requirement.

Macrobending limits under the standard test conditions

Glory's fiber optic cable bend-limits guide explains the difference between fiber-grade tests and complete-cable handling limits.

2. Select Fiber at Each FTTH Route Transition

Indoor and outdoor labels provide only an initial clue. A wide indoor riser may impose less bend stress than a compact outdoor terminal, while a wall-entry turn may be more severe than the indoor raceway that follows it. Set the fiber category wherever the route geometry or enclosure changes.

Where G.657.A1 is normally sufficient

A1 is a defensible specification when supports and slack loops are dimensioned correctly, enclosure storage is generous, the route remains above the finished cable's approved radius and post-installation handling is limited.

The linked Glory ROC drop cable page lists G.657.A1 and G.657.A2 fiber options. Its published structure includes a 3.0 × 6.0 mm PE outer sheath, two 1.2 mm FRP strength members and a 0.5 mm bare-copper toning conductor. These construction details belong in the review alongside the fiber category.

Where G.657.A2 creates measurable design value

A2 becomes more valuable near the subscriber endpoint, especially where the route contains repeated corners, shallow raceways, compact wall outlets, uncertain retrofit conduits or short pigtails stored behind adapters.

The ITU-T L.111 in-home cable guidance includes G.657.A2 or B3 in minimum-visibility in-home cable examples, supporting tighter-bend fiber in the final customer-side section when the pathway requires it.

3. Glory Route-Risk Screening Model for A1 and A2

The following quotation-stage model is an original Glory planning framework used alongside ITU-T G.657, the finished-cable data sheet and local installation requirements. Score each route section from 0 to 2 in four categories.

4. Allocate A2 Where It Changes Risk, Then Compare the Real Volume

A2's commercial value becomes measurable after the route is divided into low- and high-bend-risk sections. Consider an illustrative 1,000-subscriber design.

The project price will change by a smaller percentage because fiber is only one input in a finished cable or assembly. Jackets, reinforcement, connectors, production setup, test requirements, packing and order quantity can dominate the final quotation.

Request two quotations with the same cable construction and change only the fiber category. This produces a meaningful A1/A2 comparison and avoids mixing an outdoor PE/FRP A1 cable with an indoor LSZH/aramid A2 cable.

5. Pair the Fiber Grade with the Finished-Cable Specification

The IEC 60794-1-1:2023 generic cable specification establishes uniform requirements covering geometry, transmission performance, materials, mechanical properties, ageing and environmental exposure. These cable-level controls apply to A1 and A2 alike.

A complete specification should define:

• indoor, outdoor or indoor/outdoor application;
• flat, round, bow-type, ROC or pre-terminated construction;
• cable dimensions and manufacturing tolerances;
• PE, LSZH, PVC, TPU or project-specific jacket;
• FRP, steel wire, aramid yarn or other strength member;
• static and dynamic finished-cable bend radius;
• short-term and long-term tensile limits;
• temperature, UV, moisture, flame and water-blocking requirements;
• connector type, polish and boot geometry;
• sample approval, batch test evidence and traceability.

For pre-connectorized routes, connector dimensions and pulling protection may become the governing constraints. Glory's pre-terminated fiber route survey guide covers conduit clearance, pull points, bend review and termination space before production.

6. Validate G.657.A1, G.657.A2 and G.652.D Splices as a System

Category A fibers support G.652.D transmission and interconnection requirements, allowing A1, A2 and G.652.D to appear in the same access link. Project-specific splice evidence remains necessary because the actual result depends on the selected fibers and process.

Fusion-splice performance depends on the mode-field diameter, refractive-index profile, cleave quality, cleanliness, splicer alignment, arc calibration, program and OTDR measurement direction.

Corning's AN2020 fusion-splicing report covers Corning SMF-28 Contour family fibers, including G.652.D-, G.657.A1- and G.657.A2-compliant variants, and reports product-pair results obtained with a Fujikura 90S core-alignment splicer using the SM-AUTO program. As one documented example, SMF-28 Contour to SMF-28 Ultra produced a mean bidirectional loss of 0.02 dB at 1310, 1550 and 1625 nm, with maxima of 0.05, 0.04 and 0.04 dB respectively. Treat these values as evidence for those Corning products and test conditions.

Recommended sample-validation sequence

1. Record the fiber manufacturer and type used in every cable section.
2. Review the supplier's stated mode-field diameter and attenuation limits.
3. Prepare representative A1-to-A2 and G.652.D-to-G.657 splices.
4. Use the intended production splicer and approved program.
5. Measure each event from both directions with an OTDR.
6. Average the two directions before judging splice loss.
7. Retain the splicer model, program, operator, fiber batch and trace file.

Glory's LC single-mode pigtails support customized fiber type, connector polish, length and jacket options. State the pigtail fiber category in the BOM for a mixed A1/A2 route.

7. Turn the Fiber Decision Into a Quote-Ready FTTH RFQ

A useful RFQ defines the function and installation condition of every route segment.

8. Recommended Glory Products for the A1/A2 Procurement Workflow

The first two cards support the FTTH route addressed by this article. The third card links the separate FPV range as a related G.657.A2 application.