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Single Mode Optical Fiber G657.A1


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G657.A1

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G657.A1 Bending Insensitive Single-Mode Optical Fiber

Description of Bending Insensitive Single-Mode Fiber G657.A1:

G657.A1 is a type of bend-insensitive single-mode optical fiber (BIM-SMF) defined by the ITU-T G.657 standard. It is optimized for scenarios requiring tight bending (e.g., indoor cabling, FTTH), while maintaining core single-mode transmission characteristics to ensure compatibility with traditional G.652 single-mode fibers (the most widely used SMF globally). Unlike standard G.652 fibers (which are sensitive to bending losses), G657.A1 balances low bending loss, compatibility, and cost-effectiveness, making it a core solution for "last-mile" optical access networks.

G657.A1 is the "compatibility-focused" variant of G657.A:

It is designed to be fully backward-compatible with G.652.D fibers (the most common G.652 type), meaning it can be directly spliced or connected to G.652.D fibers without significant additional loss.
Its key advantage over G.652.D is superior bending performance: it can withstand much tighter bends (e.g., 10mm or 15mm radius) with minimal signal loss, avoiding the "macrobending loss" that plagues standard SMFs.
Operating window: Covers the core wavelength bands for optical communication—O-band (1260–1360 nm), C-band (1530–1565 nm), and L-band (1565–1625 nm)—supporting both legacy (e.g., 10G Ethernet) and high-speed (e.g., 100G/400G) transmission.

Internal Structure：

G657.A1 adopts a layered concentric structure similar to traditional SMFs, but with optimized material composition and refractive index profiles to reduce bending loss. Its cross-section consists of 3 key layers:

Layer	Composition	Function
Core	Material: High-purity silica glass doped with germanium (GeO₂) to increase refractive index. Diameter: ~9 μm	Transmits the main optical signal (single-mode propagation to avoid modal dispersion).
Cladding	Material: Pure silica glass (refractive index lower than the core, creating total internal reflection). Diameter: ~125 μm	Special doping (e.g., fluorine) to adjust the refractive index profile, suppressing bending-induced signal leakage.
Coating	Material: UV-curable acrylate Diameter: ~250 μm	Absorbs mechanical shocks, protects the cladding from scratches, and maintains fiber flexibility (critical for bending).

Features of Single Mode Fiber G657.A1:

G657.A1 fiber's core value lies in balancing bend insensitivity, G.652 compatibility, and practicality.

(1) Ultra-Low Macrobending Loss (Core Advantage)

Macrobending loss occurs when fibers are bent tightly (radius < 30mm), causing part of the optical signal to leak out of the core. G657.A1 minimizes this loss via optimized cladding design:

At 1550 nm (C-band, critical for long-distance access): Bending loss ≤ 0.1 dB/turn when bent at a radius of 15mm; ≤ 0.5 dB/turn at 10mm radius.
At 1310 nm (O-band, common for short-distance): Bending loss ≤ 0.03 dB/turn at 15mm radius.

By contrast, standard G.652.D fibers have bending losses > 1 dB/turn at 15mm radius—far too high for indoor tight bends.

(2) Full Compatibility with G.652.D

This is a non-negotiable requirement for G657.A1 (per ITU-T G.657.A):

Splicing compatibility: Splicing G657.A1 with G652.D (via fusion splicing) results in a splice loss ≤ 0.1 dB (same as splicing two G652.D fibers), avoiding signal degradation in mixed-fiber networks.
Transmission compatibility: It supports all transmission protocols designed for G652.D (e.g., GPON, XG-PON, 10GBASE-LR), requiring no modifications to existing transceivers or network equipment.
Connector compatibility: Uses the same connectors as G652.D (e.g., SC, LC, FC), enabling plug-and-play deployment.

(3) Wide Temperature Stability

G657.A1 maintains stable performance across extreme temperatures (typical range: -40°C to +85°C), making it suitable for both indoor (e.g., residential basements) and outdoor (e.g., pole-mounted cabinets) environments. Its coating materials resist thermal expansion/contraction, preventing microcracks or increased loss under temperature fluctuations.

(4) Cost-Effectiveness

Compared to G657.B (a more bend-insensitive but less compatible variant) or specialty fibers, G657.A1 uses a simpler refractive index design (e.g., step-index or shallow trench profile) that is easier to manufacture. This keeps its cost close to G652.D, making it scalable for large-scale FTTH deployments.

Typical Applications:

G657.A1 fiber's bend insensitivity and compatibility make it ideal for short-to-medium distance, tight-space optical networks, especially in "last-mile" access and indoor wiring. Key applications include:

1. Fiber-to-the-Home (FTTH) & Fiber-to-the-Premises (FTTP)

FTTH requires fibers to be routed through narrow spaces (e.g., wall cavities, door frames, or small ONT (Optical Network Terminal) cabinets). G657.A1’s ability to bend at 10–15mm radii avoids signal loss, while compatibility with G652.D ensures seamless integration with the backbone network (which uses G652.D).

Use case: Drop cables (from street cabinets to homes) or indoor jumpers (from ONT to routers).

2. Indoor Data Centers & Enterprise Cabling

Data centers and offices often require dense cabling (e.g., under floors, in server racks, or between adjacent switches). G657.A1’s flexibility reduces cable management complexity and avoids bending-induced downtime.

Use case: Connecting top-of-rack (ToR) switches to storage area networks (SANs) or 5G small cells in enterprise buildings.

3. Fiber-to-the-Apartment (FTTA) & Multi-Dwelling Units (MDUs)

In high-rise buildings, fibers must be routed through narrow risers or distributed to individual apartments via small junction boxes. G657.A1 fiber's tight-bending capability eliminates the need for large cable trays, reducing installation costs and space requirements.

4. Industrial & Harsh-Environment Wiring

While not designed for extreme industrial conditions (e.g., heavy vibration), G657.A1 fiber's temperature stability makes it suitable for mild industrial scenarios (e.g., smart factories, retail POS systems) where fibers may be bent around equipment or walls.

Changrong's Fiber Workshop View:

9 Fiber Drawing Towers ( 2 lines/Tower, totally 18 Production Lines)
Annual Output 15,000,000 kilometers
Full Sets of Cutting-edge Testing Equipment

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Colored Fiber:

Colored Fiber

Fiber Stock:

G.657.A1 Fiber Color Identification (for colored fiber)

No.	1	2	3	4	5	6	7	8	9	10	11	12
Color	Blue	Orange	Green	Brown	Slate	White	Red	Black	Yellow	Violet	Pink	Aqua

G.657.A1 Bare Fiber Technical Parameters

Optical Performance
Characteristics	Conditions	Unit	Standard Value
Attenuation	1310nm	dB/km	≤0.344
	1383nm	dB/km	≤value at 1310nm
	1550nm	dB/km	≤0.204
	1625nm	dB/km	≤0.234
Attenuation vs Wavelength Max Difference	1285nm ~ 1330nm vs 1310nm	dB/km	≤0.04
Attenuation vs Wavelength Max Difference	1525nm ~1575nm vs 1550nm	dB/km	≤0.03
Dispersion Coefficient	1285nm~1340nm	ps/(nm/km）	≤3.5
	1271nm~1360nm	ps/(nm/km）	≤5.3
	1550nm	ps/(nm/km）	13.3-18.0
	1625nm	ps/(nm/km）	17.2-23.0
Zero Dispersion Wavelength λ₀	--	nm	1300-1324
Zero Dispersion Slope S₀	--	ps/(nm²/km)	0.073-0.092
Typical Value	--	ps/(nm²/km)	≤0.086
PMD	Maximum Individual Fiber	ps/√km	≤0.06
	Link (M=20, Q=0.01%)	ps/√km	≤0.06
	Typical Value	ps/√km	≤0.04
Fiber Cut-off Wavelength λcc	--	nm	1180-1330
Cable Cut-off Wavelength λcc	--	nm	≤1260
MFD	1310nm	μm	8.8±0.4
MFD	1550nm	μm	9.7±0.6
Point Discontinuity	1310nm	dB	≤0.05
Point Discontinuity	1550nm	dB	≤0.05

Geometrical Performance
Characteristics	Unit	Standard Value
Cladding Diameter	μm	125.0±0.7
Cladding Non-circularity	%	≤1.0
Core-Cladding Concentricity Error	μm	≤0.5
Coating Diameter	μm	243±5.0
Coating Non-circularity	%	≤6.0
Coating-Cladding Concentricity Error	μm	≤10
Curl Radius	m	≥4

Mechanical Performance
Characteristics	Conditions	Unit	Standard Value
Proof Test	--	%	≥1.0
	--	N	≥8.8
	--	Gpa	≥0.69
Coating Strip Force	Peak Force	N	1.0-8.9
Coating Strip Force	Average Value	N	1.0-5.0
Tensile Strength (Weibull Probability Level)	Before -aged（sample 0.5m）（Level 15%)	Gpa	≥3.14
	Before -aged（sample 0.5m）（Level 50%)		≥3.80
	After -aged（sample 0.5m）（Level 15%)		≥2.76
	After -aged（sample 0.5m）（Level 50%)		≥3.03
Dynamic Fatigue Nd	--		≥20
Macro-bending Loss	(10 turns; Ф 30 mm) @1550 nm	dB	≤0.25
	(10 turns; Ф 30 mm) @1625 nm	dB	≤1.0
	(1 turns; Ф 20 mm) @1550 nm	dB	≤0.75
	(1 turns; Ф 20 mm) @1625 nm	dB	≤1.5

Environmental Performance
Characteristics	Conditions	Unit	Standard Value
Temperature Cycling	-60℃ ~+85℃	dB/km	≤0.05
Damp Heat Aging	85℃、 RH 85%、 30 Days	dB/km	≤0.05
Water Immersion	23℃、 30 Days	dB/km	≤0.05
Dry Heat Aging	85℃、 30 Days	dB/km	≤0.05